Calcium Fructoborate

Calcium Fructoborate is a unrated form of Boron, used in 150 on-market products and providing 2.5% elemental boron by weight.

Basis: Provisional: ~2.5% boron by weight. Matches both the '2.5% providing' note printed on labels and a stoichiometric calculation for Ca[(C6H10O6)2B]2 x 4H2O (2 B / ~846 = 2.55%); formula not independently verified

Why this tier: Only form with its own human RCT (110mg twice daily for knee discomfort, n=60, industry-affiliated authors); no comparison of boron absorption against other boron forms was located, so no tier is assigned.

Source: Pietrzkowski Z et al. 2014, Clin Interv Aging 9:895-9, PMID 24940052

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