What about the blood type diet? I do believe there is some truth to it , particularly with generalizations such as A blood types tend to be more vegetarian, B blood types do well with fish and lamb but should avoid chicken, O blood types need more protein etc. But it is not necessarily something to put one’s hope or total trust in. I think there is a lot of error to it as well, especially about diet recommendations for each blood type. For example, A blood types may not feel well with tofu and soy products. Many people do not. B blood types may do well with dairy but today’s dairy is not good quality and they may not feel very good with it nor is it necessarily healthy to indulge in those types of dairy products. O Blood types may require more protein but not necessarily do they need meat or steak all day. Some people with o blood type may have ulcerative colitis and meat may flare inflammation. So every person is very individual and there is no such thing as a perfect diet for all. Anyone who wants to say eat this and not that is just making money, trying to give people magical answers for health. But it is not accurate.
Overall I do not put much emphasis on the blood type diet. I think this is not something emphasized in the past. Even the Rambam, the greatest physician, did not differentiate between blood types.
Now, how do we know if a certain food is good for us? One person may do well with spelt flour, for example. Another may do well with oats. Someone else may feel terrible with flour products etc. etc.
One of the best ways to confirm foods that are good or not is through muscle testing. However, you need someone such as a chiropractor who is expert in these things. On your own you cannot do it because you can get a wrong response if you do not know how to muscle test correctly.
So in conclusion: I am not in favor of the blood type diet. I do not favor any diet that pushes for only one way. There is no such thing. I do believe in balance. I do believe we need enough healthy fiber in our diets. And I believe we need to be more plant based. But we also need some protein, especially small amounts of animal proteins. And I do believe not everyone has to avoid gluten although many people do have issues with the wheat quality of today. So the key is balance and to find what foods bring up your energy levels and are easy for you to digest, and what foods drag down your energy and make you sluggish, tired or not functioning well.