Okay, show me how even a rich man in the middle ages (let alone a commoner) could have a diet that satisfied getting good protein (keep in mind in those days you couldn't live as lazy as today so protein requirements higher for life being more labour intensive) and all vitamins and minerals.
I don't think protein was much of a problem most of the time. After all, soy contains enough of all the essential amino-acids except
perhaps methionine, and the dangers of getting too much methionine are probably greater than the dangers of getting too little methionine. If the only source of protein in your diet is wheat (as it is for many people around the world today), it's only then that you have a problem, namely, not getting enough lysine, which hurts the immune system. As for getting vitamins and minerals, yes, that was a problem. And not necessarily related to not eating enough meat, scurvy, because of not getting enough vitamin C, illnesses related to iodine deficiency, and sight problems due to not getting enough vitamin A, those were common place. B12 deficiency probably wasn't because the food people were eating was not sterile.
Tell me, do you think humans evolved to be vegans? We evolved as vegans?
Well, now, our ancestors millions of years ago were probably eating some insects, but, yes, they were mostly vegan. How do you think people hunted before the tools for that were invented?
I was dubious about the butter vs margarine trans fat issue too so I checked and was a little surprised
Why were you surprised? In Croatian, trans-fat acids are called "maslačne kiseline", "butter acids".
A better ‘natural’ choice would be using olive oil, avocados, nut butter or tahini, so try those instead.
But how many nutritionists would agree avocados are less harmful than margarine is? Though I haven't studied it too much, I think that not many. Most nutritionists would agree eggs are dangerous, especially to people with type-2-diabetes (and I have a family history of type-2-diabetes), because of their fat content. Well, if eggs are harmful, then so are avocados: both are around 25% saturated fat. I hope most nutritionists don't have double standards for animal-derived food and plant-derived food.
And some forms of natural trans fats found in dairy and animal meat is actually very good for you.
Most nutritionists agree all trans-fats are harmful. But, for those who oppose mainstream nutrition, no idea is crazy enough.
I mean, this is the type of reasoning those people engage in:
A: Fish is healthy because it contains a lot of omega-3-acids, which protect against atherosclerosis.
B: Here is ton of studies showing omega-3-acids in food don't protect against atherosclerosis and may even have a detrimental effect.
A: Well, maybe DHA to ALA ratio also plays a role, and not just the amount of omega-3 acids you intake. Plants generally contain a lot more ALA than DHA, fish contains a lot of DHA.
B: OK, maybe. But what you just admitted is that you have no evidence for your claim.
conjugated-linoleic-acid is also not easily made, so any (none animal based) supplement is not actually going to work.
If there are no supplements of that, that means the health claims about it can't be rigorously tested.