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Fish Bad, Sugar Good... And Other Medieval Ideas About Food

Katherine Harvey on Healthy Living in the Middle Ages

Via Reaktion Books

Katherine Harvey

July 29, 2026

Although medieval ideas about food were very different to our own, its importance was widely recognized. According to Galen, food “is probably the most important of all medical subjects,” and it dominated medieval regimens—many of which consist almost entirely of lists of foods and discussions of their properties and impact on the human body.<br>Article continues after advertisement

In order to remain healthy, it was important to know about the qualities of foods, which were categorized as hot/cold and wet/dry, with different qualities having different effects on the body, and bad foods leading to illness. The perceived connection between diet and health was underpinned by medical ideas about digestion, which was thought to be a three-stage process, similar to cooking, distillation and combustion. In the first digestion, which took place in the stomach and intestines, food was turned into chyle, with some superfluities being excreted through defecation. The second digestion happened in the liver, and produced blood, along with black and yellow bile (which were, respectively, stored in the spleen and the gallbladder). In the third and final digestion, the blood was spread around the whole body, providing it with the heat, moisture and vital spirits necessary for life.

Thanks to the English physician William Harvey (1578–1657), we now understand that blood circulates around the body, but medieval people believed that the liver was constantly generating new blood—so that digested food was incorporated into the body, and in a very literal sense a person was what they ate.

So, what did medieval people eat? Processed cereals such as pottage and bread were the key components of the medieval diet, although the quality of these foods varied with social status. Rich people ate leavened bread made from good quality wheat, while the poor usually had to make do with coarse, dense bread made from barley (which was cold and flatulent) or rye (which produced weak blood and little energy).

Nevertheless, it is clear that health was a consideration when preparing a meal.

Contrary to popular belief, medieval people also ate fruit and vegetables—though they were rather ambivalent about plants, and considered some of them to be downright dangerous. Brassicas (such as cabbage, cauliflower and broccoli) were an important part of the peasant diet, but caused both melancholy and nightmares; lettuce was dangerous because it was so cold and moist, while turnips and parsnips led to flatulence and lust. There was considerable wariness about beans, which were thought to cause flatulence and bad humours, as well as confusion, dizziness and general malaise; peas were more easily digested, and thus a much better option.

Similarly, some fruits were safer than others: citrus fruits improved digestion, especially in hot weather, while raisins were good for the stomach, lungs and liver. And nuts were nutritious and good for the brain.

But many common fruits, including apples, peaches and cherries, were viewed with suspicion, because they were cold and moist, and produced putrid humours. They could be made safer by cooking, and it is clear that many people did eat them. When Petrarch’s physician told him to avoid “apples and every kind of fruit from trees,” he declared himself appalled by “this scorn for the most beautiful things that at the same time delight the taste, the touch, the smell and the sight.”

The medical advice regarding animal produce was equally complicated. Butter was warm, moist and nourishing, and produced good blood, whereas cheese was a coarse food, hard to digest and likely to cause bladder stones—although a small piece at the end of the meal could improve digestion. Eggs were widely eaten, though the warm, moist yolks were healthier than the cold, moist white. When it came to meat, chicken was widely regarded as the healthiest...