Biomarkers of Nutrition for Development (BOND)—Zinc Review

Abstract

Zinc is required for multiple metabolic processes as a structural, regulatory, or catalytic ion. Cellular, tissue, and whole-body zinc homeostasis is tightly controlled to sustain metabolic functions over a wide range of zinc intakes, making it difficult to assess zinc insufficiency or excess. The BOND (Biomarkers of Nutrition for Development) Zinc Expert Panel recommends 3 measurements for estimating zinc status: dietary zinc intake, plasma zinc concentration (PZC), and height-for-age of growing infants and children. The amount of dietary zinc potentially available for absorption, which requires an estimate of dietary zinc and phytate, can be used to identify individuals and populations at risk of zinc deficiency. PZCs respond to severe dietary zinc restriction and to zinc supplementation; they also change with shifts in whole-body zinc balance and clinical signs of zinc deficiency. PZC cutoffs are available to identify individuals and populations at risk of zinc deficiency. However, there are limitations in using the PZC to assess zinc status. PZCs respond less to additional zinc provided in food than to a supplement administered between meals, there is considerable interindividual variability in PZCs with changes in dietary zinc, and PZCs are influenced by recent meal consumption, the time of day, inflammation, and certain drugs and hormones. Insufficient data are available on hair, urinary, nail, and blood cell zinc responses to changes in dietary zinc to recommend these biomarkers for assessing zinc status. Of the potential functional indicators of zinc, growth is the only one that is recommended. Because pharmacologic zinc doses are unlikely to enhance growth, a growth response to supplemental zinc is interpreted as indicating pre-existing zinc deficiency. Other functional indicators reviewed but not recommended for assessing zinc nutrition in clinical or field settings because of insufficient information are the activity or amounts of zinc-dependent enzymes and proteins and biomarkers of oxidative stress, inflammation, or DNA damage.

Dietary intake and zinc status in amyotrophic lateral sclerosis

“…These were homogenized and a 25 mL sample was stored in a freezer at -20 °C until analysis. All procedures related to manipulation of zinc samples were performed according to international standards for prevention of zinc contamination of the environment (18).…”

Assessing zinc in humans

“…Hair [Zn] therefore reflects the availability of zinc from the blood supply at the time of formation (2). Hair has the advantage of being easily collected and is stable indefinitely if stored appropriately.…”

“…More recently complete review of zinc biomarkers was published in a report by the Biomarkers of Nutrition for Development (BOND), zinc expert panel (2). This review considered both biochemical and functional indicators of zinc status, and classified them into four categories; "recommended", "potential", "emerging" and "not useful".…”

Zinc, Copper and Oxidative stresses in Chronic Pancreatitis

“…Zinc (Zn) and copper (Cu) are essential dietary trace metals. They are type 2 nutrients, i.e., deficiency of these produce multiple non-specific general shifts in metabolism resulting in poor growth or neurocognitive impairments 6,7 . Over 300 metalloenzymes (including anti-oxidants) require Zn as a catalyst, and almost 2500 human transcription factors require Zn to maintain their structural integrity.…”

“…This is manifested in the severe hepatocyte and neuronal injuries in Wilson's Disease where Cu overload occurs due to genetic defects in Cu excretion 7 . In humans, these metals have a limited storage pool, and depend almost exclusively on nutritional intake to meet physiological needs 6,7 .Their blood and tissue levels are tightly regulated either at the level of uptake or excretion, intestinal (Zn) or biliary (Cu) 6,7 . In what may be considered over-simplification, it can be propounded that, within the paradigm of chronic pancreatitis, Zn has considerable anti-oxidant properties while Cu, even in Division of Gastroenterology, School of Digestive and Liver Disease, IPGME&R, Kolkata, India minimally enhanced amounts, can cause serious oxidative damage to acinar cells.…”