How is zinc measured in the body?

 Bio chemical assessment of zinc:

Zinc source:

Zinc is the second most abundant trace micronutrient in body after iron. Although required in trace amount, zinc catalysis more than 100 reactions within the body . The main functions of zinc include enzyme activation, proteins, synthesis and regulations of gene expression.

 Zinc is absorbed from small intestine and prolonged low dietary intake result in zinc deficiency. Zinc deficiency is classified as an 11th major risk factor in global disease burden and can result in short stature, reduced sensitivity of taste buds, and impaired functionality of reproductive organs. 

Since the human body does not store zinc, it must be consumed as a part of regular diet. Excessive intake (>10 times of RDA) decrease immunity and can induce copper deficiency .

Importance of Zinc:

Zinc is indispensable to human health. It functions as a cofactor for over 300 enzymes, including those involved in protein synthesis, DNA synthesis, and cell division. Additionally, zinc is critical for immune function, wound healing, taste and smell, and proper growth and development during pregnancy, childhood, and adolescence.

Methods of Assessment:

Biochemical assessment of zinc involves analyzing the zinc concentration in various biological samples such as plasma/serum, erythrocytes, hair, and urine.

Serum/Plasma Zinc: Serum or plasma zinc concentration is the most commonly used biomarker for zinc status assessment. However, it only reflects recent dietary intake and does not provide a clear picture of zinc stores in the body.

Erythrocyte Zinc: Zinc concentration in erythrocytes is considered a better indicator of zinc status as it is less affected by recent dietary intake.

Hair and Urine Zinc: The zinc concentration in hair and urine can also reflect zinc body status but can be influenced by various factors such as hair treatment or renal function.

Zinc-dependent enzymes: Enzymes like alkaline phosphatase and zinc-dependent dehydrogenases can be used to assess zinc status as their activities are influenced by zinc availability.

Challenges in Zinc Assessment:

Assessment of zinc status is complex due to its ubiquitous distribution in the body and its involvement in diverse physiological functions. Additionally, there is no single sensitive and specific biomarker for zinc nutritional status. The concentration of zinc in serum/plasma, the most commonly used indicator, can be influenced by inflammation, stress, time of day, and recent meals.

Recent Advancements:

Newer methods are being developed to accurately assess zinc status. These include the use of isotopic techniques, 'omics' technologies (proteomics, metabolomics, genomics), and functional indicators of zinc status such as the response to zinc supplementation. These advanced methods are contributing to a better understanding of zinc metabolism and its role in health and disease.

Deficiency of zinc;

Zinc deficiency  mainly occurs as a result of inadequate dietary intake ,consumption of cereal based diet (low in zinc),malabsorption and rare genetic disorder.  Cereals being dietary staple contribute major part of energy particularly in developing countries, are low in bioavailable zinc. 

This is core reason of widespread micronutrient malnutrition among rice consuming population. In comparison- to adult, infants and children, pregnant and lactating women and older people are more at risk of zinc deficiency.

Measurement of zinc status 

Following are some of the method used to test the zinc deficiency among humans:

Serum and plasma zinc:

Serum zinc level followed  by conformation through zinc load test is consider as the most reliable zinc diagnosis test. However, since zinc is higher in intracellular fluids than serum, the test may not faithfully reflect the individual's status. 

Therefore, zinc level may fall towards the lower end of the normal range even in the state of zinc deficiency. It is pertinent to mention that serum zinc level may show circadian variation ( higher in the morning and lower in the evening ) depending upon its content in each meal.

 Apart from certain drugs level of serum zinc can also be affected by fasting, stress, renal failure, pregnancy, low albumin concentration and malignancy. Plasma zinc is one of the main laboratory test adopt to test the zinc deficiency. This test normally detect severe deficiency but is limited for marginal cases, since a change in zinc level of plasma is not visible until zinc intake is extremely low.

 Importantly, plasma zinc level might be affected by hypo-or hyperproteinemia, stress, acute infections, time of sampling ( delay after meal ), pregnancy and pernicious anemia.

Urinary zinc test:

Urinary zinc test is slightly unreliable as multiple factors can influence its outcomes i.e. diet, medications and supplementation. The patients should be discourage over the counter medications and multi-vitamin before undergoing test ( upon physician advice )Sample collection from patient receiving contrast media (iodinated or gadolinium based ) must be avoided for at least 72 hours post exposure.

 Likewise, collection from subjects having contrast media coupled with impaired kidney function should be avoided for at least 14 days post - exposure. Normal range is 3.3-21.4 micromol/24 hours.

Conclusion:

Accurate assessment of zinc status is critical for diagnosing and managing zinc deficiency, a public health issue affecting numerous people worldwide. Despite the challenges, advancements in biochemical methods provide promising tools for the improved assessment of zinc status. Continued research in this area is essential to further refine these methods and understand the full extent of zinc's role in human health.

By integrating conventional and advanced biochemical assessment methods, researchers and clinicians can provide a more holistic understanding of zinc status, improving public health outcomes globally.

  Bio chemical assessment of zinc

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What are the main biochemical techniques used to assess zinc levels in the human body?

Why is it crucial to measure serum zinc levels in diagnosing zinc deficiency?

How does the assessment of zinc in hair and nails contribute to understanding an individual's long-term zinc status?

What role does zinc play in enzymatic reactions and how does this knowledge aid in its biochemical assessment?

Can you elaborate on the limitations and challenges faced in the biochemical assessment of zinc levels?

How to assess zinc status?

How is zinc measured in the body?