Some types of foods are easier to incorporate into one’s diet than others. If your doctor advises you to eat more fruits or vegetables, you can quite easily select the varieties that you like best and up your intake. The same can be said for other commonly recommended health foods such as fish, nuts and seeds. But adding more fiber into your daily routine requires some planning because not all fruits and vegetables contain much and animal based foods are completely devoid of it. In my opinion, being reminded of the importance of fiber, while becoming more aware of foods that are abundant in this dietary component is the key to making it a priority.
A recent summary in the journal Nutrition Review suggests that optimal levels of dietary fiber may help prevent a wide array of health conditions, including several cancers, cardiovascular conditions, diabetes, gastrointestinal diseases and, even, obesity. The recommended target is roughly 14 grams of fiber per every 1000 calories consumed. Ideally, the majority of this fiber should come from nutrient rich foods. But fiber supplements can also be utilized if your diet regularly falls short of your fiber goals. (1)
When I reviewed the 2009 medical literature relating to fiber, two key areas of health care were most prominently featured: cancer and cardiovascular disease. Today I’ll focus on the cancer protective role of these bulking agents. I’ll also devote a separate column to the cardiovascular part of the equation.
A 4 year dietary intervention examined the effects of a strict high fiber diet (rich in fruits and vegetables) in a group of patients at an increased risk for colon polyps. A 35% reduction in polyp recurrence was found in those deemed as “super compliers” to the menu plan. This emphasizes the need for a consistently healthy diet. (2)A very large population trial entitled the “National Institutes of Health – AARP Diet and Health Study” investigated the role that dietary fiber may play in breast cancer (BC) rates. Over 185,000 postmenopausal women were followed for 7 years. Food frequency questionnaires were used to assess typical food selection and macronutrient status. The researchers determined that the women consuming the most fiber were afforded significant protection against BC. Their concluding remarks were as follows: “Our findings suggest that dietary fiber can play a role in preventing breast cancer through non-estrogen pathways among postmenopausal women.” (3)The August 2009 issue of the journal Cancer Causes and Control provided very strong evidence that a high fiber diet can reduce the likelihood of stomach cancer occurrence. More importantly, the Italian scientists behind this trial actually looked at what forms of fiber appear to be most beneficial for stomach cancer prevention. Their overall conclusion was that total fiber consumption did demonstrate a protective effect. But only fiber from vegetables and, to a lesser extent, fruit yielded positive results. Fiber rich grains did not afford any benefit at all in this investigation. (4)Reflux esophagitis and Barrett’s esophagus are inflammatory conditions that can increase the risk of developing esophageal cancer. A new study from the Netherlands determined that the intake of starchy carbohydrates increased the risk of these forms of pre-cancerous inflammation. But, higher intake of roughage was inversely related to esophageal inflammation and the related cancer. The reduced risk was noted as 56% based on a comparison of those with the highest vs. lowest dietary fiber intake. This is yet another example of how good carbs (fiber) can benefit health and bad carbs (starches and sugar) can endanger it. (5)One concern that I’ve personally had about dietary fiber is whether its bulking action may impede the absorption of other healthy components found in foods. This issue was recently addressed in a study presented in the June issue of the journal Plant Foods for Human Nutrition. 10 volunteers were provided with an antioxidant rich fiber supplement. The product contained a total of 15 grams of dietary fiber per serving. The researchers then tested the blood of the volunteers at various points following the fiber consumption. Significant elevations in serum antioxidant status were found 8 hours after the ingestion of the antioxidant/fiber blend. This indicates that “antioxidants associated with dietary fiber are at least partially bioavailable in humans, although dietary fiber appears to delay their absorption”. (6)
One the easiest and healthiest ways to boost fiber intake is to make a fiber rich smoothie. I regularly include berries, pure cocoa powder and flax seeds in my protein shakes to increase fiber content. I can now do so with the added knowledge that the naturally occurring antioxidants in these fiber sources will sustain my good health for several hours after I drink them. In effect, this may help provide valuable protection over the course of the day and night. I hope that this information and my companion column about fiber and cardiovascular disease will help inspire you to include more fiber in your diet. I believe the effort will be well worth it.
Update: December 2010 - In yesterday’s column I mentioned how increasing your intake of dietary fiber can also lead to a higher consumption of valuable nutrients including magnesium. But the protective effects of whole foods extend beyond their nutritive properties. When examining the role that fiber plays in the incidence of malignancies, it’s important to consider the antioxidants that are usually present in fiber rich foods. When doing so, it’s also vital that the issue of antioxidant transport be evaluated. A new report in the Journal of Agricultural Food Chemistry explains that “around 50% of the total dietary antioxidants, mainly polyphenolics, transverse the small intestine linked to dietary fiber”. The authors of the paper go on to state that “It is concluded that the transportation of dietary antioxidants through the gastrointestinal tract may be an essential function of DF (dietary fiber)”. This may explain why new studies continue to find a profound association between fiber consumption and protection against various malignancies including colorectal, gastric and ovarian cancer. This is also why I recommend ensuring high fiber consumption no matter which diet you choose to follow. (7,8,9)
Be well!
JP
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