We all want to believe in vitamins, especially antioxidants, hoping that they will help us live longer, prevent chronic illness, and like Popeye’s spinach, make us strong.
So when the latest JAMA published a clinical evidence synopsis from the Cochrane review about the power of antioxidants, I was intrigued. Just a reminder, the Cochrane Reviews are systemic reviews of research pertaining to human healthcare and health policy and are internationally recognized as the highest standard in evidence-based healthcare. They take a clinical question, review all the relevant studies and basically give us the bottom line after they have done an exhaustive statistical analysis.
So here is what they found in answer to the clinical question ” Are antioxidant supplements associated with a higher or lower all-cause mortality?”
They reviewed 78 randomized clinical trials which included 296,707 participants whose mean age was 63. And 46% of them were women (I wonder why not 50%, but let’s not go there). Of these, 26 of the studies where of individuals who were healthy and the remaining 54 trials assessed individuals with stable, chronic diseases that included coronary disease, diabetes, Alzheimer’s and age-related eye disease. All the antioxidants were given as oral supplements, either alone or in combination with other vitamins, minerals or other interventions. The mean duration of supplementation was three years. The reviewers then analyzed which of the studies were biased. ( An example of bias would be to ask someone who already has an illness if she or he took the antioxidant in order to prevent the illness.) They concluded that 82% of the participants had a low risk of bias. Obviously, when the low risk trials were analyzed separately from trials with a high risk of bias, the results were considered the most relevant. And here’s the surprising finding: “The antioxidant supplements were associated with a statistically significant higher all-cause mortality. The higher risk of all-cause mortality was observed for beta-carotene and vitamin E, and in some analyses for higher doses of vitamin A. Vitamin C and selenium were associated with neither higher nor lower all-cause mortality”.