The text discusses vegetarianism as a dietary practice that involves abstaining from meat and potentially other animal-derived foods and beverages. It outlines five categories of vegetarian diets, including lacto-ovo vegetarian, lacto-vegetarian, ovo-vegetarian, vegan, and raw vegan. The prevalence of vegetarianism in the United States is mentioned, with about 3.3% of the adult population reported to follow a vegetarian diet based on a 2016 national poll.
The motivations for choosing a vegetarian diet are varied and include environmental concerns, ethical considerations, the desire to reduce the risk of chronic diseases, and the avoidance of animal-borne diseases. Vegetarian diets are described as being rich in fiber, antioxidants, phytochemicals, fruits, vegetables, and carbohydrates, while being lower in protein, saturated fat, cholesterol, and processed foods. The potential benefits of vegetarian diets in preventing chronic diseases such as type 2 diabetes, obesity, hypertension, and cancer are highlighted.
The text then shifts to discuss the position of the Academy of Nutrition and Dietetics in 2016, stating that well-planned vegetarian diets can meet the nutritional needs of competitive athletes. While the impact of vegetarian diets on athletic performance is not extensively studied, the text notes that vegetarian practices are common among athletes, citing examples from surveys conducted at the Delhi 2010 Commonwealth Games and among marathon finishers. The influence of social media platforms of elite vegetarian athletes in encouraging the adoption of vegetarian diets by others is also mentioned.
The section focus is on the nutritional considerations for vegetarian athletes, highlighting potential risks of nutrient inadequacies, including proteins, essential fatty acids, iron, zinc, calcium, vitamin D, and vitamin B12. The higher risks are attributed to increased needs and losses during training, lower absorption and digestion rates of vegetarian foods, uneven nutrient distribution, and poorly planned meals. The importance of considering both exercise training and dietary practices for health and performance, along with regular monitoring of nutrition status, is emphasized.
The text provides detailed information on energy considerations, macronutrients (protein, carbohydrates, and fats), and micronutrients (iron, vitamin B12, zinc, vitamin D, and calcium) for vegetarian athletes. It discusses challenges such as inadequate energy intake, the quality of plant protein sources, and potential insufficiencies of essential amino acids. The recommended dietary allowances (RDAs) for various nutrients are mentioned, along with sources of these nutrients in vegetarian diets.
Specific concerns related to iron deficiency among vegetarian athletes are addressed, emphasizing the importance of monitoring iron status regularly. The text also discusses vitamin B12 deficiency, particularly in vegans, and recommends the consumption of fortified foods or supplements. Concerns related to zinc insufficiency, vitamin D intake, and calcium intake, especially for vegan athletes, are discussed, and strategies to ensure adequate intake are provided.
The section discusses the potential risks associated with vegetarianism, particularly in female athletes, focusing on the Female Athlete Triad. The Female Athlete Triad is a condition encompassing disordered eating, amenorrhea, and osteoporosis. While there is no established causal relationship between vegetarianism and disordered eating, it is noted that young women with anorexia nervosa more frequently adopt a vegetarian diet. The text highlights that female vegetarians, especially vegans, may be at a higher risk of developing the Female Athlete Triad due to lower intakes of iron, calcium, dietary fat, and energy associated with vegetarian diets.
To address these concerns, the text suggests that athletes, through constant monitoring and nutrient assessment, can safely and effectively achieve their body composition or weight goals by following a well-planned vegetarian diet. It emphasizes the importance of recommended practices, including the consumption of supplements and fortified foods, and regular assessment of dietary adequacy and blood work analyses to monitor the health of vegetarian athletes.
The subsequent section delves into the relationship between vegetarian diets and athletic performance. It mentions that vegetarian diets are considered by endurance athletes for higher carbohydrate intake, which is believed to enhance athletic performance and improve body composition. The text cites historical studies from the 1900s that suggested enhanced endurance performance in vegetarian athletes compared to omnivores. These studies attributed the superior performance partly to the vegetarians’ motivation and partly to their higher carbohydrate intake.
However, the text acknowledges contrasting findings from more recent cross-sectional studies that found no differences in aerobic or anaerobic capacities between habitual vegetarians and nonvegetarians. One study specifically compared fitness parameters between vegetarians and nonvegetarians, concluding that habitual consumption of vegetarian diets does not influence athletic performance. Another study comparing aerobic and endurance capacities between habitual vegetarian and omnivore athletes found higher aerobic capacity in vegetarians but no difference in endurance capacity.
The text also discusses intervention studies, including one that investigated the influence of vegetarian diets on runners completing a 1000-km run. The study found that both lacto-ovo vegetarian and regular Western diets fulfilled the demands of sports nutrition, with no significant differences in the percentage of subjects finishing the run in each group. Another intervention study compared endurance performance and immune parameters in athletes after consuming a lacto-ovo vegetarian diet and a mixed Western diet for 6 weeks. While no differences were observed in performance, a decrease in serum testosterone concentration was noted in athletes after consuming the vegetarian diet, attributed to increased fiber intake.
Biomarker studies are also referenced, such as one reporting lower iron stores in lacto-ovo vegetarian athletes despite higher iron intake, and another suggesting nonanemic iron deficiency in female runners consuming a modified vegetarian diet. The text concludes by summarizing that limited evidence indicates a neutral impact of consuming a vegetarian-style diet on athletic performance. It highlights the need for future research to control energy and macronutrient contents of diets, standardize sports engagement, and directly evaluate various performance parameters between vegetarian and nonvegetarian athletes.
The section explores the impact of vegetarian diets on the physical performance of the general population, relying on studies conducted with nonathletes to provide insights. It starts with a cross-sectional comparison from 1970 among healthy women following a vegan diet, nonvegan housewives, and office cleaners. The study found no differences in physiological responses to submaximal exercise, suggesting that a dietary deficiency of animal protein did not impair exercise-related physiological responses.
Moving forward to 1999, a study by Campbell et al. reported declines in whole-body density, fat-free mass, and whole-body muscle mass in older men following a lacto-ovo vegetarian diet with marginal total protein. This was in contrast to older men on an omnivorous diet with sufficient total protein, who experienced increases in these body composition parameters after resistance exercise. The text highlights the importance of considering food and nutrient intakes when adopting a vegetarian diet, cautioning that simply omitting meats may lead to unintended nutrient insufficiencies.
Subsequent research by Haub et al. suggests that resistance training-induced improvements in muscle strength and size were comparable between older men following lacto-ovo vegetarian and omnivore diets with sufficient total protein. The findings from these studies indicate that body composition and physical performance are not compromised or enhanced by the consumption of a vegetarian diet with sufficient total protein.
The Australian Longitudinal Study on Women’s Health is mentioned, which compared the health of young vegetarian, semi vegetarian, and nonvegetarian women. Vegetarians and semi vegetarians had lower BMIs and tended to exercise more. Another study linked animal protein intake to muscle mass index in older women, emphasizing the need for vegetarian athletes to carefully choose dietary protein sources to avoid compromised body composition.
A study by Baguet et al. compared carnosine content and buffering capacity in sprint-trained omnivorous athletes following vegetarian or omnivorous diets. Carnosine content decreased in the vegetarian group, suggesting a potential risk of decreased high-intensity exercise performance. Vegetarian athletes were advised to consider beta-alanine, naturally present in meat, fish, and poultry, in their diets.
The text also discusses a study by Hietavala et al. investigating the effects of a low-protein vegetarian diet on acid-base balance and cycling performance. While the low-protein vegetarian diet did not influence acid-base balance, higher oxygen consumption during submaximal cycling was observed, indicating a potential impact on cycling economy.
Lastly, the section notes that vegetarian diets typically contain higher antioxidant nutrients, potentially aiding in reducing exercise-induced oxidative stress. However, a study by Szeto et al. concluded that, despite consuming more antioxidants, vegetarians did not exhibit better antioxidant status. The need for further research to assess the antioxidant status of vegetarians, especially in overcoming exercise-induced oxidative stress, is emphasized.