The study Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis has been receiving enormous press coverage following its recent publication in the British journal The Lancet.
The study’s interpretation reads, “Both high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50–55% carbohydrate intake. Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality.”
That is, the study reaches two conclusions: (1) both high- and low-carb diets increase mortality relative to moderate carb diets, and (2) low-carb plant-based diets are safer than animal-based diets.
Should we be concerned about low-carb diets, and particularly animal-based ones?
Not in the very least based on this epidemiological study that used two food frequency questionnaires (FFQs) administered six years apart asking participants to recall how often they ate certain foods.
First, epidemiological studies, including those that use FFQs, cannot demonstrate dietary cause-and-effect because they cannot isolate the effects of diet from confounding lifestyle, genetic, environmental, health and psychosocial factors.
Second, FFQs are very imperfect research tools. I have personal experience with FFQs having been involved in the second Nurses Study since the 1970s. I periodically complete a multiple-choice FFQ that asks me to recall the food I ate over an entire year. It is impossible for me to fit in a form everything I ate over a 12-month span even if I could possibly remember food types and quantities – which I can’t.
Our position remains resolute: We have an abundance of valid, well-conducted scientific and clinical research that demonstrates the safety and efficacy of proper low-carbohydrate, high-fat diets, including those that are animal-based. This study does not refute the evidence.
The serious trouble with these types of studies is that their flawed conclusions are frequently publicized with authoritative language that confuses and scares rather than educates. Moreover, this study will feed – pun intended – the positions of individuals and groups that deride low-carb diets and animal-based diets even if they lack credible evidence, which this study certainly does not provide.
As Dr. Eric Westman posted this week on Facebook’s Low-Carb Support Group by Dr. Eric Westman, “Great rebuttal by Dr. Eenfeldt [of DietDoctor.com] about overblown media attention to nutritional epidemiology study. You know, after my patients with type 2 diabetes, obesity, hypertension, etc. have lengthened their life and have better quality of life because they no longer have these diseases and are no longer taking medications, they know how to be careful consumers of this type of research. Please don’t be distracted!!”