🛡️ Best Immune Support Supplements

Worth considering if a blood test shows low vitamin D, which is common and does impair normal immune function. In people who are not deficient, large trials found vitamin D did not prevent respiratory infections. At 5,000 IU (125 mcg), each softgel is above the 4,000 IU daily upper limit for adults, so it suits correcting a confirmed deficiency, guided by a retest after 8 to 12 weeks, rather than year-round use without testing. The MCT oil aids absorption of this fat-soluble vitamin.

Wellmune® is the most-studied branded beta-glucan, with more than a dozen peer-reviewed trials. 250 mg matches the dose used in them, and one trial in stressed adults reported fewer upper respiratory symptoms than placebo. It primes innate immune cells through the gut rather than acting the way vitamin D does. Aimed at daily use through demanding stretches of work, travel or training.

EpiCor® is a dried yeast fermentate, or postbiotic. 500 mg matches the dose used in its trials, which measured immune markers and self-reported cold and congestion symptoms; the evidence base is small. It is thought to act through the gut-immune axis rather than priming immune cells directly, a different route from Wellmune®.

Andrographis has been studied for shortening how long cold symptoms last and how bad they feel when it is started early. AP-Bio® is the standardised extract used in those trials, which is not the same as generic andrographis powder. It is taken for a few days at the onset of symptoms rather than every day. Unlike the other picks here, this one is for when you are already coming down with something.