Legumes Reduce Colorectal Cancer Risk
Legume foods are not only nutritious: Recent research is uncovering their ability to significantly reduce the risk of cancer.
A legume is typically considered a type of bean or seed derived from a pod. This limited definition, however, causes some confusion for some because there are seeds and nuts that are not really legumes. The more blunt definition is that legumes come from plant species in the Leguminosae family – also called Fabaceae.
This is a gigantic family of plants – and over eighteen thousand species of plants belong in this family. Further complicating the definition is that many plants in the Leguminosae family are not typically eaten as a nut, bean or seed. Some, such as those in the Astragulus genus, are medicinal herbs. Some legume species are ornamental plants.
Yet within this large family of plants we find some of the most nutritious foods. These include lentils (of different colors), black-eyed peas, green peas, snow peas, dwarf peas, pinto beans, navy beans, green beans, adasazi beans, black beans, garbanzo beans, pinto beans, soybeans, wax beans, adzuki beans, mung beans and some other beans. Surprising to most, legumes also include peanuts, alfalfa, clover and lespedeza – also called bush clover.
More specifically, research confirms that legumes reduce the risk of colorectal cancer. Legumes along with the consumption of whole cereal grains and cereal grains – many of which share compounds with legumes – has also been found to significantly reduce the risk of colorectal cancer.
Colorectal cancer is a leading form of cancer. Among both men and women in the U.S., colorectal cancer is the third most common form of cancer. Worldwide, one in ten cancer cases is colorectal cancer.
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Legumes reduce colorectal cancer incidence
A recent study that underscores the ability of legumes to reduce the risk of colorectal cancer comes from the Republic of Korea’s National Cancer Center and the Seoul National University College of Medicine and Hospital. Here researchers studied the diets of 901 colorectal cancer patients along with 2,669 control subjects. The number of control participants was based upon a multiple of three controls for every cancer patient.
The diets of the 3,740 people were analyzed for 106 different foods and graded for frequency. The researchers utilized a ten-year frequency basis. The analysis closely investigated the intake of foods that contain isoflavones. This is because several studies have shown that the intake of isoflavones decreases the risk of cancer.
The research results indeed confirmed this. Those who ate the most isoflavone-containing foods had a significantly less incidence of colorectal cancer.
The isoflavone-containing foods that decreased cancer risk included soybeans. Women who consumed the highest quartile of soy foods saw their risk of colorectal cancer reduced by between 38 and 46 percent. Men in the highest quartile of soy foods had between 33 and 44 percent reduction of colorectal cancer. But those who consumed the middle ranges of soy foods had increased risk ranging from 28 percent to 34 percent.
But it was the legumes that provided the biggest and most consistent reduction in colorectal cancer risk. Those who ate the most legumes (highest quarter) saw their incidence of colorectal cancer drop by over 50 percent – with women as high as 56 percent lower incidence. Furthermore, this reduced incidence also occurred with the other quartiles of legume consumption. As legume consumption increased, the incidence of colorectal cancer was reduced.
Whole grains and legumes reduce colorectal cancer
Similar results were found by researchers from Moores Cancer Center at the University of California at San Diego along with researchers from Jordan’s King Hussein Cancer Center and Hashemite University in Jordan.
The researchers studied 501 people, including 220 colorectal cancer patients. Once again, the diets of all the participants were reviewed and analyzed. This analysis found that those people who ate the most refined wheat bread (AKA white bread) had over three times the incidence of colorectal cancer compared to those who ate the least amount of white bread. And those who ate the most white rice also had triple the risk of colorectal cancer.
But those who ate more legumes and whole cereal grains had a significantly reduced incidence of colorectal cancer. For example, those who ate the highest amounts of whole wheat bread had a 56 percent reduction in colorectal cancer incidence.
Legumes and whole grains also reduce other cancers
Yes, we can conclude that these foods – legumes and whole grains – help prevent colorectal cancer. But what about other cancers?
Research has also found that legumes and whole grains reduce the risk of prostate cancer as well. A study from Harvard Medical School study found that those who ate the most legumes and whole grains – along with more fruits, vegetables and fish – had a 46 percent reduction in prostate incidence. This study followed 926 men that participated in the Physicians’ Health Study.
Why do legumes and whole grains reduce cancer?
Aren’t legumes and whole grains just good roughage? Why do they help protect against cancer? Is it just because they have good fiber?
No, it is not just the fiber content of these foods. Yes, they do contain good fibers – both soluble and insoluble fiber. Fiber-rich foods have the effect of keeping the intestinal tract regular, but they do much, much more.
Legumes and many whole grains contain compounds called isoflavones. As mentioned briefly above, these compounds have been found in studies to reduce the risk of cancer – particularly colorectal, breast and prostate cancers.
One of the mechanisms found for this is that isoflavones seem to increase anticancer cytokines (such as natural killer (NK) cells) and decrease cytokines that allow cancer cells to operate.
Another element of isoflavone-containing legumes and grains is that diadzen will stimulate the release of S-equol by gut bacteria. S-equol had been shown in a number of studies to reduce several cancers, including breast and prostate cancer.
Legumes and whole grains also provide a potent source of antioxidants in the form of polyphenols and anthocyanins. These help prevent free radicals from forming, whether in the gut or bloodstream. Free radicals can damage DNA, causing mutations that can form cancerous cells.
Legume foods and many whole grains also provide phytosterols that help reduce the release of low-density lipoproteins – also referred to as LDL. LDL particles are easily oxidized in the bloodstream. These oxidized particles damage the walls of our blood vessels, causing atherosclerosis and other cardiovascular problems.
But one of the greatest benefits of legumes and whole grains is that they provide potent prebiotics to our gut bacteria. These prebiotics feed those lactobacilli and bifidobacteria and thus increase their colonies. When probiotic colonies are increased, colorectal cancer risk is lessened.
Bad bacteria in our gut increases the risk of colorectal cancer. This is because these bad bacteria produce enzymes that damage the cells of our intestines. They effectively cause genetic mutation, which produces cancer.
I would add that legumes are best eaten after being soaked and cooked. Soaking and cooking will effectively reduce phytates, allowing for better mineral absorption.
Colorectal Cancer Statistics. Centers for Disease Control and Prevention.
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