Your small intestine absorbs nutrients from the food you eat. But there are situations where the small intestine cannot take nutrients to your bloodstream. This condition is called malabsorption and some of the reasons behind it are:
Weak gut or intestinal lining: Normally, the gut lining is semi-permeable — it absorbs water and nutrients from food into your bloodstream. But bad gut lining lets in more than water and nutrients — they let in the wrong kind of bacteria. This affects your digestion and protection against infections.
Bacterial growth: Small Intestinal Bacterial Overgrowth (SIBO) is when microorganism growth in your small intestine lacks balance. While bacteria is expected in your small intestine, there’s a limit. Too many or the wrong kind of bacteria causes problems as they eat proteins, vitamin B12 and bile salts. This leads to bad nutrient absorption and poor fat digestion.
Food allergies, e.g., lactose intolerance: When your body can’t break down lactose — a natural sugar — it means you’re lactose intolerant. The undigested lactose moves to your large intestine and can cause bloating or diarrhoea after interacting with the bacteria in your large intestine.