David Harper: Keto diet a healthy alternative to the standard Western diet
If you are confused by the contradictory information regarding what comprises a healthy diet, I am not surprised.
Over the past decade, nutrition science has produced robust evidence that high-carbohydrate diets contribute to obesity and chronic disease, and that very low-carbohydrate, ketogenic diets provide a healthy alternative. Then, last week, the results of a study published in the journal The Lancet Public Health concluded that low-carbohydrate diets should be avoided because they are associated with higher overall mortality and shorter average lifespans. So, which is true?
The answer to that question is especially important given that Canada is soon to release its first nutritional guidelines in 11 years. The present guidelines, that recommend a relatively high-carbohydrate (40 to 65 per cent of energy), low-fat (20 to 35 per cent) diet have coincided with skyrocketing rates of obesity and related chronic diseases, including diabetes. A coincidence? Not likely. The reason is overconsumption of carbohydrates.
Here’s how the physiology works: chronically high carbohydrate consumption causes chronically high levels of glucose in the blood. This leads to persistent, high insulin secretion and, over time, to insulin resistance. For most, this will eventually result in pre-diabetes and, for some, full-fledged diabetes. What’s more, insulin is a powerful signal for the body to store fat, which results in more weight gain, higher blood sugar levels, and an even greater likelihood of developing chronic disease.
A ketogenic diet, however, reduces carbohydrate consumption to less than five per cent of total calories. The fat and protein you consume in place of carbohydrate not only provides your body with a steady supply of efficient fuel, it also primes us to burn the excess fat that so many of us are carrying around our waists. Our glucose levels return to normal, we become less insulin resistant, we shed fat, and significantly reduce our risk of developing chronic disease. Another significant benefit is the production of ketone bodies, now the subject of intense scientific investigation due to their many health-promoting properties including protection of the brain and nervous system, reduction of systemic inflammation that’s the root cause of cardiovascular disease, and anti-cancer effects.
So, why then would a study conclude the opposite? There are many reasons, but here I’ll address just three. First, The Lancet study did not consider ketogenic diets. Their limits for “low carbohydrate” are between 30 and 40 per cent of total calories, so participants in this group were never in a state of nutritional ketosis. Second, the low-carbohydrate group in the study were typically middle-aged, obese, sedentary, diabetic smokers. No surprise they found a few years shorter life-span. Third, this study is not a randomized, controlled, double-blind experiment — the gold standard of science. It’s a meta-analysis (study of studies) that mines decades-old research data and applies statistics to produce new results. The problem is that mining data from poorly designed experiments will not produce new, meaningful results. Hardly the kind of “science” we should be relying upon to determine what to eat to stay healthy.
I have just returned from a conference on the emerging science of carbohydrate restriction and nutritional ketosis held at Ohio State University. Nutritional researchers and physicians from around the world presented their findings on the therapeutic benefits of the ketogenic diet and its potential to prevent chronic disease. As a therapeutic, the ketogenic diet has been used as a standard of care therapy for epilepsy for almost a century. We are now exploring it as a therapy for a range of chronic diseases including diabetes, cardiovascular disease, cancer and Alzheimer’s.
As humans, we lived without significant carbohydrates in our diet for more than 95 per cent of our existence. Ketogenic diets are not “the latest fad diet.” If you have adopted a ketogenic diet, I can assure you that the evidence supports it.
Dr. David Harper is an associate professor of kinesiology at the University of the Fraser Valley, a visiting scientist at the B.C. Cancer Research Centre, and a member of the Scientific Advisory Board of the Institute for Personalized Therapeutic Nutrition. His upcoming book, BioDiet, about the new science of nutrition, will be released early next year.