Tagged with "activity"
Staying Active: The Benefits of Physical Activity Tags: benefits physical activity staying alive health mental wellness word life production new quality entertainment

Although there are no sure-fire recipes for good health, the mixture of healthy eating and regular exercise comes awfully close. Most of The Nutrition Source is dedicated to singing the praises of a good diet. This is where physical activity gets its due.

 

Regular exercise or physical activity helps many of the body’s systems function better, keeps heart disease, diabetes, and a host of other diseases at bay, and is a key ingredient for losing weight. According to the 2008 Physical Activity Guidelines for Americans, (1) being physically active on a regular basis

Improves your chances of living longer and living healthier

Helps protect you from developing heart disease and stroke or its precursors, high blood pressure and undesirable blood lipid patterns

Helps protect you from developing certain cancers, including colon and breast cancer, and possibly lung and endometrial (uterine lining) cancer

Helps prevent type 2 diabetes (what was once called adult-onset diabetes) and metabolic syndrome (a constellation of risk factors that increases the chances of developing heart disease and diabetes; read more about simple steps to prevent diabetes)

Helps prevent the insidious loss of bone known as osteoporosis

Reduces the risk of falling and improves cognitive function among older adults

Relieves symptoms of depression and anxiety and improves mood

Prevents weight gain, promotes weight loss (when combined with a lower-calorie diet), and helps keep weight off after weight loss

Improves heart-lung and muscle fitness

Improves sleep

The Cost of Inactivity

If exercise and regular physical activity benefit the body, a sedentary lifestyle does the opposite, increasing the chances of becoming overweight and developing a number of chronic diseases. Despite all the good things going for it, only about 30 percent of adult Americans report they get regular physical activity during their leisure time—and about 40 percent of Americans say they get no leisure-time physical activity at all. (25) Studies  that measure people’s physical activity using special motion sensors (called accelerometers) suggest that self-reports of physical activity probably are over-estimated. (26). According to analyses by a team from the Centers for Disease Control (CDC) and Prevention, inactivity was associated with more than 9 million cases of cardiovascular disease in 2001, at an estimated direct medical cost of nearly $24 billion. (2) Another CDC analysis suggests that because individuals who are physically active have significantly lower annual direct medical costs than those who are inactive, getting people to become more active could cut yearly medical costs in the U.S. by more than $70 billion. (3)

Being a “couch potato” may be harmful even for people who get regular exercise. (4) The Nurses’ Health Study, for example, is one of many, many studies to find a strong link between television watching and obesity. (5) Researchers followed more than 50,000 middle-aged women for six years, surveying their diet and activity habits. They found that for every two hours the women spent watching television each day, they had a 23 percent higher risk of becoming obese and 14 percent higher risk of developing diabetes. Interestingly, it didn’t matter if the women were avid exercisers: The more television they watched, the more likely they were to gain weight or develop diabetes, regardless of how much leisure-time activity and walking they did. Long hours of sitting at work also increased the risk of obesity and diabetes.

More recently, studies have found that people who spend more time each day watching television, sitting, or riding in cars  have a greater chance of dying early than people who spend less time on their duffs. (6-8) Researchers speculate that sitting for hours on end may change peoples’ metabolism in ways that promote obesity, heart disease, diabetes, and other chronic conditions. (4, 7) It is also possible that sitting is a marker for a broader sedentary lifestyle.

In sum, a morning jog or brisk lunchtime walk brings many health benefits—but these may not entirely make up for a day spent in front of the computer or an evening in front of the television set. So as you plan your daily activity routine, remember that cutting down on “sit time” may be just as important as increasing “fit time.”

Physical Activity Guidelines: How Much Exercise Do You Need?

Jump Rope (jump-rope.jpg)If you don’t currently exercise and aren’t very active during the day, any increase in exercise or physical activity is good for you. Aerobic physical activity—any activity that causes a noticeable increase in your heart rate—is especially beneficial for disease prevention. Some studies show that walking briskly for even one to two hours a week (15 to 20 minutes a day) starts to decrease the chances of having a heart attack or stroke, developing diabetes, or dying prematurely. (Brisk is a relative term; read more about exercise intensity.)

The 2008 Physical Activity Guidelines for Americans recommends that healthy adults get a minimum of 2-1/2 hours per week of moderate-intensity aerobic activity, or get a minimum of 1-1/4 hours per week of vigorous-intensity aerobic activity, or a combination of the two. (1) To lower your risk of injury, it’s best to spread out your activity over a few days in of the week. (Read more about how to exercise safely.)

You can combine moderate and vigorous exercise over the course of the week—say, by doing 20 to 25 minutes of more vigorous intensity activity on two days, and then doing 30 minutes of moderate intensity activity on two days. It’s fine to break up your activity into smaller bursts, as long as you sustain the activity for at least 10 minutes. Adults should also do muscle-strengthening activities on at least two days for the week. Children should get at least 1 hour or more a day of physical activity in age-appropriate activities. Healthy older adults should follow the guidelines for adults. 

Exercise Intensity: What’s Moderate, What’s Vigorous?

Soccer Ball (soccer-ball.jpg)Moderate-intensity aerobic activity is any activity that causes a slight but noticeable increase in breathing and heart rate. One way to gauge moderate activity is with the “talk test”—exercising hard enough to break a sweat but not so hard you can’t comfortably carry on a conversation. Vigorous-intensity aerobic activity causes more rapid breathing and a greater increase in heart rate, but you should still be able to carry on a conversation—with shorter sentences.

Keep in mind that what feels like moderate activity for one person may actually be very vigorous activity for another: A typical young marathon runner, for example, could walk at a 4-mile-per-hour pace without breaking a sweat. But this same pace would likely feel very vigorous for the typical 90-year-old person.

One way to gauge how hard you are exercising is to use the Borg Scale of Perceived Exertion. It’s a relative scale that matches how hard you feel you are working with numbers from 6 to 20 (Read more about using the Borg Scale to tell how hard you are exercising). Exercise experts measure activity in a different way, using metabolic equivalents, or METs. For more info on exercise intensity, check out this list of light-, moderate-, and vigorous-intensity activities.

Walking—and Bicycling—Your Way to Health

Green Bicycle Traffic Light (bicycle-traffic-light.jpg)Walking is an ideal exercise for many people—it doesn’t require any special equipment, can be done any time, any place, and is generally very safe. What’s more, studies such as the Nurses’ Health Study, (9, 10) Health Professionals Follow-up Study, (11) Women’s Health Study, (12)  Harvard Alumni Health Study, (13) National Health Interview Survey, (14) Women’s Health Initiative, (15) Honolulu Heart Program, (16) Black Women’s Health Study, (17) and others (18, 19) have demonstrated that this simple form of exercise substantially reduces the chances of developing heart disease, stroke, and diabetes in different populations.

Though walking has health benefits at any pace, brisk walking (at least 3 miles per hour) is more beneficial than slow walking for weight control (20-22). And a recent report from the Nurses’ Health Study II suggests that bicycling offers similar benefits to brisk walking: (22) Researchers followed more than 18,000 women for 16 years to study the relationship between changes in physical activity and weight. On average, women gained about 20 pounds over the course of the study. Women who increased their physical activity by 30 minutes per day gained less weight than women whose activity levels stayed steady. But the type of activity made a difference: Women who added bicycling or brisk walking to their activity regimens were able to curb their weight gain, but women who added slow walking were not.

Brisk walking may be challenging for some people, and bicycling (even on an exercise bike) may be a more comfortable option. (22) In the Nurses’ Health Study II, for example, overweight women spent far less time walking briskly than normal weight women, but they spent about the same amount of time cycling.  If you don’t like brisk walking or bicycling, any activity that makes your heart work harder will help you meet the Physical Activity Guidelines for Americans, as long as you do it long enough and often enough. Walking and biking are also green ways to commute to work—good for the environment, and good for you.

Watch a video discussion on the importance of bicycling and walking in preventing and alleviating hypertension.

More Activity Equals More Benefit

Keep in mind that 2-1/2 hours of moderate-intensity aerobic activity a week is an excellent starting point, not an upper limit. Exercising longer, harder, or both can bring even greater health benefits. (1)  Also bear in mind that your 2-1/2 hours of activity should be in addition to the light activity that is part of everyday living. But moderate and vigorous lifestyle activities—dancing, mowing the lawn with a push mower, chopping wood, and so on—can count toward your weekly total, if they are sustained for at least 10 minutes.

Exercise for Weight Loss and Maintenance

If you’re looking to avoid “middle-aged spread,” physical activity is important, as is watching what you eat. But there’s no hard and fast rule as to how much activity you will need to keep your weight steady. Many people may need more than 2-1/2 hours of moderate intensity activity a week to stay at a stable weight, as well as to lose weight or keep off weight they have lost. (1)

Read more about exercise and weight control.

Start Slow, Increase as Your Fitness Grows

Rollerblades (rollerblades.jpg)

The Physical Activity Guidelines for Americans are general recommendations aimed at the general population. The problem with guidelines is that they try to cover as many people as possible. In other words, they aren’t right for everyone. How much exercise you need depends on your genes, your diet, how much muscle and fat you carry on your frame, how fit you are, and your capacity for exercise.

A study of more 7,000 men who graduated from Harvard before 1950 suggests that older people, those who are out of shape, or those with disabilities may get as much benefit from 30 minutes of slower walking or other exercise as younger, more fit people get from the same amount of more-intense activity. (23)

In other words, if an exercise or physical activity feels hard, then it is probably doing your heart—and the rest of you—some good, even if it doesn’t fall into the “moderate” category. If you are currently not active at all, it may be daunting to start out with 30 minutes a day of activity, five days a week. So start with a shorter, less-intense bout of activity, and gradually increase over time until you can reach or exceed this goal. (1) This “start slow, build up over time” advice for physical activity applies to everyone, but it’s especially true for older adults, (24) since starting slowly can help lower the risk of injury—and can make exercise more enjoyable.

Read more about exercise safety.

Don’t get stuck in a rut, though. As your body adapts to exercise, you’ll need to push yourself more and more to get the same cardiovascular workout. Another way to know that it’s time to pick up the pace is if you see your weight or waist size start creeping up on you.

The Bottom Line: Move More, Sit Less

Exercise is one of those rare things where the hype actually meets reality. Next to not smoking, getting regular physical activity is arguably the best thing you can do for your health. Any amount of exercise is better than none. The more you get, though, the better. And remember: Cutting back on television-watching and other sedentary pastimes is just as important as becoming more active.

References

1. U.S. Dept. of Health and Human Services. 2008 Physical Activity Guidelines for Americans. 2008.

2. Wang G, Pratt M, Macera CA, Zheng ZJ, Heath G. Physical activity, cardiovascular disease, and medical expenditures in U.S. adults. Ann Behav Med. 2004; 28:88-94.

3. Pratt M, Macera CA, Wang GJ. Higher direct medical costs associated with physical inactivity. Physician and Sportsmedicine. 2000; 28:63-70.

4. Owen N, Healy GN, Matthews CE, Dunstan DW. Too much sitting: the population health science of sedentary behavior. Exerc Sport Sci Rev. 2010; 38:105-13.

5. Hu FB, Li TY, Colditz GA, Willett WC, Manson JE. Television watching and other sedentary behaviors in relation to risk of obesity and type 2 diabetes mellitus in women. JAMA. 2003; 289:1785-91.

6. Dunstan DW, Barr EL, Healy GN, et al. Television viewing time and mortality: the Australian Diabetes, Obesity and Lifestyle Study (AusDiab). Circulation. 2010; 121:384-91.

7. Patel AV, Bernstein L, Deka A, et al. Leisure Time Spent Sitting in Relation to Total Mortality in a Prospective Cohort of US Adults. Am J Epidemiol. 2010.

8. Warren TY, Barry V, Hooker SP, Sui X, Church TS, Blair SN. Sedentary behaviors increase risk of cardiovascular disease mortality in men. Med Sci Sports Exerc. 2010; 42:879-85.

9. Manson JE, Hu FB, Rich-Edwards JW, et al. A prospective study of walking as compared with vigorous exercise in the prevention of coronary heart disease in women. N Engl J Med. 1999; 341:650-8.

10. Hu FB, Sigal RJ, Rich-Edwards JW, et al. Walking compared with vigorous physical activity and risk of type 2 diabetes in women: a prospective study. JAMA. 1999; 282:1433-9.

11. Tanasescu M, Leitzmann MF, Rimm EB, Willett WC, Stampfer MJ, Hu FB. Exercise type and intensity in relation to coronary heart disease in men. JAMA. 2002; 288:1994-2000.

12. Lee IM, Rexrode KM, Cook NR, Manson JE, Buring JE. Physical activity and coronary heart disease in women: is “no pain, no gain” passé? JAMA. 2001; 285:1447-54.

13. Sesso HD, Paffenbarger RS, Jr., Lee IM. Physical activity and coronary heart disease in men: The Harvard Alumni Health Study. Circulation. 2000; 102:975-80.

14. Gregg EW, Gerzoff RB, Caspersen CJ, Williamson DF, Narayan KM. Relationship of walking to mortality among US adults with diabetes. Arch Intern Med. 2003; 163:1440-7.

15. Manson JE, Greenland P, LaCroix AZ, et al. Walking compared with vigorous exercise for the prevention of cardiovascular events in women. N Engl J Med. 2002; 347:716-25.

16. Hakim AA, Curb JD, Petrovitch H, et al. Effects of walking on coronary heart disease in elderly men: the Honolulu Heart Program. Circulation. 1999; 100:9-13.

17. Krishnan S, Rosenberg L, Palmer JR. Physical activity and television watching in relation to risk of type 2 diabetes: the Black Women’s Health Study. Am J Epidemiol. 2009; 169:428-34.

18. Oguma Y, Shinoda-Tagawa T. Physical activity decreases cardiovascular disease risk in women: review and meta-analysis. Am J Prev Med. 2004; 26:407-18.

19. Jeon CY, Lokken RP, Hu FB, van Dam RM. Physical activity of moderate intensity and risk of type 2 diabetes: a systematic review. Diabetes Care. 2007; 30:744-52.

20. Mekary RA, Feskanich D, Malspeis S, Hu FB, Willett WC, Field AE. Physical activity patterns and prevention of weight gain in premenopausal women. Int J Obes (Lond). 2009; 33:1039-47.

21. Mekary RA, Feskanich D, Hu FB, Willett WC, Field AE. Physical activity in relation to long-term weight maintenance after intentional weight loss in premenopausal women. Obesity (Silver Spring). 2010; 18:167-74.

22. Lusk AC, Mekary RA, Feskanich D, Willett WC. Bicycle riding, walking, and weight gain in premenopausal women. Arch Intern Med. 2010; 170:1050-6.

23. Lee IM, Sesso HD, Oguma Y, Paffenbarger RS, Jr. Relative intensity of physical activity and risk of coronary heart disease. Circulation. 2003; 107:1110-6.

24. Nelson ME, Rejeski WJ, Blair SN, et al. Physical activity and public health in older adults: recommendation from the American College of Sports Medicine and the American Heart Association. Circulation. 2007; 116:1094-105.

25. National Center for Health Statistics. Health, United States, 2009: With Chartbook on Trends in the Health of Americans. Hyattsville, MD, 2009.

26. Troiano RP, Berrigan D, Dodd KW, Masse LC, Tilert T, McDowell M. Physical activity in the United States measured by accelerometer. Med Sci Sports Exerc. 2008; 40:181-8.

Terms of Use

The aim of the Harvard School of Public Health Nutrition Source is to provide timely information on diet and nutrition for clinicians, allied health professionals, and the public. The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this Web site. The information does not mention brand names, nor does it endorse any particular products.

Source: Harvard School of Public Health

7 benefits of regular physical activity Tags: benefits regular physical activity health mental wellness healthy hearts word life production feature weekly

You know exercise is good for you, but do you know how good? From boosting your mood to improving your sex life, find out how exercise can improve your life.

By Mayo Clinic Staff

Want to feel better, have more energy and perhaps even live longer? Look no further than exercise. The health benefits of regular exercise and physical activity are hard to ignore. And the benefits of exercise are yours for the taking, regardless of your age, sex or physical ability. Need more convincing to exercise? Check out these seven ways exercise can improve your life.

No. 1: Exercise controls weight

Exercise can help prevent excess weight gain or help maintain weight loss. When you engage in physical activity, you burn calories. The more intense the activity, the more calories you burn. You don't need to set aside large chunks of time for exercise to reap weight-loss benefits. If you can't do an actual workout, get more active throughout the day in simple ways — by taking the stairs instead of the elevator or revving up your household chores.

No. 2: Exercise combats health conditions and diseases

Worried about heart disease? Hoping to prevent high blood pressure? No matter what your current weight, being active boosts high-density lipoprotein (HDL), or "good," cholesterol and decreases unhealthy triglycerides. This one-two punch keeps your blood flowing smoothly, which decreases your risk of cardiovascular diseases. In fact, regular physical activity can help you prevent or manage a wide range of health problems and concerns, including stroke, metabolic syndrome, type 2 diabetes, depression, certain types of cancer, arthritis and falls.

No. 3: Exercise improves mood

 

Need an emotional lift? Or need to blow off some steam after a stressful day? A workout at the gym or a brisk 30-minute walk can help. Physical activity stimulates various brain chemicals that may leave you feeling happier and more relaxed. You may also feel better about your appearance and yourself when you exercise regularly, which can boost your confidence and improve your self-esteem.

No. 4: Exercise boosts energy

Winded by grocery shopping or household chores? Regular physical activity can improve your muscle strength and boost your endurance. Exercise and physical activity deliver oxygen and nutrients to your tissues and help your cardiovascular system work more efficiently. And when your heart and lungs work more efficiently, you have more energy to go about your daily chores.

Source: Mayo Clinic

How to boost your immune system Tags: healthy cell activity build immune system health mental wellness word life production feature blog

Excerpted from The Truth About Your Immune System, a Special Health Report from Harvard Health Publications

What can you do?

On the whole, your immune system does a remarkable job of defending you against disease-causing microorganisms. But sometimes it fails: A germ invades successfully and makes you sick. Is it possible to intervene in this process and make your immune system stronger? What if you improve your diet? Take certain vitamins or herbal preparations? Make other lifestyle changes in the hope of producing a near-perfect immune response?

The idea of boosting your immunity is enticing, but the ability to do so has proved elusive for several reasons. The immune system is precisely that — a system, not a single entity. To function well, it requires balance and harmony. There is still much that researchers don’t know about the intricacies and interconnectedness of the immune response. For now, there are no scientifically proven direct links between lifestyle and enhanced immune function.

But that doesn’t mean the effects of lifestyle on the immune system aren’t intriguing and shouldn’t be studied. Quite a number of researchers are exploring the effects of diet, exercise, age, psychological stress, herbal supplements, and other factors on the immune response, both in animals and in humans. Although interesting results are emerging, thus far they can only be considered preliminary. That’s because researchers are still trying to understand how the immune system works and how to interpret measurements of immune function. The following sections summarize some of the most active areas of research into these topics. In the meantime, general healthy-living strategies are a good way to start giving your immune system the upper hand.

Immunity in action

Immunity in action. A healthy immune system can defeat invading pathogens as shown above, where two bacteria that cause gonorrhea are no match for the large phagocyte, called a neutrophil, that engulfs and kills them (see arrows).

Photos courtesy of Michael N. Starnbach, Ph.D., Harvard Medical School

Adopt healthy-living strategies

Your first line of defense is to choose a healthy lifestyle. Following general good-health guidelines is the single best step you can take toward keeping your immune system strong and healthy. Every part of your body, including your immune system, functions better when protected from environmental assaults and bolstered by healthy-living strategies such as these:

Don’t smoke.

Eat a diet high in fruits, vegetables, and whole grains, and low in saturated fat.

Exercise regularly.

Maintain a healthy weight.

Control your blood pressure.

If you drink alcohol, drink only in moderation.

Get adequate sleep.

Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly.

Get regular medical screening tests for people in your age group and risk category.

Be skeptical

Many products on store shelves claim to boost or support immunity. But the concept of boosting immunity actually makes little sense scientifically. In fact, boosting the number of cells in your body — immune cells or others — is not necessarily a good thing. For example, athletes who engage in “blood doping” — pumping blood into their systems to boost their number of blood cells and enhance their performance — run the risk of strokes.

Attempting to boost the cells of the immune system is especially complicated because there are so many different kinds of cells in the immune system that respond to so many different microbes in so many ways. Which cells should you boost, and to what number? So far, scientists do not know the answer. What is known is that the body is continually generating immune cells. Certainly it produces many more lymphocytes than it can possibly use. The extra cells remove themselves through a natural process of cell death called apoptosis — some before they see any action, some after the battle is won. No one knows how many cells or what kinds of cells the immune system needs to function at its optimum level.

Scientists do know more about the low end of the scale. When the number of T cells in an HIV/AIDS patient drops below a certain level, the patient gets sick because the immune system doesn’t have enough T cells to fight off infection. So there is a bottom number below which the immune system can’t do its job. But how many T cells is comfortably enough, and beyond that point, is more better? We don’t know.

Many researchers are trying to explore the effects of a variety of factors — from foods and herbal supplements to exercise and stress — on immunity. Some take measures of certain blood components like lymphocytes or cytokines. But thus far, no one really knows what these measurements mean in terms of your body’s ability to fight disease. They provide a way of detecting whether something is going on, but science isn’t yet sufficiently advanced to understand how this translates into success in warding off disease.

A different scientific approach looks at the effect of certain lifestyle modifications on the incidence of disease. If a study shows significantly less disease, researchers consider whether the immune system is being strengthened in some way. Based on these studies, there is now evidence that even though we may not be able to prove a direct link between a certain lifestyle and an improved immune response, we can at least show that some links are likely.

Age and immunity

Earlier in this report (see “Cancer: Missed cues”), we noted that one active area of research is how the immune system functions as the body ages. Researchers believe that the aging process somehow leads to a reduction of immune response capability, which in turn contributes to more infections, more inflammatory diseases, and more cancer. As life expectancy in developed countries has increased, so too has the incidence of age-related conditions. Happily, investigation into the aging process can benefit us all — no matter what our age.

While some people age healthily, the conclusion of many studies is that, compared with younger people, the elderly are far more likely to contract infectious diseases. Respiratory infections, influenza, and particularly pneumonia are a leading cause of death in people over 65 worldwide. No one knows for sure why this happens, but some scientists observe that this increased risk correlates with a decrease in T cells, possibly from the thymus atrophying with age and producing fewer T cells to fight off infection. Thymus function declines beginning at age 1; whether this decrease in thymus function explains the drop in T cells or whether other changes play a role is not fully understood. Others are interested in whether the bone marrow becomes less efficient at producing the stem cells that give rise to the cells of the immune system.

Researchers at the University of Arkansas are looking at another aspect of why the immune system seems to weaken with age. They studied cell death in mice. They conducted an experiment to compare the lifespan of memory T lymphocytes in older mice with those of younger mice and found that the lymphocytes in older mice die sooner. This suggests that as the lymphocytes die off, the elderly immune system loses its memory for the microbes it is intended to fight and fails to recognize the microbes when they reappear. The body thus becomes less able to mount a vigorous immune response.

A reduction in immune response to infections has been demonstrated by older people’s response to vaccines. For example, studies of influenza vaccines have shown that for people over age 65, vaccine effectiveness was 23%, whereas for healthy children (over age 2), it was 38%. But despite the reduction in efficacy, vaccinations for influenza and S. pneumoniae have significantly lowered the rates of sickness and death in older people when compared with nonvaccination.

Yet other researchers are looking at the connection between nutrition and immunity in the elderly. A form of malnutrition that is surprisingly common even in affluent countries is known as “micronutrient malnutrition.” Micronutrient malnutrition, in which a person is deficient in some essential vitamins and trace minerals that are obtained from or supplemented by diet, can be common in the elderly. Older people tend to eat less and often have less variety in their diets. One important question is whether dietary supplements may help older people maintain a healthier immune system. Older people should discuss this question with a physician who is well versed in geriatric nutrition, because while some dietary supplementation may be beneficial for older people, even small changes can have serious repercussions in this age group.

What about diet?

Like any fighting force, the immune system army marches on its stomach. Immune system warriors need good, regular nourishment. Scientists have long recognized that people who live in poverty and are malnourished are more vulnerable to infectious diseases. Whether the increased rate of disease is caused by malnutrition’s effect on the immune system, however, is not certain. There are still relatively few studies of the effects of nutrition on the immune system of humans, and even fewer studies that tie the effects of nutrition directly to the development (versus the treatment) of diseases.

There are studies of the effects of nutritional changes on the immune systems of animals, but again there are few studies that address the development of diseases in animals as a result of changes in immunity. For example, one group of investigators has found that in mice, diets deficient in protein reduce both the numbers and function of T cells and macrophages and also reduce the production of immunoglobulin A (IgA) antibody.

There is some evidence that various micronutrient deficiencies — for example, deficiencies of zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E — alter immune responses in animals, as measured in the test tube. However, the impact of these immune system changes on the health of animals is less clear, and the effect of similar deficiencies on the human immune response has yet to be assessed. But the research at this stage is promising, at least for some of the micronutrients.

So what can you do? If you suspect your diet is not providing you with all your micronutrient needs — maybe you don’t like vegetables or you choose white bread over whole grains — taking a daily multivitamin and mineral supplement brings health benefits of many types, beyond any possibly beneficial effects on the immune system. Taking megadoses of a single vitamin does not. More is not necessarily better. Researchers are investigating the immune boosting potential of a number of different nutrients.

Selenium. Some studies have suggested that people with low selenium levels are at greater risk of bladder, breast, colon, rectum, lung, and prostate cancers. A large-scale, multiyear study is currently in progress to look at the effects of combining selenium and vitamin E on prostate cancer prevention.

Vitamin A. Experts have long known that vitamin A plays a role in infection and maintaining mucosal surfaces by influencing certain subcategories of T cells and B cells and cytokines. Vitamin A deficiency is associated with impaired immunity and increased risk of infectious disease. On the other hand, according to one study, supplementation in the absence of a deficiency didn’t enhance or suppress T cell immunity in a group of healthy seniors.

Vitamin B2. There is some evidence that vitamin B2 enhances resistance to bacterial infections in mice, but what that means in terms of enhancing immune response is unclear.

Vitamin B6. Several studies have suggested that a vitamin B6 deficiency can depress aspects of the immune response, such as lymphocytes’ ability to mature and spin off into various types of T and B cells. Supplementing with moderate doses to address the deficiency restores immune function, but megadoses don’t produce additional benefits. And B6 may promote the growth of tumors.

Vitamin C. The jury is still out on vitamin C and the immune system. Many studies have looked at vitamin C in general; unfortunately, many of them were not well designed. Vitamin C may work in concert with other micronutrients rather than providing benefits alone.

Vitamin D. For many years doctors have known that people afflicted with tuberculosis responded well to sunlight. An explanation may now be at hand. Researchers have found that vitamin D, which is produced by the skin when exposed to sunlight, signals an antimicrobial response to the bacterium responsible for tuberculosis, Mycobacterium tuberculosis. Whether vitamin D has similar ability to fight off other diseases and whether taking vitamin D in supplement form is beneficial are questions that need to be resolved with further study.

Vitamin E. A study involving healthy subjects over age 65 has shown that increasing the daily dose of vitamin E from the recommended dietary allowance (RDA) of 30 mg to 200 mg increased antibody responses to hepatitis B and tetanus after vaccination. But these increased responses didn’t happen following administration of diphtheria and pneumococcal vaccines.

Zinc. Zinc is a trace element essential for cells of the immune system, and zinc deficiency affects the ability of T cells and other immune cells to function as they should. Caution: While it’s important to have sufficient zinc in your diet (15–25 mg per day), too much zinc can inhibit the function of the immune system.

Herbs and other supplements

Walk into a store, and you will find bottles of pills and herbal preparations that claim to “support immunity” or otherwise boost the health of your immune system. Although some preparations have been found to alter some components of immune function, thus far there is no evidence that they actually bolster immunity to the point where you are better protected against infection and disease. Demonstrating whether an herb — or any substance, for that matter — can enhance immunity is, as yet, a highly complicated matter. Scientists don’t know, for example, whether an herb that seems to raise the levels of antibodies in the blood is actually doing anything beneficial for overall immunity.

But that doesn’t mean we should discount the benefits of all herbal preparations. Everyone’s immune system is unique. Each person’s physiology responds to active substances differently. So if your grandmother says she’s been using an herbal preparation for years that protects her from illness, who’s to say that it doesn’t? The problem arises when scientists try to study such a preparation among large numbers of people. The fact that it works for one person won’t show up in the research data if it’s not doing the same for a larger group.

Scientists have looked at a number of herbs and vitamins in terms of their potential to influence the immune system in some way. Much of this research has focused on the elderly, children, or people with compromised immune systems, such as AIDS patients. And many of the studies have had design flaws, which means further studies are needed to confirm or disprove the results. Consequently, these findings should not be considered universally applicable.

Some of the supplements that have drawn attention from researchers are these:

Aloe vera. For now, there’s no evidence that aloe vera can modulate immune response. Because many different formulations and compounds have been used in studies, comparing the results is difficult. However, there is some evidence that topical aloe vera is helpful for minor burns, wounds, or frostbite, and also for skin inflammations when combined with hydrocortisone. Studies have found aloe vera is not the best option for treating breast tissue after radiation therapy.

Astragalus membranes. The astragalus product, which is derived from the root of the plant, is marketed as an immune-system stimulant, but the quality of the studies demonstrating the immune-stimulating properties of astragalus are poor. Furthermore, it may be dangerous.

Echinacea. An ocean of ink has been spilled extolling echinacea as an “immune stimulant,” usually in terms of its purported ability to prevent or limit the severity of colds. Most experts don’t recommend taking echinacea on a long-term basis to prevent colds. A group of physicians from Harvard Medical School notes that studies looking at the cold prevention capabilities of echinacea have not been well designed, and other claims regarding echinacea are as yet not proven. Echinacea can also cause potentially serious side effects. People with ragweed allergies are more likely to have a reaction to echinacea, and there have been cases of anaphylactic shock. Injected echinacea in particular has caused severe reactions. A well-designed study by pediatricians at the University of Washington in Seattle found echinacea didn’t help with the duration and severity of cold symptoms in a group of children. A large 2005 study of 437 volunteers also found that echinacea didn’t affect the rate of cold infections or the progress and severity of a cold.

Garlic. Garlic may have some infection-fighting capability. In laboratory tests, researchers have seen garlic work against bacteria, viruses, and fungi. Although this is promising, there haven’t been enough well-designed human studies conducted to know whether this translates into human benefits. One 2006 study that looked at rates for certain cancers and garlic and onion consumption in southern European populations found an association between the frequency of use of garlic and onions and a lower risk of some common cancers. Until more is known, however, it’s too early to recommend garlic as a way of treating or preventing infections or controlling cancer.

Ginseng. It’s not clear how the root of the ginseng plant works, but claims on behalf of Asian ginseng are many, including its ability to stimulate immune function. Despite the claims of a number of mainly small studies, the National Center for Complementary and Alternative Medicine (NCCAM) considers there have been insufficient large studies of a high enough quality to support the claims. NCCAM is currently supporting research to understand Asian ginseng more fully.

Glycyrrhiza glabra (licorice root). Licorice root is used in Chinese medicine to treat a variety of illnesses. Most studies of licorice root have been done in combination with other herbs, so it’s not possible to verify whether any effects were attributable to licorice root per se. Because of the potential side effects of taking licorice and how little is known about its benefits — if any — for stimulating immune function, this is an herb to avoid.

Probiotics. There are hundreds of different species of bacteria in your digestive tract, which do a bang-up job helping you digest your food. Now researchers, including some at Harvard Medical School, are finding evidence of a relationship between such “good” bacteria and the immune system. For instance, it is now known that certain bacteria in the gut influence the development of aspects of the immune system, such as correcting deficiencies and increasing the numbers of certain T cells. Precisely how the bacteria interact with the immune system components isn’t known. As more and more intriguing evidence comes in to support the link that intestinal bacteria bolster the immune system, it’s tempting to think that more good bacteria would be better. At least, this is what many marketers would like you to believe as they tout their probiotic products.

Probiotics are good bacteria, such as Lactobacillus and Bifidobacterium, that can safely dwell in your digestive tract. You’ll now find probiotics listed on the labels of dairy products, drinks, cereals, energy bars, and other foods. Ingredients touted as “prebiotics,” which claim to be nutrients that feed the good bacteria, are also cropping up in commercially marketed foods. Unfortunately, the direct connection between taking these products and improving immune function has not yet been made. Nor has science shown whether taking probiotics will replenish the good bacteria that get knocked out together with “bad” bacteria when you take antibiotics.

Another caution is that the quality of probiotic products is not consistent. Some contain what they say they do; some do not. In a 2006 report, the American Academy of Microbiology said that “at present, the quality of probiotics available to consumers in food products around the world is unreliable.” In the same vein, the FDA monitors food packages to make sure they don’t carry labels that claim the products can cure diseases unless the companies have scientific evidence to support the claims. Does this mean taking probiotics is useless? No. It means the jury is still out on the expansive health claims. In the meantime, if you choose to take a probiotic in moderation, it probably won’t hurt, and the scientific evidence may ultimately show some benefit.

The stress connection

Modern medicine, which once treated the connection between emotions and physical health with skepticism, has come to appreciate the closely linked relationship of mind and body. A wide variety of maladies, including stomach upset, hives, and even heart disease, are linked to the effects of emotional stress. But although the relationship between stress and immune function is being studied by a number of different types of scientists, so far it is not a major area of research for immunologists.

Studying the relationship between stress and the immune system presents difficult challenges. For one thing, stress is difficult to define. What may appear to be a stressful situation for one person is not for another. When people are exposed to situations they regard as stressful, it is difficult for them to measure how much stress they feel, and difficult for the scientist to know if a person’s subjective impression of the amount of stress is accurate. The scientist can only measure things that may reflect stress, such as the number of times the heart beats each minute, but such measures also may reflect other factors.

Most scientists studying the relationship of stress and immune function, however, do not study a sudden, short-lived stressor; rather, they try to study more constant and frequent stressors known as chronic stress, such as that caused by relationships with family, friends, and co-workers, or sustained challenges to perform well at one’s work. Some scientists are investigating whether ongoing stress takes a toll on the immune system.

But it is hard to perform what scientists call “controlled experiments” in human beings. In a controlled experiment, the scientist can change one and only one factor, such as the amount of a particular chemical, and then measure the effect of that change on some other measurable phenomenon, such as the amount of antibodies produced by a particular type of immune system cell when it is exposed to the chemical. In a living animal, and especially in a human being, that kind of control is just not possible, since there are so many other things happening to the animal or person at the time that measurements are being taken.

Despite these inevitable difficulties in measuring the relationship of stress to immunity, scientists who repeat the same experiment many times with many different animals or human beings, and who get the same result most of the time, hope that they can draw reasonable conclusions.

Some researchers place animals into stressful situations, such as being trapped in a small space or being placed near an aggressive animal. Different functions of their immune systems, and their health, are then measured under such stressful conditions. On the basis of such experiments, some published studies have made the following claims:

Experimentally created “stressful” situations delayed the production of antibodies in mice infected with influenza virus and suppressed the activity of T cells in animals inoculated with herpes simplex virus.

Social stress can be even more damaging than physical stress. For example, some mice were put into a cage with a highly aggressive mouse two hours a day for six days and repeatedly threatened, but not injured, by the aggressive mouse — a “social stress.” Other mice were kept in tiny cages without food and water for long periods — a “physical stress.” Both groups of mice were exposed to a bacterial toxin, and the socially stressed animals were twice as likely to die.

Isolation can also suppress immune function. Infant monkeys separated from their mothers, especially if they are caged alone rather than in groups, generate fewer lymphocytes in response to antigens and fewer antibodies in response to viruses.

Many researchers report that stressful situations can reduce various aspects of the cellular immune response. A research team from Ohio State University that has long worked in this field suggests that psychological stress affects the immune system by disrupting communication between the nervous system, the endocrine (hormonal) system, and the immune system. These three systems “talk” to one another using natural chemical messages, and must work in close coordination to be effective. The Ohio State research team speculates that long-term stress releases a long-term trickle of stress hormones — mainly glucocorticoids. These hormones affect the thymus, where lymphocytes are produced, and inhibit the production of cytokines and interleukins, which stimulate and coordinate white blood cell activity. This team and others have reported the following results:

Elderly people caring for relatives with Alzheimer’s disease have higher than average levels of cortisol, a hormone secreted by the adrenal glands and, perhaps because of the higher levels of cortisol, make fewer antibodies in response to influenza vaccine.

Some measures of T cell activity have been found to be lower in depressed patients compared with nondepressed patients, and in men who are separated or divorced compared with men who are married.

In a year-long study of people caring for husbands or wives with Alzheimer’s disease, changes in T cell function were greatest in those who had the fewest friends and least outside help.

Four months after the passage of Hurricane Andrew in Florida, people in the most heavily damaged neighborhoods showed reduced activity in several immune system measurements. Similar results were found in a study of hospital employees after an earthquake in Los Angeles.

In all of these studies, however, there was no proof that the immune system changes measured had any clear adverse effects on health in these individuals.

Does being cold make you sick?

Almost every mother has said it: “Wear a jacket or you’ll catch a cold!” Is she right? So far, researchers who are studying this question think that normal exposure to moderate cold doesn’t increase your susceptibility to infection. Most health experts agree that the reason winter is “cold and flu season” is not that people are cold, but that they spend more time indoors, in closer contact with other people who can pass on their germs.

But researchers remain interested in this question in different populations. Some experiments with mice suggest that cold exposure might reduce the ability to cope with infection. But what about humans? Scientists have dunked people in cold water and made others sit nude in subfreezing temperatures. They’ve studied people who lived in Antarctica and those on expeditions in the Canadian Rockies. The results have been mixed. For example, researchers documented an increase in upper respiratory infections in competitive cross-country skiers who exercise vigorously in the cold, but whether these infections are due to the cold or other factors — such as the intense exercise or the dryness of the air — is not known. They’ve found that exposure to cold does increase levels of some cytokines, the proteins and hormones that act as messengers in the immune system, but how this affects health isn’t clear.

A group of Canadian researchers that has reviewed hundreds of medical studies on the subject and conducted some of its own research concludes that there’s no need to worry about moderate cold exposure — it has no detrimental effect on the human immune system. Should you bundle up when it’s cold outside? The answer is “yes” if you’re uncomfortable, or if you’re going to be outdoors for an extended period where such problems as frostbite and hypothermia are a risk. But don’t worry about immunity.

Exercise: Good or bad for immunity?

Regular exercise is one of the pillars of healthy living. It improves cardiovascular health, lowers blood pressure, helps control body weight, and protects against a variety of diseases. But does it help maintain a healthy immune system? Just like a healthy diet, exercise can contribute to general good health and therefore to a healthy immune system. It may contribute even more directly by promoting good circulation, which allows the cells and substances of the immune system to move through the body freely and do their job efficiently.

Some scientists are trying to take the next step to determine whether exercise directly affects a person’s susceptibility to infection. For example, some researchers are looking at whether extreme amounts of intensive exercise can cause athletes to get sick more often or somehow impairs their immune function. To do this sort of research, exercise scientists typically ask athletes to exercise intensively; the scientists test their blood and urine before and after the exercise to detect any changes in immune system components such as cytokines, white blood cells, and certain antibodies. While some changes have been recorded, immunologists do not yet know what these changes mean in terms of human immune response. No one yet knows, for example, whether an increase in cytokines is helpful or has any true effect on immune response. Similarly, no one knows whether a general increase in white cell count is a good thing or a bad thing.

But these subjects are elite athletes undergoing intense physical exertion. What about moderate exercise for average people? Does it help keep the immune system healthy? For now, even though a direct beneficial link hasn’t been established, it’s reasonable to consider moderate regular exercise to be a beneficial arrow in the quiver of healthy living, a potentially important means for keeping your immune system healthy along with the rest of your body.

One approach that could help researchers get more complete answers about whether lifestyle factors such as exercise help improve immunity takes advantage of the sequencing of the human genome. This opportunity for research based on updated biomedical technology can be employed to give a more complete answer to this and similar questions about the immune system. For example, microarrays or “gene chips” based on the human genome allow scientists to look simultaneously at how thousands of gene sequences are turned on or off in response to specific physiological conditions — for example, blood cells from athletes before and after exercise. Researchers hope to use these tools to analyze patterns in order to better understand how the many pathways involved act at once.

Source: Harvard Health Publications

RSS
Spread the word
Search

This website is powered by Spruz