Sesame

food source · 1

• →Calcium

  Most of the calcium in sesame is in the outer seed coat, the hull, and so is the oxalate that locks calcium up. The calcium in unhulled sesame is real, but its absorption is discounted, and hulling removes a large part of it. Sesame can add some calcium but cannot replace milk.

  GUIDE · moderateGUIDE · high
  Mechanism · 2

  Mechanism · Calcium and oxalate share a layer

  Calcium has to stay a dissolved ion to cross the gut wall. Most of the calcium in sesame is in the outer seed coat, the oxalate sits in the same layer, and a good share of the calcium is already bound to oxalate as insoluble calcium oxalate; the phytate in sesame locks up part of the rest. Hulled sesame loses that whole layer and a large part of the calcium with it; only unhulled sesame is worth counting for calcium, and even then its absorption is discounted.

  In practice · Unhulled, ground, and only a side source

  Tahini ground from unhulled seeds keeps much more calcium than tahini from hulled seeds, and whole sesame seeds often pass through undigested, so ground sesame is better. In the amounts people actually eat, a spoonful of sesame brings far less calcium than a glass of milk, so sesame is better treated as a supplementary calcium source. The calories in tahini come from its oil, not from the little calcium that gets absorbed.

  GUIDE · moderateGUIDE · high