It’s been called Mother Nature’s broom, and there’s ample evidence that dietary fiber cleans up in the area of longevity nutrition. “Roughage,” as it was known in our grandparents’ day, has since been shown to reduce mortality from cardiovascular, infectious, and even respiratory diseases.
Here’s a look at what fiber is, where it comes from, and what it may do for your lifespan.
What is fiber: Fiber is defined as the edible parts of plants that aren’t digested or absorbed to any degree in our intestines. There are two types of fiber, soluble and insoluble. Soluble fiber dissolves in water and helps soften the stool. It can be found in foods like oats, flaxseed, fruits and legumes. Insoluble fiber does not absorb water, so it works to bulk up the stool. Sources of insoluble fiber include whole grains, wheat bran, and vegetables.
- Read more: How to Get More Fiber in Your Diet
Since we don’t derive outright nutrition from fiber, it may seem surprising that it plays such a critical role in our overall health. But it does - fiber benefits our digestion and other bodily systems in the following ways:
- Dilutes the contents of feces in the intestine
- Reduces the transit time of stool through the intestine
- Helps the body excrete potential carcinogens by binding to them in the stool
- Lowers blood cholesterol
- Improves insulin sensitivity
- Lowers blood pressure
Fiber and longevity research: Despite the many positive effects of fiber on overall health, solid data regarding its role in longevity per se, is fairly recent. For example, a 2004 analysis of 10 different studies published in the Archives of Internal Medicine found for every 10 grams of fiber eaten per day, the risk of cardiovascular death dropped by 27%. Similarly, in a 2008 review of about 1,300 Dutch men followed over a 40-year period, every 10 grams of fiber consumed per day dropped the risk of dying from cardiovascular disease by 17% - and from any cause, by 9 per cent.
A large study published in 2011 made an even stronger case for boosting longevity through fiber consumption. Also published in the Archives of Internal Medicine, the research involved almost 400,000 people aged 50-71, as part of the National Institutes of Health (NIH) – American Association of Retired Persons (AARP) Diet and Health Study. Subjects were questioned about their diets and fiber intake, and over the nine years of follow-up, causes of death were recorded, and correlations between grams of fiber consumed each day and cause of death analyzed.
The findings? Dietary fiber was shown to reduce the risk of death from all causes, in both men and women. In particular, it was associated with a lower risk of cardiovascular disease, as well as infectious diseases (like tuberculosis and septicemia) and respiratory diseases (like pneumonia, influenza, and chronic obstructive pulmonary disease, or COPD).
Men and women consuming the most dietary fiber –- about 26-29 grams per day -- were 22% less likely to die during the 9-year study period, than those who consumed the least fiber (10-13 grams per day). The benefits to longevity held, even when factors like Body Mass Index, physical activity, and smoking were accounted for. However, in this research the greatest longevity boost was only linked to fiber from grains; fiber derived from vegetables and legumes was found to be only weakly linked to a lower risk of death, while fruits, not at all.
Interestingly, when it came to cancer, the NIH-AARP study found fiber intake was related to a reduced risk of the disease in men, but not in women. The authors propose this sex discrepancy might be explained by the differences in which particular cancers tend to be fatal in men vs. women. For example, men have higher mortality rates in cancers potentially affected by diet (and therefore fiber intake), like liver, esophagus, and kidney cancer. Past research has suggested eating more fiber might help prevent esophageal and colorectal cancers, but to date, the evidence has not been conclusive.
Eat fiber often: Frequency of fiber consumption, and not just the amount eaten, may also play a role in longevity. For example, research from the Iowa Women’s Health Study concluded that regularly eating whole grains – which contain more fiber than processed cereal products – helped subjects live longer. Tracking more than 27,000 post-menopausal women over a 17-year period, nutrition scientists found that women who ate just 4-7 servings of high-quality unrefined grains per week were 31% less likely to die during the study period, when compared with those who ate whole grains rarely, or not at all. That’s an average of less than one serving per day.
David Jacobs, epidemiologist and co-author of the Iowa Women's Health Study research on whole grains, agrees with the NIH-AARP researchers that people should pay attention to eating a variety of fiber-rich fruits and vegetables, as well as whole grains - rather than worrying too much about individual components of what we eat.
As he told me, "Nutrition should focus on foods such as whole grains, and not nutrients/constituents (which may not even act the same isolated as part of food)."
- Read more: Anti-Aging Breakfast Ideas
David R Jacobs, Jr, Lene Frost Andersen and Rune Blomhoff. "Whole-grain consumption is associated with a reduced risk of noncardiovascular, noncancer death attributed to inflammatory diseases in the Iowa Women's Health Study." Am J Clin Nutr June 2007 vol. 85 no. 6 1606-1614.
Mark A. Pereira et al. “Dietary Fiber and Risk of Coronary Heart Disease
A Pooled Analysis of Cohort Studies” Arch Intern Med. 2004;164:370-376
Park Y, Subar AF, Hollenbeck A, Schatzkin A.
Dietary fiber intake and mortality in the NIH-AARP diet and health study.
Arch Intern Med. 2011 Jun 27;171(12):1061-8.