In a recent systematic review published in nutrition journalResearchers evaluated the effects of vegetarian and omnivorous diets on exercise performance.
study: The relationship between vegetarian diet and sports performance: A systematic review.. Image credit: ME Image/Shutterstock.com
background
Saul Jiguez and Novak Djokovic are popular soccer and tennis players who have adopted a vegetarian diet. Even among vegetarians, different groups such as lactovegetarians, ovoloctovegetarians, and vegans vary widely in their calorie and fiber intakes, as do omnivorous diets.
The American Dietetic Association has proven that plant-based diets improve health and prevent medical conditions. However, nutritional deficiencies remain possible, especially deficiencies in vitamin B12, zinc, iron, calcium, omega-3 fatty acids, and protein.
Athletes need a balanced, nutritious diet that supports performance and overall health. For example, iron delivers oxygen to your muscles, so you need large amounts of non-heme iron (an essential micronutrient), especially when taken with fortifying agents like vitamin C and citric acid.
Additionally, their diet should provide enough calories to perform sports, taking into account their total energy requirements based on sport, basal metabolism, and the thermogenic effect of food.
You may also need to supplement with vitamin D, which is directly related to musculoskeletal system function, and vitamin B12, which is essential for immune system function.
Protein intake from legumes, seeds, nuts, whole grains and fats is also highly recommended for those engaged in strength sports.
Overall, vegetarian athletes need a well-planned diet with the right combination of foods to achieve high performance. Therefore, it would be interesting to know how exercise capacity changes as a function of diet.
About research
First, the researchers combed the Web Of Science, PubMed, Cochrane, and Dialnet databases using the keywords “vegetarian diet,” “vegan diet,” “performance,” “sports,” and “exercise.” Searched for.
The initial search returned 933 studies, of which 903 remained after removing duplicates. Further refinement of the search left 141 clinical trials and randomized clinical trials (RCTs) published in English and Spanish.
These studies were published between 2013 and 2023 and described the relationship between diet and sports performance using a placebo or control group. In addition, women of working age who underwent cytokine analysis and physical therapy were included.
We then thoroughly reviewed the titles and abstracts of the six studies that met our inclusion criteria. They conducted a qualitative analysis of these six studies using the PEDro scale. This is an 11-item scale based on the Delphi checklist, with a maximum score of 10 points and a minimum score of 0.
The PEDro scale helped assess the methodological quality, results, design, source of subjects, and presence of randomization, blinding, and concealment of included studies. Studies with scores of 9–10, 6–8, and 5 were of excellent, good, and fair quality, respectively.
Furthermore, the present systematic review and meta-analysis was assessed for risk of bias according to the Cochrane Handbook 5.1.0.
result
The six studies analyzed in this systematic review involved 3,363 participants, of whom 1,921 were women and 1,442 were men. Among the female athletes, 543, 652, and 726 were vegetarian, vegan, or omnivorous. Similarly, out of 1,442 male athletes, 305, 352, and 785 were vegetarians, vegans, and omnivores, respectively.
Five of the six studies presented groups of athletes consuming a vegetarian or vegan diet, and the control group included athletes consuming an omnivorous diet. The sixth observational study compared participants according to their diet and sports, including 10km races, half marathons, and full marathons. Additionally, five studies were of good quality and one of fair quality according to the PEDro methodological quality scale.
Assessing the influence of diet on athletes’ performance in various endurance tests revealed that for races shorter than 21km, male and female athletes on a vegan diet performed the most endurance tests. (14% and 10%, respectively). Meanwhile, in the half marathon, 32% of male vegans and 43% of female vegetarians performed the most tests.
On the contrary, 60% of male athletes and 37% of female athletes on omnivorous diets completed the most endurance tests during marathon or ultramarathon events.
Female half-marathon runners had the best health status, followed by marathon and ultra-marathon runners. However, as the distance increased, male runners’ physical strength decreased.
A vegetarian diet protects athletes from degenerative and inflammatory diseases and improves body composition, a factor directly related to athletic performance.
The three indicators of body composition are body weight, lean body mass, and fat mass. Vegetarian athletes weighed 11% more than omnivores, while lactovegetarians who consumed dairy products weighed 7.3% less than omnivores.
Vegetarian athletes were 11.1% more likely to be of “normal weight” according to World Health Organization (WHO) standards, or a body mass index (BMI) of 18.5 to 25 kg/m2.
Additionally, their lean muscle mass was 7% lower than omnivorous athletes. Interestingly, fat mass differed depending on the athlete’s gender. The results showed that omnivorous female athletes had 1.4% more fat than their weight based on body weight, while men showed no such variation.
Furthermore, the results suggested that athletes eating an omnivorous diet reported better psychological well-being and social relationships. However, the differences were small.
When it comes to sports performance, research analysis showed that vegetarians had higher diet and exercise compliance than omnivores (55% vs. 32%).
Additionally, vegetarian athletes performed better in endurance sports, as reflected by higher maximal oxygen consumption (VO2máx) on incremental cycle ergometer tests performed at submaximal intensities.
For strength training exercises such as shoulder press exercises and quadriceps extensions, 1RM techniques did not show any significant differences in vegetarian athletes compared to omnivores.
However, ovolactovegetarian athletes saw a 21 W increase in muscle strength during a 1-hour test at 60% of their maximum heart rate.
Macronutrient oxidation is another important indicator of sports performance. Vegetarian and omnivorous athletes oxidized fat and protein at comparable rates. However, the percentage of carbohydrates varies.
Additionally, vegetarian athletes ate more carbohydrates than omnivores (343 g vs. 322 g). As expected, daily caloric intake was lowest for vegans and highest for omnivores (2383 kcal and 2985 kcal, respectively).
Additionally, this analysis suggested that vegetarian athletes had lower intakes of protein and fat. Therefore, you should consume textured soybeans, almond drinks, and flaxseed for protein, and tahini, soybeans, and olive oil to meet your fat needs.
Intake of micronutrients, especially iron (Fe) and calcium (Ca), is also important for athletes. Analysis of this study suggested that among endurance athletes, iron consumption was higher in vegetarians than omnivores (19.4 mg vs. 15.4 mg), which was significantly different.
Similarly, calcium intake was higher in vegetarians than in omnivorous athletes, with a difference in daily intake of 266 mg.
conclusion
Athletes on a vegetarian diet performed significantly better on a variety of sports performance parameters, including relative oxygen consumption and peak power. However, performance on muscle strength-related parameters was not improved compared to athletes on an omnivorous diet.
Vegetarian and vegan athletes ate significantly more carbohydrates and less protein and saturated fat, but vegetarian women in particular showed better physical fitness.
Further research is needed to confirm whether vegetarian athletes can have higher sports performance.
Nevertheless, all athletes should strictly adhere to a diet that meets their nutritional needs, depending on the type of sport and the season of play.