A review of 30 clinical trials published between 1982 and 2022, covering about 2,400 participants in many different countries, found that vegetarian and vegan diets reduced blood levels of total cholesterol levels by seven percent, the harmful LDL cholesterol by 10 percent, and apolipoprotein B by 14 percent (European Heart Journal, May 24, 2023). These blood factors are strong predictors of likelihood to suffer a heart attack or stroke, and reducing these three factors has been consistently shown to reduce risk for heart attacks in normal-weight and obese patients. Apolipoprotein B is associated with increased risk for inflammation and insulin resistance, which are major causes of heart attacks (N Engl J Med, 2017;377:1119–1131). However, most studies show that cholesterol-lowering statin drugs lower these three blood factors more than plant-based diets do (Proc of Bayl Univ Med Cent, 2000 Oct; 13(4): 351–355).
In another study, researchers followed 5,646 healthy males and females, 40–69 years of age, for 8 to 14 years and found that those on a healthful plant-based diet were far less likely to develop Type II diabetes than those on an unhealthful diet (PLoS Med, Nov 18, 2020;17). Their definition of a healthful plant-based diet was one that severely restricted refined carbohydrates, sugar, and salty foods. The healthful diets were:
• based on plant foods such as whole unprocessed grains, fruits, vegetables, nuts, legumes, tea and coffee
• low in plant foods that cause a higher rise in blood sugar, such as refined grains, potatoes, sugar-sweetened beverages, and sugar-added foods and drinks
• low in animal foods such as meat, seafood, dairy, eggs, and animal fats
Participants who followed a healthful plant-based diet lost more belly fat and had lower triglycerides, lower bad LDL cholesterol, higher good HDL cholesterol, and lower fasting blood sugar and reduced high blood pressure.
Potential Side Effects of Vegetarian and Vegan Diets
Plant-based diets help to reduce risk for heart disease, diabetes, dementia, high blood pressure, obesity, depression, and cancers of the colon, breast and prostate (Medicina (Kaunas), 2020 Feb; 56(2): 88). However, avoiding all animal foods can increase risk for nutritional deficiencies in vitamin B12, omega-3, calcium, zinc, iron, magnesium, and high-quality protein. These deficiencies can increase risk for strokes, bone fractures, hair loss, muscle wasting, skin rashes, hypothyroidism and anemia (Progress in Cardiovascular Diseases, Sept-Oct, 2022;74:2-8). Many people now include fish in their plant-based diets (Nutrients, 2020 Aug; 12(8): 2278) because short-living fish such as salmon usually do not accumulate significant amounts of heavy metals such as mercury. Many deep water fish contain healthful omega-3 fatty acids that are associated with reduced heart attack risk.
A healthful plant-based diet should include a wide variety of different vegetables, nuts, seeds, avocados, berries, and other fruits, along with lots of whole grains and legumes, and healthful oils such as olive oil. It is also healthful to eat fish as long as you avoid very large fish that live long enough to take in a lot of heavy metals such as mercury. Avoid the large fish that lead very long lives, such as shark, swordfish, king mackerel, tilefish or large tuna.