It appears that if an item has an 'f' rating it should be avoided.
it seems quite a handy new feature - grading whether a particular food is good for a keto diet.
Whey protein is not recommended and I would be interested to know why whey protein has got this rating.
Most likely because it’s almost pure protein. I sometimes make smoothies with whey protein. The ingredient is an F, but the recipe I make (add blueberries, avocado, mct oil, unsweetened almond milk) is an A.