Focus on prebiotic and probiotic-rich foods, advises Llewellyn-Waters. Prebiotic-rich foods include apples, asparagus, artichokes, bananas, broccoli, cauliflower, fennel, garlic, legumes, leeks, onions, pak choi, wheat and oats. Probiotics, important for their live microbes, are fermented foods, like sauerkraut, fermented tempeh, miso, kefir and live natural yogurt.
Keep blood sugars stable by avoiding sugary, ultra-processed foods and following a consistent meal schedule which includes protein. Elevated blood sugars weaken our antiviral defences and promote viral replication. One 2021 study found it the most likely risk factor to explain why otherwise healthy patients get severe Covid 19.
Should we take a vitamin supplement? “Some of the key vitamins and minerals involved in supporting our immunity include vitamins A, C, D, E as well as the B-vitamins and the minerals zinc and selenium,” says Llewellyn-Waters. “For most people I’d advise focusing on getting your nutrients from your diet first, although one supplement I often recommend for people over 60 is vitamin B12, since this micronutrient becomes harder to absorb as we age. If you are elderly, or under a lot of physical or emotional stress, you may wish to consider an all-round, high-quality multivitamin supplement.”
The only vitamin supplement that immunologist Dr Jenna Macciochi takes is Vitamin D. “We’re probably not going to get sufficient quantities from our diet and there is insufficient sunlight in February [to boost your Vitamin D supply],” she says.
Harness your body clock
It isn’t just getting enough sleep that’s important to immunity – it’s when you do it. The circadian system regulates every aspect of our immune system, right down to our skin, which becomes more permeable at night, drier, itchier and with less defence against pathogens entering the body. “The immune system is turned up in daytime, but it begins to be turned down as you approach late afternoon and at night it’s low,” says Russell Foster, professor of circadian neuroscience at the University of Oxford and author of Life Time.
A cut or a burn will heal more than twice as fast if it occurs during the day rather than at night. One explanation for all this is that running permanently on full throttle raises the risk of autoimmune disease – and also requires huge energy – so our immune system is primed for daytime, when we should be most likely to need it.