Why is it not possible to obtain enough calcium from plant sources?
Calcium from plant sources has the lowest bioavailability. This includes calcium from sesame. Sesame contains phytates that bind calcium and prevent its absorption.
Calcium from plant sources has lower bioavailability compared to calcium from dairy products. This is due to the presence of antinutrients such as:
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phytates (found in sesame, nuts, legumes, for example) — they bind minerals, including calcium, and hinder their absorption in the intestine;
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oxalates (in spinach, rhubarb, sorrel) — also interfere with calcium absorption.
In the case of sesame: despite its very high calcium content (over 900 mg per 100 g), only a small portion is absorbed — about 10–20%, or even less if the sesame has not been pre-processed (soaking, roasting, fermentation).
To enhance calcium absorption from plant sources, it is beneficial to:
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combine them with vitamin D and magnesium;
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minimize antinutrients (through soaking, sprouting, fermentation).
Thus, sesame is not the best source of calcium in terms of absorbability, despite its high content.
But there is an exception – leafy vegetables without oxalates, such as broccoli and kale. Calcium from these is absorbed at 30-35%.