1. Introduction:

3, The Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine have determined that “the performance of, and recovery from, sporting activities are enhanced by well-chosen nutrition strategies” [ 1 ]. In this review, we examine physiological effects of plant-based diets that present potential safety and performance advantages in endurance sports. These include improvements in cardiovascular risk factors, improved blood flow, leaner body composition, reduced oxidative stress, reduced inflammation, and improved glycogen storage, among others. Several studies have shown that plant-based dietary patterns have particular benefits for heart health. A low-fat, vegetarian diet, along with other healthful lifestyle changes, has been shown to reverse arterial plaque [ 2 4 ]. Compared with meat eaters, vegetarians are 32% less likely to develop coronary heart disease [ 5 ]. In this review, the terms “plant-based” and “vegan” will be used interchangeably to refer to a diet without animal-derived products. Variants of vegan diets, e.g., vegetarian diets that may include dairy products or eggs, will be identified when relevant.

Arterial changes that contribute to atherosclerosis can begin early in life, even in utero [ 6 ]. By age 10 to 14 years, the majority of American children have fatty streaks in the left anterior descending coronary artery, and more than five percent have more advanced coronary disease [ 7 ]. Autopsies of U.S. soldiers who died in the Korean War revealed severe coronary atherosclerosis (75% to 90% narrowing) in 6.4% at a mean age of 20.5 years [ 8 ]. A similar study of autopsies of soldiers who died in Operations Enduring Freedom and Iraqi Freedom/New Dawn between October 2001 and August 2011 showed that, at a mean age of 25.9 years, 8.5% had coronary atherosclerosis [ 9 ]. By age 20, approximately 10% of the population in developed countries have advanced atherosclerotic lesions in the abdominal aorta, reducing blood flow and contributing to disc degeneration and lower back pain [ 10 ].

p = 0.009) [ Athletes are not immune to atherosclerosis or to cardiac events [ 11 ]. Surprisingly, endurance athletes may have more advanced atherosclerosis and more myocardial damage, compared with sedentary individuals, particularly as they age. In a 2017 study in the United Kingdom, coronary plaques were found in 44% of middle-aged and older endurance athletes engaged in cycling or running, compared with 22% of sedentary controls (= 0.009) [ 12 ]. Similarly, a study of 50 men who had run at least 25 consecutive Twin Cities Marathons (Minneapolis, MN, USA) found the runners to have increased total plaque volume, calcified plaque volume, and non-calcified plaque volume, compared with 23 sedentary controls [ 13 ]. In a study of active German marathon runners ≥ 50 years of age, myocardial damage, as measured by magnetic resonance imaging, was found in 12% of active runners, compared with 4% of sedentary controls [ 14 ]. The degree of myocardial damage was predicted by the number of marathons run [ 15 ].

Sports-related sudden cardiac deaths are uncommon, but increase with age. In older athletes, these deaths are typically attributable to coronary artery disease (more than 80% of cases), with additional cases attributable to hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, myocarditis, and valvular heart disease [ 16 ].

These studies show that well-trained athletes are at significant risk for atherosclerosis and myocardial damage. What they do not show is whether these changes are the consequences of athletic activity or of the foods often used to fuel it. To the extent that increased consumption of animal products supplies the energy for increased athletic activity, their saturated fat and cholesterol and relative absence of antioxidants and fiber may contribute to atherosclerotic changes.

Apart from increasing the risk of cardiac events, atherosclerosis may also narrow arteries to the legs, the brain, and other parts of the body, reducing blood flow and potentially impairing performance. While this is particularly evident in diagnosed peripheral artery disease [ 17 ], it may also be a factor, at least theoretically, for athletes with subclinical atherosclerotic disease.

Plant-based diets address key contributors to atherosclerosis: dyslipidemia, elevated blood pressure, elevated body weight, and diabetes, each of which is briefly discussed in the following paragraphs.

Regarding plasma lipids, dyslipidemia is a major contributor to arterial disease and is promoted by diets rich in saturated fat and, to a lesser degree, dietary cholesterol, as noted above. Dairy products and meat are the leading sources of saturated fat, and exclusion of these products predictably improves plasma lipid profiles [ 18 ], an effect that can be accentuated by the specific inclusion of soluble fiber (e.g., oats, barley, or beans), soy protein, almonds, and sterol-containing margarines. Combining these elements in a “portfolio” diet, University of Toronto researchers lowered low-density lipoprotein cholesterol levels by nearly 30 percent in four weeks [ 19 ]. Animal products are not the only offenders. Trans fats also have harmful effects on plasma lipids and pose cardiovascular risks [ 20 ].

Regarding blood pressure, vegan and vegetarian diets reduce both systolic and diastolic blood pressure, which appears to be a consequence of reduced blood viscosity, increased blood potassium, and weight loss [ 21 ]. Lower blood pressure reduces the risk of atherosclerotic changes.

Obesity is a risk factor for cardiovascular disease. Vegetarian, especially vegan, diets reduce body fat, even in the absence of intentional limitations on calories or portion sizes [ 22 ].

Regarding glycemic control, plant-based diets boost insulin sensitivity [ 23 ]. This is important for reducing the risk of type 2 diabetes and improving glycemic control in individuals with diabetes, which is a major contributor to atherosclerosis.