I hold my personal trainer certification with NASM. They recommend we have a general understanding of basic nutrition and weight management to provide general guidance. It is common for my clients to ask me questions about nutrition and what they should eat to fuel their workouts. Suggestions for food preparation, healthy snacks, hydration, carbohydrate, protein and fat basics are all within our scope as trainers. If I happen to read information regarding a certain herb, vitamin or mineral supplement I am happy to share the source of information and then direct them to speak to their physician to make sure it is right for them. I feel confident in educating my clients in helping them to make healthy food choices with factual information. For instance, I am confident everyone should avoid trans fat. That would be a subject I might have with new clients when helping them make healthy food choices. Sounds basic but it is amazing how something as simple as avoiding trans fats can help a client who may have otherwise not known.
Hope this helps!