hmmmm one thing that is supposed to help is zinc, so either supplements or food high in zinc... spinach? mushrooms? and normal amounts of red meat and dairy... does he get to eat like a carnivore enough? (as opposed to your veggo-ism )
Fish is also supposed to be good (hahah this is all so *apparently* isn't it? someone's got a case of the s'posters...) as long as it's not "fish 'n' chips" so much, which is where we always go wrong heh... then you're too full and fat to do anything haha..
Might be worth researching I'd say... especially seeing as I am not a doctor nor a nutritionist and may be full of cr@p