For the broccoli growers of the world, researchers has good news about your next crop. It turns out that broccoli may help promote a healthy gut and also protect against both liver cancer and nonalcoholic fatty liver disease.
In one study at Penn State, when mice ate broccoli with their regular diet, they were better able to tolerate digestive issues similar to symptoms of leaky gut and colitis than mice that were not placed on a broccoli-supplemented diet, according to professor Gary Perdew. He added that other vegetables, like brussels sprouts and cauliflower, may also have similar gut health properties.
“There are a lot of reasons we want to explore helping with gastrointestinal health and one reason is if you have problems, like a leaky gut, and start to suffer inflammation, that may then lead to other conditions, like arthritis and heart disease,” said
Perdew. “Keeping your gut healthy and making sure you have good barrier functions so you’re not getting this leaky effect would be really big.”
Good intestinal barrier function means that the gastrointestinal tract is helping protect the intestines from toxins and harmful microorganisms, while allowing nutrients to pass into the system, he said.
According to Perdew, the key to the process may be a receptor in the gut called Aryl hydrocarbon receptor, or AHR. The receptor helps the body regulate its reaction to certain environmental contaminants, as well as triggers other responses to toxin exposure.
The researchers, who released their findings in the current issue of the Journal of Functional Foods, suggest that cruciferous vegetables — such as broccoli, brussels sprouts and cabbage — contain an organic chemical compound called indole glucosinolates, which breaks down into other compounds, including indolocarbazole — ICZ — in the stomach.
When ICZ binds to and activates the Aryl hydrocarbon receptor (AHR) in the intestinal lining, it aids in maintaining a healthy balance in the gut flora and immune surveillance, and enhances host barrier function, according to the researchers. This may help prevent diseases, such as various cancers and Crohn’s Disease, caused by inflammation in the lining of the gut.
According to Perdew, hyper-activating the AHR can cause toxicity, but using broccoli to activate the receptor locally — in the gut — rather than systemically might help avoid some of these problems. “Dioxin, for example, activates this receptor, and if you hyper-activate it with dioxin, it will cause toxicity,” said Perdew. “What we were interested in is: Could you locally activate the receptor naturally at a level that would cause only modest AHR activation in the gut, but not cause systemic activation, which could possibly lead to negative effects?”
The researchers used two genetic lines of mice in the study to focus on AHR. One line had a low ability to bind ICZ to AHR, while the other line had a high ability to bind ICZ to AHR. They added 15 percent broccoli to the diets of both groups of mice. After adding a substance that causes digestive problems, the researchers said that the mice with a higher ability to bind ICZ to the AHR were protected from a chemical that induced digestive problems, but the mice with the lower affinity suffered from the toxic insult.
For humans, the amount in the experiment would be equivalent to eating about 3.5 cups of broccoli each day, according to Perdew. “Now, three and a half cups is a lot, but it’s not a huge amount, really,” said Perdew. “We used a cultivar — or variety — with about half the amount of this chemical in it, and there are cultivars with twice as much. Also, brussels sprouts have three times as much, which would mean a cup of brussels sprouts could get us to the same level.”
Because people with certain digestive conditions, such as colitis, are often warned to avoid too much roughage in their diets, future research may include determining the best ways for people to consume the broccoli — or other vegetables with similar effects — to receive the same health benefits, without causing any other associated digestive problems from the fibrous vegetables.
Broccoli also protects against liver cancer and nonalcoholic fatty liver
A separate 2016 study from the University of Illinois found that including broccoli in the diet may also protect against liver cancer, as well as aid in countering the development of fatty liver or nonalcoholic fatty liver disease which can cause malfunction of the liver and lead to hepatocellular carcinoma, a liver cancer with a high mortality rate.
“The normal story about broccoli and health is that it can protect against a number of different cancers. But nobody had looked at liver cancer,” says Elizabeth Jeffery, professor of nutrition. “We decided that liver cancer needed to be studied particularly because of the obesity epidemic in the U.S. It is already in the literature that obesity enhances the risk for liver cancer and this is particularly true for men. They have almost a 5-fold greater risk for liver cancer if they are obese.”
Jeffery says that the majority of the U.S. population eats a diet high in saturated fats and added sugars. However, both of these are stored in the liver and can be converted to body fat. Consuming a high-fat, high-sugar diet and having excess body fat is linked with the development of NAFLD, which can lead to diseases such as cirrhosis and liver cancer.
“We called this a Westernized-style diet in the study because we wanted to model how so many of us are eating today,” Jeffery says.
Previous research suggests that broccoli, a brassica vegetable containing bioactive compounds, may impede the accumulation of fat in the liver and protect against NAFLD in mice. Therefore, Jeffery and her team wanted to find out the impact of feeding broccoli to mice with a known liver cancer-causing carcinogen. The researchers studied four groups of mice; some of which were on a control diet or the Westernized diet, and some were given or not given broccoli.
“We wanted to look at this liver carcinogen in mice that were either obese or not obese,” Jeffery explains. “We did not do it using a genetic strain of obese mice, but mice that became obese the way that people do, by eating a high-fat, high-sugar diet.”
Although the researchers were predominantly interested in broccoli’s impact on the formation and progression of cancerous tumors in the liver, Jeffery explained that they also wanted to observe the health of the liver and how the liver was metabolizing lipids because of the high-fat diet. “There is almost no information about broccoli and high-fat associated diseases,” she says.
The study shows that in mice on the Westernized diet both the number of cancer nodules and the size of the cancer nodules increased in the liver. But when broccoli was added to the diet, the number of nodules decreased. Size was not affected.
“That was what we really set out to show,” Jeffery says. “But on top of that we were looking at the liver health. There are actually two ways of getting fatty liver; one, by eating a high-fat, high-sugar diet and the other by drinking too much alcohol. In this case, it is called non-alcoholic fatty liver, because we didn’t use the alcohol. And it is something that is becoming prevalent among Americans. This disease means you are no longer controlling the amount of fat that is accumulating in your liver.”
With NAFLD, lipid globules form on the liver. During the study, the researchers observed these globules in the livers of the mice on the Westernized diet.
“We found that the Westernized diet did increase fatty liver, but we saw that the broccoli protected against it. Broccoli stopped too much uptake of fat into the liver by decreasing the uptake and increasing the output of lipid from the liver,” she says.
Jeffery notes that adding broccoli to the diet of the mice did not make them “thin,” or affect their body weight, but it did bring the liver under control, ultimately making them healthier. “This is one of the things that makes this very exciting for us,” she says.
“I think it’s very difficult, particularly given the choices in fast food restaurants, for everybody to eat a lower-fat diet. But more and more now you can get broccoli almost everywhere you go. Most restaurants will offer broccoli, and it’s really a good idea to have it with your meal,” Jeffery adds.
Jeffery’s previous research shows that eating broccoli freshly chopped or lightly steamed is the best way to get to the vegetables’ cancer-fighting compound, sulforaphane.
Although the researchers only used broccoli in the study, Jeffery adds that other brassica vegetables, such as cauliflower or Brussel sprouts, may have the same effect.