People with type 2 diabetes (T2DM) have a metabolic abnormality called insulin resistance in which body tissues respond sluggishly to the hormone insulin. This leads to high blood sugar and abnormal blood fat levels. People with T2DM commonly have high levels of triglycerides and "bad" cholesterol, or low-density lipoprotein, and low levels of "good" cholesterol, or high-density lipoprotein. High blood sugar along with blood fat abnormalities increases the risk of heart disease and stroke among people with diabetes 2- to 4-fold, warns the American Heart Association. Fortunately, both blood sugar and blood fat levels can be improved with diet. The American Diabetes Association (ADA) recommends individualized nutrition plans that meet certain guidelines rather than specific diets. Calorie restriction is important, however, for people with T2DM who are overweight.
A Mediterranean diet refers to eating patterns of olive-growing countries along the Mediterranean sea, such as Spain, Greece and southern Italy. The diet emphasizes consumption of olive oil, fruits, vegetables, beans, grains, nuts and seeds. Moderate intake of poultry, fish, seafood, eggs, cheese and yogurt also characterizes the diet, while intake of red meat and sweets is limited. Wine with meals is common with a traditional Mediterranean diet, but may not be included if weight loss is a goal.
An August 2015 "BMJ Open" article reviewed the pooled evidence from published research examining the effects of the Mediterranean diet on T2DM and prediabetes management. The authors reported that several studies showed the diet significantly reduced total cholesterol and increased HDL. Several studies also showed that following a Mediterranean diet led to weight loss, which itself is a factor in lowering cholesterol. One reason the diet may be helpful is the abundance of omega-3 fatty acids found in some fish, oil and nuts. Omega-3 fatty acids have proved to lower triglycerides, although they might cause a slight increase in LDL.
Vegan and Vegetarian Diets
Vegetarian diets include primarily plant-based foods but allow nonmeat animal products, such as eggs, butter and cheese. Vegan diets include only plant-based foods. Both have been found to lower cholesterol levels in people with diabetes. A low-fat, vegan diet improved cholesterol in people with T2DM more than a diet based on ADA guidelines, according to an August 2006 "Diabetes Care" article. At the end of a 22-week study, LDL dropped 21.2 percent in people who followed a diet of vegetables, fruits, grains and legumes without calorie restriction, compared to a 10.7 percent decline in those following the ADA diet. Blood sugar decreases and weight loss were also greater in people following the vegan diet. However, in reviewing 6 studies on vegan and vegetarian diets, the ADA concluded that they only show consistent benefits with calorie restriction and weight loss.
Part of the benefit of vegan and vegetarian diets is thought to relate to increased intake of soluble fiber, which has a cholesterol-lowering effect. Additionally, intake of cholesterol and saturated fats is greatly reduced with these diets. According to the Academy of Nutrition and Dietetics, well-planned vegetarian and vegan diets can be nutritionally complete and healthy -- and beneficial for prevention and treatment of many diseases, including diabetes.
Because carbohydrates affect blood sugar levels, restricting dietary carbs is one approach to nutritional management and weight-loss plans for T2DM. There are many low-carbohydrate diets with variable levels of carb restriction. The South Beach and Zone diets are examples of moderately restrictive low-carbohydrate diets. Very-low-carbohydrate diets, such as the Atkins and Paleo diets, severely restrict carbohydrates to trigger a metabolic state called ketosis, in which the body burns fat for fuel instead of blood sugar.
According to the ADA, low-carbohydrate diets for weight loss may be effective for up to 1 year and are consistent with its guidelines for maintaining healthy cholesterol levels. An October 2012 "American Journal of Epidemiology" article pooled results from 23 studies comparing low-carbohydrate to low-fat diets. The researchers found that people on low-carb diets had greater reductions in total cholesterol, LDL and triglycerides, and more significant increases in HDL. However, the ADA recommends that people with diabetes on a low-carb diet have their blood fat levels, kidney function and protein intake monitored.
Nutritional therapy is a cornerstone of diabetes management. The ADA recommends that everyone with T2DM undergo nutritional counseling with a qualified nutritionist. This is essential to ensure your nutrition plan meets all of your medical needs. It's also important to consult with your healthcare provider before changing your diet because altering your eating patterns may require an adjustment in your diabetes medications.
- Diabetes Care: Triglycerides and HDL Cholesterol: Stars or Second Leads in Diabetes?
- Diabetes Care: American Diabetes Association Standards of Medical Care in Diabetes -- 2016
- BMJ Open: A Journey into a Mediterranean Diet and Type 2 Diabetes: A Systematic Review with Meta-Analyses
- Advances in Nutrition: Mediterranean Diet and Cardiovascular Health: Teachings of the PREDIMED Study
- Diabetes Care: A Low-Fat Vegan Diet Improves Glycemic Control and Cardiovascular Risk Factors in a Randomized Clinical Trial in Individuals With Type 2 Diabetes
- Journal of the American Dietetic Association: Position of the American Dietetic Association: Vegetarian Diets
- South Beach Diet: What Can I Eat?
- Dr. Sears Zone Labs: The Zone Diet
- Atkins: The Benefits of a Low Carb Diet: How Does Atkins Work?
- Journal of Diabetes Science and Technology: The Beneficial Effects of a Paleolithic Diet on Type 2 Diabetes and Other Risk Factors for Cardiovascular Disease
- American Journal of Epidemiology: Effects of Low-Carbohydrate Diets Versus Low-Fat Diets on Metabolic Risk Factors: A Meta-Analysis of Randomized Controlled Clinical Trials
- Diabetes Care: n-3 Fatty Acids in the Treatment of Diabetic Patients: Biological Rationale and Clinical Data
- Diabetes Care: Nutrition Recommendations and Interventions for Diabetes -- A Position Statement of the American Diabetes Association
- Diabetes Care: Nutrition Therapy Recommendations for the Management of Adults With Diabetes
- Journal of the American Dietetic Association: A Dietary Quality Comparison of Popular Weight-Loss Plans
- American Heart Association: Cardiovascular Disease and Diabetes