Plant-Based Diets: Can They Be Too High in Carbs for Diabetes?

By Anne Danahy MS RDN


It’s no secret that eating more plants is good for everyone’s health. The nutrients and antioxidants they provide protect cells from oxidative damage and inflammation. That may in turn, reduce the risk of developing many chronic diseases, including diabetes.

However, people with prediabetes or diabetes often ask whether diets that restrict animal protein are a good choice for managing blood sugar. Or are they too high in carbohydrates? Here’s a look at some current research and recommendations for patients regarding vegetarian and vegan diets.

Research on Diabetes and Vegetarian Diets

Vegetarian diets can range from vegan, which restricts all animal foods, to those which include eggs, dairy, and occasionally fish or chicken. All types of vegetarian diets can have health benefits. In particular, research suggests that compared to people who eat more animal foods, and especially meat, vegetarians and vegans have a lower risk of developing diabetes.

In a study on nearly 3,000 Buddhists, those with a lifelong adherence to a vegetarian diet had a 35% lower risk of developing diabetes. (1)

Research on Seventh Day Adventists, who commonly follow various vegetarian diet patterns, shows that this population has 45% of diabetes rates compared to the general public. In addition, a study that followed 8,400 Seventh Day Adventists for 17 years found that among those who ate meat just once per week, the risk of developing diabetes increased by 29%. (1)

A more in-depth look into the Adventist population and their different types of vegetarian diets found that vegans had the lowest risk of developing diabetes. They were followed by lacto-ovo vegetarians, then pesco-vegetarians, and finally, semi-vegetarians who ate meat occasionally, but not daily. (2)

Research on diabetes management also supports the use of both vegan and vegetarian diets. A meta-analysis that looked at five studies on vegans and one on lacto-ovo-vegetarians found that both types of diets reduced A1c levels over an average 24-week period. (3)

Finally, a small study on 93 Asian people with diabetes compared the effects of a brown-rice vegan diet, which provided an average 76% of calories from carbohydrates and a Korean Diabetes Association diet, which averaged 64% carbohydrate. While both improved A1c levels, researchers found the vegan diet to be slightly more effective, with a more considerable reduction in A1c levels after 12 weeks. (4)

Carbohydrates in Plant-Based Foods

Often, vegetarian and certainly vegan diets are higher in carbohydrates than those that include more animal protein. However, studies have found that after adopting a vegetarian or vegan diet, glycemic control often improves, and in many cases, patients can decrease or discontinue their diabetes medication. (1)

There are several mechanisms by which vegetarian and vegan diets are effective in preventing and managing diabetes. They tend to promote weight loss, especially visceral fat, which improves insulin sensitivity. In addition, they’re often rich in soluble fiber, which slows glucose absorption. Plant foods are also high in micronutrients especially magnesium, which is associated with improved glucose metabolism.

It’s important to remind patients though, that not all carbs are created equal. The benefits of all types of vegetarian diets come from whole eating foods versus processed foods. As dietitians are aware, French fries, chips, and mac and cheese are vegetarian foods, but not beneficial for glycemic control. Thus, to achieve the benefits of a vegan or vegetarian diet, it’s essential to incorporate a wide range of vegetables, fruits, legumes, nuts, seeds, and whole grains in their unprocessed forms.

Portion size, variety, and balance are also important considerations on a plant-based diet. Whole foods often work in synergy to provide health benefits. Consuming a variety of foods at each meal ensures not only ensures a broader range of nutrients, but also a lower glycemic index and glycemic load.

Meal Planning Tips for Patients

Patients with diabetes, or who are at risk, and who are open to following a vegan or any vegetarian diet should be encouraged to do so. Still, remind them that the most effective diet to manage their glucose is one they can stick to for the long term. The following points can help patients plan healthier meals and snacks:

Encourage them to focus on adding foods rather than subtracting. Work toward incorporating more plant foods at each meal and snack, while minimizing meat first and other animal products next.

Always aim for a whole foods diet and limit processed, packaged, and fast foods as much as possible.

Eat the rainbow. Educate patients about macronutrients and ways to incorporate a variety of plant foods into meals and snacks. Doing so provides lots of color for the antioxidant health benefits, along with the right balance of protein, carbs, and fat for satiety.

Even though plant proteins like soy also contain carbohydrates, the amino acids and other micronutrients they provide can improve insulin sensitivity and glycemic control. (1)

Finally, remember the golden rule – there is no one-size-fits-all diet. That also applies to plant-based diets. If patients feel too restricted or unable to enjoy themselves when eating out, it’s OK to add animal proteins in as needed. The bottom line should be more plants, higher quality animal proteins as desired, and more balance.


1. Olfert MD, Wattick RA. Vegetarian Diets and the Risk of Diabetes. Curr Diab Rep. 2018;18(11):101. Published 2018 Sep 18. doi:10.1007/s11892-018-1070-9.

2. Tonstad S, Butler T, Yan R, Fraser GE. Type of vegetarian diet, body weight, and prevalence of type 2 diabetes. Diabetes Care. 2009;32(5):791-796. doi:10.2337/dc08-1886.

3. Pawlak R. Vegetarian Diets in the Prevention and Management of Diabetes and Its Complications. Diabetes Spectr. 2017;30(2):82-88. doi:10.2337/ds16-0057.

4. Lee YM, Kim SA, Lee IK, Kim JG, Park KG, Jeong JY, Jeon JH, Shin JY, Lee DH. Effect of a Brown Rice Based Vegan Diet and Conventional Diabetic Diet on Glycemic Control of Patients with Type 2 Diabetes: A 12-Week Randomized Clinical Trial. PLoS ONE. 2016;11(6).