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12 Feb 2021

The truth about boosting your immune system

We cut through the headlines to tell you what's fact and what's fiction

How many stories have you read in the past year on how you can boost your immune system against coronavirus? Take the advice with a pinch of salt - most of it is nonsense and to some extent dangerous.

Adding certain foods or supplements into your diet will not leave you immune to COVID-19. It's far better and more effective to follow government advice around washing your hands and social distancing.

Read on to separate the fact from the fiction.

They say: supplements can boost your immune system

We say: the reality is there is no food or supplement that can boost your immune system in the way these stories imply.

Of course, food does have an impact on your health, and vitamins and minerals play an important role in keeping your immune system running as it should.

But there's no need to pay for 'immunity-boosting' supplements - staying healthy can be achieved by eating a varied and balanced diet, which includes plenty of fruit and vegetables.

Remember frozen, tinned and dried fruit and veg are just as good if you can't get hold of fresh.

They say: vitamin C supplements improve immunity

We say: vitamin C contributes to the normal functioning of the immune system. Adults need around 40mg of vitamin C a day to achieve this.

Vitamin C is water-soluble, so we can't store it in our bodies and this is why we need it every day.

So while there are supplements that contain up to 1,000mg of vitamin C in a daily dose, the only thing these will give you is really expensive wee.

Daily doses higher than 1,000mcg can cause diarrhoea, stomach pain and can interfere with certain medications, such as the blood-thinning drug Warfarin.

Food sources of vitamin C include oranges and citrus fruits, strawberries, red and orange peppers, broccoli and potatoes.

They say: take probiotics to help your natural defences

We say: there is currently no evidence that probiotics improve immune function or anything else. In fact, probiotics have no authorised health claims.

The European Food Safety Authority (EFSA) has rejected health claims for probiotics on the grounds of insufficient evidence, including those around improved immunity and natural defences.

We know our gut health is important for immune health but we can improve the balance of bacteria in our guts by eating a varied diet that includes lots of plant foods containing fibre, plus those that naturally contain prebiotics including onions, garlic, leeks and oats.

They say: take echinacea to fight colds and viruses

We say: the evidence that echinacea and other herbal supplements can help strengthen your immune system does not stack up.

Although the marketing might say these contain antioxidants which can help defend your body, the science shows that when taken in supplement form antioxidants don't have the same benefits as when eaten in fruit and veg.

Can this protect you from coronavirus?

Vitamin D

The only supplement that the government recommends (outside of its recommendation on folic acid during pregnancy) is vitamin D and this is simply standard advice, not special advice for living through COVID-19.

It's because we get most of our vitamin D from sunlight so it's hard to get this during the winter months and when we're all inside more than usual.

And while there are food sources (oily fish, egg yolk and fortified foods such as breakfast cereals), it's hard to get enough from these alone.

Vitamin D is also linked to our immune health so it's important to make sure we're not deficient. Research into treating COVID-19 cases with vitamin D is ongoing however so far the evidence is it's not an effective treatment.

For everyone over the age of one, the recommended dose is 10 micrograms a day (sometimes labelled as 400IU). Vulnerable and high-risk groups are being offered free vitamin D supplements by the government over the winter.

Like vitamin C, taking high doses of vitamin D is also not recommended. Vitamin D is a fat soluble vitamin so our bodies can't easily excrete it, instead any excess is stored.

Taking too much (more than 100mcg or 4000IU) over a prolonged period can cause a build up of too much calcium in the body which can weaken the bones and damage the kidneys and heart.

Read more: Which? advice on coronavirus

This story was originally published in May 2020 but has been updated for 2021.