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A Bitter Pill to Swallow: Vitamin Supplements Don’t Make Us Healthy

November 12, 2008 2:22 PM

By Joanna Schaffhausen, ABC News Medical Unit

It’s more bad news for vitamins this week. New research shows that supplements of vitamins E and C don’t prevent heart disease in men. In fact, men taking vitamin E had a slightly higher risk for bleeding in their brains. In a different study, women taking vitamin D supplements did not have any lower risk for breast cancer.

This latest research joins a growing pile of studies documenting the failed promise of vitamins. Originally, vitamin B was supposed to keep our hearts healthy, vitamin E was going to lower our risk for Alzheimer’s disease and vitamin C would keep us free from diabetes. But none of these purported health benefits proved to be true in high-quality studies.

Currently, it is vitamin D’s turn to shine, as research suggests it may fight heart disease, cancer, diabetes and multiple sclerosis. I’m skeptical. I’ve watched an alphabet soup’s worth of vitamins come up short now, and each one has followed the same pattern -- early, preliminary research makes the vitamin look good for health, only to have later studies show no benefit. So far vitamin D is on the same path.

Indeed, the first study that actually tested vitamin D’s promise finds the supplement is a bust for preventing breast cancer and colon cancer in women. Doctors randomly assigned more than 36,000 postmenopausal women to take either daily vitamin D and calcium supplements or placebo pills for seven years. Thus far the women have not seen any decrease in their breast cancer or colon cancer risk.

How it possible for vitamins to look so promising in early research only to fall flat when doctors put them to the test?

The answer lies in the type of studies used to investigate vitamins and health. First, doctors do observational studies to compare two groups of people, such as cancer patients versus healthy people. Inevitably, the sick patients have lower levels of vitamins.

Next doctors do another type of observational study. They take blood samples from a large group of people and follow them for a period of several years. Again, those with the highest levels of vitamins – be they vitamin A, B, C, D or E -- are less likely to get sick.

All these findings mean it's looking good for the vitamins. People with low levels are sick and those with high levels are healthy. Doctors everywhere start recommending that people take a daily vitamin supplement to keep diseases away.

When researchers finally do the gold standard studies, called a randomized, controlled trials, the vitamins generally fail the test. People who are given vitamin supplements do not magically become healthier.

The reason is that vitamins are often a red herring when it comes to disease. Sure, they look guilty at first because sick people are vitamin deficient, but it turns out vitamins are not typically causing the heart disease, the cancer, or whatever other illness is under investigation. Sick people have low levels of vitamins because they are sick.

Similarly, healthy people have high levels of vitamins because they engage in many behaviors that are linked to good health, including eating more vegetables and getting more exercise. When healthy people take vitamin supplements, it makes it seem as if the vitamins are giving them some benefit, when the truth is that they were already unlikely to get sick.

This causes doctors to think they can give the vitamins to unhealthy people to make them better, when really the unhealthy folks need to embrace the healthy people’s whole lifestyle – lose weight, stop smoking, eat more vegetables, and so on.

Vitamin supplements can improve health in some ways. For example, folic acid supplements taken by women prior to pregnancy can reduce birth defects in babies. Vitamin D can help build strong bones throughout the lifespan. But can it also reduce heart disease, cancer, diabetes and autoimmune disease?

We're all waiting for the final verdict, but history suggests the answer will be no.

November 12, 2008 | Permalink | User Comments (21)

User Comments

Posted by: Lauri Smith | Dec 4, 2008 5:37:41 PM

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