There are a few different classifications of fiber, and their common characteristic is resistance to digestion in the human small intestine. Eating fiber-rich foods is associated with a number of health benefits:
- Fiber promotes weight maintenance by slowing gastric emptying; and adding volume to food, promoting satiety
- Fiber helps to prevent diabetes by slowing entrance of glucose into the bloodstream, curbing glucose (and insulin) spikes after meals
- Soluble fiber (a type of fiber abundant in oats and beans) has cholesterol-lowering effects.
- Cardiovascular health – a pooled analysis of 10 prospective studies found that an increase of 10 grams of dietary fiber per day was associated with a 24% decrease in deaths from coronary heart disease.1
- Digestive health – fiber adds bulk and acts as a stool softener, making bowel movements faster and easier, and preventing constipation and diverticular disease.
- Fermentation of fiber and resistant starch by bacteria in the large intestine helps to prevent colorectal cancers 2
Fiber vs. fiber-rich foods: Fiber can be isolated and taken as a supplement or added to a processed food, but that is not the best way to get your fiber. Although fiber itself has beneficial properties, fiber-rich whole foods come packaged with disease-fighting phytochemicals. There have been inconsistencies in the results of studies on fiber and colorectal cancer, probably because it appears to be high-fiber foods (vegetables, beans, and whole grains), not fiber alone that reduces risk. In contrast, foods devoid of fiber, like meat, are associated with increased risk. 3-8
The American Heart Association recommends consuming 25 grams of fiber each day. The nutritarian diet that I recommend is primarily made up of fiber-rich, natural foods like vegetables, fruits, seeds and beans, and far exceeds that recommendation, providing about 60-80 grams of fiber each day.
A study relating dietary fiber intake to lifetime risk of cardiovascular disease was presented at the American Heart Association’s Nutrition, Physical Activity, and Metabolism conference last week. Data from the 2003-2008 U.S. National Health and Nutrition Examination Surveys were analyzed. The researchers used a mathematical algorithm to predict lifetime risk for cardiovascular disease, based on diet, blood pressure, cholesterol, smoking, and history of diabetes. All of the participants were free of cardiovascular disease at the start.
The algorithm placed participants in groups of either high or low lifetime risk of cardiovascular disease. Then they were arranged into four groups according to the ratio of their intake of dietary fiber to calories - dietary fiber only, no fiber supplements were included. The lowest fiber intake was 0.1g/1000 calories, and the highest was on par with a nutritarian diet, 49.1g/1000 calories.
Individuals aged 20-39 in the highest quartile of fiber intake were almost twice as likely to be in the low risk category than those in the lowest quartile. Middle aged individuals in the highest quartile were about 50% more likely to be in the low risk category. Interestingly though, a similar association was not seen in 60-79 year olds. The researchers theorized that many older adults with high fiber intake may have already developed significant risk for heart disease before they added more high-fiber foods to their diet. They concluded that starting to increase fiber intake at a younger age helps to decrease the risk of cardiovascular disease later in life.9, 10
It is important to eat healthfully your entire life to get maximum benefits, however once you have not eaten properly for the first 60 years, then to get the disease-protective benefits to dramatically reduce heart attack, stroke and cancer risk from a plant-based diet later in life, it is not good enough to just be flexitarian or vegan, you actually have to eat very healthfully. Many vegans eat a white grain-based diet with lots of sugar and low-micronutrient-processed foods, using vegetables only as a side dish. In order to get maximum disease protection, you must plan your diet around the most nutritionally powerful and protective plant foods – lots of green vegetables, onions, mushrooms, beans, berries, and seeds. For more information, take a look at my food pyramid.
Eating for health and longevity is a lifetime commitment – just like it takes years for heart disease to develop, it takes years to build up protection against heart disease. Once you are past middle age, the way to start is not with some wishy-washy low fat, high fiber diet. That is not good enough. You must do better than that and pay attention to the micronutrient-richness of your meals and assure you have adequate intake of all nutrients achieving comprehensive nutritional adequacy. A properly-designed diet of whole plant foods provides your body with a continuous and diversified supply of anti-cancer and anti-atherogenic phytochemicals. No matter what your age, you can benefit from improving your diet – but the point is, the change has to be significant and the time to start is right now, because it takes time for these phytochemicals to saturate your tissues and begin to undo the years of damage that may have been caused by your previous diet. Start now, with a high-nutrient (nutritarian) diet, and pay heed to the the disease-fighting nutrients in foods, especially green vegetables, mushrooms and onions, beans, berries and seeds with their beneficial phytochemicals that have powerful effects against both heart disease and cancer.
Visit Dr. Fuhrman's website.
1. Pereira MA, O'Reilly E, Augustsson K, et al: Dietary fiber and risk of coronary heart disease: a pooled analysis of cohort studies. Arch Intern Med 2004, 164:370-376.
2. O'Keefe SJ, Ou J, Aufreiter S, et al: Products of the colonic microbiota mediate the effects of diet on colon cancer risk. J Nutr 2009, 139:2044-2048.
3. Singh PN, Fraser GE: Dietary risk factors for colon cancer in a low-risk population. Am J Epidemiol 1998, 148:761-774.
4. Uchida K, Kono S, Yin G, et al: Dietary fiber, source foods and colorectal cancer risk: the Fukuoka Colorectal Cancer Study. Scand J Gastroenterol 2010, 45:1223-1231.
5. Park Y, Hunter DJ, Spiegelman D, et al: Dietary fiber intake and risk of colorectal cancer: a pooled analysis of prospective cohort studies. JAMA : the journal of the American Medical Association 2005, 294:2849-2857.
6. Michels KB, Fuchs CS, Giovannucci E, et al: Fiber intake and incidence of colorectal cancer among 76,947 women and 47,279 men. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 2005, 14:842-849.
7. Terry P, Giovannucci E, Michels KB, et al: Fruit, vegetables, dietary fiber, and risk of colorectal cancer. J Natl Cancer Inst 2001, 93:525-533.
8. Wakai K, Date C, Fukui M, et al: Dietary fiber and risk of colorectal cancer in the Japan collaborative cohort study. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 2007, 16:668-675.
9. Northwestern University (2011, March 23). Load up on fiber now, avoid heart disease later. . In ScienceDaily; 2011.
10. Ning H, Van Horn L, Shay CM, et al: Dietary Fiber Intake and Long Term Cardiovascular Risk: Findings from the National Health and Nutrition Examination Surveys (NHANES) 2003-2008. In American Heart Association: Nutrition, Physical Activity, and Metabolism 2011.