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A recent study found that significantly increasing  dietary fiber intake after a diagnosis of colorectal cancer was associated with a lower death rate - from both colorectal cancer and overall mortality (from any cause). The 1575 men and women (all healthcare professionals) in the study had received a nonmetastatic colorectal cancer diagnosis (it had not spread beyond the colon), and the follow-up was about 8 years. These results were from food, not supplements.

How much did extra dietary fiber lower the death rate? For each additional 5  grams of fiber added to their daily diet (after diagnosis) was associated with a 18% lower colorectal cancer death rate, and a 14% lower death rate from any cause. In this study, whole grains, especially in cereals, were found to be the most beneficial. Current dietary guidelines recommend a fiber intake of 25 to 38 grams per day, but most Americans eat far lessDietary fiber is found in plant foods, such as beans, whole grains, nuts, seeds,  vegetables, and fruits. Plant fiber feeds the millions of gut microbes, especially beneficial microbes (here, here, and here) - something that was not really discussed in the study.

The researchers pointed out that a high fiber diet (especially from whole grains and cereals) is linked to a lower risk of getting colorectal (colon) cancer in the first place.  Also, that "higher intake of fiber, especially cereal fiber", has been linked to improved insulin sensitivity, reduced inflammation, type 2 diabetes, cardiovascular disease, and total mortality. Other studies have found that  vitamin D supplementation, exercise, and eating fish all increase survival from colorectal cancer. From From Medical Xpress:

Fiber-rich diet boosts survival from colon cancer

A diet rich in fiber may lessen the chances of dying from colon cancer, a new study suggests. Among people treated for non-metastatic colon cancer, every 5 grams of fiber added to their diet reduced their odds of dying by nearly 25 percent, said lead researcher Dr. Andrew Chan. He is an associate professor in the department of medicine at Harvard Medical School.

"What you eat after you've been diagnosed may make a difference," Chan said. "There is a possibility that increasing your intake of fiber may actually lower the rate of dying from colon cancer and maybe even other causes." Chan cautioned, however, that the study does not prove that the additional fiber caused people to live longer, only that the two were associated.

Fiber has been linked to better insulin control and less inflammation, which may account for better survival, he suggested. In addition, a high-fiber diet may protect people from developing colon cancer in the first place. The greatest benefit was attributed to fiber from cereals and whole grains, according to the report. Vegetable fiber was linked to an overall reduction in death, but not specifically in death from colon cancer, and fiber from fruit was not linked to a reduction in death from any cause. 

For the study, Chan and his colleagues collected data on 1,575 men and women who took part in the Nurses' Health Study and Health Professionals Follow-up Study, and who had been treated for colon or rectal cancer that had not spread beyond the colon. Specifically, the study looked at total fiber consumption in the six months to four years after the participants' cancer diagnosis. The researchers also looked at deaths from colon cancer and any other cause. In an eight-year period, 773 participants died, including 174 from colorectal cancer. [Original study.]

Another study has shown health benefits from eating a diet rich in whole grains, as compared to one with lots of refined grains (think bagels, muffins, white bread). Fifty overweight Danish adults were randomly assigned to either a group where all grains eaten were whole grains or a group where all grain products were of refined grains. They did this for 8 weeks, then ate their usual diet for a few weeks (the "washout period"), and then were assigned to the other dietary group for 8 weeks.

They found that eating the diet rich in whole grains resulted in: consuming fewer calories (the whole grains made them feel fuller), losing weight, and a decrease in chronic low-grade inflammation (by measuring blood inflammation markers). The whole grain rye seemed to be especially beneficial. But interestingly, the researchers found that the whole grain diet did not significantly change the gut microbe composition. But they did find that 4 strains of Faecalibacterium prausntzii and one of Prevotella copri increased in abundance after whole grain and decreased after refined grain consumption. F.prausnitzii is a desirable and beneficial keystone species in the gut (here and here).

Other studies show that eating a diet rich in whole grains (rather than refined grains) is associated with a decreased risk of several diseases, including type 2 diabetes and cardiovascular diseases. Bottom line: choose whole grains whenever possible. From Science Daily:

Several reasons why whole grains are healthy

When overweight adults exchange refined grain products -- such as white bread and pasta -- with whole grain varieties, they eat less, they lose weight and the amount of inflammation in their bodies decreases. These are some of the findings of a large Danish study headed by the National Food Institute, Technical University of Denmark. 

The study included 50 adults at risk of developing cardiovascular disease or type 2 diabetes. Blood tests showed that the participants had less inflammation in their bodies when eating whole grains. In particular, it appeared that rye had a beneficial effect on the blood's content of inflammatory markers. Inflammation is the natural response of the body to an infection, but some people have slightly elevated levels of inflammation (so-called low-grade inflammation) even though there is no infection. This is particularly the case in overweight people. In overweight people, an increased level of 'unnecessary' (subclinical) inflammation may lead to increased risk of developing type 2 diabetes.

The study also shows that participants eat less when whole grain products are on the menu -- presumably because whole grain consumption causes satiety. While eating the whole grain diet, participants have generally lost weight. The researchers used DNA sequencing to analyze stool samples from the participants in order to examine whether the different diet types affected the participants' gut bacteria composition. Overall, the analysis did not shown major effects of the dietary grain products on the composition of the gut bacteria. [Original study.]

 A second study was just published about the benefits of eating whole grains daily - again a significantly lower risk of premature death, and again the effects were dose-related. That is, the more whole grains eaten daily, the lower the risk of early death. Like the first study, this also was a review study. This study (published in BMJ) found that whole grain consumption was associated with a reduction in the risk for death from cancer, coronary heart disease (heart attack and stroke), respiratory disease, infectious disease, and diabetes.

A slice of 100 percent whole grain bread contains about 16 grams of whole grains, and current U.S. dietary guidelines recommend 48 grams or more of whole grains daily, but this study suggests that eating even more whole grains daily is best (eating 90 grams of whole grains a day reduced the risk for mortality from all causes by 17 percent).

Grains are divided into two subgroups: whole grains and refined grains. Whole grains or foods made from them contain all the essential parts and naturally-occurring nutrients of the entire grain seed in their original proportions. This definition means that 100% of the original kernel – all of the bran, germ, and endosperm – must be present to qualify as a whole grain. Some whole grains are: whole wheat. barley. buckwheat, corn (including whole cornmeal and popcorn), millet, oats (including oatmeal), quinoa, brown rice, rye, sorghum, spelt, bulgur, and wild rice. From Eurekalert:

Seven servings of whole grains a day keep the doctor away

Eating three more portions of dietary fiber a day--say, two pieces of whole grain bread and a bowl of whole grain breakfast cereal--is associated with a lower risk for all cardiovascular diseases and for dying of cancer, diabetes, and respiratory and infectious diseases, a study just published in the BMJ has shown. The study is strong proof that consuming lots of whole grains is good for our health, says first author Dagfinn Aune, a PhD candidate at the Norwegian University of Science and Technology who is currently working at Imperial College, London.

....In general, the study showed that the higher the consumption, the better protected you are. "We saw the lowest risk among people who ate between seven and seven and a half servings of whole grain products a day, which was the highest intake across all the studies. This corresponds to 210-225 grams of whole grain products in fresh weight and about 70-75 grams of whole grains in dry weight, and is about the same as the health authorities in Norway and other Nordic countries recommend as the minimum daily allowance," says Aune.

The researchers' analyses showed fewer risk factors for people who consumed more bread and cereal with whole grains, as well as foods with added bran. On the other hand, people who ate a lot of white bread, rice or cereals with refined grains did not show reduced risk.

Nine studies with a total of more than 700,000 participants examined the risk for all types of cardiovascular disease and correlated cardiovascular deaths....The risk of dying prematurely from all causes was 18% lower for individuals who consumed a lot of whole grains compared to those who consumed lesser amounts, while three additional servings each day were associated with a 17% reduction in mortality. The risk for deaths associated with cancer (15%), respiratory diseases (22%), diabetes (51%) and infectious diseases (26%) was also lower the more whole grains individuals consumed.

 Eating whole grains is good - lower death rate, fewer cardiovascular disease related deaths, fewer cancer deaths! And recent research (a review of studies) showed that the more whole grains consumed, the lower the death rate. Current dietary guidelines suggest 3 servings a day. Whole grains include: whole wheat, barley, buckwheat, millet, oats, quinoa, brown rice, rye, bulgur, spelt,and wild rice. Whole grains provide many nutrients, such as fiber, B vitamins, and minerals. From Medical Xpress:

Eating more whole grains linked with lower mortality rates

Eating at least three servings of whole grains every day could lower your risk of death, according to new research in the American Heart Association's journal Circulation. Although dietary guidelines around the world have included whole grains as an essential component of healthy eating patterns, people aren't eating enough, according to the analysis. In the United States average consumption remains below one serving a day, despite the long-time recommendation of three servings a day.

In the first meta-analysis review of studies reporting associations between whole grain consumption and death, researchers noted that for about every serving (16 grams) of whole grains there was a: 7 percent decreased risk in total deaths; 9 percent decline in cardiovascular disease-related deaths; and 5 percent decline in cancer-related deaths.

The more whole grains consumed, the lower the death rate. According to researchers, when three servings (48 grams) were consumed daily the rates declined: 20 percent for total deaths; 25 percent for cardiovascular deaths; and 14 percent for cancer-related deaths.

"Previous studies have suggested an association with consumption of whole grains and reduced risk of developing a multitude of chronic diseases that are among the top causes of deaths, although data linking whole grain intake and mortality were less consistent," said Qi Sun, M.D., Sc.D., senior author of the study and assistant professor at the Harvard T.H. Chan School of Public Health in Boston, Massachusetts. "These findings lend further support to the U.S. government's current Dietary Guidelines for Americans, which suggest higher consumption of whole grains to facilitate disease prevention."

Whole grains, such as whole wheat, oats and brown rice, contain dietary fiber, which may help improve blood cholesterol levels, and lower the risk of heart disease, stroke, obesity and type 2 diabetes. Dietary fiber can also make you feel full longer, so you may eat fewer calories.

This analysis included 12 studies published through February 2016 and unpublished results from the National Health and Nutrition Examination Survey (NHANES) III, conducted from 1988 to 1994, and NHANES 1999-2004. Of the reviewed studies, 10 were conducted in U.S. populations, three in Scandinavian countries and one in the United Kingdom. The combined studies involved 786,076 men and women with 97,867 total deaths, 23,597 deaths from cardiovascular disease, and 37,492 deaths from cancer.