What are cruciferous vegetables and are they healthy?

Cruciferous vegetables (a.k.a. Brassica) are a group of vegetables named for their cross-shaped flowers. They include broccoli, cauliflower, cabbage, Brussel sprouts, broccoli sprouts, Chinese broccoli, Chinese cabbage, collards and kale. (1, 2, 3). All these vegetables contain organic sulphur-containing compounds with a characteristic foul smell (2). These compounds have been investigated for their potential health benefits.

Nutrients in cruciferous vegetables

Brassica vegetables are rich in antioxidant vitamins and phytochemicals (4), including vitamin C, folate, carotenoids and tocopherols (5). They are also the primary dietary source of isothiocyanates and indoles (4), the sulphurous compounds mentioned before.

Health benefits

Cancer

Isothiocyanates have been studied for their ability to inhibit enzymes that affect cellular proliferation. They may also have an effect on the estrogen receptor, which plays a role in breast cancer. In addition, they may help eliminate potential DNA carcinogens, inhibit proliferation and induce apoptosis (1, 3, 6).

In effect, research has found inverse associations between cruciferous vegetable intake and the risk of certain cancers, including breast, kidney, bladder, prostate and pancreas (1). However, a prospective study in Japan failed to find a significant association between high intake of these vegetables and risk of colorectal cancer (5). It is possible that results are due to other healthy behaviours exhibited by people who consume higher amounts of vegetables.

Inflammation

The active compounds in Brassicaceae may help reduce inflammation and oxidative stress. Scientists have found decreased levels of certain biomarkers of inflammation. However, the degree of reduction seems to depend on certain genotypes (4, 6).

Cardiovascular health

Besides the potential anti-inflammatory role of sulphur-containing compounds, they have also been found to decrease cardiovascular disease risk. In addition, some studies have found inverse associations between crucierous vegetable intake and cardiovascular disease, coronary heart disease, ischaemic heart disease, stroke, etc.

Neurological disorders

Due to their antioxidant and anti-inflammatory properties, isothiocyanates may help manage various neurological disorders, including autism, Parkinson’s Disease, Alzheimer’s Disease, multiple sclerosis, etc. Most research in this field has been done with supplements and in either animals or cell cultures, so the jury is still out (7).

Cons

Gas

The sulphur-containing compounds in cruciferous vegetables can cause gas and discomfort. These double after 5 minutes of cooking, so if you have any issues try eating them raw or steam or stir fry briefly (8).

FODMAPs

FODMAPs are fermentable carbohydrates (read more about them here) that can cause symptoms in people with conditions such as irritable bowel syndrome or inflammatory bowel disease. Broccoli stalks and broccolini are high in fructose, Brussel sprouts and Savoy cabbage are high in fructan and cauliflower is high in mannitol (9).

Food chemicals

Broccoli, broccolini, Chinese broccoli, pickled or fermented vegetables (including sauerkraut and kimchi) are high in salycilates, amines and glutamates. Cauliflower is high in salycilates and amines. Individuals with sensitivity to those food chemicals should limit the intake of the mentioned vegetables to tolerance (8).

Recommended daily intake

As a reminder, the recommended daily intake of vegetables (of any kind) is 5 serves per day. 1 serve is 75g (about 1/2 cup of cauliflower/broccoli florets) or 1 cup of shredded cabbage). Remember to mix up your vegetables to maximise benefits and minimise exposure to potential problematic compounds.

How to eat

All these vegetables can be eaten raw or cooked, depending on individual tolerance (see section above). Below are a few ideas:

Cabbage

• Raw in salads, such as coleslaw
• Braised with apple and/or a dash of vinegar
• In wedges and roasted
• In soups (like this smoked pork, ginger & cabbage one or sancochado)
• As a filling in dumplings
• Fermented (e.g. sauerkraut or kimchi)

Cauliflower

• Raw in salads (you can shred it or coarsely chop the florets)
• Pickled
• Steamed or sautéed, as a side dish or as a base for pasta sauce, stews, curry or chilli
• In stir-fries
• Roasted with olive oil and/or tahini sauce
• Mashed
• In soups (either puréed or as florets)
• As cauliflower “rice” or a substitute for cous cous
• In fritters
• As pizza base (you knew I’d say it LOL)

Broccoli

• Raw in salads (you can shred it or coarsely chop the florets)
• Steamed or sautéed, as a side dish or as a base for pasta sauce, stews, curry or chilli
• In stir-fries
• Roasted with olive oil and a squeeze of lemon
• Mashed
• In soups (either puréed or as florets)
• In an omelette or frittata
• As broccoli “rice” (follow the instructions for cauliflower “rice”)

Kale

• Raw in salads, either shredded (i.e. kaleslaw) or massaged with olive oil and salt (this is my preferred way)
• Roasted with olive oil and salt (i.e. kale chips)
• Steamed or sautéed
• Raw in green smoothies
• Added to mash (as in colcannon)
• In an omelette or frittata
• Added to stews

References

1. Li L-y, Luo Y, Lu M-d, Xu X-w, Lin H-d, Zheng Z-q. Cruciferous vegetable consumption and the risk of pancreatic cancer: a meta-analysis. World Journal of Surgical Oncology. 2015;13.
2. Blekkenhorst LC, Sim M, Bondonno CP, Bondonno NP, Ward NC, Prince RL, et al. Cardiovascular Health Benefits of Specific Vegetable Types: A Narrative Review. Nutrients. 2018;10(5).
3. Royston KJ, Tollefsbol TO. The Epigenetic Impact of Cruciferous Vegetables on Cancer Prevention. Current pharmacology reports. 2015;1(1):46-51.
4. Jiang Y, Wu S-H, Shu X-O, Xiang Y-B, Ji B-T, Milne GL, et al. Cruciferous Vegetable Intake Is Inversely Correlated with Circulating Levels of Proinflammatory Markers in Women. Journal of the Academy of Nutrition and Dietetics. 2014;114(5):700-8.e2.
5. Mori N, Sawada N, Shimazu T, Yamaji T, Goto A, Takachi R, et al. Cruciferous vegetable intake and colorectal cancer risk: Japan public health center-based prospective study. European Journal of Cancer Prevention. 2018:1.
6. Navarro SL, Schwarz Y, Song X, Wang C-Y, Chen C, Trudo SP, et al. Cruciferous Vegetables Have Variable Effects on Biomarkers of Systemic Inflammation in a Randomized Controlled Trial in Healthy Young Adults12. The Journal of Nutrition. 2014;144(11):1850-7.
7. Panjwani AA, Liu H, Fahey JW. Crucifers and related vegetables and supplements for neurologic disorders: what is the evidence? Current opinion in clinical nutrition and metabolic care. 2018;21(6):451-7.
8. Swain Anne SV, Loblay Robert. RPAH elimination diet handbook: with food & shopping guide. Sydney, Australia: Allergy Unit, Royal Prince Alfred Hospital; 2009.
9. Monash University. Low FODMAP Diet App. 2018.

[Photo by Anne Allier on Unsplash]