Something to 'Zinc' About
July 5, 2011
This morning I was musing about how difficult it can be to change some practices regardless of the evidence, especially when we memorized them as “facts” back in undergraduate school. Protein and encephalopathy, albumin or prealbumin as markers of nutrition status and zinc supplements and wound healing come to mind.
In the case of zinc it seems especially difficult to change practice based on how often this topic comes up on listservs and other forums. Perhaps clinicians continue to give zinc because there is data that a zinc deficiency will impair wound healing, and zinc is such a seemingly benign and inexpensive nutrient to supplement.
While we want to be able to be able to offer nutrition interventions that will help our patients, the data tells us that zinc supplements do not help with wound healing, unless your patient has an existing zinc deficiency. It is concerning to me that there is also little attention to the potential of nutrients to cause unintended harm, especially when we supplement with supraphysiologic doses without good data.
As an example, there is data that zinc supplements may increase the risk for urinary tract infections for patients in long-term care, and in-vitro experiments have documented that pathogens common to UTI’s thrive in a zinc-rich media (see references below).
Considering what we have learned about the negative effects of supplemental beta-carotene in those at risk for lung cancer, vitamin A as a risk for long bone fractures, that vitamin E actually increases cardiac deaths, and folate as a cancer risk, you would think that the nutrition field in general would by now be much more demanding of good evidence before considering supplements.
Due to the fact that serum zinc is not a good indicator of zinc status, if we suspect that a patient has a zinc deficiency we will treat them for 1-2 weeks, and then stop the supplement to prevent long-term competition with other nutrients or other problems. However, if your patient is zinc deficient, it is likely that there is an issue with multiple nutrients, so most often we provide a multivitamin with minerals to reduce the likihood of creating other nutrient inadequacies from supplementing high doses of selected minerals.
· Johnson AR, Munoz A, Gottlieb JL, et al. High dose zinc increases hospital admissions due to genitourinary complications. J Urol. 2007;177(2):639-43.
· Nielubowicz GR, Smith SN, Mobley HL. Zinc uptake contributes to motility and provides a competitive advantage to Proteus mirabilis during experimental urinary tract infection. Infect Immun. 2010;78(6):2823-33.
“I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.”
- Leo Tolstoy