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In Turkish cuisine there is a popular food called "tahin pekmez" (tahini with grape molasses).

According to a 2017 article on some Turkish news site, mixing these is supposedly counter-productive due to the calcium in the tahini bonding with the iron in the molasses and becoming unusable to the human body.[1] From what I can tell, the article doesn't cite any study for this claim.

Obviously I'm inclined to believe that the claim is click-bait, but I thought let's give it a chance and ask people who know their chemistry.

I hope this isn't too basic or otherwise off-topic for Chemistry StackExchange.

[1] https://www.yenisafak.com/gundem/tahin-ve-pekmezi-karistirmayin-2804300 (in Turkish)

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    $\begingroup$ Calcium itself does not react with iron. What makes iron unavailable is oxidation to iron(III), not enough acidic pH leading to precipitation and forming stable complexes with organic acids. $\endgroup$ – Poutnik Dec 13 '20 at 8:51
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    $\begingroup$ Molasses is not a very good source of iron and sensible dieticians do not recommend it as a source of iron not least because it is high in sugar and that is usually not good as a significant part of your diet. $\endgroup$ – matt_black Dec 14 '20 at 13:22
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Studies have indicated that calcium inhibits iron absorption in humans. However, numerous dietary factors influence iron absorption, and the effect of calcium may not be as pronounced when calcium is served as part of a whole diet. Calcium does not have any significant long-term effect on iron absorption. In addition, milk and milk products have not been found to affect iron absorption.

References:

  1. Lönnerdal B. Calcium and iron absorption--mechanisms and public health relevance. Int J Vitam Nutr Res. 2010 Oct; 80(4-5):293-9. doi: 10.1024/0300-9831/a000036.
  2. Grinder-Pedersen et.al., Calcium from milk or calcium-fortified foods does not inhibit nonheme-iron absorption from a whole diet consumed over a 4-d period, The American Journal of Clinical Nutrition, Volume 80, Issue 2, August 2004, Pages 404–409, doi: 10.1093/ajcn/80.2.404
  3. https://www.dairynutrition.ca/nutrients-in-milk-products/calcium/calcium-and-iron-absorption-is-there-an-interaction
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