Which form of zinc is best absorbed
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Best Absorbed Forms of Zinc: A Comprehensive Analysis
Introduction to Zinc Absorption
Zinc is an essential trace element crucial for numerous biological functions. The absorption of zinc in the human body is influenced by various factors, including the chemical form of zinc, dietary components, and individual physiological conditions. Understanding which forms of zinc are best absorbed can help in addressing zinc deficiency and optimizing supplementation strategies.
Chemical Forms of Zinc and Their Absorption Rates
Inorganic vs. Organic Zinc Compounds
Research indicates that the chemical form of zinc significantly impacts its absorption rate. Inorganic zinc compounds such as zinc oxide (ZnO) are less efficiently absorbed compared to organic forms like zinc gluconate and zinc citrate. Studies have shown that zinc oxide has a lower absorption rate, with some individuals absorbing minimal amounts 13. In contrast, organic zinc compounds, including those bound to amino acids, are absorbed more effectively 12.
Water-Soluble Zinc Salts
Among the water-soluble zinc salts, zinc gluconate and zinc sulfate are commonly used in supplements and have been found to have high absorption rates. Zinc citrate, although slightly soluble in water, has shown comparable absorption to zinc gluconate and higher absorption than zinc oxide . This makes zinc citrate a viable alternative for supplementation, especially in formulations where sensory properties are important.
Dietary Factors Influencing Zinc Absorption
Phytate and Other Inhibitors
Phytate, found in staple foods like cereals, corn, and rice, is a well-known inhibitor of zinc absorption. High-phytate diets can significantly reduce zinc bioavailability. Methods to reduce phytate content, such as enzyme treatment, germination, and fermentation, can improve zinc absorption 247. Additionally, the presence of other minerals like iron and cadmium can negatively affect zinc absorption when taken together in supplements .
Protein and Amino Acids
The protein content in meals positively influences zinc absorption. However, the type of protein matters; for instance, casein has a modest inhibitory effect compared to other protein sources 25. Amino acids such as histidine and methionine, along with low-molecular-weight ions like EDTA and organic acids (e.g., citrate), enhance zinc absorption and are often used in zinc supplements .
Comparative Studies on Zinc Absorption
Zinc Citrate vs. Zinc Gluconate and Zinc Oxide
A study comparing zinc citrate, zinc gluconate, and zinc oxide found that zinc citrate and zinc gluconate have similar absorption rates, both significantly higher than zinc oxide. This suggests that zinc citrate and zinc gluconate are preferable forms for supplementation, especially in individuals with higher zinc requirements or those at risk of deficiency .
Fortified Foods and Zinc Absorption
Zinc absorption from fortified foods varies depending on the form of zinc used and the phytate content of the food. For example, zinc absorption from low-phytate bread is higher than from high-phytate porridge. Both zinc sulfate and zinc oxide can be used for fortification, but the absorption is better when the fortificant matches the chemical form of the tracer used in studies .
Conclusion
In summary, the best-absorbed forms of zinc are organic compounds such as zinc gluconate and zinc citrate, which show higher absorption rates compared to inorganic forms like zinc oxide. Dietary factors, including the presence of phytate and the type of protein, significantly influence zinc absorption. Understanding these factors can help in designing effective zinc supplementation and fortification strategies to combat zinc deficiency.
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