Veggie diet beats vegan for diabetes prevention benefits

Including dairy in your diet may help control blood sugar levels better than a plant-only diet, a new study has found.

The study, published in Clinical Nutrition, included 30 people who followed either a lacto-vegetarian diet (plant foods plus dairy) or a vegan diet (plant foods only). Results showed that people following the lacto-vegetarian diet had lower average blood sugar levels compared to those on the vegan diet after adjusting for age, sex, body mass index, and baseline glucose concentrations.

Professor Vimal Karani, lead author of the research at the University of Reading, said: “People eating the vegan diet had more of a substance called phenylalanine after meals. When there's too much of this substance, it might make it harder for the body to use sugar properly. On the other hand, people eating dairy had different helpful substances in their blood. This might be why their blood sugar stayed more steady throughout the day.

“This research is particularly important for India, which has the second-largest diabetes population in the world. 101 million people have type 2 diabetes and 136 million people have prediabetes in India, so finding diets to improve blood sugar control could help reduce this growing health problem.”

Lower blood sugar levels for veggies

Researchers from the University of Reading and Madras Diabetes Research Foundation conducted a 14-day trial comparing two different diets in healthy adults. The diets were identical in calories, protein and carbohydrates. The only difference was that one included dairy products (about 558g daily—mostly milk with some yogurt and cheese) while the other used plant alternatives like soy milk and tofu.

The research team used special sensors attached to participants' arms to track blood sugar levels every 15 minutes for two weeks. This technology allowed them to see detailed patterns that wouldn't be visible with standard blood tests.

Blood tests showed that the dairy group had higher levels of acetyl carnitine, a compound that helps cells use fat for energy and reduces oxidative stress—the cell damage that can occur when blood sugar is too high. This protective effect may explain why the dairy group maintained lower and more stable blood sugar levels.

The vegan group had increased levels of phenylalanine—an essential amino acid found in protein-rich foods that can interfere with how the body processes sugar when levels are too high. These findings may explain why previous studies have shown that people who regularly consume dairy products tend to have lower rates of type 2 diabetes.

Zhu, X., Gayathri, R., Manasa, V.S., Abirami, K., Bhupathiraju, S.N., Anjana, R.M., Givens, D.I., Wijeyesekera, A., Sudha, V., Mohan, V., Vimaleswaran, K.S. (2025). Effects of lacto-vegetarian and vegan diets on glycemic responses and metabolite profiles in healthy adults: A randomized trial using continuous glucose monitoring and targeted metabolomics. Clinical Nutrition, 49, 138-148. https://doi.org/10.1016/j.clnu.2025.04.018