Posted on 06/24/2012 at 07:38:44 PM by Student BloggerBy Sarah Gold
Saturday's controversy session at Advances & Controversies in Clinical Nutrition- on whether or not antioxidant supplements are beneficial- was, well, not much of a debate. Turns out the chase for the perfect antioxidant supplement has led to a lot of null findings. Over and over again, observational studies suggest a benefit to antioxidants such as vitamins C & E, yet when tested in large randomized control trials, there appears to be no benefit when it comes to reducing risk of cancer of cardiovascular disease.
Much of the problem lies in the study design, according to Jeffery Blumberg, PhD. The dynamic relationship among antioxidants leaves a challenge for researchers, noted Blumberg. With about 10,000 dietary antioxidants, testing one antioxidant supplement at a time is much too simplistic of an approach for such a complicated issue. In addition, antioxidants are multifunctional molecules that play many different roles in the body beyond decreasing the adverse effects of free radicals. Yet, this tunnel vision approach has affected the way we design studies, he argued.
He questioned study protocol – the form of antioxidant, dosage, duration of the studies, compliance, and possibly most importantly the lack of measurement of the state of oxidative stress. If someone isn't under a lot of oxidative stress, then feeding him or her an antioxidant supplement will not likely provide benefit. In addition, it's possible vitamin levels are sufficient before supplementation and maybe doses beyond our needs don't provide additional benefit. It's also important to look at the details of the cohort being studied. In some studies that looked at the effect of antioxidants on cardiovascular disease, a good portion of the subjects were taking beta-blockers, calcium channel blockers, lipid lowering agents, and diuretics, which one can't ethically ask them to stop taking for the study. But it's a lot to expect one vitamin to provide greater benefit than proven pharmacological substances.
A slight debate sparked when John Moreley, MBBCH, who believes that if the FDA regulated multivitamins as a drug they would be taken off the market, took the podium. He took the debate one step further and claimed that antioxidant supplements are not only not beneficial, but they are actually harmful. “If you're going to take an antioxidant supplement, make sure what you're taking is worth dying for.” Although a little dramatic, his statement was backed by a Cochrane review of 56 trials showing that antioxidant supplements such as beta-carotene and vitamin E significantly increased mortality. The studies linking beta-carotene supplementation and increased risk of lung cancer comes to mind. We need to take a closer look as to what people died from when discussing this issue, countered Blumberg.
While testing individual foods would be very challenging (what is the placebo for a tomato or almond?), there was general agreement in the room that eating a diet full of fruits and vegetables is better than taking any one supplement or focusing on any one antioxidant. In fact, the idea of variety seems to be a common thread of the weekend thus far. Dr. Mehmood Kahn echoed this sentiment in the preceding talk of functional foods. When asked what a superfood is, he answered, “I haven't got a clue.”