Several clinical trials in the past 10 years have demonstrated that a low-carbohydrate, high-fat, high-protein diet is at least as effective as a calorie-restricted, high-carbohydrate, low-fat diet for weight loss and improvement of risk factors such as blood pressure, blood sugar and lipid levels.
While older observational studies linked dietary fat with poor health outcomes, newer systematic reviews, have absolved fat, with the exception of trans-fat. Many such studies have implicated refined sugars and starches instead.
Yet, in contrast to the robust understanding we have about diet and risk factors, our knowledge about the effect of diet on mortality is much more sparse, A new study, just published in the Annals of Internal Medicine study attempts to address this gap.
Researchers found that an animal-based low-carbohydrate dietary pattern increased the risk for death, whereas a plant-based low-carbohydrate diet lowered the risk.
Having analyzed food frequency questionnaires from 85,000 women from the Nurses’ Health Study and 45,000 men from the Health Professionals’ Follow-Up Study over 20 years’ they found:
- People who had the highest scores for an animal-based low-carbohydrate diet were at increased risk for all-cause and cardiovascular mortality.
- Those with the highest plant-based low-carbohydrate diet scores had a reduced risk for all-cause and cardiovascular mortality.
- Men who more closely followed any low-carbohydrate diet had a higher cancer mortality risk.
The question is how to understand this new information in the context of the existing knowledge on diet and health and research design.
Observational studies have great strengths but also significant limitations. For now, it seems that no one can legitimately claim that a low-carbohydrate diet is either harmful or safe with any degree of certainty.
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