You don't hear much about zinc deficiency in nutrition circles. My chief recollection of it from undergraduate school was that it was responsible for the a loss of taste as we aged. Fearing that possibility, I've always paid attention to the zinc content of foods. (Baked beans, dark meat chicken, cashews, chick peas and Swiss cheese are my favorites)
Now a new study helps to explain why we develop zinc deficiency in later life. This research may lead to a better understanding of how we can continue enjoy the taste of our food as we grow older and benefit from the many other important functions zinc performs in the body.
Reasons for Zinc Deficiency
The research was done by scientists at the Linus Pauling Institute at Oregon State University and published in the Journal of Nutritional Biochemistry. They found signs of zinc deficiency in older rats that had adequate zinc in their diets. The reason for the deficiency was a malfunction in zinc transporters. In a convoluted process, the mechanisms used to transport zinc were disrupted by changes in DNA, and the DNA was damaged by the lack of zinc.
In humans as well as rats, zinc is needed to repair the damage to DNA that goes on in the body throughout life. This study and others suggest our ability to keep up with these repairs becomes less efficient over time while the need gets greater.
One of the most serious effects of low zinc levels is an enhanced inflammatory response. Excessive inflammation is directly linked to many life-threatening diseases, including cancer and heart disease. When the rats in this study were given 10 times their dietary requirement for zinc, biomarkers for inflammation retuned to the levels of younger animals.
Given the aging of the population and rising rates of degenerative diseases, the role of zinc in controlling inflammation may be its most important contribution to a healthy retirement.
Key Facts About Zinc in the Diet
- Zinc is involved in the activity of over 100 enzymes and needed for proper immune function, DNA and protein synthesis, wound healing and cell division.
- The combination of low dietary intake of zinc and poor absorption can lead to a deficiency. Government food intake surveys found the diets of 35%-45% of people over age 60 did not meet average zinc requirements. When zinc sources from both diet and supplements were measured, 20%-25% still had inadequate intakes.
- Current Recommended Dietary Allowances (RDA) for zinc for people over age 19 are 11 mg/day for men and 8 mg/day for women. Due to lowered rates of absorption in older adults, many nutrition scientists believe the RDA for people over 50 should be increased.
- Symptoms of zinc deficiency include frequent infections, hair loss, poor appetite, loss of sense of taste and smell, poor wound healing, and mental lethargy. Many of these symptoms are also associated with other health problems so a thorough medical exam is needed to make a diagnosis.
- People with higher risk for zinc deficiency are those with digestive diseases, malabsorption syndrome, chronic liver or renal disease, sickle cell disease, alcoholics, and vegetarians.
- There are no medical tests to adequately measure zinc status. A dietary assessment is the best tool along with a review of medical history and medication use.
- Zinc toxicity can occur from overuse of dietary supplements and over-the-counter cold remedies. Signs include nausea, vomiting, and diarrhea. The Tolerable Upper Intake for men and women over age 19 is 40 mg/day.