How can I strengthen my weakening immune system?
Correcting vitamin and mineral deficiencies is the best-supported step for maintaining immune function. For more far-reaching approaches, the evidence in humans is still too limited for concrete recommendations.
As we age, the immune system gradually declines. White blood cells that recognise and fight infections lose their sharpness. As a result, vaccines are less effective, and the risk of infections, certain cancers and other age-related diseases increases. At the same time, a smouldering, low-grade inflammation develops in the body that itself contributes to heart disease and dementia. This two-sided process, declining immunity and smouldering inflammation, is one of the most robustly supported mechanisms behind the deterioration of health in later life.
The most concrete, immediately actionable step is to check whether you are deficient in any vitamins or minerals. A deficiency in vitamin A, C, D, E, various B vitamins, iron, selenium or zinc demonstrably weakens the immune system. Correcting a deficiency to the recommended level can restore that function. Note: this applies only when there is a genuine shortfall. In people who already get enough, additional supplementation has no proven benefit. Have your blood levels measured, and supplement in a targeted way where needed, not as a precautionary free-for-all.
What you eat also appears to play a role. A dietary pattern rich in vegetables, fruit, whole grains, nuts and fish is associated with lower blood levels of inflammatory markers. Whether this is a direct cause-and-effect relationship has not yet been proven, but the association is consistent and biologically plausible. The gut microbiome likely plays a part as well: a disrupted gut microbiome is associated with poorer immune function. How best to influence the gut microbiome to strengthen immunity has not yet been thoroughly studied in humans.
Research is also under way into whether eating less without becoming undernourished, or substances that mimic that effect, can suppress smouldering inflammation. The results in humans are preliminary. More advanced therapies that aim to directly reverse the ageing of the immune system are still at an early stage of investigation. It is too soon to recommend anything concrete in that area.
This answer is based on multiple review studies, including reviews on immunosenescence, inflammaging, micronutrients and diet. The decline of the immune system with age and the role of vitamin and mineral deficiencies are the most strongly supported findings. The sections on diet and the gut microbiome rest on association studies in which cause and effect have not yet been established. Therapies aimed at reversing immune ageing are not yet ready for clinical practice: the researchers describe them as largely at an early stage of investigation.
Which supplements genuinely support your immune system?
Some supplements genuinely support your immune system, but the effect is greatest when you have a deficiency: so first check whether your vitamin D or zinc levels are adequate, and supplement in a targeted way.
Does your immune system really weaken as you get older?
Your immune system demonstrably weakens with age, but vaccinations remain worthwhile and a good diet can limit further decline.
Does too little sleep weaken your immune system?
Yes, too little sleep demonstrably weakens your immune system and increases the risk of infections and chronic inflammatory conditions. Seven to nine hours of sleep is the most commonly cited guideline, and vaccinations also work better when you are well rested.
Can air pollution weaken your immune system?
Air pollution disrupts your immune system in several ways at once: a greater chance of allergic reactions, less resistance to viruses. Limit your exposure as much as possible, especially during pregnancy.
Which factors weaken your immune system?
Several factors demonstrably weaken your immune system: deficiencies in vitamin A, zinc, and iron are the best supported, but medical treatments, chronic stress, and intense exercise also play a role. If you are using high doses of steroids for medical reasons or have an HIV infection, it is wise to involve your doctor in preventing infections.
How does nutrition strengthen your immune system?
Nutrition has a clear influence on the immune system: deficiencies weaken your defences, and correcting a demonstrable deficiency (especially of vitamin D, C and zinc) helps. In people without a deficiency, the case for extra supplementation is less convincingly proven.