Some good ones to start him on are raw garlic, raw onions, coconut oil, olive oil, kale, brocolli, brussel sprouts... and as far as probiotics... buy raw fermented foods like raw saurkraut. More effective and safe... natural.
What does his diet look like? and what do you mean by carbs???
Good thing to do also would be to buy some nutritious seeds like flax and chia seeds and see how he likes them.