Food Sensitivities
Making sense of symptoms after food: diagnosis, lactase, and the limits of other supplements.
Why does a particular food cause trouble?
Bloating, pain, or diarrhea after a meal may point to a food intolerance. The label alone does not establish a diagnosis. Repeated symptoms warrant medical assessment; food allergy is different and can be dangerous. 1
Lactose offers a useful example
In lactose intolerance, there is too little lactase enzyme to break down all the milk sugar. Bacteria process the remaining sugar in the colon, producing gas. Tolerance varies, and complete avoidance of dairy is often unnecessary. 2
How can the trigger be identified?
A food-and-symptom diary can help narrow the question. Depending on the suspected cause, assessment may include temporary exclusion followed by reintroduction, or a breath test. NHS cautions against commercial home tests: unreliable results may lead to unnecessary restrictions. 1
When is it an emergency?
Sudden swelling of the mouth or tongue and difficulty breathing can signal a severe allergic reaction requiring immediate medical help. 1
Nutrients with the strongest ratings
Sorted by the largest rated effect. Bars show effect size, the letter is the evidence grade.
What can lactase do?
A crossover trial studied adults with confirmed lactose intolerance, giving the same participants lactase and placebo on separate visits. Three tablets, each containing 4,500 FCC units of enzyme activity, preceded a 25 g lactose challenge. Among 47 analyzed participants, lactase reduced symptoms and breath hydrogen. This was a specific challenge test, not a long-term study of tolerance to arbitrary foods. 3
What about probiotics?
IQWiG considers their benefit in lactose intolerance unclear. Results for one microbial strain also cannot be transferred to another. This review therefore does not rate Lactobacillus acidophilus or Saccharomyces boulardii as general solutions to food reactions. 2 5
What belongs in the dietary plan?
Lactase does not replace assessment. NIDDK advises discussing its use with a doctor, particularly for young children and during pregnancy or breastfeeding. When intestinal injury causes intolerance, treating that underlying cause may improve lactose tolerance. 4
What this page does not evaluate
Diamine oxidase, alpha-galactosidase, and invertase are not evaluated here.
Questions people ask
Is intolerance an allergy?
No. Allergy involves the immune system; lactose intolerance involves digestion of milk sugar. 1 2
Must I remove all dairy?
Often not. The amount tolerated varies between people. 2
Does lactase cure the cause?
Treatment does not increase the intestine’s own enzyme production in genetically determined lactase deficiency. 4
Are home tests helpful?
NHS does not recommend these tests because evidence of accuracy is limited. 1
Sources
- Food intolerance NHS
- Laktoseintoleranz IQWiG