Many claims without references to the scientific studies have been made that chlorogenic acid is a “drug mugger” of magnesium, iron, zinc and vitamin B1.
These claims are related to a recommendation that if green coffee extract is taken, it should be accompanied by trace mineral supplements containing all of these minerals. Since there are no strong scientific references to back-up those claims, here is a summary of the studies:
Zinc
Studies on rats showed that chlorogenic acid binds with zinc and prevents its absorption. It is highly probable that a similar effect occurs in humans. (1)
Phenolic compounds such as chlorogenic acid contained in coffee and black tea inhibit the absorption of iron. There is evidence that absorption of non-heme iron decreases with an increased concentration of coffee. (2)
When black tea is taken with a meal it reduces absorption of non-heme iron from that meal by 62% (35% by coffee). The reduction in absorption of iron is believed to be due to polyphenolic compounds such as chlorogenic acid. (3)
Another study showed that beverages containing 20-50mg of polyphenols such as chlorogenic acid reduce the absorption of non-heme iron by 50-70%. Beverages containing 100-400mg of polyphenols decreased absorption by 60-90%. Black tea showed the highest reduction in absorption of 79-94%. (4)
A cup of coffee taken with a hamburger reduced the absorption of iron by 39% and a cup of black tea by 64%. When the strength of coffee increased, the absorption fell even further. (5)
Chlorogenic acid was shown not to induce vitamin B1 deficiency, to what was believed before. (6)