Immunity 360: 12 Ways to Strengthen Your Body From the Inside Out

5. Support Gut Health: Prebiotics, Probiotics, and Fiber

The gut microbiome plays a major role in immune education and the body’s response to pathogens. A diverse diet rich in fiber feeds beneficial microbes and supports mucosal defenses. Include prebiotic foods like onions, garlic, leeks, bananas, and whole grains to nourish helpful bacteria. Fermented foods—yogurt, kefir, sauerkraut, miso—offer live cultures that can support gut balance for many people. For targeted situations, certain probiotic strains have evidence for reducing respiratory and gastrointestinal infections in specific populations; choose products backed by reputable manufacturers and look for strain-specific studies when possible. If you take antibiotics, a probiotic can help reduce antibiotic-associated diarrhea, but discuss timing and product choice with your clinician. Avoid treating probiotics as a cure-all: a food-first approach is foundational, and testing or specialist input can be useful for persistent gut issues or complex health conditions. Small, consistent changes to diet often translate to meaningful improvements in digestive comfort and immune-linked outcomes.

6. Keep Vitamin D in a Healthy Range

Vitamin D supports immune cell function and mucosal defenses, and many adults have levels lower than optimal—especially in winter or with limited sun exposure. Aim to get vitamin D status checked if you have risk factors such as darker skin, obesity, limited sun exposure, or certain chronic conditions. Safe sun exposure can boost vitamin D naturally, but supplementation is often the practical method to correct deficiency. Work with a provider to test levels and determine an appropriate dose rather than guessing. Typical daily maintenance doses vary by individual; higher doses to correct deficiency should be supervised medically. Food sources include fortified dairy or plant milks, fatty fish, and eggs, but those foods alone often don't supply enough for people with low levels. Maintaining a healthy vitamin D range supports immune balance but is one piece of a broader strategy that includes sleep, nutrition, and activity.