Do you take vitamins? Multivitamins? Antioxidant vitamins? Vitamin C? “Of course. I want to take good care of myself,” you might say. Yet, increasing evidence shows supplemental vitamins might not be as good for you as was once thought.
In my next few blog posts, I’ll be looking at the pros and cons of vitamin supplements, and compare them to vitamins from whole foods.
When asked about multivitamins, most doctors used to say that if it won’t help, it sure won’t hurt. I’d like to think that a multibillion industry pushing these products, and decades of use would give us a better answer than ‘it probably won’t hurt’. You see, while a lack of vitamins could make you sick, that doesn’t mean that extra vitamins make you healthy. This needs to be proven.
Lately, there’s a shift of opinion among medical professionals concerning the broad and indiscriminate use of vitamins. After decades of suggesting multivitamins as a nutritional safety net, an increasing number of medical professionals are changing their advice.
In this month’s edition, Harvard Men’s Health Watch issued a reappraisal of its recommendation, and suggested that average men give up multivitamins, at least until scientists solve the puzzle of folic acid and cancer. (See: http://www.health.harvard.edu/press_releases/multivitamin-and-cancer-risk.htm)
A few weeks ago I quoted the World Cancer Research Fund and the American Institute for Cancer Research recommendations: “Aim to meet nutritional needs through diet alone”.
The American Heart Association recommends that “healthy people get adequate nutrients by eating a variety of foods in moderation, rather than by taking supplements.” (http://www.americanheart.org/presenter.jhtml?identifier=4788)
What are vitamins supplements good for?
There is one clear and consistent reason for people to take a vitamin supplement: Vitamin deficiency.
A vitamin supplement will correct a primary vitamin deficiency faster than food will. For example, if a patient has scurvy -- a disease caused by vitamin C deficiency that afflicted and killed many sailors that had no access to fresh produce -- vitamin C will resolve his symptoms.
I’m sure you’ve read labels claiming vitamin C helps heal wounds, prevents cell damage, promotes healthy gums and teeth, and strengthens the immune system. If you had scurvy you’d see all these outcomes once you took vitamin C, and fast. But if you eat a varied diet you’re unlikely to experience any effects on your gums, skin, or immune system. Compare that to a hypoglycemic person: He will greatly benefit from anything with sugar, but it would be misleading to market sugar as “provides energy, vitality, and prevents fainting”. This sort of claim is similar to marketing a beautiful house as a solution to homelessness.
Healthy people who eat a varied diet are unlikely to develop a vitamin deficiency. On the other hand extremely restrictive diets, states of malabsorption, chronic diseases, and special situations such as pregnancy (folic acid in early pregnancy is proven to decrease the incidence of neural tube defects), old age and prematurity, may make vitamin deficiency possible and even likely. In such a case, a doctor will prescribe specific vitamins to address specific issues, and will follow up on progress.
Scientists have been searching for proof that vitamin supplements prevent, ameliorate or cure diseases other than vitamin deficiency for many years. The results have been quite confusing. Initially, observational studies, looking at people who take vitamins and comparing them to people who don't, showed a correlation between multivitamin consumption and other parameters such as lower rates of cancer, dementia and heart disease. Yet when randomized double-blind placebo- controlled studies where done, many times no correlation was found.
This discrepancy is largely explained by the fact that studies that look at self-selected groups have an internal bias. People who take vitamins on their own volition may seek other perceived healthy habits such as exercise, good nutrition, healthy weight, smoking avoidance etc., are more affluent or are healthier to begin with.
When the researcher randomly assigns the groups, the result is more indicative of the intervention studied, in this case, vitamin use. Adding the placebo to the control group neutralizes the effect of suggestion, which is very powerful and cannot be underestimated.
Long-term randomized clinical trials -- considered the gold standard for studying a relationship between treatment and health -- have failed to consistently show that supplements of beta-carotene, vitamin A, B-vitamins and vitamin E benefit cardiovascular health. Some trials have even shown them to cause harm. The same is true for cancer prevention and treatment.
These days, vitamin D is the new darling, with recommendations popping up to consider a vitamin D supplement, and at a higher dose than the current recommended daily allowance. Vitamin D is made by the skin in reaction to sunlight exposure, and there are very few foods that are naturally rich in this vitamin (mainly fatty fish). Several foods such as milk products, cereals and margarine are fortified with vitamin D. There have been quite a few encouraging studies correlating vitamin D intake to lower cancer rates, better cancer survival rates and lower rates of cardiovascular disease.
Although I’m hopeful that a vitamin D intervention, so simple and safe, can be possible, it reminds me a little of the antioxidant vitamin initial hype of the past that turned into disappointment with the results of larger, better studies.
Drawing conclusions from a study reported in the news, without looking at the big picture, is like looking at the presidential primaries in just one state or at just one point in time. To draw reasonable conclusions one needs to let the scientific process continue, and see where the results as a whole point to.
When I met my husband, some 14 years ago, he had a bunch of bottles with multivitamins and some vitamins in mega-doses, even though he always ate very well, and there was no reason to think he's deficient in any way. By a conservative estimate I saved at least $2000 by convincing him to quit indiscriminate use of vitamin pills (maybe an excuse to buy myself something nice?).
But the expense wouldn't have changed his mind. My reasoning back then was that there may be a downside to taking vitamin pills.
And that brings us to next week's topic: Is there a downside to taking multivitamins?