Several studies have confirmed that plant compounds called isothiocyanates, found in cruciferous vegetables, have potent anticancer activity. One particular isothiocyanate compound called sulforaphane has been shown to inhibit growth of cultured human breast cancer cells, leading to cell death.
Broccoli and broccoli sprouts have garnered a reputation for being high in these beneficial compounds, but other cruciferous veggies have them as well, including Brussels sprouts, which have actually been shown to contain greater amounts of glucosinolates than broccoli.1 Glucoraphanin is a glucosinolate precursor of sulforaphane that influences carcinogenesis and mutagenesis.2,3 Compared to mature broccoli, broccoli sprouts can contain up to 20 times more glucoraphanin.
In one study,4 men who ate about 1.5 cups of Brussels sprouts daily for five weeks had a 28 percent decrease in DNA damage, which the researchers concluded showed "that consumption of cruciferous vegetables [Brussels sprouts] may result in a decreased cancer risk." As noted by World's Healthiest Foods:5
"This connection between Brussels sprouts and cancer prevention should not be surprising since Brussels sprouts provide special nutrient support for three body systems that are closely connected with cancer development as well as cancer prevention.
These three systems are (1) the body's detox system, (2) its antioxidant system, and (3) its inflammatory/anti-inflammatory system. Chronic imbalances in any of these three systems can increase risk of cancer, and when imbalances in all three systems occur simultaneously, the risk of cancer increases significantly."
One cup of cooked Brussels sprouts also contains more than 240 percent of the recommended dietary allowance (RDA) for vitamin K1, and nearly 130 percent of the RDA for vitamin C. They're also a good source of fiber, manganese, potassium (which helps control your blood pressure by balancing the rather high sodium), choline, B vitamins, antioxidants and other health-promoting phytochemicals.
Brussels sprouts are a valuable addition to your home garden,6,7 and while they require quite a bit of space, they are among the hardiest of the cabbage family. If you time your planting to coincide with fall frost, they'll actually be tastier, as the overnight chill brings out their sweetness. While they rarely do well in hotter climates, some newer hybrid varieties allow for greater temperature variances.
Popular hybrid varieties8 include Bubbles, which has shorter maturation (82 days instead of 100), tolerates warmer weather and is resistant to rust, and Prince Marvel, which produces tighter, sweeter sprouts and has a maturation rate of about 90 days. Other recommended varieties include Jade Cross, Oliver, Royal Marvel and Valiant.
A perfect cool weather crop, plan to transplant your Brussels sprout plants into your garden about 100 days before the first frost date. You can start your plants either indoors or out. If growing them directly in your garden, plant the seeds about one-half inch deep, and once they've reached a height of about 5 inches, thin them out so that they're spaced about 2 feet apart. They'll grow best in full sun but can handle partial shade.
Alternatively, start your seeds indoors in starter containers four to five weeks before transplanting. When transplanting them into your garden, plant them a little bit deeper than they originally grew. The lowest leaves should be just above ground. Mulching around them will help retain moisture. If you let them dry out, the crop will usually fail.
As for the soil, it should drain well, but need to be packed or pressed as excessively loose soil will encourage clubroot, a common disease affecting the cabbage family.9 In the featured video, they recommend tamping the soil down with your feet.
Once or twice a month, spray the leaves with compost tea or seaweed extract. They're very nitrogen dependent, so be sure to use plenty of high nitrogen compost. Brussels sprouts also grow well next to bush peas and beans for this reason, as these plants deliver an extra shot of nitrogen to the soil. As the plant matures, remove yellowing leaves to allow the sprouts room to grow. Just be sure to leave several of the largest, healthiest leaves toward the top.
If you want or need the plant to mature faster, pinch off the top of the plant, but make sure you still have some healthy, fully expanded leaves remaining. Another growth-promoting tip is demonstrated in the MIgardener video above. You can promote maturation of the Brussels sprouts by snapping off most or all of the leaves, leaving only a healthy bunch at the crown. This will shock the plant into maturation and funnel energy toward the sprouts.
The Brussels sprouts are ready to harvest in 80 to 100 days (depending on the variety) or when they're about 1 inch in diameter. You can let them grow larger, but the smaller ones are more tender and tend to have a more pleasant flavor. Harvest the sprouts from the bottom, up, by twisting them off the stem.
Should you expect a hard freeze, you can still salvage your crop. Dig out the plant, remove any remaining leaves, hang the plant upside-down in a cool place and harvest as the sprouts mature. Sprouts that fail to develop into firm heads, remaining loosely bound instead, is a sign of heat exposure. Essentially, the weather was too warm.
Flavor goes hand in hand with freshness, so avoid storing or refrigerating your Brussels sprouts for more than two days. Also avoid washing them before storing. Simply remove any damaged outer leaves and place them, unwashed, in the vegetable bin in your fridge. Wash them right before cooking if needed.
The key to successful preparation of Brussels sprouts is to avoid overcooking. Brussels sprouts are very much like broccoli in this matter. Preparation is paramount in order to maximize their nutritional value. Here are some key considerations and helpful tips:
• How to achieve more even cooking — The outer leaves cook faster than the core, so for more even cooking, carve an X into the bottom of each stem if cooking them whole. Larger sprouts will cook more evenly if cut in half. You can tell you've overcooked them by their color. They should remain bright green; a dull green or yellowing is an indication that valuable nutrients have been lost.
• How to optimize sulforaphane content — As with broccoli (discussed in the video above),10 the sulforaphane content of Brussels sprouts is easily diminished by overcooking, as heat degrades the enzyme responsible for producing sulforaphane. To optimize retention, your best bet is to steam them for three to four minutes, until bright green.11
This will increase the available sulforaphane content by eliminating epithiospecifier protein — a heat-sensitive sulfur-grabbing protein that inactivates sulforaphane — while still retaining the enzyme myrosinase, which converts glucoraphanin to sulforaphane. Beyond the five-minute mark, you start losing valuable compounds.
• How to maximize sulforaphane even further — To further boost sulforaphane content, pair your Brussels sprouts with a myrosinase-containing food12,13 such as mustard seed, daikon radishes, wasabi, arugula or coleslaw. Of these, mustard seed has been found to contain a particularly resilient form of myrosinase.14
For a recipe pairing Brussels sprouts with shallots and mustard seeds, see Epicurious.com.15 You could also try roasted Brussels sprouts with a mustard vinaigrette made with grainy mustard or mustard seed powder,16 or my balsamic drizzled Brussels sprouts recipe, to which you could simply add a dash of mustard seed powder.
The best way to preserve your Brussels sprouts if you cannot eat them within a day or two of harvesting is to freeze them.17 But first, they need to be blanched. After picking off any damaged or coarse outer leaves, wash them and sort by size into small, medium and large.
Bring a gallon of water to a rolling boil over high heat. You can blanch 1 pound of sprouts per batch. Small heads should be blanched for three minutes; medium-sized sprouts for four minutes and large heads for five minutes. While blanching can rapidly destroy anticancer compounds like glucosinolate in broccoli, Brussels sprouts have been found to be less severely affected by the blanching process, retaining far more of their glucosinolate than broccoli when blanched.18
To stop the cooking process, immerse the Brussels sprouts in ice water for the same amount of time as the blanching. Drain the Brussels sprouts on a paper towel. Once dry, pack into a freezer container. They'll keep for up to one year if frozen at or below zero degrees F.