Don’t throw out the kale; a keto diet is still worth consideration

Study doesn’t represent all the facts, David Harper says.

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 Lancet Public Health journal 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 current guidelines, which 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 carbohydrates 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. 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 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 lifespan. Third, this study is not a randomized, controlled, doubleblind 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 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.”