Fiber is an important topic because 95% of Americans are deficient in dietary fiber intake.

Closing America’s Fiber Intake Gap, 2017
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6124841/
Adequate intake of dietary fiber is associated with digestive health and reduced risk for heart disease, stroke, hypertension, certain gastrointestinal disorders, obesity, type 2 diabetes, and certain cancers. According to consumer research, the public is aware of the benefits of fiber and most people believe they consume enough fiber. However, national consumption surveys indicate that only about 5% of the population meets recommendations, and inadequate intakes have been called a public health concern.

https://nutritionfacts.org/video/gut-dysbiosis-starving-microbial-self/
Fiber is what our good gut bacteria thrive on.

Carbohydrate quality and human health: a series of systematic reviews and meta-analyses, 2019
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31809-9/fulltext

• Observational data suggest a 15–30% decrease in all-cause and cardiovascular related mortality, and incidence of coronary heart disease, stroke incidence and mortality, type 2 diabetes, and colorectal cancer when comparing the highest dietary fibre consumers with the lowest consumers.
• Clinical trials show significantly lower bodyweight, systolic blood pressure, and total cholesterol when comparing higher with lower intakes of dietary fibre.

https://nutritionfacts.org/video/fiber-vs-breast-cancer/
Every 10-g/day increment in dietary fiber intake was associated with a significant 7% reduction in breast cancer risk.

https://nutritionfacts.org/video/how-fiber-lowers-cholesterol/

• If our liver feels there’s just too much cholesterol circulating around, it dumps the excess into the gut to get rid of it. Our enterocytes — the cells lining our intestinal wall — recycle some of that cholesterol. The more fiber we eat, the faster the dumped cholesterol zips through the intestine. So less cholesterol gets recycled.
• Here is why cholesterol is important:
  https://nutritionfacts.org/video/optimal-cholesterol-level/
  • 1:45 Optimal “bad cholesterol” LDL level is 50 to 70.
  • 2:30 Zero atherosclerosis progression is estimated to be around an LDL cholesterol of 70.
  • 3:00 The average American’s LDL level is up around 130.

https://nutritionfacts.org/video/is-fiber-an-effective-anti-inflammatory/
Significant decreases in the prevalence of inflammation are associated with increasing dietary fiber intakes.

https://nutritionfacts.org/video/how-many-bowel-movements-should-you-have-every-day/
Bowel movements should ideally be two or three times a day, which is what you see in populations on traditional plant-based diets.

https://nutritionfacts.org/video/stool-size-matters/ Ideally, transit time should be in the 24- to 36-hour range.

https://nutritionfacts.org/video/lose-two-pounds-one-sitting-taking-mioscenic-route/

• Jenkins and colleagues tested the effects of feeding people a very-high-fiber diet designed to maintain weight. [They ate 55 g fiber/1,000 kcal for an average of 142 g/day. Average fecal bulk was 906 g/day]. LDL cholesterol dropped 33% within just two weeks, even without any weight loss.
• We’ve been eating 100 grams of fiber every day for millions of years. Similar to what’s eaten by populations who don’t suffer from many of our chronic diseases.

https://nutritionfacts.org/video/bowels-of-the-earth/
Average size of bowel movements by country:

• 120 g/day in USA
• 195 g/day in Japan
• 311 g/day in India
• 531 g/day in Tonga