Despite This New Study, Everything We Know About Nutrition Remains True.
A study published this week in The Lancet found a link between high carbohydrate intake and risk of death. As a result, the headlines were dedicated to celebrating low-carb diets and low-fat vegans out to fight. But as with most dietary research, there is more to it than the headlines suggest.
Caption: Major Dietary Study Shows Carbohydrates, Not Fats, Are Bad For Your Health.
History: The low-carb versus low-fat headlines have continued without interruption over the past few decades (at least). Constant news reports allegedly show that the oil is bad, or the oil is back, or the oil is part of the Matrix, and people are misled every time. In fact, four of the most unsuccessful studies on butter from last year turned out to be largely consistent with each other, aside from the hype.
New nutritional research often builds on or is consistent with what scientists already know, rather than completely changing the situation. Today’s story is no different.
In the course of the study, scientists collected detailed questionnaires on nutrition for more than 135,000 people from 18 countries. The researchers then followed the participants for several years and collected data on events such as heart attack, stroke, death from cardiovascular disease, and death from all causes. Even though the lifetime risk of dying is 100 percent, researchers can calculate whether diet increases the likelihood of people dying at any given time.
Here’s what they found. On average, people who consume more than 77 percent of their daily calories from carbohydrates have a 30 percent greater risk of dying at any given time than people who ate less than 50 percent from carbohydrates. Unsurprisingly, the researchers also found the opposite: on average, people consuming more than 35 percent of their daily calories from fat had a lower risk of death compared to people consuming the fewest calories, accounting for about 11 percent of their daily calories from fat.
Headlines suggest that this could mean high-fat diets are protective or high-carb diets dangerous , but these interpretations miss key details.
First, because a low-fat diet is generally considered to be a diet with less than 30 percent of calories from fat, participants may still report that they are following a traditionally low-fat, high-carb diet, and do not experience increased risks at all. The “protective” effect of increased fat intake extends to anyone who consumes more than 23 percent of their calories from fat. And people who ate up to 62 percent of their calories from carbohydrates and just 16 percent from fat did not see any harmful effects. In some context, the CDC’s National Center for Health Statistics reports that the average American gets about 50 percent of their daily calories from carbohydrates and 34 percent from fat.
It is also unclear whether the increased risk seen in this study actually applies to concerned people in the Western world reading these headlines. Among the 18 countries studied, several were very low- and middle-income countries that used diets high in refined carbohydrates (such as white rice) due to limited access to a more varied and nutritious diet. Thus, some of these high-carb diets can go hand in hand with malnutrition . Participants from developing countries may have had varying access to things such as basic health care, clean water and air, or getting enough food to meet their energy or micronutrient needs, and these factors may have contributed to their greater risk of death.
If you would like to further explore study design, results, and possible confounding variables, I wrote about them in more detail here .
Bottom Line: An extremely low-fat, high-carb diet with less than 20 percent of calories from fat was associated with an increased risk of non-cardiovascular death, but moderate intake of fat and carbohydrates was not associated with an increased risk. It would be better to ignore the attention-grabbing headlines in favor of more balanced coverage, like this one from Science Daily: ” Moderate intake of fat and carbohydrates is best for health, according to international studies .”