Nutritional advice for vegan athletes
The arise of the vegan diet have many reasons: health benefits, environmental reasons, or ethical reasons. One health benefit for example might be that plant-based diets reducing the risk for developing chronic diseases (Lynch, Johnston, & Wharton, 2018). Also, carotenoids, pigment molecules, and other colored vegetables are known to enhance immune function (Fuhrman & Ferrer, 2010). The result is that the athletes missing training and competitions less (Fuhrman & Ferrer, 2010). Furthermore, the production of plant-based food is less resource-intensive and environmentally destructive (Lynch, Johnston, & Wharton, 2018). This means that there are currently 1.1 % of the population or overall, 900.000 vegans in Germany which consequently also includes various athletes (Wirnitzer, et al., 2016). Examples of famous vegan athletes worldwide would be Serena Williams, Lewis Hamilton, or Patrik Baboumian. But how can they be successful with only consuming plant-based foods? The aim of this evidence-based recommendation is to answer the question, what should vegan athletes consider, to maintain a balanced diet and thus their physical fitness?
Veganism is defined as a form of vegetarianism that prohibits the consumption of all animal products (Rogerson, 2017). So, here you must pay more attention to a balanced diet due to the limited food alternatives (Figure 1).
Figure 1 Vegan Diet Pyramid (Source: https://oldwayspt.org/sites/default/files/thumbnails/image/Veg-VeganDietPyramid_flyer_0.jpg, Retrieved from 25.05.2021)
Energy Intake
But before athletes focus on each nutrient, they must maintain their energy level. Because in every sport the nutrition priority must be the meeting of the respective energy needs with a sufficient well-structured diet (Larson-Meyer, 2018) (Rogerson, 2017). If the energy intake will be insufficient the exercisers will not only risk weight loss (Rogerson, 2017). Rather, they can also get ill which lead to time off from training and competition (Rogerson, 2017). Moreover, the athlete risks a loss of muscle mass, reduced strength, lower work capacity and a lack of satisfactory training adaptation (Rogerson, 2017). The problem with the vegan diet is namely early satiation, reduced appetite, and less energy because plant-based foods are high in fibre and low in energy density (Larson-Meyer, 2018) (Rogerson, 2017).
Macronutrients
For a balanced diet, an athlete must consider in addition all macronutrients. One of the most important macronutrients for every exerciser is protein. It serves as a substrate for exercise performance and trigger muscle protein synthesis (Larson-Meyer, 2018) (Rogerson, 2017). Also, a positive Net Protein Balance, defined as the difference between muscle protein synthesis (MPS) and muscle protein breakdown, promotes exercise recovery, adaptation, and anabolism (Rogerson, 2017). So, to trigger MPS essential amino acids (EAAs) and especially leucine will be necessary (Lynch, Johnston, & Wharton, 2018) (Rogerson, 2017). However, a vegan diet consists of proteins, but with poor quality and quantity. Plant-based proteins are incomplete, missing important EAAs, contain less leucine and have a bad biological value. It means that vegan proteins appear to be markedly less digestible than animal products (Larson-Meyer, 2018) (Lynch, Johnston, & Wharton, 2018) (Rogerson, 2017). Carbohydrate ingestion on the other side is high in the vegan diet so that adequate consumption is feasible for every athlete (Rogerson, 2017). Fat as the last macronutrient that provides energy is an element of cell membranes and is responsible for the absorption of fat-soluble vitamins (Larson-Meyer, 2018). Plant-based nutrition is lower in total and saturated fat which is primarily not unhealthy (Larson-Meyer, 2018) (Rogerson, 2017). Also, the higher consumption of n-6 fats with this kind of nutrition is healthy (Larson-Meyer, 2018) (Rogerson, 2017). Only the lower level of n-3 fatty acid in the vegan diet will be a problem (Larson-Meyer, 2018) (Rogerson, 2017).
Micronutrients
Poorly designed diets with no attention to the different micronutrients can besides lead to detrimental health and performance implications (Rogerson, 2017). Vitamin B12 is always mentioned when experts speak about the deficits of a vegan diet. It is essential for the nervous system, homocysteine metabolism, and DNA synthesis (Rogerson, 2017). An insufficient B12 level can result in morphological changes to blood cells and the development of haematological and neurological symptoms (Rogerson, 2017). It is unusual that plant-based products contain Vitamin B12 because B12 is synthesised from anaerobic microorganisms, in the rumen of cattle and sheep (Rogerson, 2017). So, human consume it from animal products (Larson-Meyer, 2018) (Rogerson, 2017). Furthermore, iron-deficiency anaemia, a decrease of red blood cells or haemoglobin, can be a concern for vegan athletes, particularly for female athletes (Larson-Meyer, 2018) (Rogerson, 2017). True, they consume a similar amount of iron but mainly the non-haem form which is less bioavailable (Larson-Meyer, 2018) (Rogerson, 2017). Also, plant-based products contain dietary inhibitors such as plant phytates, polyphenolics, tannins, and foods with high concentrations of calcium, zinc, or other divalent minerals which end in a poorer iron digestibility (Larson-Meyer, 2018) (Rogerson, 2017). All in one can this leads to tiredness and fatigue, weakness, shortness of breath, and reduced exercise tolerance (Larson-Meyer, 2018) (Rogerson, 2017). Otherwise, Zinc, a constituent of enzymes involved in metabolic processes that relate to DNA stabilisation and gene expression, is widely available in plant-based foods (Rogerson, 2017). However, plant-based foods do have a reduced bioavailability compared to animal products, but a suboptimal zinc status only occurs in vegan athletes who selected zinc-poor foods (Larson-Meyer, 2018) (Rogerson, 2017). Calcium on the other side is a big concern for vegan athletes who consume minimal dairy products (Larson-Meyer, 2018). That can lead, due to the function of calcium in vitamin D metabolism and maintaining bone structure, to a higher risk of fracture (Rogerson, 2017). To absorb Calcium and maintain bone structure, athletes must additionally consider that they consume adequately Vitamin D (Rogerson, 2017). Dietary intake of vitamin D only appears to be low in vegans who do not achieve sufficient sun exposure or have a reduced intake of Vitamin-D-containing foods (Larson-Meyer, 2018) (Rogerson, 2017). This can negatively affect muscle strength and oxygen consumption (Rogerson, 2017) The last micronutrient a vegan athlete should monitor is iodine. Poor iodine status is common in many vegans and vegetarians who do not consume table salt and sea vegetables or consume plant foods grown in iodine-poor soil (Larson-Meyer, 2018). Also, iodine is lost in sweat which is an additional risk for suboptimal status (Larson-Meyer, 2018).
In the end, it is crucial to meet the energy requirements and obtain proper nutrition (Larson-Meyer, 2018). Vegan athletes can have some deficits in their macronutrients (protein, n-3) and micronutrients (vitamin B12 and vitamin D; iron, zinc, calcium, iodine) (Rogerson, 2017). But otherwise, this diet is also higher in carbohydrates, fibre, some micronutrients, phytochemicals and, antioxidants (Fuhrman & Ferrer, 2010) (Rogerson, 2017). But more research is necessary to make an explicit conclusion on how a well-structured vegan diet affects athletic performance, especially for different sports.
On Friday you will get an overview of some techniques for vegan athletes, to maintain a balanced diet.
Literature
Fuhrman, J., & Ferrer, D. M. (2010). Fueling the Vegetarian (Vegan) Athlete. Current Sports Medicine Reports, 9(4), S. 233-241.
Larson-Meyer, E. (2018). Vegetarian and Vegan Diets for Athletic Training and Performance. Sports Science Exchange, 29(188), S. 1-7.
Lynch, H., Johnston, C., & Wharton, C. (2018). Plant-based diets: Considerations for environmental impact, protein quality, and exercise performance. Nutrients, 10 (12). Von https://doi.org/10.3390/nu10121841 abgerufen
Rogerson, D. (2017). Vegan diets: practical advice for athletes and exercisers. Journal of the International Society of Sports Nutrition, 14 (1), 36. doi:10.1186/s12970-017-0192
Wirnitzer, K., Seyfart, T., Leitzmann, C., Keller, M., Wirnitzer, G., Lechleitner, C., . . . Knechtle, B. (2016). Prevalence in running events and running performance of endurance runners following a vegetarian or vegan diet compared to non‑vegetarian endurance runners: the NURMI Study. SpringerPlus, 5, 458. doi:10.1186/s40064-016-2126-4