CAN A VEGAN DIET SUPPORT TRAINING AND RUNNING?
What does the science say about a vegan diet and its impact on sport and exercise performance?
Some athletes have adopted a vegetarian/vegan diet with a view to achieving improved performance through optimising carbohydrate intake, weight management and other performance enhancements. It has been suggested that a vegetarian diet may improve performance through,
- improved glycogen stores from increased carbohydrate intake,
- Improved immunity and reduction in oxidative stress through increased intake of phytochemicals and antioxidants, and
- Reduced intramuscular acidity which can limit exercise performance.
There are very few studies, however, that have considered the effect of vegetarian or vegan diets on athletic performance and results are mixed. A recent review of the studies which have been undertaken comparing vegetarian and omnivorous nutrition and effects on physical performance concluded that a vegetarian diet neither hinders or improves performance. The research into the effects of a vegan diet on performance are virtually non- existent, however, and there may still be some merit to the diet increasing performance due to the factors mentioned above and more research is required to definitively answer this question.
The bottom line is that the studies which have been undertaken suggest that a well-planned WFPB diet can adequately support athletic performance, while offering added health, environmental and ethical benefits.
WHAT SPECIFIC NUTRIENTS DOES A RUNNER NEED?
There are no Dietary Reference Values (DRV) specifically set for athletes in training and the Reference Nutrient Intakes (RNI) are broadly as recommended for the general population, which are designed to cover the needs of 98% of people (Department of Health, 1991). Athletes consuming the RNI, therefore, are unlikely to be deficient in a nutrient. Nutritional recommendations for improved endurance performance include a high carbohydrate (CHO) intake and adequate fluid intake to ensure high muscle glycogen and to optimise hydration. Recommendations for runners for improved endurance performance, therefore, includes a high carbohydrate intake (5-10g/kg body weight per day) balanced with adequate fluid intake.
ARE THERE ANY NUTRITIONAL CONCERNS RELATING TO A VEGAN DIET?
A number of nutritional concerns have been identified in the scientific literature for endurance runners consuming vegan diets which includes; energy, protein, iron, zinc, vitamin B12, calcium, vitamin D and riboflavin.
Exercise increases energy needs. Endurance exercise can more than double energy requirements. A vegan runner may find it difficult to consume sufficient calories and quantities of food to meet their energy needs, partly due to the high carbohydrate, high fibre content. Low energy availability (EA) can suppress immunity to viruses and have implications for respiratory health, a problem often reported in endurance athletes. Relative Energy Deficiency in Sport (RED-S) has been identified as a syndrome which refers to impaired physiological function caused by relatively low EA. Low EA can have a detrimental effect on general health, ability to train and on running performance. It is important, therefore, that a vegan runner ensures that they consume adequate energy (calories) to fuel their training and running. Calculating your personal energy requirements is a useful starting point and there are a number of useful Apps on the market you can use (MyFitnessPal, Chronometer) and armed with this information you can devise meal plans designed to optimise your training and running performance.
Dietary protein has been shown to be an important and often neglected factor in the recovery and regeneration of damaged muscle proteins after endurance exercise. The repair and recovery process along with the adaptive response to exercise and training are dependent on adequate intake of protein through the diet and are key to the improvements in muscle quality that underpin improved performance. There are two issues relating to the adequacy of protein intake when consuming a WFPB diet and these relate to;
- The quality of the protein and
- The quantity of protein
There are twenty amino acids which are constituents of proteins, nine are considered as “essential” and must come from the diet. Foods which contain all of these nine essential amino acids (EAA) are often called “complete” or “high-quality” proteins. The quality and bio-availability of the protein consumed and the amino acid profile of plant-based versus animal-based protein has been shown to affect muscle protein synthesis. Plant-based proteins exhibit lower digestibility than animal-based proteins and have incomplete composition of EAA. It is possible, however for a vegan diet to supply all EAA if sufficient total energy and a variety of protein containing foods are consumed throughout the day.
In fact, the American Academy of Nutrition and Dietetics suggest that consuming protein from a variety of plant sources including soy products (which does have a complete set of EAA) and legumes will ensure adequate intake of all EAA. The trick is to eat both high-quality WFPB protein (soy, tofu, tempeh, tvp) and other sources of protein with complimentary EAA profiles such as beans on toast, lentils and rice, beans and potatoes, muesli with oats, nuts and seeds. Combining foods from any two of these categories ensures an adequate intake of all of the EAAs.
A review of protein intake for athletes highlights several studies which have determined that endurance athletes should consume between 1.2-1.4g/kg/day. Type and timing of intake have also been suggested as prudent to enhance muscular adaptation and 20-25g of protein recommended 30-60 minutes after endurance exercise to aid recovery.
Developing meal plans which look to achieve your personalised daily energy and protein intake is important to ensure that adaptations to training and recovery are optimised.
A shortage of iron in the diet will have an adverse effect on oxidative energy metabolism, and ultimately on training adaptations and athletic performance. Iron is used for the synthesis of haemoglobin and myoglobin in the red blood cells and in the energy producing pathways in the muscle cells essential for the delivery of oxygen to the muscles. Endurance training also tends to reduce iron stores.
Vegetarian and vegan diets have been shown to have as much or more total iron than non- vegetarian diets. The concern over iron is more related to the bioavailability of iron from plant foods, iron stores, and the absorption of non-haem versus haem iron. Haem iron is only available from animal foods and is absorbed more readily by the body than non-haem iron, which is consumed through plant foods, reducing iron stores. Plant foods also contain inhibitors, such as phytate and fibre, which reduce iron absorption. Vegan athletes are therefore likely to be at risk of low iron availability and iron depletion although diets high in fruit and vegetables can help to counteract the effects of iron inhibitors and reduce the effects of lower iron bioavailability.
The scientific literature suggests that Zinc is also a nutrient of concern. Zinc is essential for immune function, protein synthesis and blood formation and is abundant in plant foods but, like iron, is not readily absorbed. Low zinc status can negatively affect physical performance, muscle strength and endurance through its effect on thyroid hormone levels, Basal Metabolic Rate and protein use. Ensuring adequate intakes of legumes, whole grains, cereals, nuts, seeds, soy and vitamin C can ensure adequate intake and absorption. The RNI for zinc is 9.5 mg/day for males and 7.0 mg/day for females.
Vitamin B12 is essential for proper nervous system function and homocysteine metabolism and is exclusively found in foods of animal origin. Elevated homocysteine levels are associated with higher risk of birth defects, dementia and depression and studies have shown it to be strongly associated with increased mortality. Vitamin B12 deficiency can slowly develop in individuals following a vegan diet. In terms of athletic performance this is associated with reduced oxygen transport and therefore impaired aerobic performance. It is recommended that fortified foods such as soy products, yeast extract or nutritional yeast are consumed, or a supplement taken. The RNI for adults is set at 1.5 micrograms per day, although 3 micrograms (mcg) per day has been recommended to minimize homocysteine. Food sources are better absorbed than supplements with 10 micrograms recommended per day from a supplement. By ensuring that a variety of fortified foods are included daily in your diet there is little need for supplementation.
Calcium intake is essential for strong bones and teeth and is important for athletic performance as it serves a key role in muscle function and nerve-impulse transmission. Absorption of calcium from plant sources is also lower than that from dairy products and therefore consideration should be given to achieving RNI from fortified as well as natural plant sources. Calcium intakes below recommended levels can result in a predisposition to osteoporosis, one of the three components of The Female Athlete Triad which also includes disordered eating and amenorrhea, although overall energy availability has been identified as being the key factor in developing the disease. Some dietary plant sources are particularly rich in calcium, as well as other vitamins and minerals which contribute to bone health, and it has been shown that it is possible to maintain calcium balance on a vegan diet. These include kale, bok choy, Chinese cabbage, watercress, Cavolo Nero and _ broccoli. Consumption of fortified alternatives to dairy are also recommended to address deficiencies and are convenient and widely available.
Defining vitamin D status and recommendations for supplementation has been a topic of debate in the scientific literature. Because vitamin D status is related to exposure to sunlight, as well as dietary intake, athletes at particular risk of low serum total concentrations of vitamin D are those who train early or late in the day, train indoors, or wear sports kit which restricts sunlight exposure. Serum levels have been shown to be low in both athletic populations and in vegans and to be deficient, particularly in the winter. The implications for athletic performance of low vitamin D status have been shown to be impaired muscle and immune function, poor bone health, and even impaired cardiovascular function with low levels being associated with reduced and high levels with increased performance. Including fortified foods in the diet can, again, help to achieve the 10 ug RNI particularly when sunlight exposure is reduced. Mushrooms which have been exposed to the sun also have the ability to absorb vitamin D and are another plant-based source to include in your diet.
Riboflavin, or vitamin B2, is another B vitamin which potentially could be below the RNI when consuming a WFPB diet and could affect running performance. It is involved in energy production from both carbohydrate and fat, and therefore contributes to the release of energy for endurance performance. Riboflavin is mainly found in dairy products, meat and eggs and the need for this vitamin has been shown to increase with the onset of running and training. It is important, therefore, to ensure an adequate intake from plant-foods, particularly at the onset of a training programme or during an increase in training volume. The RNI for riboflavin is 1.3 mg/day for males and 1.1 mg/day for females and good plant sources include tofu, nuts, seeds, grains, nutritional yeast and green leafy vegetables, asparagus and bananas.
Philip Woodbridge MSc BA(Hons) SENR
Vegan Runners UK Club Nutritionist</strong>
The above FAQ information has been summarized using the following resources and references:
Larson-Meyer, D. (2018). Vegetarian and Vegan diets for athletic training and performance. Sports Science Exchange, Vol. 29 No. 188, 1-7.
Rogerson, D. (2017). Vegan Diets: practical advice for athletes and exercisers. Journal of the International Society of Sports Nutrition, 14:36.
Woodbridge, P. (2017). Plant-Based 4 Running: Quick and easy nutritionally balanced recipes and meal plans 4 active living. https://www.p4snutrition.co.uk/Plant-Based-4-Running/
For any questions relating to nutrition and personalised one to one advice contact Phil by email: firstname.lastname@example.org