The top foods proven to support your immune system

Jan 11, 2021

Here is a list of PBHO’s top diet tips based on the scientific evidence:

  1. Eat the rainbow
  2. Nitrate rich vegetables
  3. Optimise nutrients eg Selenium, Zinc
  4. Herbs and spices
  5. High fibre foods
  6. Nutritional yeast
  7. Green tea
  8. Vitamin D

1) EAT THE RAINBOW: Fruits and vegetables are packed full of anti-oxidants, anti-inflammatory compounds and an array of phytonutrients.  These all act to improve the function our immune system. The best evidence is for flavonoids, a large group of polyphenol compounds found in many plant foods, which have been found to significantly reduce the risk of upper respiratory tract infections. High concentrations of flavonoids are found in green tea, berries and dark chocolate!

Vitamin C is an essential component of the diet and only found in fruits and vegetables. An adequate intake is required to support the immune system. Top food sources of vitamin C include red and green peppers, oranges, kiwi fruit and broccoli.

Other specific fruits and vegetables have been shown to help the immune system include, cruciferous vegetablesmushrooms, garlic and onions.



Vitamin C 

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2) NITRATE-RICH VEGETABLES have a number of health benefits. They release nitric oxide, which is important for the health of blood vessels. We are now understanding that COVID-19 is a disease that causes inflammation of the blood vessels and nitric oxide is even being considered as a treatment. Although nitrate-rich vegetables alone are not going to be the ‘cure’ for COVID-19, we know that a healthy plant-based diet can optimise the health of blood vessels.


 Foods high in nitrates. Source ‘How not to die’ by Michael Greger

3) Optimise MICRONUTRIENTS such as selenium and zinc. Both are important in maintaining a healthy immune system. One brazil nut a day will take care of your selenium needs. Foods rich in zinc include whole grains, beans and nuts. Soaking grains and beans before cooking can increase the absorption of zinc and other nutrients in the food.


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4) HERBS AND SPICES in various forms have some of the highest concentrations of anti-oxidant compounds and are associated with an array of health promoting effects. Many show anti-infective properties too, at least in the laboratory. Turmeric in particularand its active component, Curcumin, has a number of useful properties. So make sure you use a variety of herbs and spices liberally in cooking every day.


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5) HIGH FIBRE FOODS are essential for the health of our gut, in particular the microbes that live within it, which are crucial for maintaining a healthy immune system. A plant-based diet consisting of fruits, vegetables, whole grains and beans is the best way to maintain a healthy gut and studies have shown that the gut microbiome may be crucial for our defence against viral infections and COVID-19.

There is not enough data yet to recommend probiotics for prevention of infection, but we do know that changing your diet can have beneficial effects on the gut microbiome in a matter of days to weeks. Cabbage and fermented vegetables may be particularly good for the gut microbiome and COVID-19.


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6) NUTRITIONAL YEAST is a species of yeast known as Saccharomyces cerevisiae, which is grown specifically to be used as a food product. The yeast cells are killed during the manufacturing process so this is not a live product. It can be used in all sorts of dishes to add flavour and is also a great source of nutrients. Beta-glucan, one of the polysaccharide carbohydrates within the yeast, has been associated with a number of immune boosting effects. Of note, it is the beta-glucan in mushrooms that is thought to be one of the main reasons for the beneficial effects on the immune system. So add nutritional yeast (and mushrooms) to your soups and sauces daily.


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7) GREEN TEA is high in polyphenolic catechins, which have a number of potential health benefits, including anti-viral properties. Researchers are also interested in the effect of green tea compounds for COVID-19. In general 2–5 cups a day of green tea is needed.


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8) VITAMIN D SUPPLEMENTATION has been shown to reduce the risk of acute respiratory tract infection. There has been much debate on the role of vitamin D in COVID-19. Although often categorised as a nutrient, vitamin D is really a hormone and best obtained by regularly exposing the skin to sunlight. However, for many in the current situation, this is not possible and therefore we rely on food sources and supplements. Some, but not all, studies suggest that inadequate levels of vitamin D may increase the severity of COVID-19. Given the importance of vitamin D in the functioning of the immune system, it is strongly advised that adequate levels are achieved and this will require a supplement. Dosage of vitamin D is a matter of debate with many advocating for higher doses, 1000–2000IU per day, compared to the 400IU recommended by the UK Government. Vitamin D comes in two forms; vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is more effective at raising blood levels. If you are vegan, be sure to choose a plant-based source of vitamin D3, made from lichen.

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