Zinc-ascorbic acid interaction

In the diet and at the tissue level, ascorbic acid can interact with mineral nutrients. In the intestine, ascorbic acid enhances the absorption of dietary iron and selenium reduces the absorption of copper, nickel, and manganese but apparently has little effect on zinc or cobalt. Ascorbic acid fails to affect the intestinal absorption of two toxic minerals studied, cadmium and mercury. At the tissue level, iron overload enhances the oxidative catabolism of ascorbic acid. Thus, the level of dietary vitamin C can have important nutritional consequences through a wide range of inhibitory and enhancing interactions with mineral nutrients. 

Given the eflFects of ascorbic acid on the absorption of iron and copper, investigators have been interested in possibly significant interactions with zinc. The absorption of zinc and other divalent mineral ions was studied using an isolated, filled duodenal loop in situ in the rat (58). A lO -M zinc solution was infused in the presence or absence of 10" M ascorbate or dehydroascorbate. A two-thirds reduction in the... 

Clinically important, potentially hazardous interactions with ascorbic acid, zinc... 

There are numerous reports of interactions of dietary elements that cause variation in the absorption of chromium. Amino acids, which chelate chromium, prevent precipitation at the basic pH in the small intestine, which increases its absorption [13]. Other chelating agents have mixed effects. Phytates significantly decrease absorption whereas oxalates lead to increased absorption [15]. Certain vitamins such as nicotinic acid and ascorbic acid have been shown to increase absorption [16]. Starch has also been shown to increase absorption to a greater degree than glucose, fructose, and sucrose. Some metals can compete with chromium and decrease its absorption. Studies show that zinc, vanadium, and iron have a common intestinal transport mechanism with chromium and can decrease the absorption of chromium [9]. 

El-Shobaki, F. A., and Sprour, M. G., 1989, The influence of ascorbic acid and lactose on the interaction of iron with each of cobalt and zinc during intestinal absorption, Z. Erndhrungswiss. 28 310-315. 

Other nutrients and their deficiencies that can impact iron status, utilization, or anemia include vitamin A, folate, vitamin B12, riboflavin, and ascorbic acid (vitamin C). Improving iron status can also increase the utilization of iodine and vitamin A from supplements. On the other hand, it is increasingly recognized that simultaneous provision of iron and zinc in supplements may decrease the benefit of one or both of these nutrients. These complex micronutrient interactions and their implications for nutritional interventions are incompletely imderstood but have significant implications for population-based supplementation strategies. 

---