Zinc is one of the most important minerals and makes approximately 300 enzymes, which are associated with various metabolic processes, including the synthesis of the nucleic acids RNA and DNA. These enzymes act as a catalyst where they allow certain chemical reactions to take place much faster than they normally would. Zinc is a part of superoxide dismutase family, which is one of the most powerful enzymes with anti-oxidation capabilities that protect the cells from free radicals. It is highly concentrated in our bones, the pancreas, kidneys, liver, and retina. Zinc is also required for normal growth and immunity. It is required for proper function of red and white blood cells. The body has a sophisticated system for keeping zinc in a state of harmony that promotes the optimal function of the cells. Zinc works synergistically with many other vitamins or minerals such as A, C, B2, B6, B12, magnesium, and chromium to help improve immune function as well as energy production in the Krebs cycle.
Several trace elements are reported to be associated with hormonal changes during menstrual cycle. Zinc has a critical role in the opiate receptor binding within the central nervous system supporting the regulation of progesterone and prolactin activity. Studies have shown that levels of endometrial zinc during the luteal phase are increased compared to the follicular phase. Zinc is temporarily removed from the plasma and taken up by endometrial tissue during the luteal phase to regulate progesterone and estradiol binding receptors. Estrogen increases the sodium/potassium ratio prior to ovulation, which decreases zinc and raises copper levels. Even testosterone is dependent upon zinc. Clinical studies have shown that adult men with decreased zinc levels will have low testosterone because Leydig cell synthesis is very dependent upon adequate dietary zinc.
A convenient and reliable zinc assessment tool is needed to identify people who may be at risk of zinc deficiency and as an objective guidepost to determine the need for initiation of zinc supplementation or zinc fortification of the food supply. Zinc’s interrelation with other minerals like copper and iron can be very complex at times. It functions in delicate patterns throughout the body, of which we do not fully understand. Therefore, when working towards a state of nutritional balance, it is important to do so slowly and collaboratively, to get the full support that we need.
This is the simplest way of assessing zinc status, however many dietitians or nutritionist do not use this test because of too many inaccuracies. They include hormonal variation, fluctuations after meals, stress, pregnancy, certain malignancies, renal failure, low albumin and fasting.
This is the main lab test done by many physicians or nutritionist to establish zinc deficiency first, but if the plasma reveals low levels, further testing may be needed to determine accuracy. Although, it may be decent at picking up major deficiencies, it is quite insensitive for detecting low or marginal zinc levels, which many people are affected by today.
The reason for this is a change in plasma zinc does not occur until zinc intake is extremely low. Some people develop noticeable symptoms with marginally low zinc deficiencies, while others do not. This would include weight loss, abnormal growth, low testosterone, skin disorders-acne, blindness, anemia, lethargy, impaired wound healing, and loss of appetite.
There are other biomarkers for zinc status that could determine mild to moderate deficiencies such as whole red blood mineral analysis, 24 hour urine, serum alkaline phosphatase, retinol binding protein, lactate dehydrogenase, zinc taste test, and hair mineral analysis.
Red Blood Cell Mineral Analysis
The red blood cell analysis levels reflect the intra- and extracellular mineral concentration, whereas, plasma or serum levels indicate extracellular levels only. It is a powerful tool to help diagnose the causes of fatigue, anemia, dermatitis, headaches, abnormal blood pressure, depression, muscle twitches, and other symptoms undetected by the standard metabolic blood profile. Also, CDC, EPA and other regulating agencies have deemed whole red blood analysis to be the correct specimen for assessing current mineral status as well as toxicities. Some elements can accumulate in tissues causing toxic effects. The red blood cell mineral analysis provides a more accurate window into the cellular status of most minerals. In comparison, the standard serum or plasma analysis of such minerals as zinc or magnesium provides less than 1% of the level, making this specific test the gold standard for reliable and consistent measurements of essential minerals. Since the average lifetime of red blood cells is about 120 days, the results reflect an average over the past 4 months.
24-Hour Urinary Zinc
This test can be an unreliable test if done alone because low amounts may indicate zinc deficiency, but the results can be influenced by other factors. Zinc chelates to other substances, like proteins, and if an excess of those are being excreted, zinc will be as well. During malabsorption or catabolic states, (i.e. steroid usage) large amounts of zinc may be released from tissues and excreted in the urine. It is best to use the 24-hour urine together with other testing such as plasma zinc, serum alkaline phosphatase, and retinol binding protein to create a more accurate diagnosis.
Serum Alkaline Phosphatase Test
Serum alkaline phosphatase is a good marker for zinc, because this enzyme contains zinc and a low activity is indicative with a mild to moderate zinc deficiency. Many dietitians used this test regularly with their hospital patients along with plasma zinc and retinol binding protein.
Retinol Binding Protein
A relative zinc deficiency is commonly associated with low plasma concentrations of vitamin A, even when hepatic vitamin A stores are normal, suggesting there is a defect in the mobilization of vitamin A rather than in its absorption. Zinc deficiency can depress the synthesis of retinol-binding protein (RBP) in the liver, which is a carrier protein that binds retinol. So this would be another good marker for zinc status as well.
Measurements of plasma lactate dehydrogenase and plasma ribonuclease appeared to show promise as possible zinc-dependent biomarkers. Lactate Dehydrogenase (LDH) is a zinc containing enzyme, so a decrease in its activity may be a direct reflection of low zinc status. Lactate dehydrogenase (LDH) is an animal or plant enzyme, but also present in microorganisms such as lactic acid bacteria. In humans, lactate dehydrogenase helps cells convert glucose into energy in the absence of oxygen, a process known as anaerobic respiration. Even though LDH acts mainly as a backup for energy production when oxygen is low, it is an important marker for tissue damage as well. The enzyme is found in many tissues and organs through the body.
Prolactin and Testosterone Levels
Elevated prolactin levels partially blocks dopamine reducing zinc and testosterone levels. This rise in prolactin decreases zinc and alters the expression of genes involved in regulatory pathways in the pituitary gland. Actually, endocrinologists already test prolactin levels with males to determine why testosterone levels are low. Serum testosterone concentrations were significantly correlated with cellular zinc concentrations in several cross-sectional studies.
Leukocyte (WBC) zinc content correlates well with muscle zinc content and so this may offer an improved indication of zinc status. However, this test requires a large sample of blood, which needs careful handling soon after collection.
Hair Mineral Analysis Test
When our hair grows out minerals are constantly being deposited, so the hair mineral analysis would be a great test to detect zinc deficiencies or toxicities. Although the hair is dead, the minerals remain as the hair continues to grow out. A sample of hair, cut close to the scalp, provides information about the mineral activity in the hair that took place over the past three to four months, depending on the rate of hair growth.
Also, hair tissue mineral analysis is considered a standard test used around the world for the biological monitoring of trace elements and toxic metals in humans or animals species. The same technology is used for soil and rock testing to detect mineral levels. Certain chemicals or supplements should be removed for a period of time such as multivitamins, hair products like dandruff shampoos and hair treatments that involve coloring. If these are removed for approximately 8 weeks, then testing may be more accurate and beneficial.
Using the sodium-potassium ratio in a hair analysis is one way to quantify the need for extra zinc. As a rule, the “higher” the Na/K ratio above about 3/1, the more zinc is given; usually because it lowers sodium levels. The amount varies from 40mg daily for 3-6 months when the Na/K ratio is above about 16. This is recommended under the guidance of a physician or dietitian/nutritionist because zinc can be toxic at higher levels and act as an antagonist to other important minerals.
The Oral Zinc Assay
Also, the oral zinc taste test could be a guide to determine if you have sufficient zinc levels. This is a simple taste test reported in the Medical Journal, called “The Lancet.” If you have sufficient zinc levels, the oral zinc assay will taste bitter. If you are deficient in zinc, it will taste more like water. Liquid zinc sulfate must be used only! You may find this liquid zinc sulfate online; however, I have used Radiant Life and Total Health Services, and Design for Health called the Zinc Challenge.
1) Optimal zinc levels– An immediate, unpleasant, obviously adverse taste, at which the patient normally grimaces.
2) Adequate Zinc Levels– A definite, but not strongly unpleasant taste is noted immediately and tends to intensify with time.
3) Moderate Zinc– Deficient-No taste noted initially, but develops in 10-15 seconds.
4) Very Zinc Deficient-Tasteless or “tastes like water”.
Use only “Purified” water (distilled water) as the base in the Zinc Assay. The use of purified water is critical since using tap or partially (filtered) water may contain impurities which alter the taste. Some zinc challenge kits are premixed so there is no need to add purified water.
Excessive zinc can inhibit the absorption of the other minerals or vitamins such as copper, niacin, calcium, phosphorus, potassium, manganese, choline, and selenium. Too much zinc can have serious consequences on innate and adaptive immune system. Adults who take over 40mg of zinc per day, longer than 12 weeks may develop toxic effects, which have been associated with low copper status, altered iron function, severe fatigue, and decreased levels of high-density lipoproteins, (HDL the good cholesterol). Other major symptoms can include nausea, vomiting, ovarian cysts, diarrhea, metallic taste, epigastric pain, lethargy, and increased risk in certain cancers.
Normally, it is recommended to take 1mg of copper for every 15mg of zinc. When large dosages are given for long periods it has been noted to increasing susceptibility to autoimmune reactions, in part by, decreasing manganese and copper. Also, several studies have shown that a moderate to severe copper deficiency will cause a sudden drop in Dhea by 50%. Lack of copper has many negative ramifications in the body as well.
Zinc deficiency can reduce cellular immunity (TH-1) within the adaptive immune system. The effects are complex because they occur on many levels, and involve the expression of several hundred genes. Zinc participates in the absorption, mobilization, transport, and metabolism of several micronutrients, most likely through its involvement in protein synthesis and cellular enzyme functions. A common finding with zinc deficiency is low plasma concentrations of vitamin A, even when hepatic vitamin A stores are normal. Zinc is a component of retinol-binding protein, a protein necessary for transporting vitamin A out of the liver and into the blood. Zinc is also required for the enzyme that converts retinol (vitamin A) to retinal. This is one reason why some people cannot restore their night vision with just vitamin A alone. Zinc deficiency can result in abnormal dark adaptation or night blindness, a symptom primarily of vitamin A deficiency.
Low zinc levels are often seen in the elderly, alcoholics, autism, acne, sickle cell anemia, anorexia, ulcerative colitis, diabetes mellitus, attention deficit hyperactivity disorder, celiac disease, pancreatic insufficiency, and gastroparesis. Zinc deficiency has also been implicated as a factor with birth defects such as low birth weight, impaired learning, as well as delayed sexual development. Other major deficiency symptoms may include low white blood count, poor nail growth, vitiligo, stretch marks, weight loss, lack of taste or smell, growth failure, frequent infections, poor wound healing, acne, eczema, atopic dermatitis, psoriasis, hair loss, absence of menstrual period, cataracts, premature aging, and depression. Generally speaking, zinc supplementation should be approached with caution in marginal deficiency conditions, which usually only require smaller amounts of zinc supplementation to produce a favorable response.
Food Sources of Zinc
Since zinc cannot be stored and so, we must rely on foods such as eggs, beef, lamb, and poultry as our optimum food sources. The dark meat of chicken will have more zinc than the white, (chicken breast). Also, oysters contain more zinc than any other food, (87-182mg). The zinc in meat is more bioavailable than plant sources and the ratio of zinc to copper is much higher, providing a buffer for other foods higher in their ratio of copper.
The fruits highest in zinc included avocados, blackberries, pomegranates, dates and raspberries. Seeds tend to have a higher amount of zinc. Seeds that have a higher ratio of zinc/copper are pumpkin seeds, squash seeds, watermelon and sesame seeds. There is a great nutrient search tool online where you can look up the ratio of vitamin/mineral content of many different food groups.
Phytates in nuts, grain, seeds, and beans represents a serious problem in our diet today. This problem exists because we have lost touch with how to properly prepare these foods, which require soaking. Phytic acid is the principal storage form of phosphorus in many plant tissues. It chelates zinc and other important minerals, but also inhibits enzymes that we need to digest our food, including pepsin, amylase, and trypsin. However, adding a broad spectrum digestive enzyme will improve absorption.
Also, vegetarians may need as much as 35% more zinc than non-vegetarians because of the lower absorption of zinc from plant foods.
Different Brands of Zinc
Zinc monomethionine or zinc picolinate are the best bioavailable forms because they are both absorbed better by the intestines and used by the body’s cells more efficiently. Both forms are chelated, meaning the zinc atom is bound to another molecule. It has been shown in several studies that chelated zinc may easily pass through the intestinal wall for better absorption. The main difference between zinc monomethionine and zinc picolinate is the type of chelation molecule. Zinc Aspartate, as with many chelated minerals, is highly bioavailable and is popular because of its gentleness on the gastrointestinal (GI) tract.
There is a formula called ZMA with zinc monomethionine, magnesium aspartate, and B6, which is a dietary supplement utilized by many bodybuilders or athletes. It has been shown in a couple of studies to increase muscle strength and mass due to zinc’s known ability to increase testosterone levels indirectly by inhibiting the enzyme aromatase.
The recommended daily allowance is 8-12 mg/day for adult women and men, however, many nutritionists believe this is too low due to certain foods or drugs inhibiting absorption. Nevertheless, depending on the person’s health status, he or she may need to temporarily increase anywhere from 15-30mg in addition with copper. So despite the physiological and clinical importance of this trace element, balancing this mineral with other trace minerals is not as easy as many claim. Many considerations should be taken into account when formulating your own dietary recommendations, since interactions among other nutrients may determine their bioavailability.
On a more intricate level, a deficiency in one mineral often creates a surplus in another as the body makes internal modifications in an attempt to self-regulate. It can be very challenging to rectify any mineral imbalances once it has reached the cellular level and by then, some damage has already taken place.
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