News

Low zinc status in older people may lead to depressed immune response and increased likelihood of chronic disease

April 8, 2015

A new paper from the Oregon State University suggests that low zinc status in the elderly (>65 years) could be due to epigenetic changes relating to IL-6 expression resulting in increased inflammation and risk of chronic disease.

Zinc is an essential component of many important enzymes in the human body. The main source in the diet is lean meat, organ meats and shellfish (notably oysters). Whole meal flour and nuts can also make a significant contribution, but the fiber content can significantly reduce the bioavailability. Typical adult diets are said to provide between 7 and 17mg per day of zinc, but only around 20% of that is actually bioavailable (Coultate, 2008). The current recommended daily intake in the USA is 8 mg for women and 11 mg for men with an upper limit of 40 mg/day.

Zinc deficiency in the USA is around 12% but rises to over 40% in those over 65 years according to the authors of a new paper from Oregon State University1.The problem can be exacerbated by the practice of supplementing the diet of older people with wheat bran to speed up gastrointestinal transit times. The phytic acid in wheat bran contains inositol hexaphosphate which is very efficient at binding with divalent cations such as zinc and calcium. Dietary phytase enzymes could be of benefit here.

In their new study, Wong et al., set out to better understand the relationship between zinc deficiency in older people and inflammation. They were able to show that zinc deficiency leads to dysregulation of cytokine IL-6 which is key to controlling the inflammatory response. In a mouse experiment, they found older mice had lower zinc levels which resulted in increased inflammation and decreased IL-6 methylation. IL-6 methylation is an epigenetic mechanism that controls gene expression.

Currently there are no reliable biomarkers for zinc deficiency, nor any specific intake recommendations for older people.

References

  1. Wong C.P., Rinaldi N.A. and Ho E. Zinc deficiency enhanced inflammatory response by increasing immune cell activation and inducing IL6 promotes demethylationMarch 2015, Molecular Nutrition and Food Research DOI: 10.1002/mnfr.201400761
  2. Coultate T, Food – The Chemistry of its components, 5th Edition, 2008, RSC Publishing.