N

UMEROUS dietary supplements are sold

for their supposed immune-boosting

powers. Many of these health claims are

spurious, stemming from tests in petri

dishes, rather than from randomised,

controlled trials in people – the gold-

standard for any scientifically proven effect. But it’s

not all marketing guff.

Of commonly sold supplements, zinc probably

comes out best, with evidence that it can both prevent

colds and shorten their duration if started within 24

hours of the symptoms first appearing. It is thought to

work by stopping the cold virus from replicating, or

preventing it from gaining entry to cells lining the

airways. Even so, overdosing on zinc will suppress your

immune system, so care is needed.

Vitamin E has also been shown to enhance immune

function in human and animal studies. Dayong Wu at

Tufts University in Boston and his colleagues tested

vitamin E in older people – giving half of the 670

residents of a nursing home a small daily dose of

vitamin E and the other half a placebo – and found

significant differences in the rate of upper respiratory

infections. A bigger clinical trial is in the pipeline, but

the evidence is already strong enough that Wu

recommends people over 65 routinely take 200

international units (IUs) of vitamin E. Moderation is

again key, as vitamin E can be toxic in high doses.

Vitamin D, meanwhile, appears to do something

IMMUNE

BOOSTERS

Beyond cleaning regimes, there are

some things that can boost our immune

system’s performance we have more

control over. Some dietary supplements

can help – although they’re probably

not the best medicine

anything that encourages people to cut back on habits

like handwashing is dangerous.

But while being too slovenly stands a good chance

of giving us diarrhoea, in certain respects it seems we

don’t need to be too clean. In particular, you might

want to cut back on antibacterial handwashes and

laundry detergents. Not only might some of these have

less benefit than advertised, but there is some evidence

they might contribute to bacteria becoming resistant

to antibacterials and even antibiotics. There’s also

growing concern about indoor pollution connected

with overzealous use of certain household products.

How do we find the sweet spot between being too

dirty and too clean? “Targeted hygiene” could be the

answer. Although this strategy has been around since

the 1950s, it was largely limited to hospitals and

industries such as catering, pharmaceuticals, and

cosmetics. Increasingly though, hygiene experts believe

it should become an everyday feature of people’s lives.

Rather than striving for a sterile home or office,

targeted hygiene means focusing only on removing

harmful bacteria, from important surfaces, at critical

times. Most of the cleaning should focus on doorknobs,

light switches and the bathroom – anything we touch a

lot. It’s also crucial to thoroughly clean everything you

use while cooking. That includes all surfaces, chopping

boards and utensils that come into contact with raw

meat, as well as unwashed dirty vegetables, whose

bacteria can give you food poisoning just as raw chicken

can. The most important advice is to wash your hands,

after cooking, before eating and after using the toilet.

But beyond that? Well, Joan Rivers fans can take

heart: cleaning the walls, floors or the furniture really

can wait six months. If you’re not allergic to dust mites,

vacuuming is entirely optional. And you can forget

about making the bed – especially if you’re allergic to

dust mites. Mites need a humid atmosphere to survive,

so leaving the covers open in the morning might help

to kill the beasts.

Beyond these basics, it seems there is one big thing

we can do to improve our health beyond worrying too

much about the state of our homes: spend more time

outdoors. Preliminary findings hint that spending

more time doing social sports and other outdoor

activities can help restore a healthily diverse

microbiome. The best advice is quite pleasingly

wholesome and old-fashioned. Use cleaning products

sparingly, in the places that matter, open the windows

after you’ve finished, and then go out for a nice long

walk in the fresh air. ❚