Two, three, and more centuries ago, the Scots in the Highlands (and those in the Southern Uplands) were stalwart, hearty men who were able to hunt or fight in battle all day without fatigue. We know they often raised sheep, and they fished and hunted deer, but their main carbohydrates were from the oats and barley they grew.
I haven't found any descriptions of the nutritional value of the oats and barley they grew back then, but you can be sure they were more nutritious, especially in mineral content, than what is grown today. As Dr. Shanahan points out in her book, it was common practice to replace the thatching on their crofts every year, and put the used thatch on their gardens. One big difference in that practice, and the mulching we do today, is the mineral content of the thatch.
The Scots usually heated their crofts with peat fires where wood was scarce, and the smoke rose and escaped through loose areas in the thatch. The thatch itself collected minerals from the smoke. The cooking/heating fires were often directly on the floor, and crofts had a chain and hook hanging from the roof above. This could hold a potful of porridge, an iron kettle of boiling water, or a griddle for baking bannocks or flat oat bread.
The fires were seldom allowed to go out completely, and the thatch collected the smoke and minerals all year long. I suspect the carbon collected from smoke in the thatch was biochar. By putting this mineral-rich material back into their gardens when they re-thatched annually, they kept the soil re-mineralized.
We fail to do that today, not because we don't have peat fires and thatched roofs anymore, but because home garden advice stresses NPK, and occasionally calcium/lime to "sweeten" the soil. The ignored and overlooked micronutrients are so very important to good garden health, and therefore our own health.
If you truly care about health, give yourself the gift of a good soil survey (not the cheap kind from the Extension Service) that tests minerals and micronutrients. It's not necessary to do it very often once you get the soil adjusted. Your plants will thank you, and your healthy body will thank you.