Habits for Immune Health: Sleep, Activity, Nutrition, Smoking and Alcohol

Overview

Everyday habits cannot make you immune to infections, but several are linked to how the body copes with them. This page sorts what is well supported from what is only suggestive. Labels: established recommendation, promising but limited, mixed, insufficient evidence.

At a glance

Sleep

In a study of 164 healthy adults who were given a cold virus, those sleeping less than 5 hours or 5 to 6 hours a night (measured by wrist monitor) were more likely to develop a clinical cold than those sleeping more than 7 hours. Sleep broken into pieces was not linked to cold risk. [1] This was one study and shows association, not proof that sleeping more prevents colds. For sleep routines, see the NHS tips: a regular schedule, relaxing before bed and avoiding alcohol and nicotine 1 to 2 hours before bed. [7] More in Better Sleep.

Physical activity

A Cochrane review of 14 trials in 1,377 adults found no difference between exercise and no exercise in the number of respiratory infections, though exercise reduced symptom severity and the number of symptom days in a few studies. The authors rate certainty as low because of small studies and bias. [2] The NHS general guideline for adults is at least 150 minutes of moderate activity or 75 minutes of vigorous activity a week, plus strengthening on 2 days. [8] Label: mixed for infections; the guideline stands for general health. When you are ill with a cold or flu, the NHS advises rest. [9][10]

Nutrition

MedlinePlus lists malnutrition, especially too little protein, as a cause of acquired immunodeficiency. [6] The NHS says you should be able to get the vitamin C and zinc you need from a varied, balanced diet. [11][12] For supplements, see vitamin C, vitamin D and zinc. For food guides, see functional foods by wellness goal. We did not find solid evidence that any single food "boosts" immunity: proper evidence not found in the sources we read.

Smoking

A meta-analysis of 12 observational studies found ever-active smokers had higher odds of hospital admission (odds ratio 1.5) and intensive-care admission (2.2) after influenza than never-smokers, with no clear link to deaths. Secondhand smoke was linked to admissions only in children under 15. [3] The NHS says smoking can make cold symptoms worse. [9] If you want to quit, your clinician or national quitline can help.

Alcohol

A review says even moderate alcohol can influence immune responses, though often the effect is a subclinical weakening that matters only after an infection or injury. Chronic heavy drinking interferes with both innate and adaptive immunity and raises susceptibility to viral and bacterial infections. [4] We did not find a source in this review that sets a safe amount for immunity.

Handwashing and hygiene

Washing with soap and water for about 20 seconds, especially after coughing, sneezing, using the toilet and before eating, helps stop infections spreading. [5] Details in vaccines and infection prevention.

When to get help

Habits do not replace medical care. If you get repeated or severe infections, see a clinician: getting sick often. If sleep trouble is a problem, see insomnia. For stress, see Stress and Relaxation. Emergency signs such as severe trouble breathing: use your local emergency number (911 in the US).