Plant-Based Diets & Diabetes
By Sharon Palmer, MSFS, RDN
Today’s Dietitian
Vol. 25 No. 7 P. 26
A Guide for Prevention and Management
Plant-based diets are lush with colorful vegetables and fruits, earthy pulses, vibrant herbs and spices, and crunchy whole grains, nuts, and seeds. It’s an eating style widely recommended for a variety of health conditions, and the list now includes both prevention and treatment of diabetes. Benefits of plant-based diets in diabetes management include better glucose control, reduced need for medication, weight management, and reduced risks of complications typically associated with diabetes. Considering that type 2 diabetes is a rapidly increasing global epidemic, with approximately 422 million cases worldwide as of 2022, a plant-based diet may hold exciting promise.1
Today, a growing body of research is showing support for various types of plant-based diets in diabetes prevention and management. In fact, major health organizations, such as the American Diabetes Association, Academy of Nutrition and Dietetics, CDC, and Harvard School of Public Health, are recommending a more plant-based approach to eating for diabetes in recent recommendations.
“Healthful plant-based diets, rich in vegetables, fruits, whole grains, beans, lentils, nuts, and seeds, are powerful for lowering the risk of type 2 diabetes,” says Michelle McMacken, MD, FACP, DipABLM, executive director of Nutrition & Lifestyle Medicine at NYC Health + Hospitals, an associate professor of medicine at NYU Grossman School of Medicine, and an attending physician at Adult Primary Care Center and NYC Health + Hospitals/Bellevue. “Moreover, for people who already have type 2 diabetes, a healthful plant-based diet can not only improve blood sugar and potentially reduce the need for medications but it can lower blood pressure, cholesterol, inflammation, and the risk of serious complications such as heart disease and kidney disease.”
This new understanding of diabetes management isn’t a surprise for health professionals. After all, research shows that lifestyle, such as diet and physical activity, has the power to significantly prevent or delay type 2 diabetes, potentially send type 2 diabetes into remission, manage type 1 and type 2 diabetes after diagnosis, and reduce the risks of other chronic diseases and complications that tend to accompany diabetes. The landmark Diabetes Prevention Program found that lifestyle changes alone reduced the risk of type 2 diabetes in older adults by 71%.2
The Science on Plant-Based Diabetes Prevention
Science has supported the role of plant-based diets in lowering the risk of type 2 diabetes for years. The Adventist Health Study-2 found that when comparing diabetes incidence among five eating patterns (nonvegetarian, semivegetarian, pescatarian, vegetarian, and vegan), the more plant-based the diet, the better the protection against type 2; vegans had a 77% lower risk, and vegetarians a 54% decreased risk compared with nonvegetarians.3 Other studies looking at various types of eating patterns have confirmed similar results. In the UK EPIC-Oxford Study, vegetarians and vegans had a lower risk of type 2 diabetes compared with those who ate regular amounts of meat, or low amounts of meat, and fish.4 In a study in India that compared different diet patterns, vegetarian diets were linked with lower diabetes risk compared with nonvegetarian diets.5 And in Taiwan, a study comparing various diet patterns found a strong protective effect for vegetarian diet patterns compared with nonvegetarian diets.6 Furthermore, a recent scientific review, with evidence from nine nutrition studies that included more than 300,000 participants, showed that people who ate a mostly plant-based diet decreased their risk of diabetes by 23%.7
Health advantages have been found for a variety of plant-based eating patterns, including vegan, vegetarian, semivegetarian, and pescatarian; however, like the Adventist Health Study-2, much of the diabetes research has shown that the more plant-based, the better, in terms of benefits. But it’s not just any plant-based diet that yields the greatest effect. Research shows that if people eat a higher quality plant-based diet—less refined and focusing on whole forms of plant foods—they further improved their odds of preventing type 2 diabetes, compared with a lower-quality, more refined plant-based diet.8
Another factor behind the benefits of plant-based eating is meat reduction, in particular, red and processed meats. Research increasingly has linked these foods, especially processed meats, with increased risks of heart disease, type 2 diabetes, and certain types of cancer. A Harvard study found that eating processed meat was linked with a 42% higher risk of heart disease and a 19% higher risk of type 2 diabetes.9 Another study from China found that higher intakes of red meat significantly increased the risk of type 2 diabetes, leading the researchers to conclude that optimal diets should include more healthful alternatives to red meat, such as fish, tofu, and legumes.10
Diabetes Complications
One of the foremost goals of managing type 1 and type 2 diabetes is to help prevent devastating complications that affect health, productivity, and quality of life. An estimated 63% of people with diabetes have hypertension, 56% have dyslipidemia, 18% are obese, and more than one-half die of coronary vascular disease (especially heart disease and stroke). In addition, they suffer higher risks of Alzheimer’s and certain cancers, and have the potential for damage to organs, such as kidneys, eyes, and nerves, making diabetes a major cause of blindness and lower limb amputation.11
The American Diabetes Association encourages people to practice self-dietary management through nutrition as a key to managing diabetes and preventing complications, making it a perfect opportunity for dietitians to help guide patients to healthful eating patterns. One of the benefits of plant-based diets is that they can help reduce the risks of many of these predisposed conditions, such as obesity, hypertension, dsylipidemia, coronary heart disease, and certain cancers.12
Connections Between Diet and Diabetes
What are the underlying benefits of plant-based diets that aid in diabetes prevention and reduce the risk of complications? Three main threads connect diet with the onset of type 2 diabetes and other chronic conditions.
• Chronic inflammation. This condition is at the root of the development of type 2 diabetes, as well as other chronic diseases that correlate with type 2 diabetes. According to the CDC, chronic inflammation has been observed as an underlying condition in type 2 diabetes, in addition to obesity, mortality, hypertension, high cholesterol and triglyceride levels, coronary heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea, many types of cancer, low quality of life, mental illness, and body pain. Many of these conditions parallel the course of diabetes, and diet plays a powerful role in either promoting or reducing chronic inflammation in the body. Plant-based diets—rich in antioxidant and anti-inflammatory compounds—have a history of reducing levels of chronic inflammation.
• Weight. Excess body weight has long been known to increase the risk of type 2 diabetes. Women with a BMI of 30 have a 28 times higher risk of diabetes; and women with a BMI of 35 have a 93 times greater risk compared with normal BMI levels.13 Extra body fat promotes higher levels of hormones and inflammation, further feeding into insulin resistance and a chronic cycle in which overweight feeds into inflammation, creating damage to tissues and body organs that leads to diseases such as diabetes and heart disease. Inflammation and overweight also are linked to metabolic syndrome. Plant-based diets, which are rich in fiber and low in fat and energy, also have an established history of better weight management.
• The gut. Another avenue for diabetes protection is through the gut microbiome, as increasing knowledge shows that the gut interacts with diabetes in many ways regarding energy balance and immune function. People with overweight or obesity have a different profile of gut microbes than do lean individuals, and fecal transplants from lean people to insulin-resistant individuals have resulted in metabolic improvements. The gut microbiome also impacts insulin resistance and inflammation.14 The good news is that fiber-rich, plant-based diets have been shown to be beneficial to the gut microbiome profile.
Diabetes Management With Plant-Based Eating
The potential for using plant-based diets in diabetes management is promising. Emerging evidence that shows plant-based diets may improve diabetes management, reduce complications, and decrease the need for medications is exciting. Research conducted by Neal Barnard, MD, FACC, found that vegan diets improved beta cell function, insulin resistance, blood glucose, and cholesterol levels and that those with type 2 diabetes were able to get off oral medications and insulin after 25 days on a program that included plant-based eating and physical activity.15
“The exciting news for people with prediabetes or type 2 diabetes is that they may be able to turn back the clock on their diabetes diagnosis if they follow a plant-based eating plan,” says Toby Smithson, MS, RDN, CDCES, diabetes lifestyle expert for DiabetesEveryDay.com and author of Diabetes Meal Planning and Nutrition for Dummies. “There are observational studies showing that those who follow a plant-based diet have a lower risk of prediabetes and type 2. And for those who are diagnosed with prediabetes or type 2 diabetes, there’s potential for remission of diabetes.”
How do plants help manage diabetes? It’s clear that plant nutrients and compounds, such as fiber, vitamins, minerals, healthful fats, phytochemicals, and low-glycemic carbohydrates can work both individually and synergistically to provide health benefits for those with diabetes. These plant-rich diets promote healthier weight and waist circumference, better glucose control, reduced levels of inflammation, greater insulin sensitivity, lower levels of blood pressure and cholesterol, and decreased risks of disease development and progression. In particular, plant foods’ rich cache of fiber, phytochemicals, antioxidants, and magnesium promotes insulin sensitivity.16
In addition, plant-based diets low in animal foods, such as red and processed meat, are naturally lower in saturated fat, dietary cholesterol, sodium, and compounds associated with the cooking, curing, and processing of meats, such as N-nitroso compounds, heterocyclic amines, polycyclic aromatic hydrocarbons, glycation end products, trimethylamine N-oxide, and heme iron.
Another important factor is fiber, which feeds the gut microbiome and has many positive effects on the immune system, weight, inflammation, blood glucose control, and heart health. Studies have shown that low-fiber diets are linked with the development of type 2 diabetes, and a high-fiber diet, particularly with soluble fiber, improves glucose control, decreases hyperinsulinemia, and lowers LDL cholesterol levels in people with type 2 diabetes.17 The CDC now states that fiber is important in helping manage diabetes because of its powerful blood glucose control benefits. Carbohydrate foods high in fiber produce slower rises in glucose levels, as these foods take longer to break down during digestion. In addition, the CDC recognizes fiber’s role in heart health, gut health, and weight management—all important in managing diabetes. Most Americans fall short on fiber intake, getting only about 15 g per day. The official recommendation for adults is 20 to 30 g per day; however, there are benefits in aiming for even more, in the range of 40 g per day, for diabetes management. Getting more fiber-rich foods in the diet, such as pulses, whole grains, fruits, vegetables, nuts, and seeds is an important strategy.
Assembling the Plate
Given this new focus on plant-based eating for diabetes prevention and management, how can dietitians help clients and patients find success? Diabetes experts Jill Weisenberger, MS, RDN, CDCES, CHWC, FAND, author of Prediabetes: A Complete Guide, Second Edition, and Smithson offer the following guidance.
• Match strategies with patients. Are there certain patients that do better on plant-based diets? “As a registered dietitian and certified diabetes educator, I encourage plant-based eating to all my patients who have been diagnosed with diabetes, whether it’s prediabetes, type 1, or type 2 diabetes,” Smithson says. “Some patients have already begun including more plants, such as fruits, vegetables, and whole grains, into their eating plan, while others are looking for guidance on how to incorporate more plant protein sources into their eating plan.”
Weisenberger agrees: “I recommend plant-focused—not vegan or vegetarian—to all the people I work with because of the important nutrients and phytonutrients in plant foods that help with inflammation, insulin sensitivity, cancer prevention, and more.”
• Managing carbohydrate levels. Creating a more balanced plate with plant-based food sources that have higher carbohydrate levels is key. “When following a plant-based eating plan to manage diabetes, it’s all a matter of balancing your food selections,” says Smithson, who manages her own type 1 diabetes with a plant-based diet. “Since some of the plant-based choices are higher in carbohydrate content, adding lower-carb side dishes will help balance the amount of carbs per meal. For instance, if you’re eating a serving of black bean chili at lunch, balance your plate with side dishes of lower-carb vegetables like steamed green beans, a leafy green salad, roasted broccoli, or sliced tomatoes.”
Weisenberger says, “Many [people] are hesitant because they think they need to limit their carbohydrate intake too much [in order] to replace any of their animal-based options with plant-based options. I can ease them in with tofu and edamame beans because they’re lower in carbohydrate than more plant-based proteins. And I can often ease people into pulses by suggesting they add a spoonful to a green salad or mix them into chili and tacos.”
According to Smithson, “it will be trial and error” for patients taking insulin to determine “the correct dosing of insulin to carb ratio until they see a blood glucose pattern.” She says, “Personally, with managing my own diabetes, I monitor my blood glucose patterns and add two servings of vegetables with lunch and dinner to help with the carbohydrate distribution balance and help me feel satiated,” Smithson says.
• Offer diet tips and strategies to help clients manage their disease through plant-based eating. “First, start off with the plant-based meals you already eat and like,” Weisenberger says. “Add them into rotation more often. Try one new recipe every week or every other week until you have a large collection of recipes you like. If they want to boost their protein without raising their carb counts so much, I recommend more tofu and edamame beans, and I recommend combining animal and plant proteins. For example, I often eat beans and lentils with a dollop of Greek yogurt.”
Smithson says, “Plant food choices with fiber, such as nuts, seeds, beans, oatmeal, and other whole grains, can help slow down the absorption of carbohydrate, offering the benefit of a slower rise in blood sugar levels. These foods can help keep blood sugar levels steady and improve insulin sensitivity,” adding that some fruits and vegetables, such as leafy greens, root vegetables, blueberries, and grapes, have been shown to lower the risk of diabetes.
Smithson says dietitians and clients currently use total grams of carbohydrate as their guide and don’t subtract fiber from the total grams of carbohydrate. “As dietitians and certified diabetes care and education specialists, we encourage our patients to consume a diet high in fiber. On packaged goods, the term ‘net carbs’ is often used, but the American Diabetes Association cautions that subtracting fiber or sugar alcohols is not reliable. Subtracting fiber from the total carbohydrate content should not be used when calculating grams of carbs consumed. Remember, one person may not digest food the same as the next person. We need to rely on blood glucose patterns when tweaking the insulin-to-carb ratio or consuming an amount of total carbs at a meal.”
If patients measure their blood sugar levels at home, Weisenberger also recommends they do it more often before meals and two hours after meals, so they can see the effect of what they just ate. She adds, “Typically, people make more than one change at a time. They may improve their overall diet, add some exercise, and become more regular with meals or medications, so the changes add up and they can get a lot of positive feedback.”
• Discuss extra bonuses. The advantages of plant-based eating for patients with diabetes can expand in different directions. “Plant-based eating can cause a positive domino effect for people with diabetes,” Smithson says. “Consuming meat and meat products increases sleep disruptions, including sleep apnea. Improving sleep is very important for all people, but also has a key role in diabetes management. When a person with diabetes has nights of poor sleep, they often will see higher fasting blood glucose levels due to an increase in cortisol and increase in stress. If a plant-based plan is consumed as part of a balanced meal plan, it will provide a variety of vitamins, minerals, antioxidants, and phytochemicals, which in turn will reduce oxidative stress and improve immunity.”
— Sharon Palmer, MSFS, RDN, is The Plant-Powered Dietitian, author of the new book The Plant-Powered Plan to Beat Diabetes, nutrition editor of Today’s Dietitian, and cofounder of the nonprofit organization Food + Planet.
References
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