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Food · Vegetables · Leafy & Cruciferous
food source · 2
The word folate comes from the Latin folium, meaning leaf, because folate was first isolated from spinach leaves. Folate is spinach's real strength; its iron, by contrast, is hard to absorb.
Mechanism · What folate does
Folate is the vitamin needed to make DNA and let cells divide, which is why it matters so much before conception and in early pregnancy. Natural folate in food carries a chain of extra glutamate units that must be stripped off in the gut before it can be absorbed, and about 50% of it is available to the body.
Myth · Spinach is not an iron food
Spinach's strengths are folate and vitamin K1, not iron: its iron is harder to absorb than the iron in meat to begin with, and the oxalate in the leaves binds iron and calcium. Blanching and pouring off the water removes part of the oxalate, but folate also dissolves in water and is damaged by heat, so keep the blanching short and lift the leaves out as soon as they wilt.
Dark leafy greens are among the main food sources of vitamin K1, and spinach ranks near the top. K1 dissolves in fat, so it is absorbed better when eaten with a little oil.
Mechanism · Darker leaves, more K1
K1 is a part of the chain that passes electrons along during photosynthesis in the chloroplast, so the darker the leaf, the more K1 it holds. Cooked spinach has about 540 µg per 100 g, and a small bowl far exceeds an adult's adequate intake for a day. K1 dissolves in fat and needs a little oil to be absorbed well.
Safety · On warfarin, keep it steady
In healthy people, eating more greens does not thicken the blood. The people who need a roughly steady daily amount of K1 are those taking the blood thinner warfarin: K1 helps the liver make clotting factors, and that is exactly the step warfarin blocks, so the goal is a steady intake, not avoiding greens. The other form of vitamin K, K2, comes mainly from fermented and animal foods, and spinach has almost none.