Broccoli

Broccoli is a brassica: you eat the florets and the peeled stalk. Steam or roast it, or add it to soup, pasta and curry. In season in Germany June to October.

What is broccoli?

Broccoli (Brassica oleracea) belongs to the cruciferous family (Cruciferae), just like cauliflower, Brussels sprouts, kale, rocket and maca. It originally comes from Asia Minor and reached the rest of Europe via Italy. Today it gets a lot of attention in nutrition research, mainly because of its unusually high concentration of sulphur-containing plant compounds called glucosinolates.

Nutrition at a glance (per 100g, raw)

• Energy: 34 kcal – a big portion for very few calories, handy for volume eating.
• Macros: 7g carbohydrate (of which 3g fibre), 3g protein, 0g fat.
• Vitamins: Vitamin C (often more per 100g than oranges), vitamin K1, folate (B9) and beta-carotene.
• Minerals: Potassium, calcium, iron and magnesium.

Sulforaphane: why researchers are interested

The main reason broccoli is studied so much is a compound called sulforaphane. It isn't a nutrient in the classic sense but an isothiocyanate. It forms when glucoraphanin (an inactive precursor) comes into contact with the enzyme myrosinase – which happens when you cut, bite or chew broccoli (the plant's natural defence mechanism).

Sulforaphane and the Nrf2 pathway

Sulforaphane works differently from classic antioxidants such as vitamin C, which neutralise free radicals once and are then used up. Researchers are interested in it because it activates the Nrf2 signalling pathway, which switches on hundreds of genes involved in the cell's own defences.

Indole-3-carbinol

Cruciferous vegetables are also studied in connection with liver enzymes. Broccoli contains indole-3-carbinol (I3C), which researchers look at in connection with how the body breaks down oestrogen.

How to prepare it (the trick for more sulforaphane)

This is where most people go wrong: myrosinase, the enzyme that forms sulforaphane, is very sensitive to heat. Glucoraphanin (the inactive precursor) can take the heat, but if you drop broccoli straight into boiling water, you destroy the enzyme before any sulforaphane can form.

The fix (the 40-minute trick): Chop the raw broccoli into small pieces. Chopping mimics chewing and activates the enzyme. Then leave it raw at room temperature for about 40 minutes. In that time, myrosinase converts the precursor into sulforaphane. After that you can cook it as usual, as sulforaphane itself is heat-stable.

Alternative: steam it gently (just 2-4 minutes). Steaming is much kinder to the enzyme than long boiling or frying.