Immunity: Does a vegan diet make you less likely to get ill?
There is now a wealth of evidence showing how vegans tend to have a lower risk of the UK’s leading causes of death, including heart disease, type 2 diabetes and certain cancers. Part of the reason is that well-planned vegan diets are typically higher in fibre, fruit, vegetables and wholegrains and lower in saturated fat and processed meat.
They also provide nutrients that support healthy immune function while reducing or avoiding foods associated with chronic disease. But could the benefits go further? Might a healthy plant-based diet also help protect us against everyday infections, including colds and flu?
Early in the Covid-19 pandemic, emerging research suggested that people following plant-based diets might have a lower risk of infection and, if infected, less severe symptoms. This was not entirely unexpected as on average, vegans tend to weigh less than meat-eaters and are therefore less likely to develop conditions such as obesity, heart disease and type 2 diabetes – major factors associated with a greater risk of severe Covid-19.
A 2021 study published in BMJ Nutrition, Prevention & Health found that among 2,884 frontline healthcare workers across six countries, those following plant-based diets had a 73 per cent lower risk of developing moderate-to-severe symptoms of Covid compared with meat-eaters. Consequently, they were less likely to suffer fever, breathing problems, low oxygen levels in the body or need medical help. In contrast, people on low-carbohydrate, high-protein diets (eg keto, Paleo-type diets, typically high in meat, eggs and fats) were almost four times more likely to experience moderate-to-severe disease.
Later that year, the ZOE COVID Symptom Study including nearly 600,000 participants, published in the journal Gut, found that those with the highest diet quality scores (healthy plant-based diets rich in wholegrains, pulses, fruit, vegetables, nuts and seeds) had a nine per cent lower risk of catching Covid and a 41 per cent lower risk of developing severe symptoms compared with those with the poorest diet quality. In a video conference, the study authors emphasised that while people on healthy vegan diets fared best, diet quality matters more than simply being vegan – chips, chocolate and biscuits may be vegan but are not healthy!
Most recently, a 2024 study in Brazil, published in BMJ Nutrition, Prevention & Health, found that those following predominantly plant-based or vegetarian diets had a 39 per cent lower risk of catching Covid compared with meat-eaters, even after adjusting for BMI, physical activity and pre-existing conditions.
The evidence goes wider than just Covid though. In a US study of 11,955 adults, those whose diets scored highest on a healthy plant-based diet index – emphasising wholegrains, fruit, vegetables, nuts, pulses, tea and coffee – had a 14 per cent lower rate of hospitalisation for respiratory infections, including flu and pneumonia, and a 13 per cent lower rate of hospitalisation for infections overall, compared with those whose diets scored lowest.
Diet and immune function
A recent study suggests that changing what you eat may influence your immune function within weeks. In this small trial, 48 healthy adults followed either a vegan or meat-rich diet for one month. Compared with the meat-rich group, those following the vegan diet showed changes consistent with less inflammation and slower biological ageing! Persistent, low-grade inflammation is associated with a higher risk of many chronic diseases and may contribute to biological ageing.
Scientists suggest that a balanced vegan diet may help protect against infectious illnesses largely because it is typically rich in fibre, fruit, vegetables, wholegrains, pulses, nuts and seeds which, taken together, provide vitamins, minerals and thousands of bioactive compounds, including carotenoids and polyphenols. These help support normal immune-cell function and may reduce oxidative stress and inflammatory signalling.
The gut may be one of the key links
Plant wholefoods are rich in fibre, which provides fuel for the trillions of microbes living in your gut. Fermented foods such as plant-based yoghurt, tempeh, miso, kimchi and sauerkraut can also support a diverse and healthy gut microbiome. As gut microbes ferment fibre, they produce short-chain fatty acids such as butyrate, acetate and propionate which help to maintain your gut’s protective barrier and influence your immune function.
Conversely, diets high in meat, fat and processed foods can promote harmful gut bacteria that undermine gut integrity and immunity by producing toxic by-products.
What does a healthy vegan diet look like?
To repeat, a healthy vegan diet is packed with fruit, vegetables, pulses, wholegrains, nuts and seeds and diversity is key so try and vary the foods you eat each day, aiming for 30 different plant foods per week – it’s easier than you might think.
Do I need supplements?
It is better to obtain nutrients from whole foods than from supplements. A well-balanced vegan diet supports health far more effectively than a poor diet supplemented with vitamins but there are some important exceptions.
Neither vitamins B12 nor D are naturally produced by plants. B12 is made by microbes commonly found in soil, while vitamin D is made in the skin when it is exposed to sunlight. Some foods, including oily fish, egg yolks, liver, meat and UV-exposed mushrooms, provide vitamin D but according to the NHS, it’s difficult for people to get enough from food alone. Viva! therefore strongly recommends that vegans take a vitamin B12 supplement and that everyone, regardless of diet, considers taking vitamin D during the autumn and winter months.
Omega-3 fats also play an important role in immune function, helping regulate inflammation and your body’s response to infection. Plant foods such as ground flaxseed, chia seeds and walnuts provide ALA, an essential omega-3 fat that your body can convert into the longer-chain fats EPA and DHA, although this conversion is limited. An algae-based omega-3 supplement provides EPA and DHA directly. Algae are the original source of these fats in the marine food chain, with fish obtaining them by eating algae or other fish that have eaten them.
Are vegans less likely to get ill?
The fairest answer is probably yes – but vegans aren’t bulletproof. A well-planned vegan diet provides plenty of fibre, vitamins, minerals and beneficial plant compounds that help support a healthy immune system, while also being associated with a lower risk of major chronic diseases. Growing evidence suggests that a healthy vegan diet may also reduce the risk or severity of some infections, including Covid. Whether veganism specifically protects against everyday colds and flu remains uncertain but there is every reason to make plants the foundation of a diet that supports good health.
About the author
Dr. Justine Butler
Justine joined Viva! in 2005 after graduating from Bristol University with a PhD in molecular biology. After working as a campaigner, then researcher and writer, she is now Viva!’s head of research and her work focuses on animals, the environment and health. Justine’s scientific training helps her research and write both in-depth scientific reports, such as White Lies and the Meat Report, as well as easy-to-read factsheets and myth-busting articles for consumer magazines and updates on the latest research. Justine also recently wrote the Vegan for the Planet guide for Viva!’s Vegan Now campaign.
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