Dov Michaeli, MD, PhD explores the myth that antioxidant vitamins will help you live longer
This is Part 2 of RIP: The Death of Two Myths. You can find Part 1 here.
Want to live longer? If you are honest with yourself, your answer is going to be a resounding YES! (And who doesn’t?) You may qualify it by saying that you actually want to live better, not longer.
Either way, chances are you are taking daily multivitamin supplements—over 40% of Americans do. The industry is raking in $15 billion in annual sales (2011 figures), giving it an enormous leverage over Congress, which banned all regulation of the supplement industry, never mind the science. In our democracy, money is speech, and enormous amounts of it can drown out any low-decibel amount of evidence.
What does the science say?
A 2008 study published in JAMA enrolled 14,641 U.S. male physicians initially aged ≥50 years, including 754 (5.1%) men with prevalent CVD (cardiovascular disease) at randomization. The intervention consisted of supplements of 400 IU vitamin E every other day and 500 mg vitamin C daily.
Why is this study so important? Because until its publication, the received wisdom that antioxidant vitamins have a protective effect on the heart was based on basic science studies in the petri dish and in animals—both of limited relevance to humans, and on observational studies in humans—fraught with methodological problems, hence of limited utility. This study is large, long (8 years of followup), and most importantly, it used the gold standard of clinical trial design: It was randomized, double-blind, placebo-controlled.
And the results are neither vitamin E nor C supplementation reduced the risk of major cardiovascular events. In the investigators’ words, “these data provide no support for the use of these supplements for the prevention of CVD in middle-aged and older men”.
What about cancer? A recent review in the Annals of Internal Medicine concluded that “limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or CVD. Two trials found a small, borderline-significant benefit from multivitamin supplements on cancer in men only and no effect on CVD”.
Before you rush to pick up your multivitamins pill to ward off cancer, remember that the trials were small (fatal for epidemiological studies), and the benefits were borderline. But if this “academic” argument does not deter you, maybe you should consider the studies showing that excess vitamin A can cause liver damage, coma and death. As for the other popular antioxidant, vitamin E, a large study found that taking vitamin E supplements (400 IU/day) for several years increased the risk of developing prostate cancer in men.
And finally, turns out the holy grail of increased lifespan is also mythical. An increasing number of studies declare the theory of antioxidants increasing longevity as dead, or at least moribund.
How did the myth of antioxidants take root?
Good question. I think the answer can be found in the sociology of science. The end of the 19th century and beginning of the 20th saw the scientific method become increasingly analytical. Rather than observe nature undisturbed, one had to tease apart its different strands to understand it in depth.
Indeed, this approach resulted in huge leaps in the fields of biochemistry and physiology. The naive belief was that ultimately this would lead us to understanding the complexity of the healthy human, and its pathology. It also played to the way our brain works. The brain craves predictability, clear causality. (This trait has its roots in the need to understand the world around us and respond to its vicissitudes in rapid fashion.) So when oxidative damage, or the free radical theory of aging, was proposed in the late 1940s, it provided the requisite simplicity and clarity of causality.
So how come literally thousands of papers confirmed the theory? We can again find the answer in the way our brain is programmed. We tend to highlight and accept data that confirm our preconceived ideas and prejudices; and we reject and ignore evidence that does not.
This phenomenon is well known in psychology, sociology, political science, and behavioral economics. It’s called confirmation bias. This is not to say that the scientists were incompetent or dishonest in any way—it is just the way our collective brain works. It takes extraordinary expenditure of mental energy to combat it—something our lazy brains are programmed not to do.
This is why it took over 50 years for evidence to shake the foundations of the antioxidant theory and over 10 years to debunk the Resveratrol “evidence” of prolongation of survival.