Brussels sprout benefits: 177 µg of vitamin K per 100 g — which matters if you take warfarin

Key benefits

1. 01Moderate evidence

   Cruciferous vegetables tracked with lower cardiovascular disease and mortality — observational

   2017, International Journal of Epidemiology. A dose-response meta-analysis pooling 95 prospective studies across 142 publications.

   The overall result. For every additional 200 g a day of fruit and vegetables, the relative risks observed were:

   • Coronary heart disease 0.92
   • Stroke 0.84
   • Cardiovascular disease 0.92
   • All-cause mortality 0.90

   The part broken out by type is what concerns Brussels sprouts. Green leafy and cruciferous vegetables showed inverse associations with cardiovascular disease and total mortality, and cruciferous and yellow-green vegetables showed inverse associations with total cancer risk. Brussels sprouts are cruciferous.

   Risk reduction was observed up to 800 g a day (600 g for cancer).

   Three things have to be stated clearly.

   First, this pools observational studies, so it is not causation. People who eat more vegetables tend to smoke less, exercise more and earn more. Statistical adjustment reduces but cannot remove that.

   Second, it is not "because it is a Brussels sprout". What this analysis examined is the cruciferous category. Broccoli, cabbage, kale and cauliflower sit in it too, and nothing here separates out the sprout's own share.

   Third, that makes the reading simple — not "eat Brussels sprouts" but "eat more vegetables", which is also the easier thing to act on.

   Hence the moderate grade. The body of data is large, but it is observational and does not single out this vegetable.

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2. 02Nutrition data

   177 µg of vitamin K and 85 mg of vitamin C — more than an orange

   Per 100 g of raw Brussels sprouts (about five):

   • 43 kcal, protein 3.38 g, fat 0.3 g
   • Of 8.95 g of carbohydrate, 3.8 g is fibre, sugar 2.2 g
   • Vitamin K 177 µg — above the adult adequate intake (120 µg for men, 90 µg for women)
   • Vitamin C 85 mg — 94% of the 90 mg requirement
   • Folate 61 µg, potassium 389 mg, calcium 42 mg
   • Vitamin A 38 µg, manganese 0.337 mg

   The 85 mg of vitamin C is the surprising figure. An orange holds 53 mg; a lemon, 53 mg. Five Brussels sprouts carry more vitamin C than an orange. Cruciferous vegetables are generally high in it, and sprouts sit near the top.

   But vitamin C is sensitive to water and heat. Boiling leaches a good share of it away. Steaming, roasting or a short stir-fry over high heat loses less.

   Vitamin K, by contrast, holds up to heat. It is fat-soluble, so cooking does not cut it much, and eating it with oil raises absorption.

   At 43 kcal with 3.38 g of protein, the protein share is high for a vegetable, and there is 3.8 g of fibre besides.

   Frozen loses little. They are blanched and frozen soon after harvest, which can beat fresh sprouts that have spent days in transit.

3. 03Nutrition data

   The bitterness is glucosinolates — and the varieties have changed

   There is a reason Brussels sprouts are remembered as a bad vegetable, and that reason has largely gone away.

   The bitterness comes from glucosinolates, the sulphur-containing compounds common to cruciferous vegetables. When the tissue is damaged they meet an enzyme, myrosinase, and convert to isothiocyanates. That is where the bitterness and the characteristic sulphurous smell come from.

   In the 1990s breeders found low-glucosinolate varieties. Dutch researchers went through old seed banks for less bitter lines and crossed them, and those crosses are what is sold today. The Brussels sprout on sale now is not the one from thirty years ago.

   Cooking was the other half of the problem. Long boiling breaks the sulphur compounds down, worsening the smell and dulling the colour. Halved, oiled and roasted at 200°C for 20–25 minutes, the edges caramelise and turn sweet. It is hard to believe it is the same vegetable.

   What about the health effects of glucosinolates? There is a great deal of research on isothiocyanates such as sulforaphane inducing detoxification enzymes. But there is still no randomised evidence that this changes outcomes such as cancer or death in people. The cruciferous finding in the meta-analysis above is observational too.

   How bitter they taste varies by person. Variants of the TAS2R38 gene set sensitivity to particular bitter compounds. Someone who especially dislikes Brussels sprouts may not be fussy — they may genuinely be tasting more bitterness.

How to eat it well

What to watch out for