What could be causing my father's bloating?

There are several possibilities for food sensitivity that could be investigated for these symptoms. I suggest that your father consults with a dietitian with an interest in allergy and food sensitivity. See Dietitians Association of Australia website http://daa.asn.au/ to search for someone appropriate.

Whilst your waiting for an appointment with a dietician you could trial a low FODMAP diet which should make a big difference after a few weeks if a fructose malabsorption issue is occurring.  

I absolutely agree that food allergy/intolerance needs to be assessed and that guidance, with regard to optimising digestive function and the production of those substances needed to achieve this, needs to be sort.  Finding a practitioner who deals with these issues appropriately and comprehensively isn't always that easy.   I don't wish to sound alarmist, but once this has been actioned and your father still has unresolved digestive complaints, like bloating or ongoing discomfort, he might need further investigations, which would need to discussed with his specialist.   I attended a medical meeting the other day, where a case of a young lady was presented, who had bloating and other digestive issues, with a colonoscopy ultimately revealing that she had inflammatory bowel disease.   

Adding to Joy and Michaels responses it sounds as though your father’s gastrointestinal tract function is compromised. Besides food sensitivities/intolerances you may be right about IBS or fructose malabsorption. Another possibility is low digestive enzyme activity.
IBS is a functional bowel disorder characterised by abdominal pain and changes in bowel habit. These are NOT associated with any abnormalities seen on routine clinical testing.

It would be prudent talking to a Nutritionist about your fathers diet as there are many other foods which irritate the gastrointestinal tract and aggravate an already compromised mucosal barrier: High Fat foods, caffeine, alcohol and citrus to name a few. Lactose free alternatives are great.

As for the Probiotics try one with a Lactobacillus Plantarum 299V species.

As for enzymes: supplementing with digestive and/or pancreatic enzymes can increase bowel motility and improve the breakdown and absorption of foods. This relieves the pressure and inflammation within the intestines.

Stress is also a major contributor to gastrointestinal disorders.

Food intolerance is certainly a possibility and it is important you seek help from a dietitian experienced in this area as it can be quite complex. You didn't mention whether Coeliac disease was ruled out? Did your father have a duodenal biopsy taken?
The other thing to consider is his general diet. I have had many patients where a few simple changes to general eating patterns and food choices have resolved symptoms without there being any food intolerance. He may have a very healthy diet, but just eating too much of some healthy foods that can be problematic. Again, seeking help from an experienced dietitian is a sensible option. I hope your father finds relief soon.

Hi
I agree that trialing a low FODMAP diet, which still requires him to eliminate the milk based dairy foods, whilst other investigations are being done.  He could be suffering with irritable bowel syndrome, which triggers the sympotms your father is reporting he is suffering from.  The low FODMAP diet eliminates poorly digested carbohydrates e.g lactose (milk based foods), fructose (in fruit), fructans (wheat and inulin), galactans (windy vegetables like onions garlic), and polyols (fruit, artificially sweetened products).  Try following a low FODMAP diet for up to 4 to 6 weeks, ensuring he has plenty of water and fibre (rice bran, low FODMAP fruit and vegetables), and he keeps active.  I would cease the probiotics (some can agitate the sympotms) whilst doing this, and see if his symptoms improve.  Feel free to contact me via email for more assistance.  Nicole Moore (nicole.moore@menuconcepts.com.au).

The most likely reasons for  your father's bloating, now that you have excluded pathology, is as follows, and these are common in (middle aged?) men.
First, since there is burping after eating, you have hypochlorhydria, not enough stomach acid. So Nexium is not really the right medicine, since that will further deplete the stomach acid. If you give your dad a digestive enzyme which contains Betaine HcL, then he will know within a few days if this assessment is correct, because he will start to feel better.

Bile reflux is linked with hypochlorhydria, and means your father will probably feel worse after greasy, oily or spicy food. Liver bitters before food will probably take care of that. And a little apple cider vinegar in a small glass of water after meals may help too.

Last, if the lactose intolerane is a recent phenomenon (ie not life long), then you will probably find it improves once the above two issues have been corrected. He may have other food sensitivites too, yet those will probably arise also from the above two issues, otherwise he would have been suffering for the whole of his life.