Actually potatoes are not native to Ireland. They are native to the americas (south america, I believe) and were unknown in Ireland until nearly the 17th century. It's very difficult to guage the health of a people on less than 200 years of a dietary change. And being able to procreate is a very poor measure of health, because on adequate calories, even extremely poorly nourished people survive long enough to create families. They may not live to see grandchildren, but the records on the life expectancy of 18th and 19th century Europe are a bit sketchy, at least in comparison to modern times.
I'm not sure when potatoes became a staple of the poor, but even in the mid 1800's most Americans considered it only fit for animal consumption.
Also, while most cultures have a "staple" food and it's usually a starch (with the exception of people such as the arctic innuit and mongolian people who lived primarily on meat), NONE lived exculsively on the staple. No one in Ireland "lived" on exclusively potatoes. They ate a wide variety of vegetables and herbs, and lentils. Meat for the poor was scarce, but they did eat it. Often they were eating the animals and cuts of animals that were less appealing to the wealthy (organ meats, etc). Many peasants were allowed to hunt on the landholders lands, and when they weren't poaching (illegally hunting and fishing) was very common, so we can only guess at how often meat was really eaten.
Even in the arctic, where the inuit did live nearly exclusively on meat, their diet in the summer adds in plant foods such as berries and herbs. While the idea of an "exclusive food diet" is popular, it is more fiction than fact. Just adding "seasoning" herbs and vegetables (like onions, garlic, herbs, grasses and greens) can tremendously boost the nutritional content of a diet.
As for our modern "obsession" with vitamins and such. Nutrition is a "new" science. The first vitamin was discovered in the mid-1930's, so of course, it's a relatively modern phenomenon.
Though there are documents theorizing and advising on the "proper" diet as early as the first century (some with very modern sounding advice). So, I'm not sure that it's a new field of thought for people with time on their hands to do such thinking.
I think the biggest difference is that unlike ancient times, when only a few had enough leisure time to ponder on such things, we all (not just the wealthy minority) have the time to give the matter much thought.


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That's a large bulk of our food additives, flavor enhancers. MSG anyone?
