Scientific Update

By Reed Mangels, PhD, RD, FADA

More Beans Could Mean a Reduced Risk of Type 2 Diabetes

Type 2 diabetes is the most common form of diabetes, affecting around 9% of people in the United States. This form of diabetes is often linked with being overweight and not getting much exercise. A recent study suggests that people who eat more beans are at a lower risk for developing type 2 diabetes. This study was conducted in Spain and involved 3,349 older men and women who did not have diabetes, but who had a higher risk for heart disease because of their weight, blood pressure, blood cholesterol, family history of heart disease and/or smoking. Study participants were asked about their current diet and were divided into groups based on the amount of beans (not including soy products) they ate each day. The group eating the most beans averaged about an ounce of dry beans daily. The groups were studied for an average of 4 years to see who developed type 2 diabetes. The group eating the largest amount of dried beans and peas had about a one-third lower risk of developing type 2 diabetes, compared with the group eating the lowest amount of beans. When specific types of beans were examined, lentils had the largest effect with a 33% reduction in risk of type 2 diabetes in those eating the largest amount of lentils. The researchers also investigated what would be likely to happen if beans were used to replace other foods. They estimated that replacing half a serving per day of eggs with half a serving per day of beans would reduce the risk of type 2 diabetes by about 50%. Eating more beans and less rice or baked potatoes also appeared to reduce risk. This study suggests that eating at least an ounce of dried beans (about a scant half cup of cooked beans) is associated with a reduced risk of type 2 diabetes.

Becerra-Tomás N, Díaz-López A, Rosique-Esteban N, et al. Legume consumption is inversely associated with type 2 diabetes incidence in adults: A prospective assessment from the PREDIMED study. Clin Nutr. 2017 Mar 24. [Epub ahead of print]

Benefits of Plant Protein

A condition called "metabolic syndrome" is associated with an increased risk of heart disease and type 2 diabetes. People are diagnosed with metabolic syndrome if they have 3 or more of these conditions: high blood glucose, abdominal obesity, high triglycerides, low HDL-cholesterol, and high blood pressure. Various dietary changes have been tried to reduce the severity of conditions associated with metabolic syndrome. One technique is to increase dietary protein to promote satiety (feeling of content after eating) and to slow the increase in blood glucose that occurs after a meal. A recent study examined whether there are advantages to plant-based protein compared to animal-based protein. This study used results from 123 published research studies. Plant-based protein sources, especially from soy-based sources appear to be more effective than animal-based protein sources in reducing cholesterol and LDL (bad) cholesterol. Plant protein sources are associated with blood pressure reduction; no change in blood pressure occurred with animal proteins. Type of protein source did not affect weight or blood glucose.

Chalvon-Demersay T, Azzout-Marniche D, Arfsten J, et al. A systematic review of the effects of plant compared with animal protein sources on features of metabolic syndrome. J Nutr. 2017;147:281-292.

Weight Loss without Counting Calories

Can a mostly vegan diet be an effective way to lose weight and reduce the risk of heart disease and diabetes? That's the question that researchers in New Zealand set out to answer. They began their study by inviting obese or overweight adult patients from a general medical practice who had diabetes, heart disease, or high blood pressure to participate in a 6-month study. The 60 or so eligible participants were either placed in a group that was told to follow a "low-fat, plant-based diet" or a control group receiving their usual care. The group that was told to follow the diet attended 4 hours of classes a week for 12 weeks where they learned about cooking and eating out while following their diet. They were told to follow a diet that included whole grains, beans, fruits, and vegetables. They were told to avoid all animal products, high fat foods, and highly processed foods. There was no calorie restriction and subjects were told to eat until they were full. Subjects kept records of what they ate and were found to have 1-3 "indiscretions" a month where they failed to follow the diet instructions. Overall, the subjects on the plant-based diet lost an average of 26 pounds in 6 months. The control group did not lose weight. The diet group also had a greater reduction in medication use and reported higher self-esteem. They reported that "not being hungry" helped them to comply with the diet. This study suggests that a vegan diet with an emphasis on whole foods can be an effective way to lose weight without counting calories or restricting the amount of food eaten.

Wright N, Wilson L, Smith M, Duncan B, McHugh P. The BROAD study: A randomised controlled trial using a whole food plant-based diet in the community for obesity, ischaemic heart disease or diabetes. Nutr Diabetes. 2017;7(3):e256.

Vegetarians and Gallbladder Disease

Gallstones are hard particles that develop in the gallbladder, an organ in the abdominal area. When gallstones block the tubes (ducts) that connect the gallbladder to other organs, people experience pain and are said to be having a gallbladder attack. Surgery may be needed to remove the gallbladder. Those at risk for developing gallstones include women, older adults, and those with a family history of gallstones. Being obese, losing weight rapidly, and eating a low fiber diet is also associated with an increased risk of gallstones.

What about being vegetarian? Several small studies have found either no difference in risk or a lower risk of symptomatic gallbladder disease in vegetarians. A recent large study of vegetarians in the UK had different results. This study examined close to 50,000 adults, about one-third of whom were vegetarian. They were studied for almost 14 years to see who developed gallbladder disease. Vegetarians were those who said that they never ate meat or fish. Among both vegetarians and nonvegetarians, those with the highest body mass index (BMI) had the highest risk of developing symptomatic gallbladder disease. When statistical adjustments were made to control for BMI, vegetarians were at a moderately higher risk (~22%) of developing symptomatic gallbladder disease than were nonvegetarians. Differences in risk between vegans and lacto-ovo vegetarians were not reported. The study authors were unable to determine why this increased risk was seen. Although these results will need to be confirmed by other studies, this study suggests that following a vegetarian diet will not prevent gallbladder disease, especially in those who are overweight or obese.

McConnell TJ, Appleby PN, Key TJ. Vegetarian diet as a risk factor for symptomatic gallstone disease. Eur J Clin Nutr. 2017. [Epub ahead of print]

Healthy vs. Less Healthy Plant Foods

A recent study compared the risk of developing type 2 diabetes in those eating more plant foods than animal foods and in those eating more "healthy plant foods" compared to those eating "less healthy plant foods." Researchers developed a "plant-based diet index," a "healthful plant-based diet index," and an "unhealthful plant-based diet index." Healthy plant foods included whole grains, beans, fruits, vegetables, nuts, and vegetable oils. Less healthy plant foods were identified as fruit juices, sugary desserts, sugar-sweetened beverages, refined grains, and potatoes. The eating habits of more than 200,000 men and women were scored so that they received more points for higher consumption from each food group. Participants were followed to see who developed type 2 diabetes. In this study, a "plant-based diet" is not a vegetarian diet but is a diet that is higher in plant foods. Compared to those eating a more animal-based diet, those scoring high on the plant-based diet index had about a 20% lower risk of developing type 2 diabetes. Those eating more healthy plant foods had a 34% decrease in the risk of type 2 diabetes while those eating less healthy plant foods had a 16% higher risk. These results suggest that there are benefits to choosing healthier plant foods as well as to choosing plant foods in preference to animal products.

Satija A, Bhupathiraju SN, Rimm EB, et al. Plant-based dietary patterns and incidence of type 2 diabetes in US men and women: results from three prospective cohort studies. PLoS Med. 2016 Jun 14;13(6):e1002039.