Can a genetic analysis test for a food intolerance?
This is a hotly debated topic, however many intolerances and allergies have a genetic and/or epigenetic component. The amount of affect a gene or genes have on an intolerance/allergy depends on what it is you’re looking for. Peanut allergy for example has strong predisposing factors based within certain parts of the genome. Gluten intolerance (celiac disease) is hereditary and certain variants within the HLA-DQA1 and HLA-DQB1 are required to have celiac disease, but not everyone with the variants has celiac disease, meaning environmental factors could trigger this complex issue in those with the variants, which may be an epigenetic change.
Lactose intolerance has a massive genetic component, which may be totally genetic in some. Lactose intolerance is caused by a lack of lactase enzymes being produced, and the most common cause of lactose intolerance in adults is known as primary lactase deficiency (PLD). PLD is caused by variants in the MCM6 gene acting on the LCT gene which causes lower lactase enzyme levels over time, leading to lactose intolerance, this is an example of a genetic food intolerance. Some unlucky few have what is known as congenital lactase deficiency, this is caused by variants within the LCT gene itself causing an inability to consume lactose from birth, this is very rare and infants that were born before the 20th century with this condition often died due to a lack of man-made formulas and lactose free alternatives to breast milk.
It is possible to have environmentally triggered (secondary) lactose intolerance, this is often caused by inflammatory bowel disease or injury/ailment occurring to the gut, however research has shown that these conditions may cause epigenetic DNA methylation load on the MCM6 and LCT genes leading to a genetic component again causing lactose intolerance.
Further reading:
Peanut allergy - https://www.nature.com/articles/s41467-017-02188-7
Gluten intolerance - https://ghr.nlm.nih.gov/condition/celiac-disease
Lactose intolerance - https://ghr.nlm.nih.gov/condition/lactose-intolerance#genes
Lactose intolerance & epigenetics - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899171/