The No. 1 Nutrient to Eat When You Keep Getting Sick
A dietitian tells TODAY that fibre — not vitamin C — is the top immune nutrient most people lack, with strong links to gut microbiome health.
A dietitian interviewed by TODAY has identified a single nutrient for immune system support that most people consistently fall short on — and it is not vitamin C. According to the report published on 6 April 2026, people who repeatedly catch colds and infections are frequently deficient in this overlooked dietary compound, and the connection runs deeper than most people realise, reaching directly into gut health and the microbiome.
Why This Matters
Immune health and gut health are more closely linked than many people appreciate. Researchers estimate that roughly 70 percent of the immune system is housed in the gut, meaning the state of your microbiome directly influences how well your body fends off pathogens. Per TODAY, people who keep getting sick often focus on vitamin C as the default fix, while missing a nutrient that plays a more foundational role in both immune defence and gut microbiome balance. Addressing this gap could have wide-ranging effects beyond just fewer colds.
The Nutrient Dietitians Say You Are Missing
According to TODAY's report, the dietitian points to dietary fibre as the number one immune-supporting nutrient most people fail to consume in adequate amounts. Fibre is not simply a digestive aid — it is the primary fuel source for beneficial gut bacteria, which in turn produce short-chain fatty acids that regulate immune cell activity. Per the source, the average person falls well below the recommended daily intake, leaving both the microbiome and immune defences underpowered. A diverse, fibre-rich diet supports the microbial communities that act as a first line of immune defence.
What This Means for Your Health
For anyone who feels susceptible to every seasonal illness circulating at work or school, this finding suggests that rebuilding gut microbiome diversity through fibre intake could be a practical first step. Per TODAY, whole foods such as legumes, vegetables, whole grains, and fruit are among the most accessible fibre sources. Rather than reaching for a single supplement, the dietitian's guidance points toward a broader dietary shift that benefits both gut and immune function simultaneously.
If recurring illness is a pattern in your life, the evidence reported by TODAY suggests the solution may start in your gut, not your medicine cabinet. Prioritising fibre-rich whole foods could strengthen the microbiome and, by extension, the immune system — offering a more durable form of protection than any single vitamin alone.