There’s a reason these veggies get a ton of attention. Learn all about the research-backed benefits of cruciferous vegetables and how to incorporate them into your diet.
Many of us were told to eat our vegetables growing up because they would keep us strong and healthy. It turns out that veggies are nutrient powerhouses that can help us maintain good health throughout our lifespan.
The United States Dietary Guidelines for Americans recognizes five different subgroups of vegetables, including dark green, red and orange, legumes (beans and peas), starchy, and other.
Consuming a wide variety of veggies from each group is considered part of a healthy diet that gives the best chance at preventing chronic diseases.
Many dark green (and some other) vegetables fall into the classification of cruciferous vegetables, which are a recommended group all on their own.
Research has found that high intakes of cruciferous veggies are linked to reduced risk of cancer.
Here we’ll discuss what cruciferous vegetables are, the nutrients and health benefits they offer, and important information to consider regarding their role in thyroid conditions.
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What are cruciferous vegetables?
The vegetables we know as cruciferous come from the Brassicaceae (Cruciferae) family. On a botanical level, they are characterized by a cross-shaped corolla (the collective group of petals), six stamens (the male reproductive organ of flowering plants), a capsule (dry fruit that opens when ripe), and watery sap with a strong aroma.
Cruciferous vegetables are believed to be European in origin, with many of them grown in the Mediterranean region.
Ancient civilizations including Greeks, Romans, and Egyptians cultivated these vegetables, and some cruciferous veggies made their way to and became popular in Asian countries like China.
Cruciferous vegetables include:
- Bok choy
- Brussels Sprouts
- Chinese Cabbage
- Collard Greens
- Mustard Greens
The most commonly grown cruciferous vegetable crop is the species Brassica oleracea, which includes broccoli, Brussels sprouts, cabbage, collard greens, cauliflower, and kale.
Though each type of vegetable has its own unique nutritional composition, cruciferous veggies share many similarities in terms of their nutrient profile.
Nutrients found in cruciferous vegetables
Cruciferous vegetables are rich in several nutrients, particularly vitamins and minerals. They are good sources of Vitamins C and K, folate, iron, potassium, magnesium, and fiber.
Vitamin C is a powerful antioxidant that promotes wound healing, while Vitamin K makes proteins that help blood clot properly and produce healthy bone tissue. Folate (often called folic acid or vitamin B9) is involved in protein metabolism, DNA and RNA formation, and essential for preventing fetal neural tube defects during pregnancy.
Potassium helps the body maintain proper fluid levels inside cells and reduces blood pressure, while magnesium aids in body functions like muscle contraction.
Iron is necessary to provide oxygen to blood and prevent iron-deficiency anemia. Fiber helps lower cholesterol and stimulate the growth of beneficial bacteria in the gut microbiome.
Cruciferous veggies are rich in phytochemicals, which give plants pigment color and protection while also offering benefits for human health. Phytochemicals like flavonoids and carotenoids have antioxidant functions and may help reduce inflammation.
Cruciferous vegetables also contain non-nutritive metabolites called glucosinolates (GSL). GSL are sulfur-containing compounds that contribute to the veggies’ strong aroma and bitter taste.
When a raw cruciferous vegetable plant is cut or chewed, it gets broken down by an enzyme called myrosinase. Myrosinase prompts the conversion of the GSL into a biologically active form called isothiocyanates.
The human gut bacteria also perform this conversion when raw cruciferous veggies are consumed and digested.
Isothiocyanates offer many favorable effects in the human body, including anti-bacterial, antioxidant, and anti-cancer properties.
Health benefits of cruciferous vegetables
Diets rich in cruciferous vegetables are associated with a myriad of health benefits. Research indicates that the compounds in cruciferous veggies have antioxidant and anti-inflammatory functions and may help reduce risk of developing serious diseases.
Isothiocyanates have been identified as playing a role in disease prevention and treatment and are of particular interest in cancer research.
According to the National Cancer Institute, isothiocyanates have many protective mechanisms, including shielding cells from DNA damage, inactivating cancer-causing compounds, and inhibiting tumor formation and ability to metastasize.
The list below details the health benefits of cruciferous vegetables according to the scientific literature.
Cruciferous vegetables have long been linked with reducing the risk of several types of cancers, and epidemiological studies have found a correlation between cruciferous vegetable intake and reduced risk for lung cancer and colorectal cancer.
Isothiocyanates, specifically an isothiocyanate called sulforaphane, may be the key to explaining this correlation.
Sulforaphane has demonstrated consistent ability to prevent the growth and proliferation of cancer cells. Because it is found in broccoli, broccoli sprouts, and other green-colored cruciferous veggies, sulforaphane has been coined “green chemoprevention” by researchers.
Isothiocyanates contain properties that have been shown to protect against several human pathogens. A study which examined the extracts of six different cruciferous vegetables found all had strong anti-microbial activity against harmful bacteria like Salmonella and Escherichia coli (E.Coli).
Reduce risk of heart disease
There is support in both animal and human studies for cruciferous vegetables playing a role in reducing risk factors for coronary heart disease, such as oxidative stress and elevated cholesterol.
A clinical trial found that subjects who ate broccoli sprouts had reduced markers of oxidative stress after just one week of consumption, while men with high cholesterol who drank kale juice daily for three months had significant decreases in their LDL-cholesterol (bad cholesterol) and improvements in HDL-cholesterol (good cholesterol).
Reduce risk of cognitive decline
The research has indicated that isothiocyanates may lessen the risk for and degree of cognitive impairment. Sulforaphane was found to improve cognition and memory in Alzheimer’s Disease and studies using isothiocyanate-rich foods broccoli, Brussels sprouts, and cabbage found improvements in cognitive function.
The indole GSL (IGSL) in cruciferous vegetables has a positive effect on estrogen metabolism to reduce potential breast cancer risk. A study found that healthy postmenopausal women who consumed Brassica vegetables containing 70 mg of IGSL daily had significant improvements in their circulating estrogen levels.
Due to their high nutritional value, cruciferous veggies are largely considered beneficial to overall health.
However, there is an area of concern when it comes to their intake.
Cruciferous vegetables and thyroid function
The isothiocyanate compounds in cruciferous vegetables are considered goitrogens, meaning they cause enlargement of the thyroid gland.
When goitrogens are metabolized, they inhibit iodine from being fully absorbed in the thyroid gland, which causes an increased level of thyroid-stimulating hormone and can interfere with proper thyroid function.
In animal studies, goitrogenic substances were found to induce development of thyroid cancer. Additionally, human trials found increased risk for thyroid cancer among women with high intakes of cruciferous vegetables combined with low consumption of iodine.
But not to worry!
The good news is that the cooking process inactivates the myrosinase enzyme responsible for the conversion of GSL into isothiocyanates.
This means that cruciferous vegetables which have been steamed, boiled, or blanched will have significantly less goitrogens than their raw counterparts.
Those with thyroid conditions, such as hypothyroidism, Hashimoto’s thyroiditis, and Graves’ Disease, should avoid excessive intake of raw cruciferous vegetables. Additionally, it is important to consume enough iodine in the diet, as iodine deficiency is considered a risk factor for thyroid dysfunction.
For the general population, goitrogens in foods are less of a concern. It is best to consume both raw and cooked forms of cruciferous vegetables, as water-soluble vitamins like Vitamin C are significantly reduced during cooking.
Cruciferous vegetables, and diets rich in them, are linked with many beneficial health outcomes including cancer prevention, cardiovascular disease prevention and hormone regulation. They contain many vital nutrients that the body needs to stay healthy.
The United States Department of Agriculture recommends between 2 and 3 cups of vegetables per day for adult women and 3 to 4 cups per day for adult men.
For reference, 2 cups of raw, fresh leafy greens (like arugula) are equivalent to 1 cup of total vegetables, while 1 cup of cooked kale, spinach, or bok choy is equivalent to 1 cup of total vegetables.
Though certain compounds in raw cruciferous vegetables have the potential to disrupt thyroid function, risk can be reduced by keeping intake in moderation and ensuring iodine consumption is sufficient. It is recommended to eat a large variety of foods and to incorporate both raw and cooked forms of cruciferous vegetables into the diet.
A Note of Caution
Individuals with inflammatory bowel diseases (IBD) may need to exercise caution with cruciferous vegetable intake, particularly raw forms, to avoid digestive discomfort.
Individuals with thyroid conditions should avoid excess servings of raw cruciferous vegetables and get enough iodine in their diet. If you are concerned, speak with your physician and dietitian to determine an appropriate level of intake and cooking preparations.
There are multiple ways to cook cruciferous vegetables which drastically reduce goitrogen development. These include steaming, boiling, blanching, sautéing, and roasting. Check out the recipe suggestions below and try adding a serving of cruciferous vegetables to your next meal.
The Mayo Clinic offers a simple yet delicious recipe with boiled broccoli florets seasoned with garlic and lemon zest. Other cruciferous veggies can be substituted for broccoli if desired.
Oven-roasting cruciferous vegetables often adds an appealing flavor that can make the veggies seem less bitter. Roast with a drizzle of olive oil and try incorporating herbs and spices, as seen in this Cardamom Roasted Cauliflower recipe.
For a stovetop recipe full of flavor, combine caramelized onions with sauteed kale and lemon juice.
And if you’d like to step up your stir-fry game, this Sauteed Shiitake and Bok Choy with Shrimp dish may be right up your alley. This heart healthy recipe appeared in Diabetic Living Magazine and is prepared with sesame oil, oyster sauce, and low sodium soy sauce (or tamari for gluten free).
Cooking not your thing? Smoothies are a great way to sneak in extra cruciferous vegetables!
Believe it or not, kale and cauliflower are easy to add to smoothies because they don’t alter the flavor if you add the right amount. And if you’re looking for a super easy way to make a smoothie, SmoothieBox has you covered.
Their Berry Smoothie and Strawberry Banana Smoothies have cauliflower included. Their Chocolate Smoothie has kale included.
Each smoothie comes in a bag with ingredients flash frozen before hand so they don’t arrive in one big clump.
With organic ingredients and the perfect balance of fruits and vegetables, SmoothieBox is an asset to your freezer.
All included information is not intended to treat or diagnose any disease or medical condition. Always consult your healthcare provider for medical questions and before beginning or changing any dietary or supplementation regimen.