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.
Deficiencies in protein, vitamins A, E, B6 and folate demonstrably weaken the immune system. How severe that effect is depends on how serious the deficiency is, how old you are, and whether an infection is present at the same time. Older adults, young children and pregnant women are at the greatest risk of these kinds of deficiencies and the associated increased susceptibility to infection.
The micronutrients with the strongest evidence for supporting a healthy immune system are vitamin C, vitamin D and zinc. They work best in combination with other vitamins and minerals, such as vitamins A, B6, B12, folate, iron, copper and selenium. Supplementation helps when you have a demonstrable deficiency. In people without a deficiency, the benefit of taking extra supplements is considerably less certain. A randomised trial in healthy adults aged 55 and over illustrates this well: a multivitamin improved blood levels of vitamin C and zinc and the sense of wellbeing, but there was no measurable improvement in objective markers of immune function, such as the defensive capacity of white blood cells.
Vitamin D deserves special attention. Immune cells carry receptors for vitamin D and respond to it sensitively. Laboratory and animal research shows beneficial effects on both the innate defence response and the more specific immune response. In human studies, low vitamin D levels have been linked to a higher risk of conditions such as multiple sclerosis, rheumatoid arthritis, respiratory tract infections and tuberculosis. These are associations, not proven cause-and-effect relationships, but they have been found across multiple disease areas. Supplementation in people with a deficiency appears worthwhile; those who already have adequate levels have less evidence on their side.
More is not always better. Too much linoleic acid or arachidonic acid (fats), too much iron or even too much vitamin E can actually suppress the immune system. Animal research also shows that a Western diet high in fat and sugar reprogrammes immune cells over the long term, even after the diet has been stopped. That chronically elevated state of immune activation likely contributes to inflammatory diseases. Whether this works in exactly the same way in humans has not yet been fully established.
This answer draws primarily on multiple review articles on micronutrients and immune function, plus one randomised trial in healthy older adults. The associations between nutrition and immune function have been studied extensively, but much of the evidence is based on observational studies or animal research. The direct effect of supplementation on disease outcomes in people without a deficiency therefore remains uncertain. The randomised trial in older adults is valuable but limited to blood values and self-reported outcomes, not hard clinical endpoints such as infection frequency.
Does poor sleep increase my risk of cancer?
Poor sleep, and sleep apnea and night-shift work in particular, is associated with an increased cancer risk. Whether you personally face a higher risk depends on which sleep problems you have; at the very least, have any apnea symptoms evaluated.
How do you safely taper off Ozempic?
Whether gradual tapering is better than stopping abruptly is not yet known, but stopping abruptly leads to weight regain and worsening of blood pressure and other values in most people. Always discuss a stopping plan with your doctor, especially if you are also using the medication for your heart or for diabetes.
What is so-called 'Ozempic face' and how does it develop?
Rapid fat loss caused by semaglutide and related drugs can visibly hollow out the face, and the effect appears greater than weight loss alone explains. Whether and how best to correct this remains poorly studied.