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Cruciferous Vegetables in the Diet and Colon Cancer Risk

Linda Crampton is a writer and teacher with a first-class honors degree in biology. She often writes about the scientific basis of disease.

Cabbages are cruciferous vegetables.

Cabbages are cruciferous vegetables.

Decreasing the Risk of Colon Cancer

Scientists have long suspected that eating cruciferous vegetables lowers our risk of colorectal cancer. Observational studies have shown a link between the inclusion of the vegetables in our diet and a reduced risk of cancer in the large intestine. An explanation for this link has been hard to obtain, however.

Some recent research shows how a chemical called indole-3-carbinol that's made in our digestive tract after we eat cruciferous vegetables helps mice. The chemical reduces inflammation and the risk of uncontrolled cell division in the gut of lab mice. The discoveries might be applicable to humans.

What Are Cruciferous Vegetables?

Cruciferous vegetable include broccoli, Brussels sprouts, cabbage, and other examples. Today the vegetables are often classified in the family Brassicaceae. Until quite recently, the family was known as the Cruciferae. The word “Cruciferae” was transformed into the adjective "cruciferous" to describe the vegetables and is still used for this purpose. The flowers of the plants are shaped like a cross.

Some commonly available cruciferous vegetables include the following:

  • broccoli
  • Brussels sprouts
  • cabbage
  • bok choy
  • cauliflower
  • kale
  • turnips
  • rutabagas (or swedes)
  • radishes
  • horseradish

There are many more examples. The family is large and provides lots of options for someone who wants to eat the vegetables.

Glucosinolates, Myrosinase, and Bacteria

Indole-3-carbinol is produced in two ways that are relevant for us. Cruciferous plants contain chemicals called glucosinolates. When their tissue is damaged by actions such as cutting, chopping, and chewing, an enzyme called myrosinase is released from cells or cell organelles and comes into contact with the glucosinolate molecules. The enzyme reacts with the glucosinolates to produce new chemicals, including isothiocyanates and indole-3-carbinol.

The substances are also produced by the action of bacteria living in our colon (the longest part of the large intestine) when they break down the cooked vegetables. Both substances are thought to be responsible for a reduction in colon cancer risk. The latest research relates specifically to indole-3-carbinol, however.

A Plant Scientist Discusses Glucosinolates

Glucosinolates contain sulfur. They are responsible for the somewhat pungent taste of cruciferous vegetables that develops when we chew them, as the scientist in the video above mentions.

The Large Intestine

The small intestine is continuous with the large one. The colon is the first and longest part of the large intestine. It's continuous with the shorter rectum, where feces is stored before it’s released through the anus. The surface of the intestinal lining is made of epithelial cells. These absorb nutrients and produce a protective layer of mucus. I3C appears to play a role in keeping the epithelial cells healthy.

The colon is active even when it doesn’t contain undigested food that has reached it from the small intestine. The lining of both the small and the large intestine is continually being renewed. The complete replacement of the lining takes approximately four to six days. The reported times vary considerably. In addition, the large intestine contains a large and active population of living bacteria. Many of these bacteria help us in some way. Some species are harmful, but they are usually much less common than the helpful ones.

Though most bacteria in our intestine appear to be helpful for us, even “good” bacteria can produce irritating chemicals as well as beneficial ones. It’s important that the intestine has a way to monitor and neutralize these chemicals. Fortunately, it does. One method is via the action of a protein known as AHR.

The Aryl Hydrocarbon Receptor or AHR

The presence of indole-3-carbinol in the digestive tract stimulates the activity of the aryl hydrocarbon receptor, or AHR (sometimes abbreviated as AhR). The receptor is a protein and is found in the cytoplasm of both intestinal epithelial cells and cells from the immune system in the intestine. It’s also found in the cells of other barriers between the body and the outside environment, including those in the skin and the lungs.

AHR binds to a range of chemicals, including ones produced by intestinal bacteria as well as a derivative of indole-3-carbinol. This derivative is formed when I3C reacts with hydrochloric acid from the stomach. The binding is required in order to activate the protein and is a reversible process. The "ligand", or the atom or molecule that joins to the receptor, later separates.

AHR in the intestine can be thought of as a type of environmental sensor. When it’s activated by an appropriate ligand, it stimulates processes that help to prevent intestinal inflammation. Chronic inflammation in the intestine sometimes leads to cancer in the organ. Activated AHR can also stop inappropriate and excessive division of specific cells in the intestine. Excessive cell division can be a sign of cancer.

Indole-3-carbinol has other effects in the cell that are unrelated to the AHR receptor and that may reduce the risk of cancer. It appears to be a very helpful chemical.

Some of the strongest endogenous AHR ligands are derived from phytochemicals such as indole-3-carbinol (I3C) that is converted to the high-affinity AHR ligand ICZ by exposure to stomach acid.

— Amina Matidji et al, Immunity journal from Cell Press

Turnips are a cruciferous vegetable.

Turnips are a cruciferous vegetable.

I3C and Intestinal Inflammation in Mice

Researchers from the Francis Crick Institute in the UK recently studied genetically-modified mice. The animals had been "programmed" to have insufficient AHR activation due to a variety of factors. As a result of the deficiency, the intestinal lining of the mice became inflamed and they eventually developed colon cancer. If these mice were fed a diet enriched with I3C, however, they didn’t develop inflammation or cancer. In addition, if the genetically-defective mice in whom inflammation had already begun were fed the I3C-enriched diet, they developed “significantly fewer tumours which were more benign”.

The researchers also performed a dietary experiment with genetically-normal mice. Some of the mice were fed a highly-controlled and purified diet which was low in AHR-stimulating chemicals. Other mice were fed standard rat chow, which contained a higher level of AHR-stimulating chemicals than the purified diet. Yet another group of mice was fed an I3C-enriched diet. The mice in the first group developed colon cancer within ten weeks; the mice in the other two groups didn't develop colon cancer.

"Gut” is another word for the digestive tract. It's most often used to refer to the stomach or the intestine. In the experiment described below, it refers to the intestine.

Epithelial Cell Production in the Mouse Gut

The researchers also explored the effects of AHR activation on cell division in gut organoids. An organoid is a miniature organ produced from stem cells. Stem cells are unspecialized but have the ability to produce specialized cells as well as additional stem cells when they are stimulated correctly. An organoid has many of the cell types found in the real organ due to the activity of its stem cells. The cell types are also arranged correctly. Organoids are especially interesting to some people because they may reduce the need for animals in research.

The researchers found that activated AHR was essential in order for a new layer of epithelial cells to form in the mouse gut organoids. Without activated AHR, the stem cells in the organoid failed to differentiate into epithelial cells and instead kept on dividing to produce more stem cells.

The scientists made the same observation in the gut of mice without activated AHR. They also found that AHR-stimulating chemicals in the diet (including I3C) restored stem cell differentiation into epithelial cells in the gut of the affected mice. The chemicals may be necessary for the creation of a healthy gut lining.

Applicability to Human Biology

The mouse research is interesting and worth thinking about. It may apply to humans, though this is not necessarily the case. If it does apply to us, some questions need to be answered. One is whether the concentration and total amount of I3C in the enriched diet followed by the mice is relevant to what a person might obtain when eating cruciferous vegetables. Other questions are listed below.

  • What quantity of cruciferous vegetables might a person need to eat in order to experience similar benefits to the mice?
  • How often should the vegetables be eaten?
  • What factors affect the quantity of I3C provided by relevant food intake?
  • Are the vegetables best eaten raw or cooked?
  • What is the best cooking method with respect to providing I3C availability?

It's already known that vegetables have a range of health benefits, so it's important to eat them even though we don't have all the answers with respect to cancer prevention yet. Nutritionists say that some of the vegetables in our diet should be cruciferous.

A Precaution: Diet and Supplements

I have never read or heard any concerns about obtaining indole-3-carbinol by eating moderate amounts of cruciferous vegetables. The Linus Pauling Institute has a warning about taking the chemical in the form of a supplement, however. Supplements contain concentrated and isolated forms of chemicals that may produce different effects from eating them in food.

Some experts have cautioned against the widespread use of I3C ... supplements for cancer prevention in humans until their potential risks and benefits are better understood.

— Linus Pauling Institute, Oregon State University

Purple forms of normally white vegetables may offer extra health benefits due to their anthocyanin content.

Vegetables in the Diet

The Office of Disease Prevention and Health Promotion (a government organization in the United States) recommends that adults eat two servings of fruit and three servings of vegetables a day. Health Canada (also a government organization) recommends a combined total of seven to ten servings of fruits and vegetables every day for an adult, depending on their age and gender.

In 2017, scientists from Imperial College London presented a report based on their analysis of ninety-five studies of the health effects of fruit and vegetable consumption. The researchers said that although five servings of produce a day was helpful for disease reduction, ten servings a day was linked to an even better reduction in disease.

Many nutrition and medical sources say that cruciferous vegetables should be eaten regularly. Different sources make different recommendations about how often we should eat the vegetables, however. I've seen recommendations of once a day, three times a week, and once a week.

Consumption of cruciferous vegetables might reduce the risk of other types of cancer besides cancer of the colon. Some research suggests that different types of cancer require a different frequency of vegetable consumption in order to reduce the risk of disease. It's probably best to eat cruciferous vegetables at least several times a week.

Some sources say that when fruits and vegetables are grouped together in a serving recommendation, more vegetables should be eaten than fruits.

Benefits of Cruciferous Vegetables

Now that significant results have been discovered in mice, the researchers at the Francis Crick Institute plan to examine the effects of indole-3-carbinol in humans. They plan to experiment with organoids made from human gut biopsies first of all and then conduct clinical trials in people.

As the researchers say, there’s no need to wait for the results of their investigations before eating cruciferous vegetables. We already know that the vegetables contain valuable nutrients, including vitamins, minerals, and fiber. It would be a good idea to eat them even if they had no effect on cancer risk. If they do reduce the risk of colon cancer, that’s another great reason for including them in the diet.

References

  • Information about cruciferous vegetables from the Linus Pauling Institute at Oregon State University
  • Indole-3-carbinol facts from Oregon State University
  • Chemicals in vegetables and colon cancer in mice from the Francis Crick Institute
  • The environmental sensor AHR protects the colon from inflammatory damage and maintains stem cell homeostasis from the Immunity journal
  • Food serving guidelines from the Government of Canada
  • ChooseMyPlate (A food guide from the U.S. Department of Agriculture)
  • Up to ten servings of fruits and vegetables a day may prevent premature deaths from the Eurekalert news service

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2018 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on July 19, 2020:

Hi, Denise. Thank you for the comment. I hope you continue to experience good health!

Blessings to you.

Denise McGill from Fresno CA on July 19, 2020:

About 6 years ago my doctor told me I was at risk for colon cancer and needed to have regular colonoscopies every 2 years plus a whole list of foods I should stay away from. Just 2 years ago I decided to go vegan. It was a health decision but I was already feeling very iffy about meat anyway. Little did I know that adding more cauliflower and cabbage and kale to my diet was a good thing. This is huge information for me. The doctor never told me what I needed to add to the diet only what I needed to eliminate. Thanks for informing me yet again!

Blessings,

Denise

Linda Crampton (author) from British Columbia, Canada on September 16, 2018:

Hi, Ethel. Bok choy is a vegetable that's popular in China and Asia. It's common in the grocery stores where I live as well, but I don't know how easy it is to find in other areas. It's sometimes referred to as Chinese cabbage. It doesn't form a head like some other types of cabbage, though. It has white stalks with green leaves at the top.

Ethel Smith from Kingston-Upon-Hull on September 16, 2018:

Thank you Linda

As I have a long standing thyroid disorder I have to take care with some greens. But a diet rich in fresh fruit and veg will definitely help against colon cancer.

What is Bok Choy please

Linda Crampton (author) from British Columbia, Canada on September 14, 2018:

Thanks, Roberta. I ate some broccoli today, but it's time that I bought cabbage again. I eat cruciferous vegetables quite regularly but tend to stick to the same types. I want to try some new varieties.

RTalloni on September 14, 2018:

So useful on every level. Thanks for the info and the encouragement to eat cruciferous veggies. I wish I had gone ahead and bought that head of cabbage today...

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

It was funny. I'll have to do a survey of people I know to see what they think of the vegetable.

Larry Rankin from Oklahoma on September 08, 2018:

Actually, I like them. Just thought that was funnier:-)

I got lots of friends that just genuinely hate them.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

Thanks for the amusing and kind comment, Larry. I used to hate Brussels sprouts as a child, but I like them now.

Larry Rankin from Oklahoma on September 08, 2018:

Brussel sprouts get a bad rap. Most suspect they're healthy, but think they're bad.

Put some time and effort into them, though, they're actually...bad;-)

But everything else on the list is wonderful.

I tease, but I love your articles.

Linda Crampton (author) from British Columbia, Canada on August 26, 2018:

Hi, Genna. Yes, the vegetables can taste delicious, especially if they're prepared in a way that someone likes. I appreciate your comment.

Genna East from Massachusetts, USA on August 26, 2018:

Hi Linda. Several of the veggies on your Cruciferous list are my favorites. You posed some interesting questions. How much of these should we consume daily? The benefits - other than they taste darn good if prepared properly -- are substantial. Excellent article, as always... well researched and beautifully presented. Thank you.

Linda Crampton (author) from British Columbia, Canada on August 25, 2018:

I agree. Thanks for commenting.

Eman Abdallah Kamel from Egypt on August 25, 2018:

Very useful vegetables.

Linda Crampton (author) from British Columbia, Canada on August 25, 2018:

Thank you very much, Devika. I think it's a good plan to eat lots of vegetables, including cruciferous ones.

DDE on August 25, 2018:

This is one of your best hubs. Enjoyed learning about vegetables to prevent cancer. I eat most of these veges.

Linda Crampton (author) from British Columbia, Canada on August 22, 2018:

I agree. Cruciferous vegetables are good for health. I enjoy eating them.

Minimalist Logo on August 22, 2018:

Very good for health

Linda Crampton (author) from British Columbia, Canada on August 22, 2018:

Thank you very much for commenting and for sharing the interesting information, Adrienne. My family has lost two dogs to cancer. It would be horrible if it happened again.

Adrienne Farricelli on August 22, 2018:

Thanks for researching this in such depth and sharing with us. So many good reasons to adhere to Grandma's Law: "eat your broccoli and then you can have ice-cream." I saw the other day a supplement called Broccomax made for humans and am thinking of giving it to my dog as it looks like it can help reduce chances for cancer and read about a veterinary oncologist suggesting it. Knowing that my dog's not eager to eat cruciferous veggies I may give it a try. I think though that the best thing is always to eat things fresh as nature intended.

Linda Crampton (author) from British Columbia, Canada on August 22, 2018:

Hi, Bede. Growing curly kale sounds like a great idea. The Health Canada recommendations depend on factors such as a person's age, but they are all higher than the U.S. agency ones. My guess is that the Canadian organization has incorporated the latest suggestions about produce consumption.

manatita44 from london on August 22, 2018:

Thanks Linda.

Bede from Minnesota on August 22, 2018:

Linda, I confess to hunger pangs as I read this article. These are some of my favorite vegetables, especially curly kale. I grew it last summer and eat it fresh in a salad. Thanks for the good info. It’s curious why Health Canada recommends about twice the amount of fruit and vegetables that the U.S. agency suggests.

Linda Crampton (author) from British Columbia, Canada on August 22, 2018:

Hi, Manatita. I think it's worth eatimg more vegetables. They seem to have many benefits.

manatita44 from london on August 22, 2018:

Alas! I need to eat more vegetables. Used to be the fruit that suffered but now the table has reversed.

Some very useful information on the cruciferous vegetables. I'll start eating more.

Linda Crampton (author) from British Columbia, Canada on August 21, 2018:

Thanks, Peggy. There do seem to be good reasons for eating vegetables!

Peggy Woods from Houston, Texas on August 21, 2018:

This gives us even more of a reason to eat these types of vegetables. Good article Linda!

Linda Crampton (author) from British Columbia, Canada on August 21, 2018:

Hi, Mary. It's often surprising to discover that another part of a plant can be eaten. I think it's interesting to see what the different parts of edible plants taste like.

Mary Norton from Ontario, Canada on August 21, 2018:

This is really very useful information as it makes me understand the value of including cruciferous to our diet. I have not thought of horseradish leaves before. Something new to try. You are right that even before any cancer warning, it is important to have more vegetables in our diet.

Linda Crampton (author) from British Columbia, Canada on August 20, 2018:

Hi, Heidi. I agree that ten servings could be a challenge, though I've found it surprising how small one serving is of some types of produce. I just try to eat lots of vegetables, like you do. Thanks for the visit.

Heidi Thorne from Chicago Area on August 20, 2018:

Though I love broccoli and cauliflower, I do have to say that up to 10 servings of fruits and veggies would be a challenge! But I do understand the benefits and do try to get more and more greens and such every day. Great information, as usual!

Linda Crampton (author) from British Columbia, Canada on August 20, 2018:

Thanks, Dora. I'm going to keep on eating my veggies, too!

Dora Weithers from The Caribbean on August 20, 2018:

My first lesson on I3C. Thanks for the information including the warnings. We'll just keep on eating our veggies.

Linda Crampton (author) from British Columbia, Canada on August 20, 2018:

That's an interesting thought, Liz! I might have read the article that you're thinking of. The one that I read referred to the "humble" cabbage. I think the cabbage deserves better attention. I like the fact that different colours of the vegetable are available.

Linda Crampton (author) from British Columbia, Canada on August 20, 2018:

Thanks for the comment, Bill. I hope you enjoy eating cruciferous vegetables if you try them.

Linda Crampton (author) from British Columbia, Canada on August 20, 2018:

Thanks, Pamela. Fortunately, I like the vegetables, too, especially when they're cooked. It's nice when healthy food is tasty.

Liz Westwood from UK on August 20, 2018:

I noticed something about this in the news last week. Shopping for the weekend I made sure to buy cabbage! I wonder how much sales increased last week?

Bill Holland from Olympia, WA on August 20, 2018:

Wow! I don't eat any of those. Suddenly I'm hungry for kale. lol Thanks for the information, Linda!

Pamela Oglesby from Sunny Florida on August 20, 2018:

I like several of these vegetables raw or cooked, and I am glad to know that they may prevent colon cancer. Excellent article.

Linda Crampton (author) from British Columbia, Canada on August 19, 2018:

Thank you very much, Flourish. It's interesting to hear that you have trouble eating the vegetables when they're cooked. For me, it's the other way round. I do eat some of them raw, but I prefer to cook them.

FlourishAnyway from USA on August 19, 2018:

Excellent article. Now if I could only convince myself to eat them. I have no trouble eating them raw but cooked is another story.