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‘Exercise is my number one tip for staying healthy,’ says Professor Janet Lord, an expert in immunity and ageing at the University of Birmingham.
‘Using muscles during exercise has an anti-inflammatory effect and helps immune cells called neutrophils get to an infection site quicker.
‘It also helps other immune cells called macrophages — “guard” cells that patrol the body for signs of attack — function better,’ she explains.
Exercise can also reduce the effects of ageing on the immune system. A study of 125 keen cyclists aged 55 to 79 found they had immune systems of people decades younger, reported the journal Aging Cell in 2018.
‘The thymus [a gland with two lobes behind the breastbone], which makes immune cells called T-cells, starts to shrink from the age of 20 and makes fewer T-cells,’ explains Professor Lord.
‘In this study, the cyclists’ thymuses were making as many T-cells as those of a young person.’
Another study, by the University of Birmingham, involving 200 people over the age of 65 found those who regularly walked 10,000 steps a day had the neutrophil function of a person in their 20s.
‘Any regular exercise that gets your heart rate up seems to be able to “turn back the clock” of the immune system,’ says Professor Lord. ‘We don’t know how little you have to do to make this happen, although 10,000 steps a day seems to be enough to get neutrophils circulating around the body.
‘But any exercise is better than none. You need to move as much as possible, even if it’s only getting up and down a few times in an armchair every hour or walking up and down the stairs a couple of times a day.’
LAY OFF THE SALT
A diet high in salt may reduce the efficiency of the immune system, according to a study published last week.
When scientists fed mice a high-salt diet, they became more prone to bacterial infections.
And when human volunteers doubled the recommended 6g a day intake of salt (the amount in two portions of burgers and chips), their immune systems got worse at fighting off bacteria.
COUNT YOUR CALORIES
‘People should be careful not to eat too much as becoming obese can cause inflammation in the body,’ says Arne Akbar, a professor of immunology at UCL and president of the British Society of Immunology.
‘Fat cells produce toxic chemicals that can affect the body’s immune response — we liken the effect of these chemicals to “friendly fire.” ’ However, older people should not cut back. ‘There aren’t many people in their 80s who are overweight,’ adds Professor Akbar. ‘It’s possibly because their metabolism changes, so they need their calories and shouldn’t restrict them.
‘But younger people should keep to a healthy weight.’
The authors of the study, published in the journal Science Translational Medicine, said the body creates hormones to remove excess salt, and glucocorticoids — a group of hormones — have an immune-suppressing effect.
‘Excessive salt is also known to potentially increase a certain type of cell called T-helper 17 cells which increases potentially harmful inflammation,’ adds Jenna Macciochi, a lecturer in immunology at the University of Sussex.
STICK TO OFFICIAL BOOZE GUIDANCE
While it’s tempting to have a few drinks in lockdown, excess alcohol is no good for the immune system. ‘Drinking to excess can affect production of immune cells produced in the bone marrow,’ says Jenna Macciochi. ‘These are needed to replace older cells that are less effective.’
When scientists exposed white blood cells in a laboratory to the equivalent of five units of alcohol (roughly three glasses of wine) every day for a week, the cells produced 75 per cent less of a molecule called type 1 interferon, which is critical to mounting an anti-viral response, reported the journal BMC Immunology in 2011.
‘Alcohol is also a sleep disruptor and poor quality sleep can also impair immunity,’ adds Jenna Macciochi. Excess alcohol can also damage the lining of the gut, where 70 per cent of the body’s immune system is located.
So stick to the government’s recommendation of no more than 14 units of alcohol a week.
TOP UP THE SUNSHINE VITAMIN
‘Vitamin D has lots of good effects on the immune system,’ says Arne Akbar, a professor of immunology at University College London and president of the British Society of Immunology.
‘Many people in the UK are deficient at this time of year as the body needs exposure to sunlight to make it, so a supplement is useful. I take one myself.’
The recommended daily dose is 10mcg a day in winter, as the sun isn’t strong enough in the UK for the body to produce its own. You can get some vitamin D from your diet but it is hard to get enough from food alone — you would need to eat large amounts of shiitake mushrooms and oily fish, for example.
A 2016 study in the Journal of the American Geriatrics Society found older people in care homes given high doses of vitamin D — equivalent to 90mcg per week — were 40 per cent less likely to suffer acute respiratory illnesses.
KEEP TAKING THE STATINS
Around seven million people in the UK take cholesterol-lowering drugs called statins and this may have unexpected benefits for their immune systems.
A study of 64 patients at the University of Birmingham found those aged over 55 hospitalised with pneumonia who were given 80mg of simvastatin daily for seven days had a higher neutrophil function than those given a placebo.
The study, in the American Journal of Respiratory and Critical Care Medicine last year, also found that after a year, those in the statin group had a lower death rate than those in the placebo group.
‘As we age, neutrophils are slower to reach the site of infection and when they get there they are less effective at killing the infection,’ says Professor Lord.
‘However, in this study, statins seemed to rejuvenate the neutrophils. This hasn’t been adapted as standard practice yet because we need larger studies to confirm these findings.
‘In the meantime, if you are already prescribed statins, don’t forget to take them.’
EAT FOOD OF MANY COLOURS
Despite the hype around certain foods, there is no ‘superfood’ that boosts your immune system on its own, says Megan Rossi, a dietitian at King’s College London. What is important, she says, is feeding your gut microbiota, the trillions of microbes that call your intestine home.
‘Your microbiota has been linked with stronger immunity and plays a key role in training, maintaining and supporting our immune system,’ says Megan Rossi.
To maintain a healthy microbiota, she recommends eating a wide variety of plant-based foods. ‘The more variety, the better: vegetables, fruit, wholegrains, legumes (beans and pulses), nuts and seeds,’ she says.
‘Frozen, tinned and dried all count, and go for different colours — think red and yellow peppers, green and black grapes.
‘That way, you’ll be feeding your diversely skilled team of microbes each their preferred foods.’
AND FINALLY… ZINC IS GOOD FOR US
Older people aged 55 to 87 who took zinc supplements had lower rates of infection than those taking a placebo, according to a study in the American Journal of Clinical Nutrition in 2007.
‘There is some evidence that zinc is good for the immune system, but we don’t know how much is beneficial and for how long you should take it,’ says Professor Akbar.
The NHS recommends that men get 9.5mg a day, and women 7mg. Zinc is found in meat, shellfish, dairy products and fortified cereals.
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