Submitted to: Biological Trace Element Research
Publication Type: Proceedings
Publication Acceptance Date: July 18, 2001
Publication Date: N/A
Interpretive Summary: Manganese is an essential nutrient that also may be toxic when consumed excessively. Under most conditions, limited amounts of manganese are absorbed from the gut but some dietary interactions with other nutrients may alter the amount of manganese that is absorbed and made available to the animal. This study examined whether the form of dietary fat affects manganese absorption and utilization. Rats were fed diets high or low in manganese and enriched in saturated or unsaturated fats. Manganese absorption by animals fed saturated fats was less than 10% that of animals fed unsaturated fats. Although absorption was lower, animals fed saturated fats retained the absorbed manganese longer than animals fed unsaturated fats. The only biochemical change noted was animals fed low manganese and saturated fats, as compared to other diets, had reduced activity of a manganese-containing enzyme in the heart. This study demonstrates that the type of fat in a meal influences manganese absorption. However, but other mechanisms compensate for the change in absorption, thus maintaining a relatively constant amount of manganese in the body.
Technical Abstract: There is evidence that manganese (Mn) metabolism is influenced by dietary fat. Also, saturated fats, as compared to polyunsaturated fatty acids (PUFAs), promote iron (Fe) absorption, and the absorption of Fe and Mn are inter-related in many aspects. These studies were conducted to determine whether saturated fat, as compared to unsaturated fat, affected Mn absorption, retention and metabolism. In experiment I, adult rats were fed diets containing either 0.7 or 100.4 ug/g Mn with the fat source as high-linoleic safflower oil or stearic acid. After two days, the animals were fed a test meal of 54**Mn followed by whole-body counting for ten days. Manganese absorption was significantly (p<0.05) lower in the stearic acid group (0.9-4.8%) than in the safflower oil group (20-33.8%); however, the biological half-life was shorter in the safflower oil group. Retention of 54**Mn and total Mn was always significantly (P<0.05) greater in the safflower oil group when dietary Mn was low, but was the same when dietary Mn was high. In experiment II, weanling rats were fed 1.3, 39.3 or 174.6 ug Mn/g and either stearate, high oleic safflower oil or high linoleic safflower oil for 8 weeks. Long-term feeding of the stearate and low Mn-containing diet resulted in significant (p<0.0001) reduction in heart superoxide dismutase activity and kidney and liver Mn concentrations compared to the other diets. These data show that stearic acid inhibits Mn absorption, but may not inhibit Mn retention when dietary Mn is high.