Weak Immunity

Most of the immune system lives around the gut

The majority of the body's immune cells are found in gut-associated lymphoid tissue, in constant contact with gut bacteria, which helps explain why gut health and general susceptibility to infection are so closely linked. A randomised, double-blind, placebo-controlled trial gave 120 children with recurrent respiratory tract infections either a combination of two specific probiotic strains, Bifidobacterium animalis subsp. lactis and Lactiplantibacillus plantarum, or a placebo for 180 days. The probiotic group had significantly fewer and shorter episodes of fever, cough, and respiratory infections, including pneumonia, than the placebo group.

Source: Probiotic Supplementation Reduces RRTIs and Enhances Gut Microbial and Immunity in Children

A similar pattern in adults prone to colds

In adults who reported catching the common cold four or more times in the past year, a 12-week randomised trial testing a specific multi-strain probiotic drink found measurable improvements in infection rate. Separate research in adults aged 60 to 65, an age group more vulnerable to seasonal infections, found a specific probiotic strain improved natural killer cell activity and immunoglobulin A levels, both genuine markers of the body's frontline defence against infection.

Source: Testing the Immunomodulatory Effects of Probiotic Bacillus coagulans SNZ 1969 in Healthy Adults

As with any probiotic, these strains only keep working if they're properly fed. Taking a probiotic without also supplying fibre and plant compounds gives it far less chance of establishing itself well enough to genuinely support immune function over months of use, rather than just passing through.

What this means for you

Frequent infections, especially if severe, unusual, or accompanied by other symptoms like unexplained weight loss or persistent fatigue, are worth a doctor's assessment to rule out an underlying medical cause, since a general immune-support approach isn't a substitute for proper diagnosis. Given the genuine trial evidence above, a specific, well-studied probiotic strain is a reasonable addition for children with recurrent infections or adults who catch colds unusually often, alongside good sleep, nutrition, and hand hygiene. A varied, plant-rich diet supports the same gut bacteria this research ties to a stronger immune defence. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.