Constipation

Constipation is fundamentally a symptom of hypothyroidism and a slowed metabolic rate, which reduces all digestive secretions and the rhythmic muscular contractions of peristalsis. 3 Ray Peat argued that the classical signs of low thyroid function—constipation, dry skin, and falling hair—were common knowledge among doctors fifty years ago, but this clinical perception has been largely abandoned. 9 The resulting slow transit time allows for the proliferation of Gram-negative bacteria, increasing the production and absorption of endotoxin (lipopolysaccharide), which triggers systemic inflammation, serotonin release, and a further suppression of energy metabolism. 2

The derangement of intestinal rhythm is not merely a slowing but can involve a nocturnal reversal of peristalsis, driven by stress signals from nocturnal hypoglycemia. 1 When blood sugar falls during the night, a chaotic mixture of parasympathetic and sympathetic signals excites the intestine randomly, causing a backward flow that can carry markers from the rectum to the mouth, contributing to bad breath and acid reflux. 1 Peat emphasized that keeping blood sugar stable, particularly by consuming carbohydrates like orange juice before bed, is the first line of defense against this stress-induced reversal. 1 More broadly, physical inactivity is a major contributor to sluggish digestion, as reflexes between the legs and the intestine mean that a daily habit of walking for an hour or so can significantly improve motility and the sense of well-being. 4

Mechanistically, Peat identified several factors that inhibit peristalsis. A waterlogged, inflamed state of the intestinal tissues prevents the muscles from contracting effectively, an inflammation driven by the conversion of dietary polyunsaturated fats into prostaglandins. 9 Stress increases both adrenaline and the intestine's natural endogenous opiates (endorphins), which act like morphine to halt intestinal action; Peat noted that anti-opiate drugs have been proposed to cure chronic spontaneous constipation for this reason. 9 To counteract these forces, he recommended using sugar and salt to lower adrenaline, and sometimes a small amount of thyroid supplement to restore energy production. 9 Aspirin and antihistamines like Benadryl were also cited as simple remedies to lower the inflammatory mediators that cause waterlogging and histamine release. 9

The strategic use of indigestible fiber is a central intervention. Peat contrasted the average American transit time of 72–76 hours with the 12-hour transit seen in populations eating a diet high in fibrous foods like potatoes, a difference he linked to the huge disparity in bowel cancer incidence. 2 However, he warned that not all fibers are beneficial; some, like lignin, are themselves estrogenic, while others can be fermented by bacteria into toxins. 2 The anti-estrogenic effect of a well-chosen fiber is the result of accelerated transit, which speeds the elimination of estrogen excreted in the bile and prevents its reabsorption. 2 This is the basis for the well-known raw carrot salad, which uses a fibrous, indigestible material to stimulate peristalsis, bind endotoxin, and lower the estrogen burden that blocks thyroid function. 2 Georgi Dinkov has extended this framework by highlighting the role of vitamin B1 (thiamine) as a key determinant of gut motility, explaining that its bioenergetic role in oxidative metabolism raises CO₂ levels, which has anti-inflammatory and anti-serotonin effects that support proper peristalsis. 7

When fiber and dietary adjustments are insufficient, Peat acknowledged the historical and physiological basis for using laxatives like aged cascara sagrada to prevent the systemic poisoning that arises from a stagnant, inflamed bowel. 2 He challenged the medical campaign against laxatives, arguing that the brown pigmented colon blamed on their use is actually caused by the chronic irritation of constipation itself, and that proper laxative use reduces this irritation. 6 Danny Roddy has noted that while cascara can be a reliable intervention, some individuals find it too aggressive, and that directly addressing thyroid function with a supplement like T3 can sometimes resolve lifelong constipation entirely, making other interventions unnecessary. 8