Hi, I am not a healthcare professional nor medical person but have sufficient knowledge and believe probiotics may help your friend. However, he should confirm with his own competent healthcare professional or doctor.
I would suggest that your friend may have unhealthy digestive system with poor, harmful and pathogenic flora. This prevents your friend from absorption of nutrients consumed.
The first thing to consider is to put right the digestive system with probiotics. Not just any probiotics like "freeze dried" powder or tablet or weak solutions like yoghurt. It should be 100% live lactic bacteria and multi-strains so that the bacterium can work effectively in both the small and large intestines. That way it will help rid the system of toxins created and restore health and even boost the immune system.