Dietary Double Take

A really interesting study was just published in the Journal of the American Medical Society (JAMA). Like many prior studies, it attempted to compare the health benefits of a plant-based diet vs other dietary patterns. This particular study took a unique approach at addressing this question. 

You see, in many medical research studies, two groups of people are compared: one group undergoes the intervention, or receives the medication, or eats a certain diet, and the other group is the “placebo” or control group. And if there are differences between the groups at the end of the study, then you attribute those differences (good or bad) to the treatment. But if there are baseline differences between the two groups before you even start the trial, then it becomes hard to know whether the change in outcomes between the two groups is from the intervention, or simply because the two groups were different from the start. For example, if the group receiving a new medication was found to have fewer heart attacks at the end of the trial, but they also had healthier people at the start, then we couldn’t know for certain that it was only the intervention that led to the beneficial outcome. These unbalanced characteristics are called “confounding factors”. This is especially true in studies that look at diets. Vegans usually differ from nonvegans in many factors that may influence diet and health, including smoking rates, exercise amounts, etc.

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There are ways to get around this, with the most common being randomization. Randomly dividing people between the two groups theoretically evens out confounding factors between the two groups. But randomization doesn’t always work, and there can still be underlying differences between the groups that aren’t recognized. 

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Which brings us to the discussion of this recent study, which used a totally novel and unique approach: they compared identical twins! If you do an intervention to one twin, and use the other as the “control”, then you should be negating many of these “confounding factors”. 

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This recent clinical trial randomized 22 pairs of twins to a vegan or to an omnivorous diet (1 twin per diet). BOTH diets emphasized vegetables, fruits, and whole grains while limiting added sugars and refined grains. The goal was minimally processed foods comprising a balanced plate with vegetables, starch, protein, and healthy fats. For the first four weeks, all meals were provided by a national food delivery company, so the contents of the diets were strictly controlled. The diets were NOT designed to get the participants to lose weight. Both groups ate healthy diets during the study. Even the omnivorous participants improved their diet quality during the 8-week intervention, with increased vegetables and whole grain intake and decreased added sugars and refined grains. 

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The results? After just 8 weeks, the twins randomized to the vegan diet experienced significant decreases in LDL-C (“bad cholesterol”) levels, fasting insulin levels, and body weight. LDL-C dropped by 14mg/dL, and weight dropped by 4-5lbs, after just 8 weeks!

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Triglycerides, glucose, and TMAO levels also dropped from baseline compared with omnivores, but these changes weren’t statistically significant at 8 weeks.

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This data falls right into line with so many other research studies that have been performed in the last few decades. As a result, we have seen an evolution in the thinking about the role of diet and nutrition in our health. As time goes on, research reveals over and over that the best diet for overall health is a plant-based diet. In fact, clinical practice guidelines from the American Heart Association now recommend that doctors encourage patients to choose healthy sources of protein, mostly from plants, to promote cardiovascular health. 

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To paraphrase Dr. Kim Williams, a mentor of mine: there are only two kinds of people out there: vegans, and those who haven’t yet learned the health benefits of being a vegan.

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At Wisconsin Cardiology Associates, we counsel our patients to aim for a healthy, plant-based diet, emphasizing fruits, vegetables, beans, lentils, whole grains and nuts.

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References

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Landry M et al. JAMA Netw Open. 2023;6(11):e2344457.