To most scientists, it's a complex system of T cells, interleukin-2, and killer cells to manipulate with the latest array of high-tech drugs.
To everyone, it's a mystery.
Why does the immune system lose strength when people grieve the loss of a loved one? Why does it decline as most people age, but remain vigorous in some seniors? And how can even subtle deficiencies of vitamins or minerals weaken our ability to fight off disease?
That's what Ranjit Chandra wants to know. For more that 30 years, the pioneering researcher at the Memorial University of Newfoundland has probed the cryptic links between nutrition and immunity.
How can people optimize their immune systems with food, vitamins, and exercise? Here's what we know.
Q: Do our immune systems change as we grow older?
A: Yes. As a group, older people -- I'm talking about 65- or 70-plus-year-olds -- have a reduced immune response, especially the part that depends on a kind of white blood cell known as the T lymphocyte, or T cell.
The severity of this reduction varies from very mild to very significant. Yet for reasons that are not clear, a small proportion of senior citizens retain a very vigorous immune response. They tend to have less illness.
Q: Do you have any idea why?
A: Based on animal studies, we think that certain genes give some individuals a stronger immune system. But environmental factors like food and nutrient intake and physical activity are also significant. So is stress, like the stress of bereavement or stress from a serious disease like cancer. If you lose your spouse or friend, your immunity goes down for several weeks or months.
Q. Can retirement harm the immune system?
A: Yes, it could also be a cause of stress if you don't have an alternative activity or occupation to go to. And compounding the problem is that sometimes people become sedentary at retirement, too.
Q: How can people boost their immunity?
A: I recommend a simple multivitamin to correct nutrient deficiencies. We know that older people have a higher prevalence of vitamin and mineral deficiencies than young or middle-aged adults. Seniors may have a deficiency of one or more nutrients and may not know it.
Q: Which nutrients?
A: Probably the most common are vitamin B-12, vitamin C, vitamin E, zinc, and protein.
Q: What's the impact of these deficiencies on the immune system?
A: Nutrient deficiencies are certainly associated with a reduced vigor of the immune system's T cells, which fight against bacterial and fungal infections and cancer cells. And if you treat these people and correct the deficiencies, you see an improved immune response. So there is a cause-and-effect relationship between nutrition and immunity.
Q: Do good studies show fewer infections?
A: Yes. We found fewer infections and stronger immune systems in a well-controlled study.(1)
We gave 86 apparently healthy, independently living men and women over the age of 65 either a [look-alike but inactive] placebo or a multivitamin-and-mineral supplement that contained doses of antioxidants like beta-carotene and vitamins E and C that were slightly higher than the U.S. Recommended Daily Allowances (USRDAs).
During the study, the supplement-takers experienced 23 days of infection-related illness, compared with 48 days for the placebo-takers. The supplement-takers also showed significant improvement in seven measures of immune function, including how well they produced antibodies in response to a flu vaccine.
The volunteers who showed signs of nutrient deficiencies at the beginning of the study improved more than those who didn't. The placebo-takers didn't improve at all over the twelve months.
Q: Can high doses of vitamins cause harm?
A: Yes. For instance, in one study immunity was depressed with daily doses of about 1,600 IU of vitamin E.(2) The USRDA is 30 IU a day, so 1,600 IU is a very large dose. And in other studies, more than 50 mg of zinc a day impaired immunity.(3) [50 mg also lowers HDL "good" cholesterol. -- Ed]
That's why it makes sense to take modest amounts of everything, and then increased amounts of those nutrients that are more often deficient in seniors, or that are likely to be needed in larger amounts, like antioxidants.
Q: Which nutrients boost immunity in higher-than-USRDA doses?
A: Three or four may be beneficial in slightly increased amounts. We gave several different levels of nine vitamins and minerals to 11 to 15 senior citizens for one year and then measured the changes in their levels of natural killer cells, T cells, and interleukin-2. We also looked at how often they got sick.
We found for example, that a daily supplement of 44 IU of vitamin E plus whatever was in the diet, say 10 IU, gave us a peak immune response, compared with the next higher dose, which was about 150 IU a day. So I would recommend between 50 and 100 IU of vitamin E a day.
Q: Are there any adverse effects at that level?
A: We haven't found any. It's unlikely unless the person has an underlying problem like liver disease or is taking many other medications. In those people, the vitamin E could impair blood clotting.
Q: What other nutrients should seniors take at higher-than-USRDA levels?
A: Vitamin C. In our studies, the optimum level -- from food and our supplement -- was close to 100 mg a day. We also found that about 25 mg of zinc a day may be optimal, which means about 10 mg from diet, on average, and 15 mg from a supplement. And we think that older people should get about 24 mg of iron a day, which means about 16 mg from a supplement and the rest from food. [See "What to Take."]
Q: That's in addition to USRDA levels of other vitamins?
A: Yes. If B-6 is deficient, you definitely would have a reduction in immune response. But there's not much evidence that you need more than the USRDA. That is also true for vitamin A and many other nutrients.
Q: What about beta-carotene?
A: In our study, we found that a supplement of about 16 mg [25,000 IU] of beta-carotene a day was optimal for the immune system. That's about four times the average intake.
Q: But haven't large doses of beta-carotene caused cancer?
A: That's what happened in a large clinical trial that looked at heavy smokers. I think the dangers of large amounts of beta-carotene are not well-studied as yet. [See "What to Take."]
Q: What about the herb Echinacea and other supplements that are sold as immune boosters?
A: What I have seen is more anecdotal, rather than properly controlled studies. I have offered to study the preparations of several prominent herbal experts with the proviso that whatever the results, we will make them public. But I have had no positive responses. I think some people don't have the confidence because even one negative study could have a bad impact.
There are a lot of claims made and lots of money being charged for herbal therapies, but I want to see for myself what would improve health.
Q: Should all older people take a vitamin-and-mineral supplement?
A: Yes. First of all, in our studies in Newfoundland, 35 to 40 percent of older people have deficiencies. Second, it isn't just one nutrient that is deficient. Third, finding out which ones are deficient is impractical and very expensive because you'd have to measure both dietary intake and blood levels of 20 different nutrients.
Fourth, if you give these substances in modest amounts -- let's say two times the USRDA -- there is no evidence that any one of them, even given for a long period, would produce any toxic or side effect. Finally, you should take more than one nutrient because there are interactions between them. If you take too much iron, for instance, your copper and zinc may go down and vice versa.
So, from the point of view of public health, the individual, and cost-containment, I think it's practical to opt for a multivitamin-and-mineral supplement.
Q: Should nursing homes and other institutions give supplements to older patients?
A: Yes. Two or three institutions have started studies to see how effective supplements are. People are getting a placebo or the multivitamin we used in our 1992 study, and researchers will measure infections and other symptoms of illness.
Q: Should people in their 40s or 50s -- or even younger people -- take supplements to boost immunity?
A: Unfortunately, there's no good data available for people this age. But since we don't know exactly when immunity begins to decline and this decline probably begins gradually, I advise middle-aged people to start taking a good multivitamin once a week. Then they should slowly increase the frequency until they're taking it every day by their late 60s.
Q: Is any one time of day best to take a multivitamin?
A: No. For most nutrients, absorption may be best between meals, because fiber, phytate, and other things in food may cause problems with absorption. But some people feel gastric irritation unless they take supplements with meals.
Q: How else can people boost their immunity?
A: Physical activity helps. If you are in reasonably good shape and undertake moderate exercise for about half an hour, three or four times a week, you're more likely to have a stronger immune system than someone who is sedentary.
(1) Lancet 340: 1124, 1992.
(2) Blood 50: 327, 1977.
(3) J. Amer. Med. Assoc. 252: 1443, 1984.
RELATED ARTICLE: RANJIT CHANDRA
Ranjit Chandra, who is a member of Nutrition Action's Scientific Advisory Board, has twice been nominated for the Nobel Prize in medicine. He is the holder of five honorary doctorates and is a visiting professor at universities on four continents.
All of which counted for little on a recent afternoon as he shuttled among the small examining rooms in the Janeway Child Health Centre in St. John's, Newfoundland, where he heads the hospital's immunology and allergy department. The young patients likely had no idea they were being treated by one of the world's foremost specialists.
For someone in perpetual motion, Chandra never seems to hurry. That morning, the 57-year-old pediatrician had already spoken at a medical conference, worked on an article for one of the two international scholarly journals he edits, and visited the World Health Organization Centre for Nutritional Immunology he heads in St. John's.
The theory he is painstakingly testing seems surprisingly simple: What a person eats affects his or her ability to resist disease. His research -- which focuses on how malnutrition in mothers leads to immune deficiencies in their children and how being undernourished lowers immune resistance in the elderly -- has already won enough trophies and citations to fill his modest office. More honors would certainly follow if Chandra and his 15-person international team succeed in their latest quest -- establishing a connection between nutrition and the HIV virus.
The son of a physician, Chandra graduated as the top high-school science student in Punjab province. As a 22-year-old medical student in India, he and a colleague discovered an ailment affecting the lungs, heart, and sinuses that still bears their names. In his early 30s he first noticed that many of the children who died after being admitted to the hospital where he worked suffered from malnourishment.
Chandra's international honors have led to visiting professorships at John Hopkins University in Baltimore, New York Medical College, and at medical schools in Beijing, Santiago, and Naples.
When not teaching, editing, conducting research, and seeing patients, life is simple and fulfilled -- hour-long six a.m. walks with friends, daily vegetarian lunches with his 93-year-old father, who moved from India two years ago, and visits to the local Hindu temple where he worships.
RELATED ARTICLE: WHERE'S THE EVIDENCE?
A multivitamin supplement boosted the immune systems of older people in Ranjit Chandra's study of healthy Canadians.(1) What about other evidence?
Surprisingly few studies have tested multivitamins on apparently healthy people.(2) And some of them have come up empty. For example, in a short, four-month study in central France, 103 healthy 60-somethings who were given a multivitamin had no fewer infections than 101 similar people who got a placebo.(3)
But other findings support Chandra's. "In our studies, taking a typical multi has consistently improved the delayed dermal hypersensitivity of older people," says John Bogden, professor of preventive medicine at the New Jersey Medical School in Newark.(4)
"That's an important test of how robust their immune systems are. I recommend that people 60 years of age and older take a basic multivitamin-and-mineral like Centrum Silver every day."
What about higher doses of antioxidants like vitamins E and C? A daily dose of 200 IU of vitamin E strengthened the immune response to some vaccines in a recent small study of older people.(5) In another study, 28 days of 800 IU of vitamin A, 100 mg of vitamin C, and 50 IU of vitamin E a day raised the number of disease-fighting T cells in elderly institutionalized people.(6)
"We're testing whether taking a multivitamin plus extra antioxidants is better than taking just a multi," says Bogden. "Within a year, we hope to be able to tell if that results in fewer illnesses."
(1) Lancet 340: 1124, 1992.
(2) John D. Bogden and Donald B. Louria, "Micronutrients and Immunity in Older People," in Preventive Nutrition, ed. Adrianne Bendich and Richard J. Deckelbaum (Totowa, New Jersey: Humana Press, 1997).
(3) Inter. J. Vit. Nutr. Res. 63: 11, 1993.
(4) Am. J. Clin. Nutr. 60. 437, 1994.
(5) J. Amer. Med. Assoc. 277: 1380, 1997.
(6) Age and Ageing 20: 169, 1991.
WHAT TO TAKE
Want a supplement to strengthen your immune system? You won't find Ranjit Chandra's. It's patented, but no one's selling it yet.
Here's what we recommend instead:
* Get a good start. if you're over 50, start with a good multivitamin-and-mineral supplement like Centrum Silver, Theragran-M, or Nature Made Mature Balance. (If you're under 50, try one like regular Centrum or the many Centrum look-alikes.) They'll give you most of the nutrients that protect not only your immune system, but your heart (folic acid), bones (vitamin D), and nervous system (vitamin B-12).
* Add E. Consider taking an extra 100 IU a day of vitamin E. The evidence that roughly that amount boosts immunity -- and cuts the risk of heart disease -- isn't complete, but it's growing.
* C for yourself. Chandra's supplement supplied 80 mg of vitamin C. But recent studies suggest that it takes about 200 mg to saturate body tissues. You can easily get that much from a diet rich in fruits and vegetables. If you want insurance, take a supplement.
* Keep up your calcium. Calcium doesn't heighten immunity, but most people -- especially women -- don't get enough from food, and the multis supply only about 200 mg. Unless you eat three or four dairy products a day, take 500 mg or so from a calcium carbonate supplement like Tums. (Try calcium citrate if the carbonate causes constipation.)
* Hold the iron. Chandra's supplement had 16 mg of iron. But some seniors get enough iron from their food, and roughly one out of a hundred are in danger of iron overload. If you eat few iron-rich foods -- like fortified breakfast cereals, meat, poultry, and beans -- ask your doctor to check your blood ferritin levels to see if you need more iron.
* Get your beta-carotene from food. Chandra's supplement had 16 mg (about 25,000 IU) of beta-carotene. But recent studies suggest that high doses -- 20 to 30 mg (30,000 to 50,000 IU) a day -- raise the risk of lung cancer, at least in smokers. That raises the possibility that it could cause cancer in anyone. The low doses in most multis -- typically 1 to 3 mg (1,500 to 5,000 IU) -- are not worrisome.
To play it safe, get your beta-carotene from fruits and vegetables (which lower the risk of cancer). The best sources: sweet potatoes, carrots, apricots, spinach, collard greens, canned pumpkin, and cantaloupe.
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|Title Annotation:||includes related articles on Chandra, evidence of how a multivitamin improved a person's immune system; researcher Ranjit Chandra|
|Publication:||Nutrition Action Healthletter|
|Article Type:||Cover Story|
|Date:||Sep 1, 1997|
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