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Food · Vegetables · Leafy & Cruciferous
food source · 3
Weight for weight, raw broccoli has about as much vitamin C as citrus fruit, or more. Many people think only fruit supplies vitamin C, but cruciferous vegetables are an underrated source.
Mechanism · It dissolves in water and fears heat
Vitamin C dissolves in water and is damaged by heat. When broccoli is boiled for a long time, the vitamin C is poured away with the cooking water; stir-frying, steaming or a quick blanch keeps more of it.
Numbers · Several nutrients on one plant
Raw broccoli has only about 30–35 kcal per 100 g and is about 90% water. Its vitamin C sits on the same plant as vitamin K1 and folate, and one long boil strips both of the heat-sensitive, water-soluble ones, vitamin C and folate, together.
Dark green cruciferous vegetables such as broccoli are also a source of vitamin K1. K1 dissolves in fat, so it is absorbed more easily with a little oil.
Mechanism · Fat-soluble, so it needs fat
K1 is plentiful in the dark green florets; it helps make clotting factors and is also involved in bone. It does not dissolve in water, and the contents of the small intestine are basically a pot of water, so K1 first has to dissolve into tiny droplets formed with fat, called micelles, before it can reach the gut wall. A little olive oil or a few nuts is not fussiness; it is what gets K1 absorbed.
Numbers · The K1 in a serving of broccoli
Cooked broccoli has about 140 µg of vitamin K1 per 100 g, less than kale or spinach, but a modest serving comes close to an adult's adequate intake for a day. People taking the blood thinner warfarin should keep their daily K1 roughly steady rather than avoid it.
Broccoli is an everyday source of folate, which sits on the same plant as vitamin C and K1. Folate suffers from long boiling, and stir-frying or steaming keeps more of it.
In practice · How to keep the folate
The folate in broccoli sits on the same plant as vitamin C and K1. It is an everyday source, less dense than dark leafy greens such as spinach. Folate dissolves in water and is damaged by heat, so long boiling loses a lot of it, while stir-frying or steaming keeps more.
Clinical · Why pregnancy calls for folic acid
Preparing for pregnancy cannot rest on this one vegetable. About 50% of the natural folate in food is available to the body; the synthetic folic acid used in fortified foods and supplements is more stable and better absorbed, which is one reason supplementation before conception and in early pregnancy uses the synthetic form.