IN GOOD The power of three

Melanie Leyshon

As we head into the bleak midwinter amid the deadly backdrop of Covid-19, it’s never been more important to keep our immune systems in tip-top condition.

A healthy diet, a proper night’s sleep, regular exercise and weight management are high on everyone’s stay-well list.

But to help fight viral infections that are rife at this time of year and give us the best chance of fighting Covid-19, our bodies need ammunition in the form of top nutrition.

Our immune systems are a complex network of cells and chemicals that work together to defend against infections, says Bridget Benelam, nutrition scientist for the British Nutrition Foundation.

“We need a range of essential nutrients to support immune function, but zinc, selenium and vitamin D may be particularly important for anti-viral immunity,” she says.

Professor Philip Calder of Nutritional Immunology at the University of Southampton picked out these three nutrients in the fight against Covid-19 at the British Nutrition Foundation’s Virtual Conference on coronavirus last month.

He said studies on humans have shown if people are given supplements of vitamin D, zinc and selenium, their markers of immunity can be improved.

Here’s how to build up your defences:

VITAMIN D

This vitamin is great for warding off bacterial and viral attacks.

“It helps us fight upper respiratory tract illness, such as colds, flu and perhaps also Covid-19, which can become more severe if it goes to our lower respiratory tract,” says Prof Calder.

Around half of the UK population aged over 45 have low levels, with around 15 per cent of people being deficient in winter.

A blood test is the only way to test your levels, though tell-tale signs of a deficiency include extreme muscle and bone aches. HOW MUCH WE NEED: “We should all consider a daily supplement of 10 micrograms during the winter months to ensure we’re getting enough,” says Benelam.

This is Public Health England’s recommendation and studies have shown this is the optimum amount.

Susan Lanham-new, Professor of Human Nutrition and Head of the Nutrition, Food and Exercises Sciences Department at the University of Surrey, says: “higher doses of 25 micrograms (1,000iu) and above are not needed. It’s also better to take a 10 microgram dose daily rather than one or two higher 25 microgram doses once or twice a week.”

Only people who have been diagnosed as severely vitamin D deficient by a GP need a high dose on prescription. Too much vitamin D can be dangerous. It causes calcium to build up in the body, which can weaken the bones and damage the kidneys and heart, says the NHS. GOOD SOURCES: Oily fish such as trout, mackerel, herring, salmon, eggs, foods fortified with vitamin D such as mushrooms that have been UV irradiated, Kellogg’s breakfast cereals, Alpro soya drink, and Warburtons’ half white, half wholemeal thick-sliced bread.

ZINC

Important for fighting viruses, zinc also stops them replicating inside the cells that line our lungs, says Prof Calder. “Zinc has effects that interfere with replication, inhibiting the enzyme that copies the genome of some types of virus, including coronaviruses.”

Studies already show zinc supplements can improve immunity in older people with low intakes and can lower the risk of death from pneumonia.

Recommended daily intakes are 9.5mg for men and 7mg for women. Check food labels for NRV (nutrient reference values). Around 5 per cent of UK women and 10 per cent of UK men have low intakes. Tell-tale signs are repeated colds and

Zinc stops viruses replicating in the cells that line our lungs

HOW MUCH WE NEED:

When it was reported that vitamin D could help in the battle against Covid-19, the supplements flew off the shelves. But your body actually needs a trio of nutrients to fight bugs effectively, discovers

gastro-intestinal infections (stomach flu).

GOOD SOURCES: Offal, beef, lamb and pork, Quorn, pulses, seeds, nuts and wholegrain bread, pasta and rice.

SELENIUM

This nutrient is often overlooked, says Prof Calder, despite being important in the prevention of viruses mutating and becoming more virulent.

Studies in mice found selenium deficiency increased their risk of viral infections and hampered their immune responses.

It’s one of the nutrients that we are getting less of, partly due to depleted sources in the food chain, from our food being grown in selenium-depleted soil and cattle and poultry getting less of the nutrient from their feed.

HOW MUCH WE NEED: Women need 60 micrograms and men 75 micrograms. Around 50 per cent of women and 25 per cent of men in the UK have low intakes. GOOD SOURCES: Meat, poultry, fish and nuts. A 30g portion of Brazil nuts has 76 micrograms. A 140g fillet of fresh tuna or cod each give you 60 micrograms. A 125g chicken fillet has 20 micrograms.

Find out more at The British Nutrition Foundation website, nutrition.org.uk