Brilliant brassicas: a look into the benefits of cruciferous vegetables

When you were growing up, your parents probably said, “Eat your Brussels sprouts — they’re good for you.” Well, your parents were right! Brussels sprouts and their other well-known family members cabbage, broccoli, kale and cauliflower are all part of the cruciferous family. They are extremely beneficial for your health and contain some unique phytochemicals that have superior disease-fighting properties.

Cruciferous vegetables belong to the Brassicaceae plant family. They are some of the most nutrient-dense foods you can eat. These super vegies offer a variety of impressive health benefits including lowering cholesterol levels and the risk of cancer and heart disease, boosting liver detoxification and immunity, and even balancing hormone levels.

The brassica family includes broccoli, kale, cabbage, cauliflower, Brussels sprouts, bok choy, collard greens, rocket, watercress, rutabaga, turnips and turnip greens, daikon, wasabi, kohlrabi, radish, maca and mizuna.

Nutrients

Brassicas are loaded with disease-fighting vitamins, minerals and phytochemicals. Most of brassicas’ beneficial effects are linked to their unique phytochemicals that have antioxidant, anti-inflammatory and lipid- and blood sugar-lowering effects. This makes them excellent food choices for helping prevent chronic diseases such as cancer, cardiovascular disease and type-2 diabetes.

You’ll find plenty of vitamin A and carotenoids (beta-carotene, lutein and zeaxanthin) in them — vital nutrients that help support eye health and good vision and reduce the risk of degenerative eye conditions such as macular degeneration.

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These super vegetables are also excellent sources of vitamins C, E and K, which are needed by the body to strengthen the immune system, promote healthy blood clotting and improve cardiovascular and bone health. Brassicas also provide a good dose of folate and iron, for red blood cell production, and calcium and phosphorus for strong bones. In addition, they deliver a good dose of selenium, a powerful antioxidant mineral that helps fight free radicals and lowers the risk of cancer.

Brassica vegetables are rich in protective flavonoids (flavonols and anthocyanins). Flavonoids are beneficial for improving cardiovascular health as they help prevent the oxidation of LDL “bad” cholesterol and lower the risk of diseases such as atherosclerosis, cancer and chronic inflammation. Anthocyanidins are responsible for the vibrant red, blue and purple colour of fruits and vegetables. Anthocyanidins are found in particularly high levels in purple kale and cabbage.

You will also be boosting your soluble and insoluble fibre intake by eating brassica vegetables. It’s important to include both of these types of fibre in your diet to support bowel and cardiovascular health.

What makes this family of vegetables unique is that they contain a group of phytochemicals called glucosinolates, which include sulforaphane, glucosinolate and indole-3-carbinol. These are naturally occurring sulfur-containing chemicals that are responsible for brassicas’ characteristic pungent aroma and bitter mustard flavour.

When brassicas are cut or cooked, an enzyme called myrosinase is activated which converts glucosinolates into an active phytochemical called isothiocyanates, which has outstanding health benefits and disease-preventing properties. Isothiocyanates have been found to reduce inflammation and help detoxify carcinogenic compounds before they can cause damage to cells.

Health benefits

Cancer prevention

Numerous studies show an association between the consumption of brassica vegetables and cancer prevention. Glucosinolates, in particular indole-3-carbinol and sulforaphane, have been studied extensively for their anticancer effects. They have been found to inhibit the development of bladder, breast, colon, liver, lung and stomach cancer in animal studies. According to a study published in JAMA in 2001, women who eat greater amounts of cruciferous vegetables had a lower risk of breast cancer. Glucosinolates can help protect against DNA damage, along with inactivating carcinogenic substances, as well as inhibiting tumour blood vessel formation and tumour cell migration.

Skin health

Including plenty of brassicas in your diet will also improve your skin health by boosting your sulfur intake. Many of us aren’t getting sufficient sulfur in our diets. Sulfur is found in all cells of the body, especially in the hair, skin and nails and is required for healthy, youthful-looking skin. Adequate amounts of sulfur help to maintain collagen production and give skin its structure and strength. Poor collagen production is one of the main contributors to wrinkles and ageing skin.

Liver health & detoxification

Brassicas contain key nutrients needed to support liver function and detoxification, including glucosinolates and isothiocyanates, sulfur, vitamins E and C as well as selenium. Isothiocyanates help support both phase I and II liver detoxification. Phase I liver detoxification is the body’s first line of defence against toxic substances. In this phase, toxins are converted to less harmful substances, but they also produce by-products that are highly toxic and can build up in the liver. Phase II neutralises these toxins and removes them.

Sulfur attracts heavy metals and other toxins and assists their safe transport out of the body. Sulfur is also required to make glutathione, one of the body’s most valuable antioxidants. Glutathione plays a vital role in liver detoxification and helps protect the body from environmental toxins and cancer development. Glutathione levels are greatly influenced by the amount of sulfur-containing foods consumed.

One of the best ways to promote better liver health and detoxification is to eat a variety of brassica vegies. Fermenting them can actually increase their sulfur content and make the sulfur more bioavailable. Sauerkraut and other fermented brassicas can be enjoyed in salads and wraps as well as with curries and stir-fries.

Reducing inflammation

Brassicas have outstanding anti-inflammatory properties. In a study published in the Journal of the Academy of Nutrition and Dietetics, higher intakes of cruciferous vegetables were associated with up to a 25 per cent reduction in inflammatory markers among 1005 women. Brassicas make an excellent addition to an anti-inflammatory diet to help alleviate inflammatory conditions such as asthma, rheumatoid arthritis and ulcerative colitis.

Regulate blood sugar levels & weight loss

Brassicas provide plenty of dietary fibre, which helps slow down digestion and the absorption of sugars into the bloodstream. Eating brassicas can help keep blood sugar levels more balanced. A Chinese study in 2016 found that higher intakes of brassica vegetables were associated with a significantly decreased risk of type 2 diabetes among 306,723 participants.

In just one cup of cooked broccoli you will find 5.1g of fibre, which is more than 20 per cent of your daily recommended fibre intake. One cup of cooked Brussels sprouts provides 4.1g of fibre and 1 cup of kale delivers 4g of fibre.

Eating fibre-rich foods is also a good way to help promote healthy weight loss. Brassicas’ high fibre content helps to promote satiety and reduces sugar cravings. Brassicas are also low in calories, making them perfect for those wanting to lose weight.

Heart health

Increasing your consumption of vegetables in general is known to help decrease your risk of heart disease. Brassicas, however, are super heart-healthy vegetables due to their high fibre and antioxidant content, as well as their ability to lower cholesterol levels and reduce the risk of atherosclerosis. Compounds in brassicas help control cholesterol levels by binding to bile acids and removing them from the body. The role of bile is to help digest and absorb fats. The body replaces lost bile acids with its own cholesterol stores, which helps to bring cholesterol levels down.

In a study published in Biomedical Environmental Science 2008, men with high cholesterol who supplemented with 120mL of kale juice daily for 12 weeks saw a 10 per cent reduction in LDL “bad” cholesterol and a 27 per cent increase in HDL “good” cholesterol.

Researches followed 134,794 adults over a 10-year period and found that those who consumed a higher intake of vegetables, especially cruciferous vegetables, had a lower risk of death from heart disease.

Hormonal balance

Eating brassicas can also help balance oestrogen levels and alleviate symptoms associated with oestrogen dominance, including irregular periods, weight gain, bloating and premenstrual syndrome. Researchers have found an association between brassica vegetable consumption and oestrogen levels. Brassicas’ hormone-balancing effect is due to their indole-3-carbinol content. This compound has been found to help regulate oestrogen activity and metabolism.

Recommended intake

For disease prevention, a variety of brassicas should be included in your daily diet. Researchers recommend eating at least five servings of these tasty superfoods per week; however, for optimal health and protection against disease, eating a variety of these vegies daily is ideal.

These versatile vegetables can be prepared in a variety of ways including baked, steamed, pan-fried and fermented, and can be easily added to soups, stir-fries and curries, or eaten raw in salads with dips or in green smoothies.

Which brassicas are the best?

Dark-green leafy brassicas come out on top. These include broccoli, kale, collard and turnip greens, watercress and arugula rocket. The darker and more colourful the vegetable, the richer their antioxidant content. Purple kale and cabbage contain more protective antioxidants due to their anthyocyanin content. Darker-green vegies are richer in nutrients than paler varieties.

The florets of brassicas tend to contain the highest levels of nutrients, but the stalks and leaves are still healthy choices and shouldn’t be wasted. Try chopping up the leaves of cauliflower and adding them to your curry.

Researchers have found that brassica sprouts have even higher levels of glucosinolates and a stronger anti-cancerous effect compared to the mature plants. Broccoli sprouts contain 10–100 times more glucosinolates compared to mature broccoli. According to an Australian study by Australia’s Rural Industries Research & Development Corporation (RIRDC), broccoli sprouts had the highest levels of glucosinolates of all brassica sprouts. To get the most out of your sprouts, eat them fresh and raw and chew them well. Brassica sprouts are available from green grocers or can be easily and cheaply grown at home.

Are brassicas beneficial for everyone?

Even though brassicas have many impressive health benefits, there are some people who need to be mindful of how they consume them. Some people experience digestive upsets like excess wind and bloating when they consume too many, due to their high sulfur content. Sulfur is broken down in the large intestine to produce hydrogen sulfide, which can produce smelly “rotten egg” flatulence. Brassicas also contain raffinose, which passes through to the large intestine undigested. Bacteria in the large intestine ferment the raffinose and one of the byproducts is excess gas, which causes bloating and flatulence.

The best way to make brassicas easier to digest and reduce these unwanted symptoms is by cooking them and chewing them well and by starting off by reducing your intake and slowly increasing it. Taking a digestive enzyme with meals or having apple-cider vinegar 15 minutes before a meal will also help improve your digestion and reduce excess wind.

Brassicas also contain natural chemicals called goitrogens, which can interfere with thyroid hormone production by slowing iodine uptake by the thyroid. Goitrogens can be inactivated by cooking and fermenting, so people with hyperthyroidism can still enjoy cooked brassicas, sauerkraut and other fermented brassica vegies. Anyone with an under-functioning thyroid should avoid eating raw brassicas and limit their brassica intake to 1–2 servings a day.

Best ways to cook brassicas

To get the most out of your brassicas, eat them as fresh as possible. This is when they have the highest content of myrosinase, which converts the glycosinolates into their useable forms. You can activate these enzymes by cutting your brassicas and leaving them for 5–10 minutes before cooking.

One of the healthiest ways to cook brassicas is to steam them. When broccoli is steamed for five minutes it retains the highest levels of glucosinolates, along with the enzyme myrosinase. Microwaving and boiling brassicas destroys these important compounds. Light stir-frying is another healthy way to preserve more glucosinolates.

A great way to enjoy brassicas includes adding raw kale to salads. Massage your chopped kale first for a few minutes, using some olive oil and lemon juice to break down its tough fibres. Whole cauliflowers are delicious covered in spices and oven-baked. Cauliflower also makes a delicious gluten-free pizza base or “rice” to go with curries and dhals. Add shredded cabbage to salads or make healthy coleslaw. Brussels sprouts taste best pan-fried or roasted with spices and olive oil. Toss leafy brassicas like collard and mustard greens and rocket through salads.