Study on Antioxidants and Aging a New Piece in the Puzzle, Not Earth-Shattering News
Earlier this month, Yee, Yang and Hekimi published an article in journal Cell on mitochondrial reactive oxygen species’ signaling in the roundworm in response to the herbicide Paraquat, which induces the formation of the free radical superoxide. They found that the roundworm had a longer lifespan when reactive oxygen species from Paraquat were introduced. These results were enthusiastically reported on today in the Daily Mail as a warning against “antioxidant vitamins”, with comments from one of the authors “the so-called free-radical theory of ageing is incorrect. We have turned this theory on its head”.
But is this the case? The article from the Daily Mail explains that increased oxidative stress can induce cells to increase their defense mechanisms and extend their lifespan, and that antioxidants may interfere with this mechanism. This goes against the conventional thinking that prevailed from the late 1990s until the mid-2000s, which is that antioxidants may counteract oxidative stress and prevent damage caused to cells. Since then, research has been emerging from different research groups that point to a complex relationship between oxidative stress and antioxidants (Speakman and Selman). Genetics and environment can both affect how well antioxidant defense mechanisms protect against oxidative stress, and the modify effects on health and lifestyle. The Yee article is not ground-breaking, but rather supports a more nuanced view on the free-radical damage theory of aging.
The Daily Mail article also contains a number of factual errors. First of all, even though the words “antioxidants”, “antioxidant vitamins”, and “vitamins” can refer to the same substance, for example, vitamin E, they cannot be used interchangeably as there are plenty of substances that will only fit into one category, such as anthocyanin, vitamin B12, and quercetin. Unfortunately the article does not make that differentiation, and even refers to vitamin A as an antioxidant, which it is not. This is important, as the information presented later in the piece refers to supplements in general, “antioxidant vitamins” and “vitamin supplements”, and not necessarily antioxidants, which are the topic of the article.
A second point is the reason why people take antioxidant supplements. While I do not have data for the UK population that was the focus of the newspaper article, in the US, most people take supplements “to improve overall health” and “to maintain health”, according to Bailey and co-workers. Anti-aging does not feature in the list, nor does extending the lifespan or keeping people looking youthful. The top antioxidant taken is humble vitamin C, which 7% of supplement users take, and the most common reason is immune health. Thereafter, 3.7% of supplement users take vitamin E “to improve overall health”.
A third problem is that supplements are assumed by the author to be high dose and therefore at levels unable to be obtained from the diet. This is clearly not true, as the most common supplement taken is a multivitamin, which contains the recommended dietary intake of nutrients. In fact, a glass of orange juice contains approximately 120 mg vitamin C, whereas a leading brand* of multivitamins contains only 60 mg vitamin C. The levels of nutrients in the supplements used by most people contain levels that are obtainable by the diet.
Furthermore, the authors of the scientific paper certainly did not test whether antioxidants could speed up aging in humans. Rather they showed that inducing oxidative stress with a herbicide increased the lifespan of roundworms, and that the pattern of gene expression was consistent with cell defensive mechanisms rather than programmed cell death. A far cry from claiming that antioxidant supplements are harmful.
Yee C, Yang, W, Hekimi, S. The Intrinsic Apoptosis Pathway Mediates the Pro-Longevity Response to Mitochondrial ROS in C. elegans Cell, Volume 157, Issue 4, 897 – 909. http://www.cell.com/cell/abstract/S0092-8674(14)00359-6
Naish, J. Think antioxidants will make you live longer? Think again: We spend millions on them but now researchers say supplements may make our bodies age FASTER. May 27, 2013. http://www.dailymail.co.uk/health/article-2639929/Think-antioxidants-make-live-longer-Think-We-spend-millions-researchers-say-supplements-make-bodies-age-FASTER.html
Bailey RL, Gahche JJ, Miller PE, Thomas PR, Dwyer JT. Why US adults use dietary supplements. JAMA Intern Med. 2013 Mar 11;173(5):355-61. doi: 10.1001/jamainternmed.2013.2299. http://www.ncbi.nlm.nih.gov/pubmed/23381623
Speakman JR, Selman C. The free-radical damage theory: Accumulating evidence against a simple link of oxidative stress to ageing and lifespan. Bioessays. 2011 Apr;33(4):255-9. doi: 10.1002/bies.201000132. Epub 2011 Feb 2. http://www.ncbi.nlm.nih.gov/pubmed/21290398
Thompson, J and Manore, M. 2007. "Nutrients Involved in Antioxidant Function", Ch. 10, page 55 in The Science of Nutrition. Pearson Education Inc. Publishers. http://www.aw-bc.com/info/thompson_majors/assets/pdf/chapter_10.pdf
*TalkingNutrition does not recommend any particular brand of supplements. For illustrative purposes, this value was taken from Centrum® Adults tablets (http://www.centrum.com/centrum-adults#tablets).