SCIENTIFIC UPDATE

Dietary choices have a huge effect on an individual's health and on planetary well-being. The global transition to diets higher in meat, refined sugar, and processed foods has contributed to an epidemic of obesity, as well as increased greenhouse gas production, deforestation, and habitat destruction. What will happen if we continue on the path we're on? If things don't change, environmental researchers predict that by 2050 we'll see an 80% increase in greenhouse gas emissions due to food production and a reduction in life expectancy due to the increased incidence of heart disease, type 2 diabetes, and other diet-related illnesses.

Environmental researchers writing in the journal Nature predict, based on forecasts of income and current trends, that by 2050 the average diet will have fewer servings of fruits, vegetables, and plant protein and more pork, poultry, beef, eggs, dairy, fish, seafood, and empty calories. These changes will have a devastating effect on our planet. Consider that beef production results in 250 times the greenhouse gas emissions as does legume production on a per gram of protein basis.

If, instead of moving towards a diet high in animal products and processed foods, the global diet became a vegetarian or near-vegetarian diet, these researchers hypothesize that the projected 80% increase in greenhouse gas emissions could be avoided. This shift could also markedly decrease demands for land clearing. Additionally, health improvements would be expected.

Moving away from meat-based diets and towards plant-based diets can slow both planetary effects and human health effects. Every environmentalist should be promoting (and eating) a plant-based diet.

Hyperthyroidism is a condition in which the thyroid gland makes more thyroid hormone than the body needs. It affects about 1% of people and can cause a rapid and irregular heartbeat, fatigue, and weight loss. The most common cause of hyperthyroidism is an autoimmune disorder. Researchers from Loma Linda University surveyed 65,000 Seventh-day Adventists in the United States and Canada. Study participants were classified as "vegans" (eat animal products less than once a month), "lacto-ovo vegetarians" (eat fish or meat less than once a month), "pesco vegetarians" (eat meat less than once a month), "semi-vegetarians" (eat meat less than once a week but more than once a month), and "omnivores." Participants were asked if they had been diagnosed with hyperthyroidism.

"Vegans" had a 52% lower risk of hyperthyroidism compared to "omnivores." "Lacto-ovo vegetarians" and "pesco vegetarians" also had a lower risk but not as low a risk as "vegans." Semi-vegetarians' risk of hyperthyroidism was similar to that of "omnivores." Lower body weights in the "vegans" and dietary factors may explain these results, although additional research is needed.

Ovarian cancer causes more deaths than any other cancer of the female reproductive system. A recent study suggests that flavonoids are associated with a lower risk of ovarian cancer. The study involved more than 150,000 women who were studied over about 20 years. During that time, 723 women developed ovarian cancer. Women whose diets were highest in flavonoids had a modestly lower risk of developing ovarian cancer. The association between flavonoids and ovarian cancer was strongest for the more aggressive form of the disease. The main dietary sources of flavonoids in this study were black tea, onions, citrus fruits and juices, and apples. In terms of specific foods, black tea was the only individual food associated with a reduction in risk. Subjects who drank more than 1 cup of black tea per day had a significantly lower risk of ovarian cancer. These results are in accord with studies that suggested that a plant-based diet rich in fruits and vegetables was associated with a reduced risk of ovarian cancer.

In India, about 35% of the population follows a vegetarian diet, typically a lacto vegetarian diet. This rate varies by region and ranges between 10% and 62%. Most choose to eat a vegetarian diet because of religion, culture, or community; health is not as common a motivation. A study conducted in four regions of India examined more than 6,500 men and women, one-third of whom were vegetarian. In contrast to studies in the UK and the USA, vegetarians did not have a lower body mass index (BMI) and were less physically active than nonvegetarians. Vegetarians ate more fiber, vitamin C, folate, and calcium. Despite weight status that was similar to nonvegetarians, vegetarians had lower blood cholesterol, lower LDL cholesterol, lower triglycerides, lower blood pressure, and lower blood glucose concentrations. These differences may be because of better dietary practices by vegetarians.

About 11% of adults in the United States have been diagnosed with diabetes; another 35% have pre-diabetes. The most common form of diabetes is type 2 diabetes, a disease in which blood sugar (also called blood glucose) is too high. In type 2 diabetes, people's bodies do not make or use the hormone insulin well. Some studies have found that moving from a nonvegetarian to a vegetarian diet led to a reduction in blood sugar, which suggests that vegetarian diets could be helpful in preventing and treating type 2 diabetes. Researchers from the USA and Japan combined results from a number of different studies to see what effect a vegetarian diet has on blood glucose. They also looked at blood concentrations of hemoglobin A1c, which indicates how well blood glucose is controlled. The researchers combined results of 6 studies involving 255 subjects, most of whom were vegan. Overall, use of a vegetarian diet significantly reduced hemoglobin A1c, suggesting better control of blood glucose. Moving to a vegetarian diet was associated with lower intakes of calories, fat, cholesterol, and protein and higher intakes of carbohydrate and fiber. The results support vegetarian diets for the prevention and treatment of type 2 diabetes.

We've known for a long time that the mother's diet affects the fetus's development in utero. More recent research has examined long-term effects of the maternal diet. During pregnancy, it's important to get enough protein to support organ, muscle, and bone growth. However, there may not be an advantage to high protein diets in pregnancy, especially if the protein is mainly from animal sources. A recent study suggests that protein from animal sources, principally from meat products, was associated with an increased risk of obesity in offspring 20 years later. This study was conducted in Denmark in the late 1980s. Close to 1,000 pregnant women completed dietary and lifestyle questionnaires. Twenty years later, almost 70% of the women's children's BMIs were measured. Female children of the women eating the highest amount of animal protein during pregnancy had a 3 times greater risk of being overweight at age 20 than did female children of women eating the least amount of animal protein during pregnancy. Male offspring followed a similar pattern, with those whose mothers ate the highest amount of animal protein during pregnancy having a 2 times greater risk of overweight when they were 20 years old. When specific food groups were examined, meat products were associated with increased risk of overweight female offspring, and grains and cereals were associated with a decreased risk. No specific food group effects were seen in male offspring. We don't know what the children's diets and eating habits were after birth. These results are intriguing, but more research is needed to see if similar findings would occur in groups consuming higher and lower amounts of protein and to see if dietary differences persist after pregnancy.