Scientific Update
by Reed Mangels, PhD, RD, FADA
A Review of Recent Scientific Papers Related to Vegetarianism
Red Meat Consumption Is Associated with an Increased Risk of Type 2 Diabetes
More than 36 million people in the United States have type 2 diabetes, the most common form of diabetes. In 2021, the most recent year for which information is available, diabetes was the eighth leading cause of death in the United States. In 2022, the total estimated cost of diagnosed diabetes in the United States was $412.9 billion.1 These facts highlight the importance of identifying ways to reduce the risk of diabetes. A recent comprehensive study2 provided strong, consistent evidence that red meat consumption is associated with increased risk of type 2 diabetes.
The study included more than 200,000 U.S. participants who were followed for 25-30 years and whose diet was assessed every 2-4 years. Intake of total red meat, processed red meat (e.g., hot dogs and sausage), and unprocessed red meat (e.g., hamburgers and pork chops) were all strongly associated with an increased risk of developing type 2 diabetes. For example, when subjects were divided into five groups based on their reported red meat consumption, those who ate the most red meat had a 62% higher risk of developing diabetes compared to those who ate the lowest amount of red meat. Every serving per day increase in processed red meat consumption was associated with a 46% greater risk for type 2 diabetes; a one-serving-per-day increase in unprocessed red meat was associated with a 24% greater risk of type 2 diabetes. The researchers calculated that replacing a serving of red meat with a serving of legumes and nuts per day would be associated with a 30% lower risk of type 2 diabetes. Nuts and legumes appeared more effective as substitutes for red meat than other foods, including fish, poultry, eggs, and dairy products.
The study's authors conclude, "Our study emphasizes the importance of different alternative sources of protein [other than red meat] for type 2 diabetes prevention."
This report provides solid evidence of the benefits of eliminating red meat consumption.
1 Parker ED, Lin J, Mahoney T, et al. Economic costs of diabetes in the U.S. in 2022. Diabetes Care. 2024;47:26-43.
2 Gu X, Drouin-Chartier JP, Sacks FM, et al. Red meat intake and risk of type 2 diabetes in a prospective cohort study of United States females and males. Am J Clin Nutr. 2023;118:1153-1163.
Vegans Using a Vitamin B12 Supplement Have an Adequate Vitamin B12 Status
Vitamin B12 is not found in significant amounts in plant-based foods. Vegans need to use foods fortified with vitamin B12 and/or a supplement providing vitamin B12 to meet their needs for this essential nutrient. A recent study of German vegans, lacto-ovo vegetarians, and nonvegetarians examined vitamin B12 status of these groups. The subjects were young (over 18 years; average age was 28 years), were healthy, and had consistently followed their current diet for at least the past 24 months. There were 38 vegans, 37 lacto-ovo vegetarians, and 40 nonvegetarians. All subjects kept records of what they ate for 4 days and which supplements they used. The subjects' vitamin B12 status was assessed by measuring several different substances in their blood. As one would expect, dietary vitamin B12 intake was highest in nonvegetarians and lowest in vegans. Most vegans (almost 90%) took a supplement containing vitamin B12 with a median intake of 250 micrograms daily. Based on analysis of their blood, both vegans and nonvegetarians had an adequate vitamin B12 status. Lacto-ovo vegetarians, who were less likely to use a vitamin B12 supplement than were vegans, had a poorer vitamin B12 status. This suggests that using vitamin B12 supplements can reduce the risk of vitamin B12 inadequacy in vegans. Storz MA, Müller A, Niederreiter L, et al. A cross-sectional study of nutritional status in healthy, young, physically-active German omnivores, vegetarians and vegans reveals adequate vitamin B12 status in supplemented vegans. Ann Med. 2023;55:2269969.
Vegan and Vegetarian Diets May Offer Benefits to Sports Performance
A recent review and analysis combined results from 10 studies of plant-based diets and athletic performance. Study subjects on plant-based diets were either lacto-ovo vegetarians (6 studies) or vegans (4 studies). Three studies were of aerobic performance and seven were of strength/power performance. Aerobic performance is important for activities such as running, bicycling, swimming, and brisk walking. Strength/power performance is relevant for weight training.
Compared to nonvegetarians, vegetarians (including lacto-ovo vegetarians and vegans) showed higher aerobic physical performance and similar strength/power performance. Overall physical performance was similar between the groups. When vegans were analyzed separately, the results were similar to those for vegetarians. Vegans had higher aerobic performance, similar strength/power performance, and similar overall physical performance compared to nonvegetarians. These results provide important evidence that a vegan/vegetarian diet does not compromise sports performance and may benefit performance in some sports.
Damasceno YO, Leitão CVFS, de Oliveira GM, et al. Plant-based diets benefit aerobic performance and do not compromise strength/power performance: a systematic review and meta-analysis. Br J Nutr. 2024;131:829-840.
Dietary Guidelines for Americans Could Be Adapted for Lactating Vegans
Dietary Guidelines for Americans is a document that the U.S. government produces every five years. It is the basis for federal food policy including programs such as WIC and school meals. The most recent Dietary Guidelines, released in 2020, endorses "a Healthy Vegetarian Dietary Pattern" as one of three recommended dietary patterns. While the "Healthy Vegetarian Dietary Pattern" provides alternatives for cow's milk, it includes eggs and is not a vegan plan.
Updates for the Dietary Guidelines for Americans are in process. As a part of this process, computer modeling is being done to determine if the "healthy vegetarian dietary pattern" could be modified to meet the needs of vegans, lacto vegetarians, and others. A recent study used these modeling techniques to modify the "healthy vegetarian dietary pattern" so that it included only vegan foods and to evaluate adequacy during lactation.
In this study, the "dairy food group" was replaced with fortified soymilk and fortified soy yogurt. Eggs were replaced with a combination of beans, peas, lentils, nuts, seeds, and soy foods. Vegan patterns that supplied 2,200 and 2,400 calories per day were created and evaluated both with and without the addition of a prenatal multivitamin/multimineral supplement. The resulting vegan dietary patterns were analyzed for nutritional adequacy and compared to the original Healthy Vegetarian Dietary Patterns that contained dairy products and eggs.
All patterns, including the original Healthy Vegetarian Dietary Pattern, without the use of a prenatal supplement were quite low in vitamin D, vitamin E, and choline. The vegan pattern was also slightly below recommendations for vitamin A and zinc. When a prenatal supplement was added, only vitamin D and choline were below recommendations for all vegetarian patterns, including the vegan pattern. Iodine, an important nutrient, was not evaluated.
This study suggests that use of a multivitamin, multimineral supplement can be beneficial in lactation, depending on an individual's diet. Vegan diets can be developed to meet needs for most nutrients in lactation. This study included only fortified soy beverages and fortified soy yogurt as replacements for dairy products. Additional studies should examine the use of other fortified plant milks and determine the minimum amount of these products needed.
The results of this study and similar studies support the inclusion of vegan dietary patterns in the 2025-2030 edition of Dietary Guidelines for Americans.
Hess JM, Comeau ME, Swanson K, et al. Modeling ovo-vegetarian, lacto-vegetarian, pescatarian, and vegan USDA food patterns and assessing nutrient adequacy for lactation among adult females. Curr Dev Nutr. 2023;7:102034.
