Hi. My American Bulldog has been shedding really heavily lately. We give him dry food. Maybe he lacks some vitamins/minerals? The hair itself is good but it just falls out a lot. Thanks in advance.
All animals go through a moult during spring and fall, so extra shedding this time of year is perfectly normal. Dry food is fine as long as it's not regular retail food. I would suggest that you switch him over to holistic or natural food. It's much, much healthier for your dog, and will improve his eyes, teeth, general health, and even his coat. It will also "somewhat" reduce the shedding. Retail foods don't have the proper nutrients to nourish your fur kid and all of his parts. There are far too many fillers and garbage ingredients in them.

If there are no other signs of a possible illness (his overall behaviour, activity level, appetite and stool haven't changed) I'd agree with the post above - it's just a moult. More frequent brushing in this period would help remove dead hair.