What Matters

Fiber in the new year


The start of a new year provides us the opportunity to reflect on the past year, relish in our successes, ruminate about things we did less well, and make resolutions. For 2014, I resolve to take better stock of, and encourage in my patients an increased use of, fiber.

Fiber is a simple and cheap intervention. So simple and cheap that I have increasingly neglected to assess and instruct my patients on its use and benefits. The recommended amount of dietary fiber is 20-35 g/day, and some of us may feel quite sure that many of our patients are not coming close to this amount of intake.

Recall that total dietary fiber is a combination of both insoluble (e.g., wheat bran, whole grains, vegetables) and soluble (e.g., psyllium, nuts, and some fruits and vegetables) components. Soluble fiber can reduce the risk for type 2 diabetes, control blood glucose in individuals who already have diabetes, and reduce the risk for coronary heart disease (CHD) and cardiovascular disease (CVD, i.e., fatal or incident stroke plus CHD).

But how much does fiber reduce the risk for cardiovascular disease? Is there a dose effect?

In a recent systematic review of the literature, investigators endeavored to determine the dose-response relationship between dietary fiber and reductions in CHD and CVD risks. Prospective studies reporting associations between fiber intake and CHD and CVD endpoints were included if they had a minimum of 3 years of follow-up and were published between 1990 and 2013 (BMJ 2013;347:f6879).

The literature review included 22 studies. Total dietary fiber intake was associated with a reduced risk for CVD (risk ratio, 0.91 per 7 g/day; 95% CI: 0.88-0.94) and CHD (RR, 0.91; 95% CI: 0.87-0.94). Insoluble fiber seemed to have the greatest reduction, although the authors encouraged caution in the interpretation of the data on the specific subtypes of fiber, which need further study. We should focus on the total daily intake.

The take-home message is that patients should be encouraged to increase their intake of whole foods (unprocessed and unrefined). For every additional 7 g of total fiber per day, a 9% lower risk for CVD and CHD clinical endpoints can be achieved. For patients who are unable to achieve higher fiber intake through diet, supplementation with psyllium or methylcelluose, soluble fibers common in popular OTC brands, may be beneficial.

Dr. Ebbert is a professor of medicine, a general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author. He reported having no conflicts of interest.

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