In addition, which test(s) are the most accurate when it comes to zinc status: 1) serum blood test, 2) zinc taste test, and 3) HTMA (Hair Tissue Mineral Analysis)?
Answer:
Zinc taste test can help identify insufficiency though loss of taste may be due to other reasons. Serum zinc may be normal despite insufficiency due to a variety of factors. RBC and hair zinc may better reflect long-term zinc status.
Loss of taste is not unique to zinc insufficiency and may be due to other factors. These include antifungal and antihypertensive use; upper respiratory and middle ear infections; radiation therapy; and inflammation of associated nerves (Shaikh 2022).
If serum zinc levels are optimal and no other causes of loss of taste are identify, further investigation into zinc status may be conducted including detailed evaluation of zinc intake.
Serum zinc may be within optimal range despite early or mild insufficiency as zinc is mobilized from tissues into circulation in order to maintain serum levels. Therefore, serum zinc levels alone are insufficient for a thorough evaluation. Red blood cell zinc levels may better reflect long-term zinc status as they are not as acutely affected by eating, stress, inflammation, infection, hormone therapy, steroids, or mild zinc deficiency as are serum levels (Noland 2020).
The zinc taste test can help identify zinc insufficiency and correlates with serum zinc levels, sweat-mineral analysis, pregnancy, post-partum serum zinc, post-partum depression, salivary carbonic anhydrase, and frequency of illness (Zdilla 2015).
Hair concentrations of zinc may provide some information about long-term zinc status as levels are generally stable in hair, skin, skeletal, and heart muscle. A low concentration in hair may indicate chronic insufficiency despite normal or optimal serum levels (Han 2016).
A review of signs and symptoms associated with zinc insufficiency would also be warranted though they are not unique to zinc insufficiency. These include diarrhea, malabsorption, loss of appetite, skin rash, hair loss, impaired wound healing, immune insufficiency, decreased heme production, impaired protein synthesis (Gropper 2021), hypertension (Olechnowicz 2018), hypothyroidism (Betsy 2013), stress, inflammation (Noland 2020), and reduced alkaline phosphatase levels (Ray 2017). Low levels of carbonic anhydrase may also be a sign of compromised zinc status. Carbonic anhydrase is the enzyme responsible for interconversion of carbon dioxide and carbonic acid (Lukaski 2005).
Ultimately, assessment of zinc status should include a variety of factors including evaluation of malabsorption or malnutrition; dietary intake and factors such as phytate that can reduce absorption; review of signs and symptoms of zinc insufficiency; and levels of alkaline phosphatase, serum and RBC zinc; and hair mineral levels if available. Other potentially useful measurements of zinc status include sweat mineral analysis, urinary zinc, and fingernail concentrations.
References
Betsy, Ambooken et al. “Zinc deficiency associated with hypothyroidism: an overlooked cause of severe alopecia.” International journal of trichology vol. 5,1 (2013): 40-2. doi:10.4103/0974-7753.114714
Han, Tae Hwan et al. “Hair Zinc Level Analysis and Correlative Micronutrients in Children Presenting with Malnutrition and Poor Growth.” Pediatric gastroenterology, hepatology & nutrition vol. 19,4 (2016): 259-268. doi:10.5223/pghn.2016.19.4.259
Gropper, Sareen S.; Smith, Jack L.; Carr, Timothy P. Advanced Nutrition and Human Metabolism. 8th edition. Wadsworth Publishing Co Inc. 2021.
Lukaski, Henry C. “Low dietary zinc decreases erythrocyte carbonic anhydrase activities and impairs cardiorespiratory function in men during exercise.” The American journal of clinical nutrition vol. 81,5 (2005): 1045-51. doi:10.1093/ajcn/81.5.1045
Noland, Diana, Jeanne A. Drisko, and Leigh Wagner, eds. Integrative and functional medical nutrition therapy: principles and practices. Springer Nature, 2020.
Ray, Chinmaya Sundar, et al. "Low alkaline phosphatase (ALP) in adult population an indicator of zinc (Zn) and magnesium (Mg) deficiency." Current Research in Nutrition and Food Science Journal 5.3 (2017): 347-352.
Shaikh, Fahad H. and Abhinandan Soni. “Physiology, Taste.” StatPearls, StatPearls Publishing, 21 April 2022.
Zdilla, Matthew J et al. “A Taste-intensity Visual Analog Scale: An Improved Zinc Taste-test Protocol.” Integrative medicine (Encinitas, Calif.) vol. 14,2 (2015): 34-8. https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/26770137/