The influence of gastrointestinal pH on speciation of copper in simulated digestive juice Original paper

What was studied?

This study investigated the speciation of copper (Cu) in simulated digestive juices and how gastrointestinal (GI) pH influences the copper forms that affect its solubility and bioavailability. By using a range of model solutions simulating different pH levels and digestive components, the researchers aimed to understand how copper speciation changes during digestion. They tested the copper concentrations and electrode responses at different pH levels and also looked at how food components like amino acids, organic acids, and proteins interact with copper ions. The results provide insight into the bioavailability and potential toxicity of copper in the digestive system.

Who was studied?

The study focused on copper solubility and speciation in model solutions that simulate the human gastrointestinal (GI) tract, including gastric and intestinal fluids. Researchers used food components such as amino acids (e.g., histidine, glycine), organic acids (e.g., citric acid, malic acid), and protein sources (e.g., casein, whey protein) to observe how these ligands interact with copper in a simulated digestive environment. The copper speciation was assessed at pH values ranging from 2.0 to 7.5, which corresponds to the acidic conditions in the stomach and more neutral conditions in the intestines. This approach aimed to simulate real-world digestion and offer insights into how copper behaves in the body.

Most important findings

As the pH increased, the solubility of copper decreased, particularly in solutions containing simple carbohydrates like glucose and fructose, where copper formed insoluble hydroxides at higher pH levels. However, in the presence of organic acids and amino acids, copper remained soluble, and its concentration was higher in the dissolved form. The study found that food components like histidine and glutamic acid formed stable complexes with copper, maintaining its solubility even at higher pH levels. Additionally, the presence of proteins like casein and whey protein decreased copper solubility, possibly due to the formation of larger complexes that could not pass through the membrane filters used in the experiments. The electrode response, measured by ion-selective electrodes (ISE), showed that copper ions (Cu²⁺) were most soluble at low pH (2.0–4.0) and less soluble at higher pH, with the highest solubility and electrode response observed in organic acid solutions.

Key implications

These findings highlight the importance of gastrointestinal pH in determining the bioavailability and toxicity of copper. In clinical practice, this could help clinicians understand how dietary components might influence copper absorption and its potential toxicity. The study also suggests that certain food components can modify copper solubility and bioavailability, which could have implications for individuals with copper-related diseases or those taking copper supplements. For microbiome studies, this information can help inform how copper interacts with gut microbiota, especially in individuals with altered pH levels or those consuming specific diets rich in organic acids or proteins. By adjusting copper intake or optimizing its bioavailability through dietary changes or supplementation, it may be possible to reduce copper-induced toxicity while maintaining adequate copper levels for physiological functions.