Zinc absorption - EFR 5-44

Bill Evers will be in Chicago from Friday, October 27, 1995 through Thursday, November 2, 1995 attending the American Dietetic Association's Annual Meeting and Exposition. Two issues of EFR are being sent this week (numbers 43 and 44). This is the SECOND of the two issues.

The following article on zinc reinforces the idea that just getting a nutrient in the diet or from a supplement is not of much value unless the nutrient is absorbed into the body.

(submitted by Mary Cheatham, Extension graduate assistant)

Source: Agricultural Research, USDA/ARS, June, 1995, page 15

Zinc is important in our bodies for protection against infection, for wound healing, for growth and normal development, for taste sensitivity, and for metabolism of energy, protein and carbohydrate.

"Zinc is a major constituent of many enzymes, so many of the body's metabolic processes depend on zinc", according to Agricultural Research Service animal physiologist William A. House. He is at the U.S. Plant, Soil, and Nutrition Laboratory at Ithaca, New York.

Meat is the major source of zinc, but in most developing countries, the amount of meat in the diet is limited. Thus, vegetarians may also have a problem with getting enough zinc. Growing children, pregnant women and those having recently had surgery require extra zinc and may be at risk for deficiency. Increasing the intake of zinc in these populations may be difficult, but increasing the zinc absorbed from the diet may be possible.

Increasing the amino acid methionine content of plants increases the availability of dietary zinc from plants. New research with rats shows that those receiving methionine supplements absorbed 82 percent of the dietary zinc, versus the usual 64 percent. Rats receiving methionine and lysine supplements absorbed 89 percent of the zinc in their diet.

One factor that can decrease zinc absorption is phytate, a form of phosphorus found in fiber. Phytate ties up zinc in the intestine, making it insoluble and unavailable for absorption. While fiber is good for us, it can increase the zinc we need in our diets! This research to increase the methionine content in plants could help combat the problem of decreased zinc absorption in high fiber foods. Also eating foods high in methionine should increase zinc absorption. Some nuts and seeds have high methionine contents (of course meats do also, but this is often not an option). Brazilnuts, soybeans, sesame seeds and watermelon seeds are some of the foods high in methionine.