Not all vegan diets are good for health
Plant-based diets loaded with whole grains, fresh fruit and vegetables are known to reduce the risk of heart disease, but some plant-based foods are not so helpful. They can be harmful.
The wrong kind of exclusively plant-based diet, one that includes a lot of refined grains and sweetened beverages, can increase the risk of coronary heart disease, according to a new study published in July by the Journal of the American College of Cardiology.
The study also suggests that reducing intake of animal products while boosting consumption of fruits, vegetables and whole grains, while continuing to indulge modestly in animal foods, can do a body nearly as much good as a well planned all-plants diet — and more good than one built around french fries, cookies, chips, candy and pasta.
“Less healthy plant foods and animal foods were both associated with increased risk, with a potentially stronger association for less healthy plant foods,” according to the study, “Healthful and Unhealthful Plant-Based Diets and the Risk of Coronary Heart Disease in U.S. Adults.”
Piles of research suggest that diets that emphasize fresh, fiber-packed plant foods carry big benefits, including significantly lowering the risk of coronary heart disease. But “going vegan” can lead to trouble when people choose low-fiber, sugary or fatty foods merely because they don’t contain meat or dairy. And just try finding something to eat at the airport that’s not dairy, not meat, fresh, full of fiber and appetizing.
The study, which the authors say is “one of the largest prospective investigations of plant-based diet indices and incident coronary heart disease in the world,” reviewed data from two iterations of the Nurses’ Health Study and one from the Health Professionals Follow-Up Study.
Each involved tens of thousands of adults who tracked their health behaviors and medical histories through questionnaires completed every two years. This gave researchers at Harvard’s T.H. Chan School of Public Health two decades worth of data — more than 4.8 million person-years of follow-up data to analyze.
Over two decades, 8,631 participants developed coronary heart disease. Using these data, the authors created three diet indices:
An overall plant-based diet index in which plant foods got a positive score and animal foods got a negative score.
A healthful-plant-based diet index, assigning positive scores to whole grains, fruits, vegetables, nuts, legumes, oils, tea and coffee, and negative scores to juices and sweetened beverages, refined grains, potatoes and fries, and sweets.
An unhealthful plant-based diet, with positive scores for the heavily processed plant foods and negative scores for the healthful plant and animal foods.
The researchers observed that the people with a higher adherence to the general plant-based diet index had an inverse association with coronary heart disease, and that this relationship got even stronger for the nutritious plant-based diet index. In other words, those who ate a diet rich in whole grains, fruits and vegetables had substantially lower risk of disease.
The unhealthful plantbased diet index had a positive association with coronary heart disease: more sweetened drinks, refined grains, potatoes and sweets, more disease.
The results track those of an earlier study in which the same researchers studied the relationship between plantbased diets and Type 2 diabetes.
“When we examined a diet that emphasized both healthy plant and healthy animal foods, the association with coronary heart disease was only slightly attenuated relative to that with the healthy plant-based diet index,” the authors wrote. “Thus … moderate reductions in animal foods … can be largely achieved by lowering intake of less healthy animal foods such as red and processed meats.”
In an editorial appearing alongside the study, Dr. Kim Allan Williams Sr. of Rush University Medical Center in Chicago translated the findings for cardiologists in the real world. Instead of pushing an “all-or-none” diet, he wrote, start with “smaller dietary tweaks.”
In other words, he wrote, quoting author Michael Pollan, “Eat food. Not too much. Mostly plants.”