Technician-scored stool consistency spans the full range of the bristol scale in a healthy US population and differs by diet and chronic stress load

Authors: Lemay, Danielle; BALDIVIEZ, LACEY - University Of California, Davis; Chin, Elizabeth; Spearman, Sarah; CERVANTES, EDUARDO - University Of California, Davis; Woodhouse, Leslie; Keim, Nancy; Stephensen, Charles; Laugero, Kevin

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2021
Publication Date: 3/10/2021
Citation: Lemay, D.G., Baldiviez, L.M., Chin, E.L., Spearman, S., Cervantes, E., Woodhouse, L.R., Keim, N.L., Stephensen, C.B., Laugero, K.D. 2021. Technician-scored stool consistency spans the full range of the Bristol scale in a healthy US population and differs by diet and chronic stress load. Journal of Nutrition. 151(6):1443-1452. https://doi.org/10.1093/jn/nxab019.
DOI: https://doi.org/10.1093/jn/nxab019

Interpretive Summary: Stool consistency—hard, soft, or normal—is an indication of bowel function. Previous studies have shown relationships between diet and chronic diarrhea and/or constipation. In the current study, we sought to understand how diet, physical activity, and stress influence whether stool produced by healthy people is normal, hard, or soft. Healthy adults provided a single stool sample which was independently evaluated by a technician. Adults who consumed more saturated fat were more likely to have hard stool. Other dietary factors which influenced stool form included moisture, dairy, sodium, vegetables, fruit, alcohol, and the types of fat. Physical activity was not associated with stool form. Stool was less likely to be normal with a high physiological stress load, particularly influenced by the stress hormones norepinephrine and cortisol. In summary, both diet and stress influenced stool consistency in healthy adults.

Technical Abstract: Background. Prior studies of adults with constipation or diarrhea suggest that dietary intake, physical activity, and stress may affect stool consistency. However, the influence of these factors is unresolved and has not been investigated in healthy adults. Objective. We assessed stool consistency in healthy adults via independent technician-scoring and investigated the association of stool form scores with self-reported diet, objectively monitored physical activity, and quantifiable markers of stress. Methods. Stool consistency was scored by an independent technician using the Bristol Stool Form Scale (BSFS) from samples provided by healthy adults, aged 18-65, BMI 18–44 kg/m2 in the USDA Nutritional Phenotyping Study (n=364). A subset of participants (n=109) were also asked to rate their sample using the BSFS. Dietary intake was assessed with two to three 24 hr recalls completed at home in the 7d period preceding the stool collection. Diet quality was estimated by the Healthy Eating Index (HEI). Energy expenditure from physical activity was monitored during the same period using an accelerometer. Stress was measured using the Wheaton Chronic Stress Inventory and allostatic load. Results. Technician-scored BSFS scores were significantly different from self-reported scores. There was no association of physical activity with stool consistency. Hard stool was associated with a lower HEI compared with non-hard stool. Hard stool was associated with higher intake of saturated fat relative to normal stool. Allostatic load scores were lower with normal stool. Machine learning analyses revealed dietary components—saturated fat, fatty acids, dairy, sodium, moisture, vegetables, fruit, and alcohol—as well as physiological characteristics—HDL, cholesterol, and BMI—and stress hormones—norepinephrine and cortisol as being predictive of stool consistency. Conclusions. Technician-scored stool consistency was associated with dietary intake and stress hormones, but not with physical activity, in healthy adults.