Australia boasts a controversial television chef who spruiks – without peer-reviewed evidence – a particular type of diet. He goes by the name of “Paleo Pete”.
Readers prone to gambling might like to place a small wager on the likelihood that in a very short period of time the popularity of Paleo Pete will be truly eclipsed by someone called (perhaps) Keto Kevin.
Increasingly, diet-obsessed magazines and websites are enthusiastically extolling the virtues of an eating regime called the ketogenic diet. This is an approach to food that emphasizes the consumption of very large amounts of fat and very small amounts of carbohydrates.
It’s been around for several years, but was recommended only as an intervention for the control of severe epilepsy in children.
In recent times it has been embraced by some weight-loss companies, but many dieticians and medicos doubt its efficacy.
However, an increasing number of studies – mostly using mouse and rat models – are reporting that ketogenic diets are linked to reduced memory deterioration and healthier old age.
The regime works by depriving the body of carbohydrates, thus dramatically reducing the reserves of glucose available for the body to use as energy. As a result, the body switches to burning stored fats in a process called ketosis, which results in water-soluble molecules called ketones being pumped into the blood.
These ketone bodies are readily metabolised by cell mitochondria and used as an alternative source of energy. Ketosis happens spontaneously not only when carb reserves are exhausted but also after periods of prolonged intense exercise or when a person has undetected Type 1 diabetes.
In some cases, prolonged ketosis can lead to a condition known as ketoacidosis, which can increase the acidity of the blood, affect insulin levels and lead to life-threatening diabetic coma.
Reports of ketoacidosis arising from ketogenic diets are uncommon and usually involve only mild symptoms. However, there are reports of cases with severe health effects.
In a new study published in the journal Cell Metabolism, Eric Verdin from the Buck Institute for Research on Aging in Novato, California, reports that a ketogenic diet restricts memory loss in ageing mice.
Working with lab-partner John Newman, who is also a geriatrician at University of California San Francisco, Verdin fed three cohorts of mice on different diets, one of which was ketogenic.
The ketogenic cohort was fed the full keto diet only intermittently, because obesity can be a side-effect. The researchers report that the diet did not increase lifespan, but the keto-fed mice did better at memory tests by the time they hit old age (which, for a mouse, is around two years old).
Verdin cautioned that the results of the mouse trial could not be scaled up to human level, and that no one should undertake a ketogenic diet without first consulting a doctor.
“Exercise also creates ketone bodies,” he added. “That may be one of the mechanisms why it shows such protective effects on brain function and on healthspan and lifespan.”
Helen Truby, from the Department of Nutrition, Dietetics & Food at Monash University in Australia was not involved in the study.
She said the results were “intriguing”, but warned people not to try to replicate them at home.
“So, should people start ketogenic diets?” she asks.
“Answer: not unless there is a medical indication to do so and under the guidance of an accredited practising dietitian who can ensure nutritional adequacy.
“In terms of ketosis being the cure for memory loss – I doubt anyone would be able to stick to the sort of strict low carb regimen necessary for long term use and therefore its applicability to humans is currently limited by the unpalatability of the dietary pattern that is required.”
Andrew Masterson is a former editor of Cosmos.
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