Poor Nutrient Absorption

When bacteria end up in the wrong part of the gut

Most gut bacteria live in the large intestine, where they belong. Small intestinal bacterial overgrowth, or SIBO, happens when bacteria multiply excessively further upstream, in the small intestine, the section responsible for absorbing most nutrients from food. This overgrowth can physically damage the villi, the small finger-like projections that absorb nutrients, and disrupt the mucosal barrier that normally controls what gets through. A study of confirmed SIBO cases found villous blunting, a flattening of these nutrient-absorbing structures, in around a quarter of cases, along with increased immune cell activity in the gut lining in around a quarter as well.

Source: Small Intestinal Bacterial Overgrowth and Childhood Malnutrition: A Comprehensive Review of Available Evidence

A cycle that reinforces itself

Malnutrition and gut bacterial imbalance can each make the other worse. Malnutrition can itself disrupt the healthy gut microbiome, and a disrupted microbiome, through SIBO or a related overgrowth, further reduces how well nutrients are absorbed. This cycle is a significant concern in children, since malnutrition combined with malabsorption during critical growth periods can affect long-term physical and cognitive development. In parts of the world with limited access to clean water and sanitation, a related condition called environmental enteric dysfunction, marked by similar villous damage and chronic low-grade gut inflammation, is thought to be a major contributor to childhood stunting.

Coeliac disease and other overlapping causes

Malabsorption isn't caused by SIBO alone. Coeliac disease, an autoimmune reaction to gluten, damages the same villi through a different mechanism, and the two conditions can overlap, since SIBO is more common in people with coeliac disease that hasn't fully healed on a gluten-free diet. Other causes include pancreatic insufficiency, inflammatory bowel disease, and previous gut surgery. Identifying which of these is driving malabsorption, rather than assuming SIBO by default, is an important part of getting the right treatment.

What this means for you

Unexplained weight loss, persistent diarrhoea, bloating, or signs of nutrient deficiency such as fatigue, brittle nails, or numbness need proper medical investigation, including testing for coeliac disease and, where appropriate, a SIBO breath test. Malabsorption isn't something to self-diagnose or self-treat, since the underlying cause determines the right treatment, whether that's antibiotics for SIBO, a gluten-free diet for coeliac disease, or something else entirely. Once a cause is identified and treated, a varied, plant-rich diet, reintroduced gradually if the gut has been inflamed, supports the same gut bacteria and gut lining this research shows get disrupted by malabsorption. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.