Today, a dear friend of mine forwarded me a link from Dr. Mercola entitled, “Cutting carbohydrates from your diet can make you live longer.” Like usual, I clicked the link and read the article.
In my opinion Dr. Mercola sometimes oversimplifies research, makes erroneous assumptions and draws conclusions that are not there. I think this newsletter of his is one of those instances and I will explain why.
Dr. Mercola, references research done by Dr. Cynthia Kenyon, a well-known professor from UCSF, known for her anti-ageing research in the small worm known as c. elegans. Her laboratory discovered that a single gene, DAF-2, speeds up aging and when the mutated, increases life span by two-fold in the organism. The hormones, insulin and IGF-1, activates the DAF-2 gene and promotes aging1. Her research has implications for humans since we have both insulin and IGF-1 genes and leads one to believe, we could live longer if we have less glucose and insulin in our blood.
There are serval ways to lower circulating glucose and insulin levels. One method is through calorie restriction, a very well established method for increasing longevity in rodents2. The second way to achieve this is by limiting dietary foods that cause a rapid surge in glucose or insulin; the most obvious being sugary foods. Sugar, when consumed, causes rapid rise in both glucose and insulin. Drs. John McDougall, Dean Ornish and others use this approach with their patients, and is thought to have the same benefit as calorie restriction.
Chronic elevations of either insulin or glucose can damage the infrastructure of the cell and reduces longevity. Many people, mistakenly believe that sugary foods are the is biggest culprit driving the glucose and insulin pathway. I presume this is why Dr. Mercola wrote his article in the fashion that he did. However, research by others suggests that more is at play than carbohydrates alone.
Research by Holt et.al. concluded, that “insulin responses are not closely related to the carbohydrate content or glycemic effects of some foods 3.” Many dietary proteins and fats raise blood insulin levels without raising glucose 4. Remember, both chronically high levels of both glucose and insulin are bad. Furthermore, NOT all grains cause a rapid rise in glucose. In fact, some proteins can raise insulin as much as carbohydrates. For example, beef can trigger an insulin surge that is on par with brown rice and fish can raise insulin levels about the same amount as grain bread3.
I think Mercola is being too simplistic with his prima facie statement, “Limit your intake of carbohydrates, primarily in the form of fructose and grains, and you’ll achieve these results without any negative drug-induced side effects!” I think we need to limit foods that spike both insulin and glucose, i.e. overly processed foods, including proteins and fat, not simply carbohydrates.
If you are interested in learning more about Dr. Cynthia Kenyon’s work on c. elegans, she has a video series posted on Youtube. The first video of the series is posted here.
1. Kenyon, C. A Conserved Regulatory System Minireview for Aging. Cell, Vol. 105, 165–168, April 20, 2001
2. Mattson MP “Energy intake, meal frequency, and health: a neurobiological perspective”. Annu. Rev. Nutr. 25: 237–60. doi:10.1146/annurev.nutr.25.050304.092526. PMID 16011467
3. Holt, Susanne HA, Miller, Janette C, Petocz, Peter. An insulin index of foods:the insulin demand generated by
1000-kJ portions of common foods. Am J Clin Nutr November 1997 vol. 66 no. 5 1264-1276
4. Shepherd, P. R. Secrets of insulin and IGF-1 regulation of insulin secretion revealed. Biochem. J. (2004) 377
5. Toyoshima, Y. Dietary protein deprivation upregulates insulin signaling and inhibits gluconeogenesis in rat liver. Journal of Molecular Endocrinology (2010) 45 329-340; DOI: 10.1677/JME-10-0102