Wednesday, August 31, 2011
Go to Health: the link between fiber, overweight and cancer
You may be confused, and skeptical, about the importance of a high fiber diet. The connection between dietary fiber and a reduced risk of colon cancer has been disputed because of conflicting studies and differing measurements of dietary fiber. However, according to the American Institute for Cancer Research (AICR – a non-profit that fosters research on diet and cancer), a diet high in whole grains, fruits, legumes and vegetables is valuable to reduce both overweight and several cancers. AICR looked at over 7,000 studies worldwide, finding evidence that whole grains in the diet do lower the risk of colorectal cancer. In a large prospective cohort study, subjects who ate the most whole grains had a 20% lower risk of colorectal cancer than those who ate the least.
As readers know – whole grains include minimally processed wheat, spelt (an ancient variety of wheat) oats, rye, corn, barley, millet, quinoa and amaranth. When buying these grains as bread, crackers or pasta, it is important to read the label, and make sure that your product does not contain a deceptive sprinkle of whole grain but is 100% what you are looking for - the whole grain.
Foods high in fiber are relatively low in energy density; they contribute to a feeling of fullness and reduce the risk of overweight. Here is another way that whole grains prevent disease. Overweight is related to an increased risk of several cancers, including colon, uterine, breast (in women post menopause), esophagus, pancreas, gall bladder, liver, and kidney.
A study from Tufts University showed that the distribution of body fat varied with whole and refined grain intake. Subjects with the highest intake of whole grains had the lowest amount of deep abdominal fat – known as visceral adipose tissue. Around our waists and in our buttocks and thighs, fat lies under our skins, which we can feel by pinching ourselves gently. This fat poses less of a problem in normal-weight people. However, visceral fat lies inside the abdominal cavity, packed in between the stomach, liver, intestines and kidneys. This visceral fat has been shown to be a risk factor for insulin resistance, type 2 diabetes, cardiovascular disease and a shorter life. Visceral fat is associated with chronic inflammation in the body, and higher insulin levels – both linked to an increased risk of cancer. It is also linked to higher total and LDL cholesterol, and lower HDL (good) cholesterol.
Obviously, fat in the diet is essential – for the absorption of vitamins A, D, E and K from foods, for essential fatty acids like omega-3s, for taste, satiety and maintenance of stored energy reserves. Healthy fat intake is good, but having excess amounts of visceral fat is dangerous.
Here’s advice from Harvard Medical School on how to reduce visceral fat.
*Regular moderate intensity physical exercise – 30 to 60 minutes a day. This would include brisk walking, biking, and gym workouts. Check with your MD or NP before beginning a program if you have not been active.
*Reduce portion size and emphasize whole grains and lean protein over white flour, rich desserts, sugary food and drinks, and alcohol.
It’s that simple – in theory at least – and such a program will work. Many people welcome the help of a program such as Weight Watchers or Overeaters Anonymous to get started and keep going.
Marion Nestle, a professor in the Department of Nutrition at New York University and the author of many books on food and food policy, has a daily blog which you may enjoy: www.foodpolitics.com. She has short, humorous and cogent posts on the latest in food science, how to eat, and how to improve our food system.
Sadja Greenwood, MD, MPH – back issues on this blog