Many athletes compete on a high level without consuming animal products; however, even though a vegan diet may be appropriate at all stages of life, there are certain factors to take into consideration when establishing a balanced plant-based diet for athletes, especially in bodybuilding, where muscle growth is emphasized, while aesthetics are judged.

Study: Going Vegan for the Gain: A Cross-Sectional Study of Vegan Diets in Bodybuilders during Different Preparation Phases. Image Credit: ME Image / Shutterstock

Plant-based diets can result in reduced appetite and early satiation since they have low-calorie density and high amounts of fiber. This can be useful when trying to lose weight but can be an issue when the management of an athlete's energy balance is required. Vegan athletes should look out for the quality and quantity of ingested proteins since plant-based proteins can often be incomplete due to fewer essential amino acids (EAAs) than animal proteins. However, combining different plant protein sources can help improve the overall quality of protein meals. Moreover, plant-based proteins might have lower digestibility as compared to animal proteins due to the presence of anti-nutritional factors that limit the absorption of nutrients. Simple domestic preparation methods such as soaking, fermentation, germination, and cooking can help to reduce the anti-nutritional factors and improve protein bioavailability.

An adequately designed vegan diet can meet the protein requirements of an athlete through only whole foods but might not be suitable to maximize muscle growth. Judgment of athletes takes place according to their muscular proportions, muscle size, and conditioning in competitive bodybuilding. Athletes undergo extensive resistance training and dietary manipulations to reduce fat mass and increase muscle mass. The nutritional strategies vary as per their competitive cycle phase, which comprises the muscle-gaining phase or "bulking" and contest preparation phase or "cutting." Bulking phase involves an increase in muscle mass without an increase in body fat with a protein requirement of 1.6 to 2.2 g/kg of body mass. The cutting phase involves a reduction of body fat and maintenance of muscle mass that is gained during the bulking phase. Additionally, during this phase, most bodybuilders follow a high protein calorie-restricted diet, isometric "posing practice," and aerobic exercise along with resistance training.

Traditional bodybuilding diets include a significant amount of animal-source food as well as high-quality protein supplements such as whey protein powder to reach high protein targets. Whey proteins are known to be high-quality proteins due to their high quantity of essential amino acids and digestibility. This can be challenging for bodybuilders following a vegan diet since vegans avoid common sources of proteins such as dairy products and meat. Foods rich in plant-based proteins and vegan protein powders can be useful since they can provide concentrated sources of protein during workouts as well as throughout the day. Recent research reports vegan protein powders to be efficient in improving muscle hypertrophy post-resistance exercise as well as improving exercise performance and indices of body composition. However, most research on vegan diets in athletes is limited to endurance sports.

A new study in the International Journal of Environmental Research and Public Health aimed to compare the nutritional intakes of vegan and omnivorous bodybuilders at different stages of preparation for a bodybuilding competition.

About the study

The study included bodybuilder participants affiliated with the Italian World Natural Bodybuilding Federation (WNBF). They were divided into a control group of omnivores and a group of vegans. The participants had to complete an online questionnaire on years of training and competition, anthropometric measurements, diet type, and training hours per week. Participants had to record their food intake on an online diary for 5 days at both the bulking and cutting phases. The data collection took place two months apart for the two phases for all athletes.

The quantities of food were recorded in portions or grams, along with information on dietary supplement consumption. Analysis of the participant's diet took place using the WinFood nutritional analysis software. Information on the daily intake of macronutrients was collected in grams per kilogram of body weight (g/kg/day). Calculation of micronutrients such as iron, sodium, and calcium took place in milligrams per kilogram of body weight per day (mg/kg/day), while vitamins B1 and D took place in micrograms per kilogram of body weight per day (mcg/kg/day). Finally, dietary intake was compared as per the recommended dietary allowances (RDAs).

Study findings

The included 18 bodybuilders who practiced bodybuilding for 6 years and trained for 8 hours per week. A reduction in several dietary components was observed during the preparation phase in both the vegan and omnivore group. Omnivores were reported to increase their protein intake during the cutting phase as compared to the bulking phase, while vegans were reported to reduce it.

Omnivores were reported to reach the recommended protein levels during the bulking and cutting phase, while vegans reached the recommended levels only during the bulking phase. Neither omnivores nor vegans were observed to reach RDA for calcium during the bulking and cutting phase. Vegans were observed to reach RDA for vitamin D during the bulking and cutting phase, while omnivores reached it only during the bulking phase. Additionally, none of the groups reached RDA for vitamin B12. However, the intake was reported to be higher among vegans compared to omnivores during both phases. Both vegan and omnivore males were reported to reach the RDA for iron, while vegan and omnivore females failed to reach it. Vegan males and females were reported to fail to reach the RDA for zinc, while omnivore males and females were reported to reach the recommended levels.

Therefore, the current study demonstrates that vegan bodybuilders might struggle to meet their protein needs while consuming a calorie-deficit diet. They can benefit from the assistance of nutritional professionals to understand the amount of protein required to maintain muscle mass. Further research is needed to highlight whether nutritional interventions can help athletes on a vegan diet reach protein recommendations while undergoing calorie deficit.

Limitations

The first limitation of this study is that the nutritional analysis software did not have sufficient information to estimate vitamin B12 in all food. Second, factors such as the amount and intensity of sun exposure must also be kept in mind during the assessment of vitamin D status. Third, there was a lack of variety in the diet. Fourth, participants' self-reporting of anthropometric data can result in parameter alterations. Finally, low energy among female athletes during the cutting phase might place them at risk of developing amenorrhea, leading to a condition known as relative energy deficiency in sport (RED-S).

Journal reference:

• Amatori, S. et al. (2023). Going Vegan for the Gain: A Cross-Sectional Study of Vegan Diets in Bodybuilders during Different Preparation Phases. International Journal of Environmental Research and Public Health. doi: https://doi.org/10.3390/ijerph20065187. https://www.mdpi.com/1660-4601/20/6/5187