The results from a newly-published trial on the effects of a dietary intervention in overweight adults are impressive: 14 lbs weight loss, increased insulin sensitivity, a 19.3 mg/dL reduction in total cholesterol, 15.4 mg/dL reduction in LDL cholesterol, and reduced fat distribution in the liver and muscles (associated with reduced risk for fatty liver and insulin resistance) over the course of a 16-week dietary intervention. The headlines predictably latched onto the low-fat, vegan components of the diet, unsurprisingly given that these terms were used in the article’s title. However, the intervention was much more complex than this suggests, and our takeaway must be similarly nuanced.
Here is a better description of the actual dietary intervention, summarized from the description in the paper: higher in fiber, higher in phytonutrients, greater nutrient density, low glycemic/low in added sugars, low in processed foods and additives. Yes, it was also vegan and low in fat, and likely also lower in calories than the comparative diet. In addition to the diet, the intervention included coaching and life skills training in how to prepare foods, how to shop for healthier foods, and how to navigate restaurant menus to avoid unhealthy foods. Any one of these factors, and most likely the combination of these factors, could have been the reasons for these beneficial health outcomes.
In our experience, vegan diets are not universally healthy. Vegan diets require significant amounts of attention to nutrient sufficiency, especially complementary proteins, minerals such as zinc and iron, vitamin B12, an essential nutrient which can only be found in animal foods, and longer-chain polyunsaturated fats such as EPA and DHA. Proper instruction from a qualified expert is key for maintain long-term health.
We also caution that simplified conclusions drawn from studies such as this one may miss the additional factors that make up a healthy diet – like abundant whole plant foods and avoidance of processed foods and sugars. And are what lead to confusion and seemingly-conflicting data from one dietary study to the next.
Related: Our Nutrition Programs Director, Romilly Hodges, quoted in the Wall Street Journal article What to Know Before Resolving to Eat Less Meat.