Kale belongs among cruciferous vegetables.
Cruciferous vegetables got their name from the Latin word for crucifix because the blossoms of these plants resemble a cross. The cruciferous family includes: bok choy, broccoli, Brussels sprouts, cabbage, cauliflower, Collard/spring greens, horseradish, kale, kohlrabi, mustard, radish, rocket, turnip, watercress and wasabi. Sometimes this vegetable family is also called brassicas.
What’s all the fuss about?
The reason why these green powerhouses are so highly praised is that all cruciferous vegetables contain very powerful natural compounds that have a strong cancer-fighting effect. Their consumption can thus help protect against many types of cancer (digestive tract cancers, breast, lung, prostate and kidney). These compounds are called glucosinolates and their breakdown products, such as isothiocyanates, are believed to be responsible for their health benefits.
To make the most of these compounds, you need an enzyme that’s in the veggies and helps the breakdown products to do their magic but it can get destroyed by heat. Hence it’s best to eat some cruciferous vegetables raw (cabbage, kohlrabi, radish, rocket, watercress) or only steam them lightly (bok choy, broccoli, spring greens, kale). When cooking with them, you can get around this problem by adding a pinch of mustard powder which contains the necessary enzyme so you get full health benefits.
Daily dose of green goodness
Cruciferous vegetables are packed with antioxidants which help maintain good health, protect your organs and strengthen your immune system. Most of these veggies also contain a specific type of antioxidants called carotenoids (lutein, zeaxanthin and beta-carotene) that are very helpful for protecting your eyes against age-related macular degeneration (deteriorating eyesight). Beta-carotene is a precursor to vitamin A and cruciferous vegetables are a great source.
The cruciferous family is also a good source of other essential nutrients such as folic acid (folate), vitamins C, E and K and fibre. Vitamin K plays an important role in blood chemistry, calcium metabolism and regulates inflammatory response of the body. We only need very little of it so any dose of cruciferous vegetables will cover the need. On top of that, cruciferous veggies pack a good dose of minerals such as calcium, potassium and iron, contain a fair amount of protein and are a good source of healthy omega-3 fats.
We need omega-3 fats (polyunsaturated fats) as an essential part of our diet: they fulfil many important functions in the body and help fight inflammation. Vegetables as such are low-fat foods but what little fat there is in cruciferous vegetables has a higher omega-3 content. Hence it’s a win-win – you eat only a little fat in each portion but it’s precisely the good fat you need!
Omega-3s can get damaged by heat so again, best to steam your cruciferous veggies or eat them raw when possible.
Recommended daily intake
Food – nutrient content
Vitamin E mg/100g
Folic acid mcg/100g
Vitamin C mg/100g
Broccoli – raw
Broccoli – boiled
Brussels sprouts – boiled
Cabbage – raw
0.02-1.15 (green outer leaves have more than inner leaves)
Cabbage – boiled
Cauliflower – raw
Cauliflower – boiled
Kale – raw
Kale – boiled
Mustard and cress leaves -raw
Radish (red) – raw
Spring greens – boiled
Turnip – boiled
Watercress – raw
All these vegetables are an excellent source of fibre which helps our digestion work better, helps to regulate blood fats and sugars and also encourages beneficial gut bacteria. These friendly gut bacteria thrive on fibre and vegetables in general and help to improve our metabolism, keep the intestines healthy and help lower inflammation.
Aim for one or two portions daily to get the best health benefits. There is, however, a warning for health food enthusiasts – eating large quantities of raw cruciferous vegetables can affect your thyroid by interfering with iodine metabolism. So, if you’re juicing or making smoothies daily that can pack in a large amount of kale, you might need to check how many portions of cruciferous vegetables you actually have in a day.
The known side-effects occur only with extremely high intake – about two to three pounds a day – but it’s worth keeping an eye on your iodine intake. If you have enough iodine in your diet, it’s unlikely that cruciferous veggies would cause trouble. Seaweed is a good iodine source but don’t overdo it – once a week is enough as some types of seaweed can contain very high amounts. Fruit and vegetables, grains and nuts contain some iodine (depending on where they’re grown) but not enough so it’s best to rely on seaweed or iodised salt.