Are there immunity benefits from eating a plant-based diet?

Could following a plant-based diet improve your health or is it not that simple? Here's what experts say…

There has been a consistent interest in plant-based diets over the last five years – with the number of vegans and vegetarians in Britain believed to be between 7-10%. There is also evidence some healthy plant-based diets may benefit the immune system.

So what are plant-based diets? They are “mostly based on foods derived from plants, such as grains, vegetables, fruit, pulses and nuts, but can include a smaller proportion of animal-derived foods, such as meat, fish, eggs and milk”, says Sara Stanner, Science Director at the British Nutrition Foundation. They include flexitarian, Mediterranean, vegetarian and vegan diets.

Immunity benefits of plant-based nutrition

Healthy plant-based diets have been linked to a “reduced risk of heart disease, strokes and Type 2 diabetes”, and to “lowering blood pressure, reducing blood cholesterol and promoting a healthy body weight”, according to the British Nutrition Foundation. The reasons for this are unclear. However, we know our cells – including those in the immune system – require good nutrition to function optimally.

Plants are packed with vitamins and minerals. But according to Stanner, “the key to a healthy plant-based diet is eating a wide variety of plant foods, but not necessarily cutting out animal products altogether”. Meat and fish contain many micronutrients and trace nutrients, such as iron, zinc, B vitamins, vitamin A and copper, which support immune function – although it is possible to get most of these from a vegan diet.

“Each micronutrient plays a different role in the immune system – don’t make a hero of just one”, says Stanner. There is “no individual nutrient, food or supplement that will boost immunity, or stop us getting highly infectious viruses”, says Stanner. For more information about the nutrition requirements for your age and gender, see the BBC Food Nutrition Calculator.

Fibre and phytochemicals for gut health and immunity

Eating a wide variety of plant foods encourages different types of good bacteria to thrive in the gut. “I recommend 30 different types of plants a week”, says Tim Spector, Professor of Genetic Epidemiology and lead on the Covid-19 Zoe symptom study app. “A healthy gut microbiome is crucial to a healthy immune system”, he continues. Most of the body’s immune cells are in the lining of the intestine, and microbes in the gut play a crucial role in keeping this system healthy.

Plant-based diets are typically higher in fibre, a key nutrient needed for a healthy gut microbiome. For example, gut bacteria ferments, or “feeds on”, fibre and creates short-chain fatty acids, which have been shown to improve immunity against pathogens.

It’s important to eat the recommended 30g fibre per day, but adults eat an average of 18g. Foods high in fibre include many fruits such as berries, pears and oranges, vegetables such as broccoli, carrots and sweetcorn, brown pasta, brown rice, wholegrain bread, beans, lentils, chickpeas and nuts.

Phytochemicals, compounds produced by plants including fruits, vegetables, grains and beans, are also believed to increase some types of beneficial gut bacteria. The colour of a plant is determined by the phytochemicals it contains, and some of these are associated with “positive benefits for the immune system”, says dietitian Sophie Medlin. The wider the variety of different coloured plants you eat, the more types of phytochemicals you’ll consume. Red, orange, yellow and green plants contain carotenoids, which have been associated with boosting immunity. Although evidence for the benefits of phytochemicals to immunity is not conclusive, there is no health downside to eating five a day.

Eating for a healthy gut is a long-term approach. While modifying your diet can positively impact your gut bacteria and immune parameters within three months, research finds the alterations do not “reflect the degree of change that occur with a long-term vegetarian diet”.

How to boost the plants in your diet

There are benefits to eating whole plant foods rather than processed ones, and a Zoe study associates highly processed products with “bad” gut microbes and poorer health markers. “‘Plant-based’ does not guarantee ‘healthy’”, says Stanner, so it’s a good idea to check nutrition labels and opt for foods with less saturated fat, salt and sugar, and to think about the balance of your overall diet.

Making your diet plant-based could be as simple as adding more vegetables or plant protein sources, such as beans and lentils, than meat, to your shop and to individual dishes. Read our guides on healthy ways to go vegan or vegetarian.

Nutrition for vegans

Meat, fish and animal products, such as eggs and dairy, are good sources of immune-supporting nutrients, so if you are cutting out animal foods, make sure you’re getting enough of these nutrients, including protein, vitamin B12, calcium, iron, zinc, iodine, and long-chain fatty acids.

Protein- or amino acid- (the building blocks of protein) deficiency can impair immune function, but protein deficiency is rare. For those following a vegan diet, complete protein sources (ie, contain all nine essential amino acids) include soy, quinoa, hemp, chia seeds, Quorn and buckwheat. You can also create a complete protein by pairing some vegan foods, such as beans on toast or lentils with rice.

This article is not intended as a replacement for medical advice. If you are concerned about your immunity, visit your GP.

Originally published August 2021