Ancient Egypt was one of the great civilizations, lasting for 3,000 years, its knowledge of medicine vastly underestimated. They had medical subspecialties. The pharaohs, for example, had access to physicians dedicated to be guardians of the royal bowel movement, a title alternately translated from the hieroglyphics to mean Shepherd of the Anus. How’s that for a resumé builder?

Today, the primacy of its importance continues, with some calling for bowel habits to be considered a vital sign of how the body is functioning, along with blood pressure, and heart and breathing rates. Although we may not particularly like hearing the details of someone else’s bowel movement, it is a function that nurses and doctors need to assess.

Surprisingly, the colon remained relatively unexplored territory, one of the body’s final frontiers. For example, current concepts of what “normal” stools are like primarily emanate from the detailed records of 12 consecutive bowel movements in 27 healthy subjects from the United Kingdom, who boldly went where no one had gone before. Those must have been really detailed records.

The reason we need to define normal, when it comes to bowel movement frequency, for example, is how else can we define concepts like constipation or diarrhea if we don’t know what normal is. Standard physiology textbooks may not be helpful in this regard, implying that anything from one bowel movement every few weeks or months to 24 a day can be regarded as normal. Once every few months?

Of all human bodily functions defecation is perhaps the least understood and least studied. Can’t you just ask people? Turns out people tend to exaggerate. There’s a discrepancy between what people report and what researchers find when they actually have them recorded. It wasn’t until 2010 when we got the first serious look, defining normal stool frequency as between three per week and three per day, based on the fact that that’s where 98% of people tended to fall. But normal doesn’t necessarily mean optimal.

Having a “normal” salt intake can lead to a “normal” blood pressure, which can help us die from all the “normal” causes, like heart attacks and strokes. Having a “normal” cholesterol level in a society where it’s “normal” to drop dead of heart disease—our #1 killer, is not necessarily a good thing. And indeed, significant proportions of people with “normal” bowel function reported urgency, straining, and incomplete defecation, leading the researchers to conclude that that kind of thing must just be normal. Normal, maybe, if you’re eating a fiber-deficient diet. But not normal for our species. Defecation should not be a painful exercise. This is readily demonstrable. For example, the majority of rural Africans eating their traditional fiber-rich, plant-based diets can usually pass, without straining, a stool specimen on demand. See, the rectum may need to accumulate four or five ounces of fecal matter before the defecation reflex is fully initiated, and so if you don’t even build up that much over the day, you’d have to strain to prime the rectal pump.

Hippocrates thought bowel movements should ideally be two or three times a day, which is what you see in populations on traditional plant-based diets, on the kind of fiber intakes you see in our fellow great apes, and what may be more representative of the type of diets we evolved eating. It seems somewhat optimistic, though, to expect the average American to adopt a rural African diet. We can, however, eat more plant-based and bulk up enough to take the Hippocratic oath to go two to three times a day.

No need to obsess about it. In fact, there’s actually a “bowel obsession syndrome,” characterized in part by ideational rambling over bowel habits, but three times a day makes sense. We have what’s called a gastrocolic reflex, which consists of a prompt activation of muscular waves in our colon within 1 to 3 minutes of the ingestion of the first mouthfuls of food. Even just talking about food can cause your brain to increase colon activity. This suggests the body figured that one meal should be just about enough to fill you up down there. So, maybe we should eat enough unprocessed plant foods to get up to three a day, a movement for every meal.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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