There are many health benefits associated with including more plant-based foods in the diet. However, as vegan diets exclude all animal products a poorly put together vegan diet could predispose a person to macronutrient and micronutrient deficiencies. Not getting the right nutrients can also result in reduced training adaptations and poorer performance.
Research suggests that vegans tend to consume less energy than omnivores, and compared to diets that include animal protein sources, vegetarian and vegan diets tend to be lower in protein, fat, vitamin D, calcium, B12, Riboflavin, zinc and iron. There is currently limited information about veganism in sport but it is important to consider various nutritional aspects to optimise both health and performance.
It appears that vegan athletes consume less protein compared with omnivores and vegetarians. It is very important that vegan athletes optimise their protein intake by considering both the quantity and quality of protein.
Plant-based sources of protein are often incomplete, which means that important essential amino acids are missing, and contain less Branched Chain Amino Acids (BCAA) compared to animal protein sources. Although it was once thought that protein sources needed to be combined in every meal in order to achieve a complete amino acid profile, this is no longer the case. The important factor is that a variety of protein sources are consumed throughout the day to ensure that all essential amino acids are present and so that there is an adequate intake of BCAA to achieve adaptation from training as well as recovery. Foods such as grains, nuts, seeds, legumes (beans, peas, lentils) should be included in a vegan diet to ensure this is achieved.
The digestibility of plant-based protein is less than that of animal products, and therefore vegans might need to consume more protein than meat eaters to make up for the poor digestibility. It is recommended that vegan athletes aim for a daily protein intake of:
1.4 to 2g per kg per day (during weight maintenance or weight gain)
1.8 to 2.7g per kg per day (during weight loss phases)
Fats are important for health and performance. Because vegan diets do not include fish, eggs or sea food, vegan diets tend to lack the omega-3 fatty acids EPA and DHA, which are extremely important for cardiovascular health and functions in the brain. Plant-based foods such as walnuts, chia seeds and flax seeds are a source of ALA which can be converted to EPA and DHA but this is not an efficient process. Vegans can obtain DHA and EPA from microalgae oil and some foods are fortified with DHA.
Because vegan diets lack animal and dairy products, vegans have an increased risk of vitamin B12 deficiency. Long-term B12 deficiency can lead to irreversible neurological damage. The body has limited capacity to absorb oral B12 supplements, therefore 6ug per day is the recommended supplement intake for vegans. Vegans should also consume fortified foods such as B12 fortified breakfast cereals and nutritional yeast.
Studies indicate that vegans consume less calcium, and are at higher risk of fracture because of this lower calcium intake.
Vegetables such as bok choy, broccoli and kale contain calcium. However, some veg such as arugula and spinach contain oxalates which can hinder calcium absorption. Other foods containing calcium include tofu, tahini, oranges and fortified foods such as calcium- fortified orange juice and calcium fortified soy.
Iodine is an essential trace element. It is needed for growth and development and also plays an important role in metabolism and thyroid function. Iodine is therefore important for health and performance. Data shows that vegans tend to consume either excessively high amounts or excessively low amounts; either can lead to thyroid dysfunction. Some vegetables that contain goitrogens such as cabbage and cauliflower can reduce iodine utilisation in the body when large amounts are consumed. However, cooking veg can destroy many of the goitrogenic compounds.
Seaweed and sea vegetables are vegan sources of iodine. However, excessively high amounts of iodine intakes have been reported in vegans that regularly consume seaweed. The amount of iodine in seaweed varies, and the British Dietetic sources suggest that seaweed might not be a reliable iodine source. Iodised table salt, potatoes and some breads contain iodine.