Do Plant-Based Diets Make You Weak?

There is a pervading belief among the general population that eating only plants and avoiding meat and other animal-sourced food products reduces physical performance.  This idea has been debunked by much analysis over the last couple of decades illustrating that, though plant-based diets may not provide advantages for athletes, neither do they confer disadvantages in strength, anaerobic, or aerobic exercise performance.  Moreover, they bring with them other major bonuses.  Plant-based diets reduce the risks of numerous chronic diseases and are healthier for the environment than diets that include animal-sourced foods (1).

Remarkably, investigations into plant-based diets are now demonstrating that they may actually be performance boosting compared to other ways of eating.   For instance, a study of elite adult endurance athletes (27 plant-based eaters (15 vegans and 12 lacto-ovo vegetarians) and 43 omnivores) discovered that, though the peak strength of all participants was similar, the VO2 max (a measurement of cardiovascular fitness) of the vegetarian/vegan group was significantly higher compared to that of the omnivores. This difference was most predominant in the female subjects with the overall aerobic capacity among the female vegetarians/vegans being 13% greater than that of the female omnivorous subjects.  The study authors concluded that following a vegetarian or vegan diet “may adequately support strength and cardiorespiratory fitness development and may even be advantageous for supporting cardiorespiratory fitness.”  (2)

Very recent research, performed in April 2020 by the Department of Exercise Science at the University of Quebec in Montreal, delved into this idea more deeply.  This exploration studied 56 healthy lean physically active women in their 20s, half of whom were vegans (eating only plant-based foods) with the other half being omnivorous (eating a mixture of plant-based and animal-based foods).  They were followed for at least two years and were tested for their body composition, maximal oxygen consumption (VO2 max), endurance and muscle strength.  All participants had a healthy BMI (Body Mass Index) of between 20 and 24 and were comparable in physical activity, percent body fat, amount of lean body mass and muscle strength.  However, the vegans showed a 6.5% increase in VO2 max and 27.9% improvement in a submaximal endurance test (prolonged activity at 70% of VO2 max) compared with the omnivores.  The study concluded that vegan diets adequately support maintenance of muscle strength and appear to be more effective for endurance performance than diets that include animal-sourced products (3).

Adding to this information, a study published in February, 2021 confirmed that obtaining dietary protein from a plant source is just as efficient for increasing muscle mass as protein derived from an animal source.   Researchers compared muscle mass in the legs of young men who were undergoing twice-weekly resistance training and following either a vegan diet or an omnivorous diet. All participants experienced similar gains in muscle regardless of the protein source (10).

What is VO2 max? Considered the gold standard for aerobic or cardiovascular fitness, VO2 max is the measurement of the maximum amount of oxygen an individual consumes during intense exercise.   VO2 max is reached when oxygen uptake remains constant despite increases in the intensity of the exercise test.  VO2 max calculates the volume of oxygen in milliliters used in one minute per kilogram of body weight (ml/kg/min).  The more oxygen used during an activity, the more energy will be generated from body cells.   In other words, VO2 max is an assessment of the efficiency of a body in obtaining oxygen from the air and delivering it to the muscles and establishes the aerobic endurance of an athlete (4,5).  In addition, research has found that VO2max is associated with lower risk of cardiovascular disease and a longer lifespan (4).

Research from 2019 digs into the reasons behind the effect of dietary choices on endurance.   These investigators begin by revealing that, contrary to popular belief, athletes are not immune to cardiac events such as atherosclerotic plaque build up in blood vessels and heart attacks.  In fact, endurance athletes in particular have shown more advanced atherosclerosis and heart muscle damage than people who are sedentary, especially as they age (6).  For instance, a study from the United Kingdom examined middle-aged and older athletes who had participated in endurance exercise such as running marathons over a time period of 18 to 44 years.  These athletes were compared to a sedentary control group of similar age, sex and low Framingham 10-year coronary artery disease risk score.  Though about 60% of all the participants did not show signs of coronary artery disease, the prevalence of atherosclerotic plaques in the male athletes was 44% while plaques were present in only 22% in sedentary male controls (7).  A study of marathon runners over 50 years of age revealed heart muscle injury whose severity could be predicted by the number of marathons they had run (8).   A 2012 review of previous studies on this topic concluded that regular moderate to high-intensity exercise for one to two hours daily has proven cardiovascular benefits.  However, extreme exercise training and regular competition in endurance events can lead to heart damage and heart rhythm disorders.  It appears that harm can result from frequent sustained elevations in heart rate, blood pressure and cardiac output which generate large quantities of free radicals, overcoming the buffering capability of the system such as available antioxidant capacity (9).

The 2019 review pointed out that plant-based diets have beneficial effects on all key contributors to cardiovascular disease including elevated blood lipids (fats), blood pressure, blood sugar and body weight.  In addition, several physiological effects of plant-based diets may be other mechanisms leading to both increased safety of endurance sports and performance advantages when athletes eat mostly plants.

Here are the key points from this review (6).

1. Plant-based diets are high in required nutritious components including ample protein covering all essential amino acids; fiber; vitamins; minerals; and phytonutrients. 

2. Plant-based diets are low in health-destructive components such as saturated fat, trans fat, cholesterol and animal-based protein.

3. Plant-based diets significantly reduce the viscosity (thickness) of blood, increase the diameter of arteries, and improve their flexibility resulting in better blood flow and superior athletic performance. These effects not only lower blood pressure but also increase the amount of oxygen delivered to tissues.  Athletic activity depends on good circulation to provide oxygen and nutrients to active muscles and to remove waste products. 

4. High blood sugar is a major contributor to atherosclerosis. Plant-based diets boost insulin sensitivity, reducing the risk of type-2 diabetes and improving control of blood sugar in individuals who have diabetes.

5. Plant-based diets reduce body fat and increase lean body mass because of their lower fat and higher fiber content. They also boost the number and activity of mitochondria, small organs within cells that are involved in energy production, thereby increasing metabolism and energy output. As well, plant-based diets support a healthier microbiome, reducing the leaking of endotoxins into the bloodstream which have a negative effect on cell metabolism.  All these effects contribute to increased aerobic capacity (higher VO2 max) and enhanced endurance.  

6. Plant-based diets promote more efficient storage of glycogen. Carbohydrate is the prime energy source for moderate and high-intensity exercise.  Glycogen, a form of carbohydrate stored in the liver and muscle tissues for use during long-term activity, is increased by the high-carbohydrate intake derived from eating plants.

7. Antioxidants and other healthful phytonutrients are found only in plants. The more plants eaten by an individual, the higher the antioxidant activity in their body.  Antioxidants are necessary to neutralize reactive oxygen species (free radicals) which result from the normal function of mitochondria and other cell components that create oxidative stress throughout the body.  The production of free radicals can be especially high during exercise.  When the number of free radicals exceed the antioxidants required to defuse them, damage is the result, increasing the possibility of atherosclerosis, cell injury and DNA mutation.  Such oxidative stress also results in muscle fatigue, reduced athletic performance and slowed recovery.  

8. Plant-based diets help reduce inflammation. Intense exercise is inflammatory, leading to muscle soreness and joint symptoms.  Eating plants has shown reductions in markers of inflammation such as C-reactive protein.  This effect may come from both the high antioxidant levels found in plants and the avoidance of the inflammatory protein and fat present in animal-based foods.

 

Summing up:

Eating a plant-based diet provides benefits in many different ways.

It supports a high level of cardiovascular fitness and increased endurance (2,3,6).

It adequately supports maintenance of muscle strength (1,2,3,10)

It protects from the possibility of harm resulting from extreme endurance sports (6).

It reduces the risk of numerous chronic diseases including cardiovascular disease, diabetes and many cancers (1).

It protects the environment through reduced use of resources and lower levels of greenhouse gas emissions compared to the raising of animals for human consumption (1).

 

 

SOURCES:

1 Lynch, H., Johnston, C., Wharton, C.  Plant-Based Diets: Considerations for Environmental Impact, Protein Quality, and Exercise Performance.  Nutrients 2018; 10(12): 1841; https://doi.org/10.3390/nu10121841

2  Lynch, H.M., Wharton, C.M., Johnston, C.S.  Cardiorespiratory Fitness and Peak Torque Differences between Vegetarian and Omnivore Endurance Athletes: A Cross-Sectional Study.  Nutrients 2016; 8(11): 726.

3  Boutros, G.H., Landry-Duval, M.-A., Garzon, M., Karelis, A.D.  Is a Vegan Diet Detrimental to Endurance and Muscle Strength? European Journal of Clinical Nutrition. April 20, 2020; https://doi.org/10.1038/s41430-020-0639-y

4  The Complete Guide To VO2 Max – Why It’s Important & How to Measure it (runnersblueprint.com)

5  https://www.verywellfit.com/what-is-vo2-max-3120097

6  Barnard, N.D., Goldman, D.M., Loomis J.F., Kahleova, H., Levin, S.M., Neabore, S., Batts, T.C.  Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports.  Nutrients. Jan, 2019; 11(1): 130.

7 Merghani, A., Maestrini, V., Rosmini, S., Cox, A.T.,  Dhutia, H. et al.  Prevalence of Subclinical Coronary Artery Disease in Masters Endurance Athletes With a Low Atherosclerotic Risk Profile.  Circulation. 2017 Jul 11; 136(2): 126-137.

8  Möhlenkamp, S., Lehmann, N., Breuckmann, F., Bröcker-Preuss, M., Nassenstein, K. et al.   Running: The Risk of Coronary Events : Prevalence and Prognostic Relevance of Coronary Atherosclerosis in Marathon Runners.   Eur Heart J. Aug, 2008; 29(15): 1903=1910.

9  O’Keefe, J.H., Patil, H.R., Lavie, C.J., Magalski, A., Vogel, R.A., McCullough, P.A.   Potential Adverse Cardiovascular Effects From Excessive Endurance Exercise.   Mayo Clin Proc. 2012 Jun; 87(6): 587–595.

10  Hevia-Larraín, V., Gualano, B., Longobardi, I., et al. High-protein plant-based diet versus a protein-matched omnivorous diet to support resistance training adaptations: a comparison between habitual vegans and omnivores. Sports Med. 2021;51(6):1317-1330. Doi: 10.1007/s40279-021-01434-9.