Plasma zinc measures zinc concentration in the plasma (the liquid portion of blood). Zinc is an essential trace mineral required as a cofactor for over 300 enzymes and 2,000 transcription factors involved in immune function, protein synthesis, wound healing, DNA synthesis, antioxidant defence, and taste and smell sensation.
Plasma zinc has significant limitations as a marker of zinc status because it represents only about 0.1% of total body zinc and is tightly regulated within a narrow range. It can appear normal despite significant tissue zinc depletion. Plasma zinc is affected by inflammation, albumin (which carries zinc in plasma), time of day, and fasting status, making interpretation complex.
FAQs
Is plasma zinc an accurate measure of body zinc status?
It has significant limitations. Plasma zinc represents a tiny fraction of total body zinc and is tightly regulated. Inflammation, low albumin, and fasting status all affect it. RBC zinc provides a longer-term measure, and functional tests of zinc-dependent enzymes may better reflect true zinc status.
What are the symptoms of zinc deficiency?
Common symptoms include poor wound healing, recurrent infections, hair loss (particularly diffuse scalp hair loss), altered taste and smell, skin rashes (particularly around body orifices), delayed wound healing, low appetite, and in children, growth failure.
Can a vegetarian or vegan diet cause zinc deficiency?
Plant-based diets are lower in bioavailable zinc because plant zinc is bound to phytates that inhibit absorption. Vegetarians and vegans often need 50% more dietary zinc than omnivores. Regular zinc monitoring is recommended, and supplementation may be beneficial.
Can zinc supplementation be harmful?
Yes. Long-term supplementation above 40 mg/day can impair copper absorption and cause copper deficiency anaemia and neurological symptoms. Zinc supplements at appropriate doses are safe, but higher doses require medical oversight.
