This is a follow up on this post. Just to recap, an interesting hypothesis has been around for quite some time about a possible negative effect of ketosis. This hypothesis argues that ketosis leads to the production of an organic compound called methylglyoxal, which is believed to be a powerful agent in the formation of advanced glycation endproducts (AGEs).
In vitro research, and research with animals (e.g., mice and cows), indeed suggests negative short-term effects of increased ketosis-induced methylglyoxal production. These studies typically deal with what appears to be severe ketosis, not the mild type induced in healthy people by very low carbohydrate diets.
However, the bulk of methylglyoxal is produced via glycolysis, a multi-step metabolic process that uses sugar to produce the body’s main energy currency – adenosine triphosphate (ATP). Ketosis is a state whereby ketones are used as a source of energy instead of glucose.
(Ketones also provide an energy source that is distinct from lipoprotein-bound fatty acids and albumin-bound free fat acids. Those fatty acids appear to be preferred vehicles for the use of dietary or body fat as a source of energy. Yet it seems that small amounts of ketones are almost always present in the blood, even if they do not show up in the urine.)
Thus it follows that ketosis is associated with reduced glycolysis and, consequently, reduced methylglyoxal production, since the bulk of this substance (i.e., methylglyoxal) is produced through glycolysis.
So, how can one argue that ketosis is “a recipe for accelerated AGEing”?
One guess is that ketosis is being confused with ketoacidosis, a pathological condition in which the level of circulating ketones can be as much as 40 to 80 times that found in ketosis. De Grey (2007) refers to “diabetic patients” when he talks about this possibility (i.e., the connection with accelerated AGEing), and ketoacidosis is an unfortunately common condition among those with uncontrolled diabetes.
A gentle body massage is relaxing, and thus health-promoting. Add 40 times to the pressure, and the massage will become a form of physical torture; certainly unhealthy. That does not mean that a gentle body massage is unhealthy.
Interestingly, ketoacidosis often happens together with hyperglycemia, so at least part of the damage associated with ketoacidosis is likely to be caused by high blood sugar levels. Ketosis, on the other hand, is not associated with hyperglycemia.
Finally, if ketosis led to accelerated AGEing to the same extent as, or worse than, chronic hyperglycemia does, where is the long-term evidence?
Since the late 1800s people have been experimenting with ketosis-inducing diets, and documenting the results. The Inuit and other groups have adopted ketosis-inducing diets for much longer, although evolution via selection might have played a role in these cases.
No one seems to have lived to be 150 years of age, but where are the reports of conditions akin to those caused by chronic hyperglycemia among the many that went “banting” in a more strict way since the late 1800s?
The arctic explorer Vilhjalmur Stefansson, who is reported to have lived much of his adult life in ketosis, died in 1962, in his early 80s. After reading about his life, few would disagree that he lived a rough life, with long periods without access to medical care. I doubt that Stefansson would have lived that long if he had suffered from untreated diabetes.
Severe ketosis, to the point of large amounts of ketones being present in the urine, may not be a natural state in which our Paleolithic ancestors lived most of the time. In modern humans, even a 24 h water fast, during an already low carbohydrate diet, may not induce ketosis of this type. Milder ketosis states, with slightly elevated concentrations of ketones showing up in blood tests, can be achieved much more easily.
In conclusion, the notion that ketosis causes accelerated aging to the same extent as chronic hyperglycemia seems more like fiction than fact.
De Grey, A. (2007). Ending aging: The rejuvenation breakthroughs that could reverse human aging in our lifetime. New York: NY: St. Martin’s Press.