There is no doubt that the very-low-carb “ketogenic” diets can lead to weight loss , although studies have also shown that in the long term, weight loss is independent of the composition of fat, carbohydrate and protein in a diet as long as caloric intake is reduced. However, not everyone is “doing keto” to lose weight. Some are seeking better brain function, improved control of blood sugar, help with neurological ailments, or even starvation of tumour cells by limiting their supply of glucose.
The most significant evidence for keto benefits is in childhood epilepsy. Hippocrates, the most famous of the ancient Greek physicians, noted that fasting reduced the frequency of epileptic seizures. That idea was not put to a test until the early 20th century when clinical trials demonstrated seizure improvement after two to three days of fasting. When it was found that starvation resulted in elevated blood levels of acetone, beta-hydroxybutyric acid and acetoacetate, these compounds became candidates for the therapeutic effect. Such “ketone bodies” form when due to a lack of glucose, as in a low-carb diet, the body has to resort to the use of its fat stores to supply energy. It is the breakdown of fat that yields the ketones that can serve as an alternative energy source for the brain and their use instead of glucose somehow reduces seizures.
Since epilepsy is a brain disorder that responds to an influx of ketones into the brain, it raises the question of whether general brain function may be improved by a ketogenic diet. When scientists try to answer such questions, they usually first turn to rodents. Mice and rats can be trained to navigate mazes and avoid electric shocks, and indeed they do show an improvement in memory when they are on a ketogenic diet. That doesn’t mean much, because, with some notable exceptions, human brains are more sophisticated than those of rodents.
As far as humans go, there is much internet chatter about improved brain function, with all sorts of theories being proposed. Ketosis reduces symptoms of stress and anxiety by increasing the production of gamma-aminobutyric acid, an inhibitory neurotransmitter. Ketones make nerve cells function better because they are a more efficient fuel for neurons than glucose. Ketones reduce oxidative stress in the brain by increasing production of the antioxidant glutathione. Interesting theories, with no real evidence. There are claims of greater “mental clarity” and alleviation of “brain fog” on a keto diet, but there are no compelling studies to back up the claims.
That hasn’t stopped supplement manufacturers from cranking out a variety of “keto” products, mostly containing beta-hydroxybutyrate, with claims of improved mental function, neuroprotection, increased fat-burning and optimizing athletic performance, but without any significant supporting evidence. In fact, studies have shown that in professional cyclists, performance is actually impaired with such supplements, and that ketogenic diets turn out to be disastrous for race walkers.
The scenario is a lot more optimistic for Type 2 diabetes, where keto diets can result in greatly improved glucose control and better insulin sensitivity, in some cases even eliminating the need for medication. At least one study has shown better glucose control in Type 1 diabetes, along with fewer adverse events.
When it comes to claims about treating cancer, Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), and Parkinson’s disease, not only is the jury out, there isn’t even enough evidence to assemble one. With cancer, the theory is that insulin stimulates the division of cells, and that cancer cells rely on glucose for energy more than other cells, so that reducing glucose in the bloodstream results in less insulin production as well as less fuel for cancer cells. An interesting possibility with no clinical evidence.
Keto diets are not without concern. Starting such a diet can lead to headaches, fatigue, irritability and nausea, symptoms referred to as the “keto flu.” Constipation can be a problem due to lack of fibre but surprisingly, cardiovascular risk factors are not increased.
Many keto diets feature an abundance of meat. Not a great idea, given that according to a recent study of some 15,000 adults over 25 years, mortality rate increased on a low-carb, high-meat diet. This, however, was not found when carbs were replaced by plant sources of protein. So, for those interested in giving the keto diet a shot, whether it be for weight loss or control of diabetes, the best bet is to follow a version in which protein comes from vegetable sources, supplemented with fish or poultry. And drenching everything with butter is not a requirement.
Conclusion? A keto diet can have some remarkable outcomes with no significant risk, although studies longer than six months are lacking. It is noteworthy that while there are essential proteins and fats, there are no essential carbohydrates; the body can make glucose from proteins and fats. However, it should be pointed out that not all high-carb diets are problematic. The longest life expectancy in the world is on the Okinawa Islands of Japan where calories from carbohydrates in the diet outnumber those from protein by 10:1! Of course, their carbs don’t come from sugar or refined grains, but rather the likes of sweet potatoes, bitter melon and soybeans. It seems that nobody has a monopoly on the “healthiest” diet.
Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.
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