“Eat your fruits and vegetables.” How many times have you heard that? But there’s truth to those words. You SHOULD munch on veggies and fruits. One reason is that plant-based foods contain natural compounds called phytochemicals that help cells behave better. In other words, these compounds may help tame the disorderly proliferation of cells we know of as cancer. These classes of chemicals show anti-cancer activity in a lab setting and in animal studies. Let’s look at these plant-based compounds and what plant-based foods you find them in.
Glucosinolates and Isothiocyanates
Glucosinolates are compounds you find naturally in cruciferous vegetables. When you devour these foods, assuming you don’t overcook them, an enzyme called myrosinase converts a portion of the glucosinolates to isothiocyanates. The resulting isothiocyanates reduce the activation of carcinogens and help speed up their removal from the body before they can do damage.
Some of the best sources of these chemicals are broccoli, kale, watercress, Brussels sprouts, and cabbage. In addition, broccoli sprouts contain the highest level of any food as they are immature sprouts. It’s best to eat these foods raw or lightly cooked as heat inactivates the myrosinase enzyme that turns glucosinolates into myrosinase. Another caveat. Frozen broccoli is blanched before freezing. This destroys most of the myrosinase enzyme. Therefore, frozen broccoli has less potential anti-cancer activity.
Polyphenols
Polyphenols are a broad group of compounds with antioxidant activity. Polyphenols seem to exert their anti-cancer benefits through their antioxidant and anti-inflammatory activity. Plus, they interfere with pathways that cancer cells use to grow and thrive. Polyphenols fall into a variety of classes, including phenolic acids, flavonoids, lignans, and stilbenes. You’ll probably recognize some foods that contain polyphenols. These include berries, dark chocolate, citrus fruits, green tea, coffee, red wine, soy, apples, beans, and flaxseed, to name a few. In fact, many fruits and vegetables fall into this class. Studies also link polyphenol-rich foods with a lower risk of heart disease as well.
Sulfur Compounds
The most common sulfur compound in foods is diallyl sulfide. Sulfur compounds, including diallyl sulfides, are abundant in garlic and onions. Other sources are scallions, leeks, and chives. These compounds are best known for their heart-health benefits, but there is also evidence that they may lower the risk of some intestinal cancers. For example, population studies show a link between garlic intake and a lower risk of cancers of the pancreas, colon, stomach, and esophagus. The evidence seems to be strongest for stomach cancer and colon cancer. One way in which garlic may protect against stomach cancer is by killing Helicobacter pylori, a bacterium associated with a higher risk of stomach cancer.
The best way to get the full benefits of the sulfur compounds in garlic is to crush garlic before heating and let it sit for 10 minutes. This maximizes the release of the sulfur compounds in this potent spice. You’ll also get more benefits if you consume garlic raw rather than cooked.
Flavonoids
Flavonoids are a sub-category of polyphenols. All flavonoids are polyphenols, but not all polyphenols are flavonoids. Flavonoids are subdivided into various sub-types. These include flavones, isoflavones, flavonols, flavanones, flavanols, and anthocyanins. These compounds all have somewhat similar activity, usually of an anti-inflammatory nature, but they differ in structure. The anti-inflammatory benefits of flavonoids are important as inflammation plays a role in a variety of health problems, including cancer. Though flavonoids are a type of polyphenol, they’re of such importance as signaling molecules, molecules that tell cells how to behave, that they deserve recognition independently of the polyphenol class as a whole. They’re abundant in a variety of fruits and vegetables as well as tea, wine, and chocolate.
Dithiolethiones
It’s a mouthful to say, but dithiolethiones are so powerful that research is looking at whether they could be incorporated into cancer treatment protocols to help control already established cancer. They also appear to have protective benefits. For one, they turn on NRF2 genes, genes that boost the body’s antioxidant defenses and defenses against inflammation. Plus, they activate phase 2 enzymes that help cells detoxify. Dithioethiones are most abundant in cruciferous vegetables such as broccoli, kale, watercress, Brussels sprouts, arugula, radishes, and Bok choy.
Eat Your Vegetables!
While the potential benefits of these natural chemicals are interesting in isolation, the real benefit comes from how they behave synergistically. These components of fruits and vegetables work together in ways we don’t completely understand. That’s why taking a component as a supplement may not have the same benefits as eating colorful fruits and vegetables in their unaltered state.
Do the benefits of eating fruits and vegetables to lower cancer risk hold up under scrutiny? According to the National Cancer Institute, eating a fruit and vegetable-rich diet is linked with a lower risk of cancer of the lung, esophagus, stomach, throat, and mouth. Studies also suggest a reduction in cancer of the pancreas and colon with a diet rich in vegetables and fruit. Eating fruits and veggies has other health benefits as well. They’re rich in fiber and contain an abundance of vitamins and minerals. In fact, per calorie, leafy greens and berries are the most nutrient-dense foods you can eat.
The Bottom Line
Fruits and vegetables are rich in an abundance of natural chemicals that demonstrate anti-cancer activity in the laboratory. Unfortunately, we don’t eat enough of them! A survey found that top vegetables people eat are fried potatoes and tomato products, like tomato sauce and ketchup. We can do better! Aim for 5-9 servings of fruits and vegetables daily. Choose fruit and vegetables in a variety of colors to maximize the range of phytochemicals you get. Remember, they work together!
To fit in your 5+ daily, start in the morning by adding fruits and veggies to breakfast, your first meal of the day. Then try to eat a few more servings at lunch and dinner. A serving is equivalent to a half-cup of raw vegetables or a full cup of cooked ones. Challenge yourself to try new fruits and vegetables you’ve never eaten before and experiment with new recipes. Most of all, enjoy!
References:
· Nutrients. 2016 Sep; 8(9): 552.
· Nutrients. 2016 Aug; 8(8): 515.
· National Cancer Institute. “Garlic and Cancer Prevention”
· Future Medicinal Chemistry. Vol. 10, No. 10. 11 May 2018.
· Semantic Scholar. “Dithiolethiones for cancer chemoprevention: where do we stand?”
· Mol Cancer Ther. 2008 Nov;7(11):3470-9. doi: 10.1158/1535-7163.MCT-08-0625.
· National Cancer Institute. “Cruciferous Vegetables and Cancer Prevention”
· American Institute for Cancer Research. “New Study Links Plenty of Fruits, Veggies with Reduced Risk of Certain Breast Cancers”
· National Cancer Institute. “Fruit and Vegetable Consumption”
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