Maybe something's not functioning properly, maybe get him for a check up and make sure there's no underlying cause for it or some intolerance to any products such as lactose (a milk sugar).
Something like a colonic irrigation may help clear out any old crap and improve function.
His diet may be good but even good things can cause flatulence such as beans, sprouts and members of the cabbage family including cabbage, broccoli, cauliflower. Other things are onions, celery, corn, apples, dried fruits and prune, apple and grape juices, carbonated drinks, articificial sweetners, bran/fibre, carbonated drinks, chewing gum, tea, coffee, olive oil and animal and vegetable fats, highly refined white flour and white sugar products such as croissants, focaccias.
Eating slowly and chewing food well is important. Does he eat lots of smelly foods such as strong curries or other spicy food, onions or garlic or things which are hard to digest or drink alcohol a lot?
Wearing flase teeth and swallowing too much air eg smoking or gulping a lot can also contribute to quantity rather than smell.
There are some herbal remedies about and exercise can be a big help as can probiotics and live organic yoghurt.
Try here for some more info...
http://betterhealthchannel.vic.gov.au/bhcv2/bh carticles.nsf/pages/Flatulence?open
http://www.nutrihealth.org/pages/flatulence.ht ml
http://www.bbc.co.uk/dna/ww2/