Cereal fiber

The foods we eat can impact our gut microbiome, which in turn can impact a number of health functions, including immune response and inflammation. In a small study of people randomized to either a high-fiber diet or a high-fermented-foods diet, fermented foods were found to improve the diversity of the microbiome and decrease inflammation, while high-fiber foods were found to impact the microbiome and trigger a personalized immune response.
Cell. 2021 Aug 5;184(16):4137-4153.e14. doi: 10.1016/j.cell.2021.06.019. Epub 2021 Jul 12. (Wastyk HC et al.)

In a recent study, researchers enrolled over 400,000 participants and followed them for 5 years, analyzing their diet and health outcomes. The researchers found that the participants who ate the most red or processed meat had the highest risk of developing colorectal cancer. There was also an increased risk of colorectal cancer in participants who drank the most alcohol. Interestingly, the group that ate the most red and/or processed meat also tended to have a higher intake of alcohol, a lower intake of fruits and vegetables, and were more likely to smoke tobacco. The group with the highest intake of fiber from grains had the lowest risk of colorectal cancer. This study indicates that diets high in red or processed meats and lower in whole grains may be associated with an increased risk of colorectal cancer.
International Journal of Epidemiology. 2019 Apr 17. pii: dyz064. doi: 10.1093/ije/dyz064. (Bradbury KE, et al)

Hepatocellular carcinoma, a common type of liver cancer, has been on the rise in the US, and researchers wonder if eating habits might play a role. In a study of 125,455 adults followed for 24 years, those eating the most whole grains (33g per day, or about 2 servings) were 37% less likely to develop hepatocellular carcinoma than those eating the least whole grains (7g per day, or less than half a serving). When looking at the isolated relationship of fiber, bran, and germ, the results were not statistically significant, indicating that whole grains are greater than the sum of their parts.
JAMA Oncology. 2019 Feb 21. doi: 10.1001/jamaoncol.2018.7159. [Epub ahead of print] (Yang W et al.)

It’s important to get your fiber from a variety of foods, since different sources of fiber are associated with different health benefits. Researchers analyzed the eating patterns of 2,135 patients with breast cancer and 2,571 controls to see how different foods and fibers might relate to breast cancer risk. Those eating the most fiber (more than 26.5 grams per day) were 25% less likely to have breast cancer than those eating less than 15.2 grams of fiber per day. Similarly, those eating the most beans (more than 3.9 oz per day) and grains (more than 13.8 oz per day, of both whole and refined grains) were 19% and 18% less likely to have breast cancer, respectively, than those eating the least amount of beans and grains.
Cancer Medicine. 2018 Mar 23. [Epub ahead of print] (Sangaramoorthy M et al.)

Osteoarthritis is a painful joint condition in which the flexible tissues at the ends of bones get worn down. To see how eating patterns might relate to joint pain in this condition, scientists analyzed the diets of 5,227 US adults (average age = 61) with (or at risk of) osteoarthritis. Those eating 20.6 grams of fiber per day were 30% less likely to develop symptomatic osteoarthritis than those eating only 8.6 grams of fiber per day, and scientists noted a dose-response relationship (meaning that higher fiber intakes are correlated with a lower risk of symptomatic osteoarthritis). Similarly, the researchers found that those eating the most cereal fiber (the type of fiber in whole grains) had a 14% lower risk of knee pain worsening than those eating the least (8.4 grams vs 2.8 grams). However, results were not statistically significant for other types of fiber (such as fiber from fruit or nuts).
Annals of the Rheumatic Diseases. 2017 May 23. [Epub before print.] (Dai Z et al.) 

Whole grains have long been associated with chronic disease prevention in adults, but research suggests that children may benefit as well. In this study, researchers analyzed the 7-day food records of more than 700 Danish children and confirmed whole grain intake by also taking biomarkers of whole wheat and rye intake. They found that whole grains and fiber were linked with lower levels of serum insulin, indicating healthier blood sugar management. Additionally, oats were linked with less body fat, and lower systolic blood pressure (the first number in your blood pressure reading), insulin, and LDL (bad cholesterol).
Journal of Nutrition. 2017 May 1;147(5):816-824. (Damsgaard CT et al.)

Grains have been at the core of traditional diets for millennia, but some misguided celebrities and fad diets have moved away from this tradition. Using national health survey data from 9,341 adults in Australia, researchers found that those avoiding core grain foods were significantly more likely to be overweight or obese than those who eat grains, despite consuming fewer calories, fruits, vegetables and less fiber than grain eaters. After adjusting for age, sex, and calorie intake, avoiding grains was also linked with a higher BMI and waist size.
Nutrients. 2017 Feb 18;9(2). pii: E157. (Fayet-Moore F et al.)

Food may be known to influence our mood, but little is known about the relationship between food choices and mental health. In an Australian study, scientists evaluated the Glycemic Index (a measure of how quickly carbohydrates spike blood sugar) and carbohydrate choices of 1,918 adults’ diets. Participants whose eating habits were highest on the Glycemic Index had a 55% higher likelihood of having depressive symptoms, compared to those with the lowest Glycemic Index intakes. When analyzed by the source of fiber, diets higher in total fiber (more than 27 grams per day), and fiber from vegetables and breads/cereals (mostly whole grain) were associated with a 42%, 46%, and 41% reduced likelihood of having depressive symptoms, respectively. Vegetable consumption was also linked with a significantly lower risk of depressive symptoms.
British Journal of Nutrition. 2016 Dec;116(12):2109-2114. (Gopinath B et al.)

Researchers analyzed 10 years of extensive health and nutrition data in a study of more than 1,600 Australian adults, to see how carbohydrate nutrition (Glycemic Index, Glycemic Load, total carbs, sugars, and fiber) relates to successful aging. The researchers defined successful aging as absence of disability, depression, cognitive problems, respiratory problems, or chronic disease (like heart disease or cancer). Adults eating the most total fiber were significantly more likely to age successfully. Additionally, those eating the most cereal fiber (the type of fiber in whole grains) were 78% more likely to age successfully than those eating the least, and those eating the most fruit fiber were 64-81% more likely to age successfully. Those eating a higher Glycemic Index at the beginning of the study were more likely to die throughout the study, but neither Glycemic Index, Glycemic Load, total carbohydrate, nor sugar intake were significantly associated with successful aging. 
The Journals of Gerontology: Series A, Biological Sciences and Medical Sciences. 2016 Jun 1. pii: glw091. [Epub ahead of print] (Gopinath B et al.)

Whole grains are well known for their fiber; however, fiber is not the only benefit of a diet rich in whole grains. This study uses nutritional metabolomics (a field of that looks at how different foods affect metabolism) to explore how the different compounds in whole grains may affect metabolism, and suggests scientific reasons behind the health benefits of whole grains, beyond just their fiber content. Specifically, this analysis suggests that whole grains may have positive effects on insulin sensitivity and protein metabolism, and may contain other beneficial compounds, such as glycine betaine.
Proceedings of the Nutrition Society. 2015 Aug;74(3):320-7. doi: 10.1017/S0029665114001542. Epub 2014 Oct 23. (Ross AB et al.)