Cruciferous Vegetable Guide: Why These Veggies Should Be On Your Plate

You know vegetables are good for you, but are all vegetables created equal? When it comes to disease-fighting, gut-health-promoting, blood-sugar-regulating, vitamin-packed goodness, there's one group of vegetables you can't beat: cruciferous vegetables. Part of the Brassica family, these veggies are so nutritious, experts like Michael Greger, M.D., author of the book How Not to Die suggest having a serving every single day as part of your recommended 2 to 3 cups of vegetables. So which vegetables are cruciferous, and what makes them so healthy? Here, we break down everything you need to know about this powerhouse group of vegetables:

Named for the cross shape their petals grow in, it turns out some of the trendiest (lookin’ at you, kale and cauliflower) and most delicious veggies are cruciferous. Here are some of our favorites:

You already know that fruits and vegetables can help prevent illness and disease, but it turns out some vegetables may be extra healthy. In fact, cruciferous veggies have been shown to reduce the risk of many common cancers. In one study that looked at the dietary patterns of 182,145 women, it was found that those who consumed the highest amounts of cruciferous vegetables had the lowest rates of breast cancer, especially the most aggressive forms. Cruciferous vegetables have also been found to reduce the risk of other hormonal cancers, like endometrial and cervical cancers. Researchers believe this may be due to a hormone-balancing compound in cruciferous vegetables called indole-3-carbinol1. In the body, indole-3-carbinol promotes the production of a less potent form of estrogen, suppressing tumor growth.

Cruciferous vegetables have also been found to reduce the risk of other types of cancer, including colon, lung2, stomach, and rectal. Along with being a great source of antioxidants, researchers believe a compound found in cruciferous veggies, called glucosinolates, may be the key to their cancer-fighting capabilities. During digestion, the body breaks down glucosinolates3, which produce anti-carcinogenic compounds called indoles, nitriles, thiocyanates, and isothiocyanates4. These compounds have been found to prevent cancer growth and development5 by protecting DNA, initiating the death of damaged cells, inhibiting tumor formation, and triggering antioxidant activity. Just one more reason to munch on some cauliflower-crust pizza (topped with kale, of course).

The isothiocyanates derived from glucosinolates aren't just good for fighting cancer; they can also help lower blood sugar levels. Sulforaphane, a specific type of isothiocyanate, works by targeting genes responsible for elevating glucose production in the liver. When tested in animal models, sulforaphane was found to be as effective as prescription diabetes medications at lowering blood sugar levels. A study of over 306,723 individuals' diets found a similar association between increased cruciferous vegetable intake and decreased risk for diabetes.

Another way in which cruciferous vegetables may help diabetics manage their disease is through alpha-lipoic acid (ALA). ALA is a potent antioxidant found in cruciferous veggies that has been shown to lower blood glucose levels6. It can also help prevent and reverse diabetic neuropathy, a common symptom of diabetes. In multiple studies7, ALA supplementation was found to reduce pain and numbness and improve nerve function in patients with diabetes.

Probiotics and fermented foods are famously gut-friendly (kombucha, anyone?), but did you know your diet plays a key role in gut health, as well? Eating a healthy diet—full of cruciferous veggies, of course—can also support the microbiome8, a collection of trillions of bacteria that live in our gut. For starters, the "bugs" in our gut feed off of prebiotic fiber, so to keep our gut happy and thriving we have to eat fiber-rich foods like whole grains and vegetables.

Beyond fiber, cruciferous vegetables offer specific gut-friendly benefits that boost the immune system. Research has found that a protein in leafy greens stimulates the production of crucial immune cells called innate lymphoid cells (ILCs) in the gut. This is a prime example of how the microbiome, the immune system, and digestive health are intricately connected. The ILCs work with the microbiota in our gut to fight off "bad" bacteria in the intestines to ensure a favorable environment of "good" bacteria. The ILCs may also prevent food allergies, inflammatory diseases, obesity, and colon cancer. So by consuming cruciferous veggies like leafy greens, we can promote a healthy gut and a strong immune system.

Eating for heart health isn't all omega-3s and oatmeal—cruciferous veggies deserve some serious credit here, too. A meta-analysis of eight studies9 found that leafy green vegetable consumption significantly reduced the risk of cardiovascular disease by 15.8 percent. This may be because cruciferous vegetables—like kale, broccoli, and collard greens—are a great source of vitamin K. There are actually two forms of vitamin K: K1 and K2. The K2 form of vitamin K plays a crucial role in bone and heart health. K2 vitamins bind with calcium in the blood to transport it to the bones for use. In turn, this keeps the arteries clear of calcium build-ups, which can be a risk factor for heart attack and stroke. In fact, a study of Australian women found an inverse relationship between cruciferous vegetable intake and arterial wall thickness, a measurement of plaque and calcium buildup. So it's not just your taste buds that love kale—your heart heart loves it too.

Is there such a thing as too much of a good thing? When it comes to cruciferous veggies, maybe. It turns out, glucosinolates—yup, those cancer-protective blood-sugar-slashing magical compounds in cruciferous vegetables—can potentially inhibit thyroid function. This is because they compete with iodine for uptake in the thyroid10. Iodine is crucial for hormone production, and if the thyroid is unable to get enough, it can cause a goiter (a swelling of the thyroid) and dysfunction. Consumption of large amounts of cruciferous vegetables has been shown to bring on goiters and hypothyroidism in animal models11. For this reason, many people with thyroid conditions are told to avoid this group of vegetables.

Interestingly, studies in humans12 have not found vegetables to cause or exacerbate thyroid issues. This may be because the amount of cruciferous vegetables you would need to eat in order to cause an iodine deficiency far exceeds normal consumption habits. So even if you suffer from hypothyroidism you should be good to go on greens, just be sure to consult with your doctor first.

We all know that vegetables are good for us, but sometimes it's really nice to know exactly why they are so healthy. Learning the science behind our leafy-green-rich diet can help motivate us to keep on meal prepping, hitting the farmers market, and shopping mostly in the produce section.