Healthy Eating Tip:
Anywhere on the healthy diet spectrum, fiber matters!
I go back to talking about fiber at least four times a year because it is just that important! No matter if you are following a moderate diet like the DASH diet or a more effective lifestyle modification plan involving the plant-based whole foods diet, fiber matters!
What we are talking about when we mention the phrase “whole foods” is an “unprocessed” food. Orange juice is a great example. Orange juice isn’t a better choice than a soda, and the reason is all about fiber. As I learned in the West Indies running kitchens in high-end resorts that make their own fruit juices for breakfast, you can go through as many as 12-15 cases of oranges a week even for a small hotel. It takes a ton of oranges to make even a small amount of orange juice. All of the calories contained in 4-5 oranges are condensed down into just one glass of orange juice. Orange juice qualifies as a calorically dense processed food and shouldn’t be considered “healthy” just because it isn’t soda pop! Even a moderate diet like the DASH diet asks you to consume at least 30 grams of fiber a day, and drinking orange juice isn’t helping you reach that goal. What you want to do is eat the orange as an unprocessed whole food with all of the associated fiber, not just drink the juice with all of the calories and none of the fiber.
High fiber diets aid weight loss and offer strong protection against cardiovascular disease, diabetes, and hypertension.
Dietary fiber is the portion of plant material that passes through the stomach and small intestines largely undigested to the large intestines where it is minimally digested by gut flora and then forms the solid portion of fecal matter and performs an essential water absorption function. A further definition differentiates soluble fiber, fiber that dissolves in warm water, and insoluble fiber, fiber that does not dissolve in warm water. Soluble fiber retains water and turns to gel during digestion. It slows digestion and nutrient absorption from the stomach and intestine. Soluble fiber is found in foods such as oat bran, barley, nuts, seeds, beans, lentils, peas and some fruits and vegetables. Insoluble fiber speeds the passage of foods through the stomach and intestines without the retention of water and adds bulk to the stool. It is found in foods such as wheat bran, vegetables, and whole grains. What we refer to as “processing” removes the fiber portions of foods to yield what we readily recognize as modern processed food products. This process turns whole wheat into white flour, brown rice into white rice, and whole kernels of corn into corn starch. The bran and germ are removed, and what remains is quickly digestible starch. Fiber was once thought to be useless because it is not absorbed by the body and exhibits no readily observable nutrient value. Fiber’s inactivity as a provider of nutrients veils its considerable contribution to disease mediation.
Our knowledge of the physiological effects of dietary fiber comes to us largely due to the tireless end-of-life efforts of Dennis P. Burkitt, MD (namesake of Burkitt’s lymphoma). Based on his population comparisons between Africa and Western populations in the United States and the United Kingdom, Burkitt was almost single-handedly responsible for the reemergence of fiber’s popularity in the 1970s and the decision taken by major U.S. cereal companies to reintroduce fiber into their breakfast cereal products. Before there was substantial migration between African countries and the US and UK, Burkitt, with his associate Hugh C. Trowell MD, was able to study their differences easily. Diseases that were then labeled “Western-style diseases” like diabetes, heart disease, hypertension, and obesity were nearly non-existent in Southern Africa, where the population had not adopted our lifestyle of low exercise and consumption of highly processed foods almost entirely void of dietary fiber. Burkitt and Trowell published many papers in peer-reviewed journals that are still cited liberally today. Many of these were compiled and published in book form. Though falling short of showing direct causation, they established an ill refutable relationship between lifestyles, including highly refined food products, and diseases prevalent in western industrialized cultures, but almost completely absent in rural African populations except where contact with western culture was implicated.
For researchers, scientists, doctors, and medical team members the term “direct causation” is almost an unattainable level of certainty. That’s one of the very confusing things about the way people with a science education think and talk. That’s why an interview with a scientist about something like nutrition can be confusing. For a scientific researcher, there is nothing that is absolutely 100% certain. For a scientist, the sky may not be blue. There is a valid argument that the sky is every color but blue because blue is the color that is reflected and perceived in our eyes as “real.” When something reaches what is called “consensus” there is general agreement among the members of the scientific community. That may be as close as a scientist will get to certainty. For us mere scientific mortals, consensus is, in fact, certainty. We have all seen an unscrupulous commentator or interviewer with questionable motives trick a scientist into admitting that he or she is not 100% certain about something that there has been consensus on and then turn to the camera and say “you heard it, folks, there is no certainty on that issue.”
That ill refutable relationship between low consumption of fiber and Western-style lifestyle diseases established by Burkitt and Trowell has now reached the level of consensus. A “meta-analysis” is a powerful research tool used to determine if consensus has been achieved. It is a separate study of the results of many other studies compiling extremely large sets of data.
One such meta-analysis of 16 studies published in the European Journal of Epidemiology in 2013 showed stabilization of blood sugar with consumption of whole-grain bread, whole-grain cereals, wheat bran and brown rice. The same study showed an increased risk of diabetes with the consumption of processed white rice.
Another meta-analysis drawing on some of the best and largest studies of coronary heart disease published results in the Journal of Nutrition in 2006 showed a reduced risk of coronary heart disease based on increased consumption of high fiber fruits and vegetables. This meta-analysis used data from the Health Professionals Follow-Up Study (40,000+ subjects), the famous Nurses’ Health Study (75,000+ subjects), the Women’s Health Study (40,000+ subjects), the Atherosclerosis Risk in Communities study (ARIC) (60,000+ subjects), the NHANES follow-up study (40,000+ subjects), and the Baltimore Longitudinal Study of Aging (BLSA) (40,000+ subjects); just name a few.
Yet another very large meta-analysis of 25 studies with over 500,000 subjects published the American Journal of Clinical Nutrition in 2014 showed protection from ischemic heart disease, stroke and diabetes derived from increased consumption of nuts and beans high in fiber.
You can get the fiber you need by either eating a whole foods diet or by reading the nutrition facts label and choosing foods that provide fiber. One of the benefits of eating a plant-based whole foods diet is that you never have to worry about getting enough fiber. Some amount of fiber is in every food except animal products, which have none. If you follow a moderate diet like the DASH, the recommendation is for 30 grams of fiber a day, and you can easily achieve that by starting your day with a large bowl of steel-cut oats, Fiber-One or Grape Nuts cereal which will give you about 10 grams right at the start of your day!
Denis Burkitt wrote a small 100 page easy to read book in 1979 entitled; “Eat Right-To Stay Healthy and Enjoy Life More: How Simple Diet Changes Can Prevent Many Common Diseases.” There is a UK reprint available under the title “Fibre In Your Diet.” It takes under an hour to read and does a great job of explaining the importance of fiber!
The DASH diet (dietary approaches to stop hypertension) is an easy to follow diet that will help you control your blood pressure. As a side effect, you will lose a little weight, drop your cholesterol some, and lower your fasting glucose a little. You can read more about the DASH diet here.
Here are the references for today’s Healthy Eating Tip:
Burkitt DP. Some diseases characteristic of modern western civilization. British Medical Journal. 1973;1:5848:274-8.
Burkitt DP, Trowell HC. Refined Carbohydrate Foods and Disease: Some Implications of Dietary Fibre. London: Academic Press, 1975.
Burkitt DP, Trowell HC. Western Diseases, Their Emergence and Prevention. Cambridge, Mass: Harvard University Press, 1981.
Trowell, H. “Definition of dietary fiber and hypotheses that it is a protective factor in certain diseases.” Am J Clin Nutr 29.4 (1976): 417-27.
Trowell HC. Dietary-Fiber Hypothesis of the Etiology of Diabetes Mellitus. Diabetes 1975;24:8:762-5.
Kapoor R, et al. Impact of High Fiber Diet on Cardiovascular Risk Markers in Comorbidity of Hypertension and Type 2 Diabetes. Abstract P528. Presented at: ACC Middle East Conference; Oct. 3-5, 2019; Dubai, United Arab Emirates.
Aune D, Norat T, Romundstad P, Vatten LJ. Whole grain and refined grain consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies. European Journal of Epidemiology. 2013;28(11):845-858.
Luc Dauchet, Philippe Amouyel, Serge Hercberg, Jean Dallongeville. Fruit and Vegetable Consumption and Risk of Coronary Heart Disease: A Meta-Analysis of Cohort Studies. Journal of Nutrition. 2006;136(10): 2588–2593.
Afshin A, Micha R, Khatibzadeh S, Mozaffarian D. Consumption of nuts and legumes and risk of incident ischemic heart disease, stroke and diabetes: a systematic review and meta-analysis. American Journal of Clinical Nutrition. 2014;100(1):278-288.