Prebiotics

Philip J. Goscienski, M.D.

February 2010

One of the most serious nutritional deficiencies of our time is that of dietary fiber. Our Stone Age ancestors as well as pre-Columbian Native Americans ate an estimated 80 to 150 grams per day based on analyses of ancient dwelling sites, fossilized fecal matter and comparison with modern-day hunter-gatherers. That sounds like a lot — and it is. The average American takes in only about 10 to 15 grams of fiber per day, reflecting our national disdain for fruits, vegetables and whole grains.

Dietary fiber is either soluble or insoluble. The latter contributes to normal bowel regularity by absorbing water and providing bulk. Whether or not it decreases the risk of colon cancer is still being debated. Studies that claim no effect ignore the fact that our modern high fiber diet would be seen as a pathetically low fiber diet back in the Stone Age.

Soluble fiber is the especially healthy form. Acted upon in the large intestine by the friendly bacteria that we described in last week's column, it releases nutrients that increase the absorption of calcium, enhance immunity, lower total and LDL cholesterol, reduce the risk of heart disease as well as peripheral artery disease and help to keep blood sugar in the normal range. Preliminary studies of the effects of soluble fiber combined with beneficial bacteria in inflammatory bowel diseases such as ulcerative colitis and Crohn's disease are promising but not yet conclusive.

In the millennia before the Agricultural Revolution humans had no problem getting enough soluble and insoluble fiber among the scores, perhaps hundreds of plants that grew in the temperate climates where virtually all of them lived. Even a century or so ago in the United States the daily intake of fiber had not decreased by very much. That changed dramatically in the mid-twentieth century. Today's supermarkets offer only a couple dozen different vegetables and an equally small variety of fruits. These are bred for starchiness and sweetness and they have relatively less fiber than the versions our grandparents enjoyed.

Whole-grain cereals and legumes (beans, lentils) offer the most fiber. A wholesome diet includes fiber-rich fruits (apples, oranges, strawberries, bananas, figs) and vegetables such as broccoli, carrots, green peas and sweet potatoes. White potatoes, including the skin are good sources of fiber but French fries are not.

A side benefit is that high-fiber foods are calorie-sparse, giving a sense of fullness that curbs appetite.

Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at drphil@stoneagedoc.com.