Scientific Update
A Five-Year Review of Scientific Papers Related to Veganism
By Reed Mangels, PhD, RD, FADA
Forty years ago, in 1982, a grand total of two scientific papers focusing on vegan nutrition were published; in 2021, there were 193 papers published. In the past 40 years, more than 900 scientific papers about vegan nutrition have appeared in scientific journals. With each issue of Vegan Journal, we summarize some of the recent relevant research. In this anniversary issue, we'll look at what we think is some of the most intriguing research related to vegan nutrition that has been published over the past five years.
Chronic Disease
Research shows that vegans have a lower risk of several chronic diseases compared to nonvegetarians and lacto-ovo vegetarians. Over the past five years, we've seen more use of a statistical technique called meta-analysis that allows researchers to combine results from many studies. This has produced more information about the association between vegan diets and risk of chronic diseases.
A meta-analysis of studies in which people were on nonvegetarian, lacto-ovo vegetarian, or vegan diets for at least two weeks found that those on vegan diets had the greatest reduction in blood pressure.1 Another meta-analysis determined that those choosing to follow a vegetarian (including vegan) diet had a 27% lower risk of developing diabetes compared to nonvegetarians.2 Vegetarian dietary patterns were shown to be effective in controlling blood glucose and lipids and reducing body weight in adults with type 2 diabetes and they were recommended as a technique for managing diabetes.3,4
Bone Health
The past five years saw several reports of studies of vegans and vegetarians with conflicting results. An example of this conflict was seen in studies of the risk of hip fracture in vegans. Based on results from a large observational study in the United Kingdom, researchers concluded that vegetarians had a 25% higher risk of hip fractures than did meat eaters while vegans had more than twice the risk.5 These researchers did not examine use of calcium supplement or vitamin D intake. In contrast, a study of Seventh-day Adventists living in the United States and Canada found that vegan women had a markedly higher risk of hip fracture compared to nonvegetarian women, but vegan men and lacto-ovo vegetarians did not.6 Vegan women who used calcium and vitamin D supplements did not have a higher risk of hip fractures.6 These results suggest that adequate amounts of calcium and vitamin D are important for healthy bones.
Vegan Babies and Children
There's long been a dearth of research on vegan babies and children. The past five years saw several reports from researchers in Germany who found that vegan diets can be nutritionally adequate for young children (1-3 years old), especially with the use of supplemental vitamin B12 and vitamin D and attention to good sources of calcium.7
Young vegan children had normal growth.8 Older vegan children and teens grew normally, were very likely to use vitamin B12 supplements, and had adequate intakes of most nutrients.9
Studies of infants with vegan mothers from Germany and Israel found that the infants had birth weights in an acceptable range.10,11 An important way to reduce the risk of having an infant whose birth weight is considered to be too low is to gain pregnancy weight in accordance with recommendations. And, in a review of studies of vegan and vegetarian breastfeeding, researchers found that milk of well-nourished vegan and vegetarian women was nutritionally equivalent to the breast milk of well-nourished nonvegetarian women.12
Environment
Many research studies used a variety of methods to estimate the effects of dietary choices on the environment. Vegan diets offered distinct advantages in terms of environmental effects in the production of food. For example, a study examining the connection between food choices and air quality found that the health effect of red meat production on air quality was about 10 times higher than that of nut and seed production and 15 times more than that of the production of other plant foods.13 An international collaboration reported that the food system accounts for 20-30% of global greenhouse gas emissions, most of which are from dairy and meat production.14 An examination of multiple impacts on the environment found that producing a single serving of red or processed meat has 10 to 100 times the impact that producing a serving of plant foods has on greenhouse gas emissions, land use, acidification, and eutrophication.15 These are just a few examples of the many studies that demonstrated the environmental benefits of vegan diets.
A recent review of the scientific literature related to vegetarian diets concluded, "Plant-based diets are more sustainable than diets based on animal products, since they use fewer natural resources and produce fewer GHG [greenhouse gas] emissions. Vegetarian and vegan diets provide protection against a number of common chronic diseases... Both a vegetarian and vegan diet are appropriate for all stages of the life cycle..."16
It's been an exciting five years, and we look forward to even more vegan-related research in the next five years. The Vegetarian Resource Group is grateful to the many researchers who have advanced our knowledge and understanding of vegan diets.
References
1 Lee KW, Loh HC, Ching SM, Devaraj NK, Hoo FK. Effects of vegetarian diets on blood pressure lowering: A systematic review with meta-analysis and trial sequential analysis. Nutrients. 2020;12(6):E1604.
2 Lee Y, Park K. Adherence to a vegetarian diet and diabetes risk: A systematic review and meta-analysis of observational studies. Nutrients. 2017;9(6):603.
3 Viguiliouk E, Kendall CW, Kahleová H, et al. Effect of vegetarian dietary patterns on cardiometabolic risk factors in diabetes: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2019;38(3):1133-1145.
4 Austin G, Ferguson JJA, Garg ML. Effects of plant-based diets on weight status in type 2 diabetes: A systematic review and meta-analysis of randomised controlled trials. Nutrients. 2021;13(11):4099.
5 Tong TYN, ApAppleby PN, Armstrong MEG, et al. Vegetarian and vegan diets and risks of total and site-specific fractures: Results from the prospective EPIC-Oxford study. BMC Med. 2020;18(1):353.
6 Thorpe DL, Beeson WL, Knutsen R, Fraser GE, Knutsen SF. Dietary patterns and hip fracture in the Adventist Health Study 2: Combined vitamin D and calcium supplementation mitigate increased hip fracture risk among vegans. Am J Clin Nutr. 2021;114(2):488-495.
7 Weder S, Keller M, Fischer M, Becker K, Alexy U. Intake of micronutrients and fatty acids of vegetarian, vegan, and omnivorous children (1-3 years) in Germany (VeChi Diet Study). Eur J Nutr. 2022;61:1507-1520
8 Weder S, Hoffmann M, Becker K, Alexy U, Keller M. Energy, macronutrient intake, and anthropometrics of vegetarian, vegan, and omnivorous children (1-3 years) in Germany (VeChi Diet Study). Nutrients. 2019;11(4):832.
9 Alexy U, Fischer M, Weder S, et al. Nutrient intake and status of German children and adolescents consuming vegetarian, vegan or omnivore diets: Results of the VeChi Youth Study.Nutrients. 2021;13(5):1707.
10 Ferrara P, Sandullo F, Di Ruscio F, et al. The impact of lacto-ovo-/lacto-vegetarian and vegan diets during pregnancy on the birth anthropometric parameters of the newborn. J Matern Fetal Neonatal Med. 2019;1-7.
11 Kesary Y, Avital K, Hiersch L. Maternal plant-based diet during gestation and pregnancy outcomes. Arch Gynecol Obstet. 2020;302(4):887-898.
12 Karcz K, Królak-Olejnik B. Vegan or vegetarian diet and breast milk composition-a systematic review. Crit Rev Food Sci Nutr. 2021;61(7):1081-1098.
13 Domingo NGG, Balasubramanian S, Thakrar SK, et al. Air quality-related health damages of food. Proc Natl Acad Sci U S A. 2021;118(20):e2013637118.
14 Watts N, Amann M, Arnell N, et al. The 2020 report of The Lancet Countdown on health and climate change: Responding to converging crises. Lancet. 2021;397(10269):129-170.
15 Clark MA, Springmann M, Hill J, Tilman D. Multiple health and environmental impacts of foods. Proc Natl Acad Sci U S A. 2019;116(46):23357-23362.
16 Craig WJ, Mangels AR, Fresán U, et al. The safe and effective use of plant-based diets with guidelines for health professionals. Nutrients. 2021;13(11):4144.
