Infection rates in older people living at home are not helped by taking vitamin or mineral tablets, researchers have found.
The study looked at how vitamins helped fight infections
The Aberdeen University study looked at the effects of daily multivitamins compared with dummy placebo tablets.
It found that taking supplements seemed to make no difference in infection rates between the groups.
The research, published in the British Medical Journal, covered 900 people aged over 65 who were living at home.
At least 10% of older people have a vitamin or mineral deficiency, which can lead to poor immunity and increased risk of infection.
About a quarter of older people in the UK take nutritional supplements.
But the study found no clear evidence of influence on infections.
Researchers looked at contacts with primary care for infection, the number of days an infection lasted and quality of life.
Numbers of antibiotic prescriptions and hospital admissions were also taken into account.
The study authors said: "Regular use of commonly available multivitamin and multimineral supplements is unlikely to reduce the number of self-reported infections or associated use of health services for people living at home.
"It remains to be seen whether those at higher risk of infections, such as older people living in care, would benefit from supplementation."