Got Zinc?

Posted: 4th August 2013 by Jon in Exercise and Fitness, Nutrition and Performance

lobstersImportance of  Zinc

This is a follow-up piece to the recent ” Got Magnesium” article. I decided to discuss the overall aspect and implications of zinc considering the close association to magnesium. Zinc is also one of the most underrated, underused, and perhaps misunderstood minerals and its use in supplementation. Undoubtedly, the role of zinc within the body serves as a foundation for numerous physiological processes. Zinc is implicated in a wide variety of processes of cellular metabolism, and is required throughout the breakdown of approximately 100 enzymes (IOM 2001). Early reports shown that it serves a crucial function in immune system response (Prasad 1995), protein synthesis, wound healing and immunity, cell division, and DNA synthesis (Prasad 1995). Another key aspect of Zinc is its role in supporting normal growth and development, as well as during youth and pregnancy (Meret 2006). Interestingly enough, Zinc is also essential for a suitable sense of taste and smell (Prasad 1997).

Zinc is probably most notable for its powerful antioxidant properties and its positive impact on hormonal production. Therefore, the importance and awareness of zinc is important for strength and conditioning professionals, lifters, and personal trainers to know concerning the many functional implications within the body, as zinc plays a pivotal role in numerous health and performance outcomes.

Status and Intake

The daily recommend intake for zinc for adult men is 11mg, and 8mg for females. This value only increases slightly for pregnancy (11mg) and lactation (12mg). However, the daily value (seen on nutritional labels) for zinc is 15 mg for adults, although the tolerable upper intake level are 40mg, for both males and females. Unfortunately, food labels are not required to list zinc content unless a food has been fortified with it. Foods providing 20% or more of the DV are considered to be high sources of a nutrient. An interesting fact, oysters contain more zinc per serving than any other food.

However, the majority of Americans obtain most of their zinc from various meats and poultry. Additional quality sources of zinc include beans, nuts, seafood (lobster and crab), whole grains, fortified breakfast cereals, and dairy products (IOM 2001, USDA 2011). However, although whole grains and legumes contain zinc, they are bound to phylates, which inhibits their absorption thus making the zinc inaccessible to the body (IOM 2001,Wise 1995). Some evidence suggests that zinc intakes for older adults might be negligible. Research from Ervin (2002) found that 35%–45% of adults aged 60 or older had low levels of zinc below the estimated average requirement of 6.8 mg/day for elderly females and 9.4 mg/day for elderly males. When the researchers considered intakes from both food and dietary supplements, they reported that 20%–25% of older adults still had insufficient zinc intakes (Ervin 2002).

Deficiency

Although Zinc deficiency does not appear to be as common as magnesium deficiency, it’s still important to address the concern, as certain groups of individuals are at greater risk for zinc deficiency. Overall, zinc deficiency in America is uncommon (IOM 2001). However, those that are zinc deficient usually attributed to inadequate consumption or absorption, higher incidence of loss from the body, or increased requirements for zinc (Prasad 1996, King 2005). One unique symptom of zinc deficiency is abnormalities and altered sense of taste. Decreased concentrations of zinc are characterized by loss of appetite, and weakened immune response. As zinc deficiency worsens, there is evidence of hair loss, delayed sexual maturity, diarrhea, reduced testosterone, testicular shrinkage, and eye and skin lesions (Meret 2006, Wang 2005, Prasad 2004). However, it is important to recognize that many of these symptoms are general and can result from a variety of medical conditions other than zinc deficiency.

There are specific groups of people who are at greater risk for developing zinc deficiency. Early studies have reported that those individuals with gastrointestinal and digestive disorders have a reduced concentrations and absorption of zinc, mainly through loss of the GI tract (Naber 1998, Valberg 1986) Hambridge 1989). Another group of individual at risk for zinc deficiency are alcoholics. Approximately 30%–50% of alcoholics have low zinc levels. Due to the ethanol consumption in the alcohol and in combination with limited food consumed by many alcoholics, this will reduce intestinal absorption and increase urinary zinc output (Prasad 2004).

Vegetarian’s 
are another group of who suffer from zinc deficiency, and may require up to 50% more zinc of the RDA, compared to their normal counterparts. Considering that vegetarians do not consume meat, which constitutes a high amount of zinc, they are more susceptible for zinc deficiency. Vegetarians consume more grains, legumes and plant-based foods, which, as previous mention contain phylates, that inhibit the absorption of zinc (ADA 2003, Hunt 2003).

The standard test for assessing zinc concentration or deficiency is plasma or serum levels. However, this is not a clear and overall representation of whole-body distribution, as highly regulated homeostatic control mechanisms are involved (Meret 2006). Furthermore, the nutritional status of zinc is challenging to adequately measure (IOM 2001, Hunt 2003), mainly due to its distribution throughout the body as a factor of various proteins and nucleic acids (Hambridge 2007). When assessing via a serum test, other contributing factors could cause inaccuracies including stress, diurnal variations, and even fluctuations in meals. It is best to perform a zinc test to in order to measure your levels, and then supplement accordingly.

Zinc Health and Performance

Zinc is also notable for its positive impact on hormonal production, which has serious implication for strength athletes and those involved in training. Recently, Neek et al (2011) reported that when giving trained athletes a zinc supplement for 4-weeks (30g/day) prior to exhaustive exercise resulted in higher post-workout testosterone than the placebo. The authors further noted that zinc increases the conversion rate of androstenedione to testosterone, and with the combination of training, enhanced testosterone production. On a side note, low levels of zinc can result in greater aromatization (greater conversion of testosterone to estrogen), via the increase in estrogen receptors and reduced androgen receptors in men, which is definitely not a good thing. Chang recently reported (2011) that 88 men age 40-60 showed that individuals with normal testosterone levels has greater zinc content compared to those with low testosterone.

Cancer and Immune Function

Having adequate levels of zinc ensures proper immune system function and regulation. Zinc is involved in the nature of many cancers, due to its contribution in cell proliferation. Evidence indicates an association between zinc deficiency to cancers of the colon, breast, ovaries, and prostate (Prasad 2003, Gumulec 2011). Moderate amounts of zinc deficiency can damage macrophage and neutrophil abilities, as well as natural killer cell activity. Zinc is also required for development and activation of T-lymphocytes (Wintergerst 2007, Beck 1997). Some individuals with low zinc levels have shown to have a decreased lymphocyte response to mitogens and other adverse alterations in immune function that may be improved by zinc supplementation (Prasad 2000).

 Zinc and Cognition

Investigations in humans show that many children with ADHD have lower zinc concentration compared to healthy children, as zinc is highly associated with ADHD in children (Dodig 2009). Research completed on 400 children with ADHD found that taking 150mg/day of zinc sulfate improved impaired social behavior and reduced hyperactivity and impulse behavior than a placebo (Billici 2004.) It was also reported that those with higher BMI and decreased fatty acid levels experienced greater improvements in social behavior from taking zinc.

 Zinc and Diabetes

It is known that Zinc deficiency is a common in diabetic patients and metabolic syndrome, as chronic low intake of zinc is associated with the greater risk of diabetes as diabetes also impairs zinc metabolism (Miao 2013). In theory, the use of zinc supplementation should prevent metabolic syndrome, diabetes, and its complications. However, limited available data and differences in methodology do exist.

Zinc is also viewed as an anti-inflammatory agent involved in cardiovascular function. Zinc provides an anti-inflammatory effect by helping to reduce and/or eliminate markers via C-reactive protein, assisting in the maintenance of cell integrity. Recently, Ortega (2012) found that in Spanish school children, there was a direct relationship between low zinc levels, greater body fat, and insulin resistance. Those children who were zinc deficient had poor insulin sensitivity and increased glucose intolerance.

References

1). Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001.

2). Prasad AS. Zinc: an overview. Nutrition 1995;11:93-9.

3). Maret W, Sandstead HH. Zinc requirements and the risks and benefits of zinc supplementation. J Trace Elem Med Biol 2006;20:3-18

4). Prasad AS, Beck FW, Grabowski SM, Kaplan J, Mathog RH. Zinc deficiency: changes in cytokine production and T-cell subpopulations in patients with head and neck cancer and in noncancer subjects. Proc Assoc Am Physicians 1997;109:68-77.

5). U.S. Department of Agriculture, Agricultural Research Service. 2011. USDA National Nutrient Database for Standard Reference, Release 24. Nutrient Data Laboratory Home Page,

6). Wise A. Phytate and zinc bioavailability. Int J Food Sci Nutr 1995;46:53-63.

7). Ervin RB, Kennedy-Stephenson J. Mineral intakes of elderly adult supplement and non-supplement users in the third national health and nutrition examination survey. J Nutr 2002;132:3422-7.

8). Prasad AS. Zinc deficiency in women, infants and children. J Am Coll Nutr 1996;15:113-20.

9). King JC, Cousins RJ. Zinc. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins, RJ, eds. Modern Nutrition in Health and Disease, 10th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2005:271-85.

10). Wang LC, Busbey S. Images in clinical medicine. Acquired acrodermatitis enteropathica. N Engl J Med 2005;352:1121.

11). Prasad AS. Zinc deficiency: its characterization and treatment. Met Ions Biol Syst 2004

12). Naber TH, van den Hamer CJ, Baadenhuysen H, Jansen JB. The value of methods to determine zinc deficiency in patients with Crohn’s disease. Scand J Gastroenterol 1998;33:514-23

13). Valberg LS, Flanagan PR, Kertesz A, Bondy DC. Zinc absorption in inflammatory bowel disease. Dig Dis Sci. 1986 Jul;31(7):724-31.

14). Hambidge KM, Mild zinc deficiency in human subjects. In: Mills CF, ed. Zinc in Human Biology. New York, NY: Springer-Verlag, 1989:281-96.

15). American Dietetic Association, Dietitians of Canada. Position of the American Dietetic Association and Dietitians of Canada: vegetarian diets. J Am Diet Assoc 2003;103:748-65.

16). Hunt JR. Bioavailability of iron, zinc, and other trace minerals from vegetarian diets. Am J Clin Nutr 2003;78 (3 Suppl):633S-9S.

17). Hambidge KM, Krebs NF. Zinc deficiency: a special challenge. J Nutr 2007;137:1101-5

18). Neek, L., Gaeini, A., Choobineh, S. Effect of Zinc and Selenium Supplementation on Serum Testosterone and Plasma Lactate in Cyclist After an Exhaustive Exercise Bout. Biological Trace Element Research. 9 July 2011.

19). Chang, C., Choi, J., Kim, H., Park, S. Correlation Between Serum Testosterone Level and Concentrations of Copper and Zinc in Hair Tissue. Biological Trace Element Research. 14 June 2011

20). Prasad, Ananda. Zinc Deficiency. British Medical Journal. 2003. 326, 409-410.

21). Gumulec, J., Masarik, M., et al. Molecular Mechanisms of Zinc in Prostate Cancer. Clinical Oncology.2011. 24(4), 249-255.

22). Wintergerst ES, Maggini S, Hornig DH. Contribution of selected vitamins and trace elements to immune function. Ann Nutr Metab 2007;51:301-23.

23). Beck FW, Prasad AS, Kaplan J, Fitzgerald JT, Brewer GJ. Changes in cytokine production and T cell subpopulations in experimentally induced zinc-deficient humans. Am J Physiol 1997;272

24). Prasad AS. Effects of zinc deficiency on Th1 and Th2 cytokine shifts. J Infect Dis 2000;182 (Suppl):S62-8.

25). Dodig-Cukovic, K., Dovhang, J., et al. The Role of Zinc in the Treatment of Hyperactivity Disorder in Children. Acta Medica Croatica. 2009. 63(4), 307313.

26). Bilici, M., Yildrim, F., et al. Double-Blind, Placebo-Controlled Study of Zinc Sulfate in the Treatment of Attention Deficit Hyperactivity Disorder. Progress in Neuropsychopharmacology and Biological Psychiatry. 2004. 28(1), 181-190.

27). Miao X, Sun W, Fu Y, Miao L, Cai L. Zinc homeostasis in the metabolic syndrome and diabetes. Front Med. 2013 Mar;7(1):31-52.

28). Ortega, R., Rodriguez, E., et al. Poor Zinc Status is Associated with Increased Risk of Insulin Resistance in Spanish Children. British Journal of Nutrition. 2012. 107, 398-404.

  1. […] in Zinc (Jonathan Mike, a colleague of mine at Elitefts recently published this article on Zinc (Zinc Article), But other common deficiencies include Calcium, Magnesium, Potassium, Iron, Vitamin D, […]

  2. Jason Mitchell says:

    I have been trying to understand the difference between zinc and magnesium’s role when it comes to the cell integrity and DNA synthesis. Which would you say is more important for cell metabolism and DNA synthesis? Or do you think the importance level is about equal? In other words, if someone is lacking in both nutrients, which would have a greater impact on DNA damage? From my understanding, it sounds like zinc is involved a lot more in gene expression, so if that comes before DNA synthesis then I’m wondering if that would give zinc a larger role. But then, it sounds like magnesium has a larger role in enzymatic activity.

  3. […] in Zinc (Jonathan Mike, a colleague of mine at Elitefts recently published this article on Zinc (Zinc Article), But other common deficiencies include Calcium, Magnesium, Potassium, Iron, Vitamin D, […]