Hi kib1, the problem is not all of us do eat grassfed meat, and wildcaught fish, free range eggs, organic chicken, etc, because it’s just not possible. Now Dr. Paul Mason’s opinion is that it’s not a problem if we eat grainfed meat (high in omega 6), so long as we then get our omega 3 from other sources such as fish, and both Mason’s and Dr. Malcolm Kendrick’s opinion is that supplements become both neccessary and beneficial, when we can’t get all those vitamins and minerals from our food stuffs, the soil being depleted, etc.
Now, I do eat fish, but it’s likely to be farmed fish (as there’s no information regarding this and wildcaught would be a selling point). And I imagine I’m not alone. So because the keto or carnivore WOE for a lot of people is not 100% optimal (aka grainfed meats, farmed fish) supplements might be beneficial. As to vitamin D I hardly get any sunlight. So I know I require vitamin D, and I take vitamin D3. Don’t actually know what the 3 stands for. It is important to take into consideration individual circumstances, not everyone can afford to buy grassfed, wildcaught, organic etc. And not everyone gets enough sunlight.