The mid-Victorian diet may be the most healthy diet you've never heard of. The years between 1850 and 1872 in England may have been a "mini golden age of nutrition":
Spectator Health: Forget paleo, go mid-Victorian: it's the healthiest dietPeople ate a varied diet, high in nutrients, and there was no famine. Provided people lived through their childhood years - infant mortality was still high - they had almost the same life expectancy as now, around 74 years. And apparently many people lived healthy full lives, with agricultural laborers regularly working into their 70s.
Then something happened and health and life expectancy took a dive, reaching a bottom around the year 1900.
Interestingly this drop in health coincided perfectly with the introduction of vast quantities of cheap refined sugar into the diet.