It is a subject rarely studied, there are some studies on vitamin absorption after gastric bypass. It would be very interesting to study how it behaves physiologically the excluded stomach mucosa after gastric bypass.
I haven't come across any problems I just thought it would make an interesting topic of research. Dietary intake may be low post gastric bypass and I'm not sure if absorption would be affected. It poses more of a threat if someone is not taking their multivitamins or they are on an insufficient dose.
Biotin (vitamin B7) is a vitamin found in foods like eggs, milk, and bananas. Biotin deficiency can cause thinning of the hair and a rash on the face. Biotin is an important part of enzymes in the body that break down substances like fats, carbohydrates, and others.
It is reported that some bariatric patients can get extreme hair loss, presumably this is related to biotin levels.
Good bariatric services should offer lifetime long term nutritional surveillance.