SCIENTIFIC UPDATE

The Adventist Health Study-2 includes more than 89,000 adult Seventh-day Adventist participants whose diets range from vegan to nonvegetarian. This variety of diets allows researchers to look at food choices. Study participants are categorized based on their degree of avoidance of animal products. For example "nonvegetarians" eat meat or fish at least weekly, "lacto-ovo vegetarians" eat dairy products and eggs but eat meat or fish less than once a month, and "vegans" eat any animal products less than once a month. Perhaps not surprisingly, "vegans" ate more legumes, soy products, nuts, seeds, grains, potatoes, fruits, and vegetables than other groups. Specifically, "vegans" and fish-eaters ate more leafy green vegetables, vegetables from the cabbage family, and sweet potatoes. "Vegans" ate markedly lower amounts of sweets and snack foods compared to nonvegetarians, with "lacto-ovo vegetarians" in between. Interestingly, "lacto-ovo vegetarians" ate lower amounts of eggs and dairy than "nonvegetarians."

These results suggest that "vegans" (and to a somewhat lesser extent other vegetarians) in this population are more likely to get nutrients from a variety of sources. Their diets include a diversity of plant-based foods. Additionally, fewer unhealthy foods — sweets, solid fats, refined grains — were eaten. Food choices were similar to those recommended in Dietary Guidelines for Americans.

People choose to follow a vegan diet for different reasons. For example, some people identify their primary motivation as their own health while others report that they are motivated by concerns about animals. How do different motivations affect lifestyle choices? That's the question that researchers set out to answer in a study of 246 adult vegans. Participants completed an online survey examining their motivations, health behaviors, and food choices. Forty-five participants listed their health as their main motivation for following a vegan diet; the remaining 201 participants primarily chose their vegan diet for ethical reasons.

Groups had similar BMIs. Those citing ethical motivations were more likely to take a multi-vitamin and supplements of vitamins D and B12. They consumed more soy products and sweets. Despite differences in amounts eaten, neither group ate an excessive amount of sweets, staying below 1 serving per day on average. Those choosing a vegan diet mainly for health reasons ate more fruit and drank more juice. The ethically-based group had been vegan for a longer time period than the health-based group.

Childhood obesity is an increasingly common problem that can set children up for a lifetime of chronic health conditions. Clearly, effective treatments for childhood obesity are needed. Researchers at Cleveland Clinic and Case Western Reserve University placed obese children (age 9-18 years) and parents on either a vegan diet or the kind of diet that is prescribed by the American Heart Association. The Heart Association diet is not a vegetarian diet. Twenty-eight adult-child pairs were studied — 14 pairs on each type of diet. Each group attended cooking and nutrition classes. They followed their assigned diet for 4 weeks. Although the participants on the vegan diet were instructed to avoid all animal products, they were not always compliant; they reduced their animal protein intake significantly but did not entirely avoid animal products. Their diet had 18% of calories from fat and 3.6% from saturated fat. The group on the Heart Association diet ate more fat (25% of calories) and saturated fat (7.6% of calories).

Both groups of adults and children lost weight.The children and adults on the vegan diet also reduced blood pressure and blood cholesterol. Both types of diets received similar scores from participants on their enjoyment of the foods, overall satisfaction, and ease of preparation. Participants on the vegan diet reported more difficulty with purchasing food. Intakes of vitamins D and B12 were lower in the group on the vegan diet. If this diet was used long-term, more instruction on sources of these nutrients and advice on food shopping would be needed.

This study suggests that a vegan diet can help with weight loss and high cholesterol in obese children and adults.

Several studies have reported that, on average, vegans have a lower weight than other vegetarians or nonvegetarians. This information suggests that there may be something about a vegan diet that helps with weight control. Researchers at the University of South Carolina decided to investigate this further. They placed 50 overweight adults on a variety of plant-based diets for 2 months. Participants were randomly assigned to either a nonvegetarian diet, a semi-vegetarian diet (red meat once a meat, poultry no more than five times a week), a pesco-vegetarian diet (includes fish but no meat), a lacto-ovo vegetarian diet, or a vegan diet. They attended classes about their diet and were encouraged to avoid high-fat foods. They were not told to limit calories. After the 2 months were up, participants were encouraged to follow their diet for the next 4 months and continued to attend classes.

All groups lost weight. The vegan group lost the most weight, followed by the lacto-ovo vegetarians, the pesco-vegetarians, the semi-vegetarians, and the nonvegetarians. After 6 months, the vegan group had lost an average of 7.5% of their starting weight. Vegans had lower intakes of calories, fat, and saturated fats and higher intakes of fiber than the other groups. About half of the vegan group met the researchers' goals for complying with the guidelines for a vegan diet. This level of compliance was similar to that of other groups. All groups had low intakes of calcium, iron, vitamin D, and potassium and high intakes of sodium.

The results of this study suggest that vegan diets are an effective way to lose weight. Education about good sources of important nutrients is needed to ensure that the diets are nutritionally adequate.

Many more people are surviving heart attacks than in the past. Diet plays an important role in heart health, so heart attack survivors are often motivated to make dietary changes. We don't really know what the best diet is for heart attack survivors, although a sensible recommendation is to achieve and maintain a healthy weight. After a heart attack, some people follow low-carbohydrate diets, which can be high in animal protein and fat. Harvard researchers investigated the effects of these diets by studying more than 2200 women and 1800 men who survived a heart attack. Subjects were part of a larger study and had been asked about their diet before their heart attack and completed at least one other diet questionnaire two years later.

Use of a low-carbohydrate diet based on animal products after the first heart attack was associated with an increased risk of death from all causes and heart-related causes. A plant-based low-carbohydrate diet did not affect risk of death. In other words, a low-carbohydrate plant-based diet was no better or worse than a higher carbohydrate diet in terms of avoiding death. The researchers hypothesize that the higher saturated fat in the animal product-based low-carbohydrate diet is one reason for higher mortality in this group. They conclude, "[post heart attack] patients who intend to follow an LCD [low-carbohydrate diet] should avoid consuming mainly animal sources of fat and protein."