April 25, 2016
By Shilpa Ravella
If you could make only one change to your diet, what would it be? The options are endless. You can cut out specific foods like meat, grains or gluten. You can play with ratios of fat, carbohydrates and protein. You can eat only fruit or go on a juice cleanse. There is one change, however, that provides the biggest health return for the investment: Fiber.
Dr. Denis Burkitt, an Irish-born surgeon best known for his description of the pediatric cancer Burkitt’s lymphoma, wrote an international bestseller in 1979 called Don’t Forget Fibre in Your Diet. While working in Uganda in the 1960s, Burkitt noted that many of our most common and deadly diseases such as heart disease and cancer were rare in populations consuming large amounts of fiber, which is found solely in plant foods.
“Anyone asked to list the 20 or more most important advances in health made in the last few decades would be likely to include none of what I consider to be among the most significant,” he wrote over three decades ago.
Since the Industrial Revolution, American diets increasingly contain animal fats, salt and sugar, all of which have displaced fiber. The recommended daily fiber intake is 25g per day for women and 38g per day for men, but most Americans average only 15g per day.
Fiber content of selected whole foods
Amount of fiber, in grams:
Boiled split peas, 1 cup, 16.3g
Boiled lentils, 1 cup, 15.6g
Boiled black beans, 1 cup, 15g
Boiled artichoke, 1 medium, 10.3g
Raspberries, 1 cup, 8g
Whole-wheat spaghetti, cooked, 1 cup, 6.3g
Pear with skin, 1 medium, 5.5g
Boiled broccoli, 1 cup, 5.1g
For more examples, see this chart from the Mayo Clinic.
Research continues to confirm Burkitt’s assertion. Earlier this year, a study conducted at the Harvard School of Public Health and published in the journal Pediatrics concluded that high fiber intake during adolescence can reduce a woman’s risk of getting breast cancer. The women who consumed at least 28g of fiber per day had a 24 percent lower risk of breast cancer compared to those who ate only 14g.
In addition to breast cancer, fiber can protect us from many other ailments. High fiber intake has been associated with a lower risk of heart disease, diabetes and obesity. It can decrease blood cholesterol, promote satiety and dampen the glucose and insulin spikes after meals. Fiber improves gastrointestinal health, warding off chronic bowel disease, constipation, diverticulosis and hemorrhoids.
Loving your gut
While fiber is important for our bodies, it is also critical for the germs inside of us. The human gut is home to around 40 trillion bacteria known as the gut microbiome, an internal ecosystem that wields considerable influence over our health. When digested by intestinal bacteria, fiber leads to the production of beneficial by-products like short-chain fatty acids that nourish the gut barrier and help prevent inflammation.
Stephen O’Keefe, a gastroenterologist at the University of Pittsburgh, suspected as Burkitt did many years ago that a high fiber diet could explain lower colorectal cancer risks in native Africans as compared to African-Americans.
In a 2015 study published in Nature Communications, O’Keefe put 20 rural South Africans on a high-fat meat-heavy diet including hot dogs and hamburgers, and he put 20 African-Americans on a high-fiber diet including corn porridge, beans and fruit.
In just two weeks, inflammation of the colon (which increases the risk of cancer) decreased in the African-Americans and increased in the rural Africans. O’Keefe also saw changes in gut bacterial byproducts associated with cancer risk. In African-Americans, there was an increase in butyrate, a short-chain fatty acid thought to prevent colon cancer, while the rural Africans had a decrease in butyrate.
Drilling down into the research
Burkitt was convinced that fiber was the solution to good health, but did he focus too narrowly on it? High fiber intake seems to be a promising way to prevent many diseases, including cancer, but the research can be confusing at times.
For example, some studies have shown that high fiber intake prevents colon cancer, while other studies have not found this association. Results may vary because the quality and quantity of fiber in each study is not constant. Fiber in a salad is different from fiber in a box of cereal, and the “high-fiber” groups in some studies barely meet the daily recommended intake.
In addition, whole plant foods have many different vitamins, minerals, antioxidants and complex carbohydrates, all of which can promote health. We know that fiber supplements or foods fortified with fiber have failed to provide the same benefits as whole foods. Fiber may be a marker for healthy eating, or most effective when consumed in whole foods.
Fiber’s importance for boomers
Older adults can be especially affected by nutrient deficiencies, and most don’t have enough fiber in their diets. The incidence of many diseases increases with age including cancer, heart disease, high cholesterol, high blood pressure and stroke.
Common colonic issues like constipation and diverticulosis are also more common in older adults. For example, diverticulosis is seen in nearly 30 percent of people over 50 and in 50 percent of those over 70. Fiber can be important in the prevention and treatment of these problems.
For most of human existence, our guts have been exposed to coarse roughage. Paleolithic fossilized feces, when analyzed, display high amounts of undigested plant remains. Today, research continues to show us that fiber can prevent disease and keep our gut bacteria healthy.
How much is enough?
How much fiber should you aim for? The recommended daily intake of 25g to 38g is a minimum. In populations where many of our lethal diseases are unknown, such as rural Africa and China, the average intake is around 60g to 100g a day. This is similar to the amount our Paleolithic ancestors used to consume.
Returning to this way of eating by including as many minimally processed whole plant foods as you can — a high-fiber diet — is one of the best ways to stay healthy. (from PBS Next Avenue)