Vegan Diets – Endurance Athletes

Vegan Diets

It is hard to ignore that vegan diets are gaining popularity – for some it is for ethical reasons, for some environmental reasons and others because they simply believe it is ‘healthier’.   Often it is a combination of both. 

I use the word healthier cautiously as what is healthy for one individual is not necessarily healthy for another – genetics, gender, lifestyle, our gut microbiome, and our age all impact our metabolism and result in us having unique nutritional requirements.

There are a number of considerations for anyone on a vegan diet in terms of nutrient deficiencies but what are the considerations for an endurance athlete who has much higher nutrient (and energy) requirement than an average individual.  Can a vegan diet meet these needs?

Research specifically into vegan diets for athletes is scarce but there are a number of anecdotal successes of athletes who thrive on them such as Venus Williams, Lewis Hamilton, Scott Jurek and Hillary Biscay (US ironman champion and ultra-endurance runner).  

However, you don’t know to what extent are they supplementing and do be aware that it can take years for some nutritional deficiencies to become apparent so correlations can be hard to make. 

Here are some of the main things you need to think about:

The Ketogenic Diet,Vegan Diets,Age Grouper

Macro-Nutrient Considerations:

Overall energy intake may fall as plant-based diets are usually higher volume and higher in fibre so satiety is increased.   If weight loss is not your goal, you need to ensure you eat enough nutrient dense foods such as nuts, nut butters, coconut-based products and seeds etc. 

Whilst many athletes are happy to lose a few pounds, too much weight loss too quickly can result in muscle loss instead of fat as well as impacting immune function.  Compromised immune function can lead to frequent colds, infections such as URTIs (upper respiratory infections), not uncommon in endurance athletes, leading to time off training and we all know consistency in training is key! 


There are few complete protein vegan sources ie those that contain all the essential amino acids (EAAs) found in animal products.  In order to ensure you obtain all the EAAs, it is important to eat a wide variety of plant-based protein daily. 

Grains are commonly missing the amino acid lysine (essential for collagen production) while pulses/legumes are often missing methionine and cysteine (required for new cell repair, detoxification amongst many other roles). 

In addition, it has been shown that most vegan diets are lower in overall protein and endurance athletes have a higher protein requirement than Mr or Mrs Average; it may well be that some form of protein supplementation is required. 

When I run blood tests on vegan athlete clients, protein markers are frequently low backing up this finding.  The standard recommendation for an endurance athlete is 1.2-1.4 g/kg of protein a day.   

High levels of beans and legumes can result in elevated levels of phytic acid which binds essential minerals such as calcium, magnesium, iron and zinc so always soak beans first to help to reduce phytic acid levels. 

Finally, be careful of over consumption of soy (which does contain all the EAA’s) due to much of it being genetically modified and its high levels of phytoestrogens which can mimic oestrogen. Whilst potentially playing a useful role in menopause years, they can disrupt hormones causing potential dysfunction.


The essential omega-3 fatty acids EPA and DHA, needed for all cell membranes, a healthy nervous system and, very importantly particularly in athletes, for also reducing inflammation are not readily available from vegan sources. 

There are also well-studied genetic variations impacting the ability of some people to convert alpha-linoleic acid (found in flax, walnuts, chia, hemp, algae (EPA) and seaweed (EPA and DHA)) to the essential omega 3’s.  Vegans consistently show plasma EPA and DHA levels that are up to 60% lower than those who consume seaweed.

Vegan supplement sources of DHA and EPA are now available and it is recommended that the optimal total amount of DHA and EPA for athletes is 1-2g/day at a ratio of 2:1


Vegan diets are typically high in carbohydrates.  So long as these are from unprocessed sources this should not present too much of a problem assuming other macro-nutrient requirements are being met. 

However, care should be taken if you have any form of insulin resistance (you can test) or potential gut dysfunction where high amounts of fibre or lectins from grains may be problematic.  If you are in doubt or think you have certain food intolerances, get advice. 

Individual Micronutrient considerations:

B12 – B12 is not available from a vegan diet.  There are fortified sources available but relying on processed cereals or bread for this nutrient is not a great choice.  

Long term deficiency in B12 can cause irreversible nerve damage so I recommend testing and supplementing appropriately.

IRON – iron can be found in plant-based foods but it is not readily available (poor bio-availability).  Eating foods high in vitamin C with iron-based plant products can increase the absorption of iron and it is recommended that you reduce consumption of foods high in phytic acid (as above) that bind essential minerals.  

Levels of iron can take time to fall and again, testing is the best option to determine your levels.  Supplementation is often required.

Zinc – similar to iron, this nutrient can be found in plant-based sources but is not readily bio-available.  Avoid foods high in phytic acid to increase its absorption. 

Zinc is essential for immune function, a healthy gut lining and skin – vegan sources include pumpkin seeds, oats, nutritional yeast.

Calcium – deficiency in calcium places athletes at a higher risk of fractures.  Fermented tofu, leafy greens, tahini and fortified dairy-free milks are good vegan sources and you should be looking to get at least 1000mg/day. 

Vitamin D – calcium needs vitamin D to get into the bones and it is recommended that everyone supplements with vitamin D in the non-summer months as it is hard to get from food sources, including non-vegan.  

In addition, not everyone converts inactive vitamin D to its active form well – more genetic variations and individuals with any underlying chronic inflammation can have a very high need for vitamin D.   Vitamin D again is needed for immune function (along with many other jobs) and it is easy to test via the GP or privately.

Supplementation should be done in conjunction with vitamin K and optimal levels of vitamin D are 125-225 nmol/l (note this is not the NHS range which is set to avoid frank deficiency).

Iodine – vegan sources of iodine vary according to factors such as how much iodine there is in the soil, farming methods etc.  Seaweed and sea vegetables are good sources but the type of seaweed matter – Nori is low in iodine while kelp is high. 

Choline– an often-overlooked nutrient, predominantly found in eggs and animal/fish products and essential for healthy cell membranes, nerve function and an essential process called methylation.  

Bear in mind if your cell membranes don’t work properly, hormones and neurotransmitters cannot do their jobs properly.  There is a small amount in broccoli and almonds but simply not enough to reach adequate intake.

A little functional medicine add-on:  if you ‘don’t feel good’ eating protein and perhaps one of the reasons you feel better on a vegan diet, this can be an indicator of gut dysfunction. There are many reasons why this maybe but some common ones are:

  • Stress (physical, physiological and psychological) which reduces production of hydrochloric acid, required for the breakdown of protein.
  • Similar to the above ‘eating on the go’ and rushing your food – the body will not prioritise digestion and thus acid production. Practise eating mindfully – something many of us have forgotten about in our world of rushing around where food is not given enough thought.
  • Underlying gut infection of which a common one is H Pylori. H Pylori is associated long term with ulcer formation so worth investigating if you are suspicious.  Other signs of H Pylori can be reflux, frequent burping, nausea and bloating. 
  • ‘IBS’ – a bucket term by conventional medicine where they have no idea what is causing your symptoms. If you suffer from frequent loose bowel movements, for example, you will not be absorbing your nutrients from your food and the chances are you will find protein harder to digest.  In the functional medicine world, we would consider again, underlying pathogens/parasites which can linger undetected for years, potential SIBO, liver and gall bladder function (intricately linked to digestion), dysbiosis and last but not least, stress.  Often if it is a combination of factors. 

Conclusion:  Nutritional requirements for an endurance athlete on a vegan diet is unlikely to be met without supplementation.  Carefully planning is required from both a macro and a micro perspective in order to do it well. 

This blog has been written by our resident Nutritional Expert and Coached Athlete, Katherine Caris-Harris. If you want to find out more you can contact Katherine via

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