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Zinc is an essential trace element present within all bodily tissue and of huge importance for healthy cell division.
Benefits of zinc are numerous: from establishing hormonal balance in the body to stronger immunity.
In addition, zinc is responsible for a number of functions in the human body and helps stimulate the activity of at about 1000 different enzymes.
If we take into consideration zinc benefits our entire body, it is natural to presume this trace element affects thyroid functioning as well.
How does zinc affect the thyroid?
We will elaborate its impact on this gland further in this article.
Zinc and Hypothyroidism: Effect on T3, T4, TSH
Zinc may be one of the most versatile supplements for thyroid function.
While some vitamins (Vitamin C, D, etc.) , minerals (such as Magnesium, Selenium, etc), and other nutrients are only effective for one aspect of thyroid function, zinc uses a multifaceted approach to thyroid health.
For instance, zinc is essential for healthy levels of thyroid hormone triiodothyronine (T3).
One study found that zinc-deficient rats had lower T3 and thyroxine levels compared to healthy controls.
In addition, hypothalamic thyrotropin-releasing hormone content was reduced in the zinc-deficient animals compared to their healthy counterparts.
Scientists concluded their research explaining that zinc deficiency may impair extrathyroidal production of T3[i].
A team of researchers at the University of Pennsylvania carried out a study whose primary objective was to assess the effects of zinc supplementation on T3, T4, and thyroid-stimulating hormone (TSH) concentrations as well as resting metabolic rate.
They discovered that zinc plays an essential role in concentrations of T4, T3, and resting metabolic rate.
In fact, zinc supplementation proved to be effective in increasing levels of these hormones[ii] in the body.
Furthermore, a study from the Biological Trace Element Research found that levels of T3, T4, TSH were brought close to their normal levels after zinc supplementation.
These results indicate the positive role of zinc in thyroid hormone metabolism[iii].
The above-mentioned examples are important for depicting the relationship between zinc and thyroid.
Your thyroid produces T3 and T4 hormones, which regulate the body’s temperature, heart rate, and metabolism.
In the case of hypothyroidism, the thyroid gland is underactive and production of these hormones declines.
Benefits of zinc for thyroid hormones don’t stop at increasing levels of T3, T4, and TSH.
Evidence shows that zinc supplementation improves conversion of T4 to T3[iv].
According to the CDC, about 17.3% world’s population is deficient in this mineral, but up to 30% people are at risk of developing it[v].
Zinc deficiency is more common in developing countries in South, Southeast Asia, Sub-Saharan and Central Africa[vi].
Of course, this doesn’t mean you can’t develop this mineral deficiency if you live elsewhere.
Zinc deficiency was first discovered in Iranian man back in 1961 and since then, it has been considered as an important malnutrition problem worldwide.
The problem is more prevalent in areas with high cereal and low animal food intake.
Symptoms of zinc deficiency depend on the severity of condition i.e. to what extent a patient is deficient in the mineral.
Organ systems known to be affected by this health issue are epidermal, gastrointestinal, central nervous, immune, skeletal, and reproductive[vii].
When the body has an insufficient amount of the mineral, it is unable to produce new, healthy cells. Common signs and symptoms of zinc deficiency include:
- Behavioral problems
- Impaired memory and overall cognitive functioning
- Impairment in physical growth and development
- Lack of alertness
- Loss of appetite
- Open sores on the skin
- Reduced sense of smell and taste
- Unexplained weight loss
- Wounds heal slowly
Insufficient levels of zinc in the body can affect your thyroid too.
As seen above, lower levels of the mineral affect the production of thyroid hormones.
Evidence shows that clinical signs of zinc deficiency or thyroid alteration revolve primarily around growth rate.
Changes in organ and glandular weights and serum thyrotropin levels reflect alterations in thyroid hormone concentration.
Studies show that zinc deficiency is associated with enhanced expression of hepatic thyroxine-5’-monodeiodinase activity[viii].
Thyroxine-5’-monodeiodinase is an enzyme that catalyzes the inactivation of thyroid hormone.
In a study of healthy young men who were fed with low-zinc diet for 54 days, there was a trend toward a decrease in thyroid hormone concentration.
The major decrease in T4 should have been followed by a reciprocal increase in TSH as a part of the healthy feedback control of thyroid hormones.
That said, zinc deficiency is also linked with the downward trend in TSH, thus suggesting an effect at the level of either pituitary or hypothalamus.
The decrease in TSH may have been secondary to thyrotropin-releasing hormone (TRH) concentration.
Typically, this particular hormone is released by the hypothalamus and works to stimulate the pituitary release of TSH.
Therefore, decrease in TRH levels lead to reduced concentration of TSH and indirectly decrease the production and levels of T4[ix].
Zinc deficiency also affects one common symptom of hypothyroidism – hair loss.
A research whose findings were published in the International Journal of Trichology shows that zinc is required for synthesis of thyroid hormones and, conversely, these hormones are essential for the absorption of the mineral.
Just like zinc can lower levels of thyroid hormones, hypothyroidism can induce zinc deficiency as well. This particular study presents a case of a patient with symptoms of hypothyroidism including diffuse hair loss.
Scientists found that hair loss attributed to hypothyroidism may not improve with thyroxine unless zinc supplementation is added[x].
Zinc and Memory
Impaired memory is a common symptom of hypothyroidism and zinc supplementation can help tackle this problem.
Studies show that several measures of visual memory, working memory, attention, and reaction time improve with zinc supplementation[xi].
Dietary zinc deficiency is strongly linked to memory impairment, but underlying mechanisms are still not clear.
Evidence shows that zinc modulates synaptic plasticity (the ability of synapses to strengthen over time in response to increases or decreases in their activity).
The ability of the mineral to influence both ion channels and synaptic plasticity predicts that zinc has a major impact on learning and memory[xii].
While zinc is beneficial for sharper memory, excessive amounts can do the opposite.
A study whose findings were published in the PLoS One discovered that synaptic zinc plays an important role in hippocampus-dependent learning and memory, but high dose zinc supplementation induces zinc deficiency which further impairs memory and learning[xiii].
Mineral supplementation often gives us a false sense of security i.e. we go by the logic it’s good for our health and assume the higher the doses, the better results will occur.
That’s not the case!
These findings support benefits of zinc for memory but within normal dosages, meaning you should stick to the recommended dose or the amount suggested by the doctor.
Zinc and Hyperthyroidism
Evidence suggests that individuals with hyperthyroidism have higher than normal urinary excretion of zinc[xiv].
High consumption of zinc can contribute to hyperthyroidism or Graves’ disease due to the fact that zinc acts as a stimulator to the thyroid. In instances of hyperthyroidism, patients have abnormally high production of thyroid hormones and high intake of zinc enhances it even more.
While zinc levels are high, copper levels decrease; this is important to bear in mind because copper suppresses production of thyroid hormones.
Copper and zinc work in a seesaw relationship i.e. when levels of one mineral increase the amount of other mineral declines.
Signs of zinc and copper imbalance include:
- Age-related macular degeneration
- Emotional disturbances
- Frequent panic attacks
- Gastrointestinal problems such as diarrhea
- High rate of chronic infections and sickness
- Mental lethargy or chronic fatigue
- Night blindness
- Reduced appetite and weight loss
- Skin problems like roughness and blisters
- Slow recovery rate from healing ulcers, wounds
Zinc and Immune System
Thyroid health and immune system are deeply connected to one another.
Cells of the immune system are strongly associated with “the regulation of thyroid hormone activity in normal physiological conditions and during times of immunological stress,” according to this research study. [xv]
Even though the underlying mechanism of this relationship is poorly understood, evidence reveals it reflects “a process of local intrathyroidal synthesis of TSH mediated by bone marrow cells that traffic to your thyroid gland.” [xvi]
In other words, Zinc has a direct effect on TSH and by extension, the thyroid as well as the immune system of our bodies.
According to another study, the bone marrow cell population has the potential to micro-regulate thyroid hormone secretion leading to major changes “in metabolic activity, that aren’t dependent on pituitary TSH output.”[xvii]
The relationship between thyroid hormones and immune cells is complicated, but growing body of evidence confirms that T3 and T4 may module immune system responses through both genomic and non-genomic mechanisms[xviii].
Zinc participates in numerous processes in your body and the immune system is one of them.
Studies show this mineral decreases markers of oxidative stress and generation of pro-inflammatory cytokines in both young adults and elderly individuals[xix].
According to several research studies, this mineral affects multiple aspects of the immune system, and it is crucial for “normal development and function of cell-mediating innate immunity, neutrophils, and natural killer cells.”
Bearing in mind that zinc is an intracellular signaling molecule, it has a vital role in cell-mediated immune functions and oxidative stress.
Plus, zinc has anti-inflammatory properties[xx] which protect our body from infections, and many diseases and health conditions.
Recommended daily zinc intake
The reality is that we rarely stick to the recommended daily amounts of different nutrients and zinc is not an exception. Intake of zinc doesn’t yield expected benefits if the consumption is insufficient.
According to the National Institutes of Health suggested daily value of zinc is[xxi]:
- 0-6 months – 2mg for boys and girls
- 7-12 months – 3mg for boys and girls
- 1-3 years – 3mg for boys and girls
- 4-8 years – 5mg for boys and girls
- 9-13 years – 8mg for boys and girls
- 14-18 years – 11mg for boys and 9mg for girls
- 19+ years – 11mg for males and 8mg for female
Sources of zinc
Unlike some other nutrients, it is entirely possible to obtain recommended daily doses of zinc through diet.
Below, you can see the list of foods that are great sources of this mineral:
- Chickpeas and legumes
- Cocoa powder
- Fortified breakfast cereals
- Grass-fed beef
- Kefir or yogurt
- Pumpkin seeds
- Whole grains
If your diet doesn’t allow you to get necessary dose of zinc, alternatives are supplementation with thyroid supplements or other natural methods of re-balancing thyroid hormone.
Consulting your doctor before purchasing zinc (or any other) supplements is always a good idea.
Zinc is a mineral that takes part in a multitude of health processes in the body.
The mineral is essential for cell functioning, immune system, reproductive health, and affects thyroid function as well.
Low levels of zinc affect production of thyroid hormones which has a major impact on hypothyroidism patients.
[i] Morley JE, Gordon J, Hershman JM. Zinc deficiency, chronic starvation, and hypothalamic-pituitary-thyroid function. American Journal of Clinical Nutrition. August 1980, vol. 33 no. 8, 1767-1770 http://ajcn.nutrition.org/content/33/8/1767.short
[ii] Maxwell C, Volpe SL. Effect of zinc supplementation on thyroid hormone function. Annals of Nutrition and Metabolism June 2007;51:188-194. Doi: 10.1159/000103324 https://www.karger.com/article/Abstract/103324
[iii] Pathak R, Dhawan D, Pathak A. Effect of zinc supplementation on the status of thyroid hormones and Na, K, and Ca levels in blood following ethanol feeding. Biological Trace Element Research May 2011, vol. 140 no.2, 208-214. Doi: 10.1007/s12011-010-8691-4 https://link.springer.com/article/10.1007/s12011-010-8691-4
[iv] Fujimoto S, Indo Y, Higashi A, et al. Conversion of thyroxine into triidothyronine in zinc deficient rat liver. Journal of Pediatric Gastroenterology and Nutrition 1986 Sep-Oct;5(5):799-805 https://www.ncbi.nlm.nih.gov/pubmed/3761111
[v] Micronutrient facts, CDC https://www.cdc.gov/immpact/micronutrients/index.html
[vi] Wessells KR, Brown KH. Estimating the Global Prevalence of Zinc Deficiency: Results Based on Zinc Availability in National Food Supplies and the Prevalence of Stunting. Bhutta ZA, ed. PLoS ONE. 2012;7(11):e50568. doi:10.1371/journal.pone.0050568. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3510072/
[vii] Roohani N, Hurrell R, Kelishadi R, Schulin R. Zinc and its importance for human health: An integrative review. Journal of Research in Medical Sciences : The Official Journal of Isfahan University of Medical Sciences. 2013;18(2):144-157. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3724376/
[ix] Wada L, King JC. Effect of low zinc intakes on basal metabolic rate, thyroid hormones, and protein utilization in adult men. Journal of Nutrition 1987, 116:1045-1053 https://www.researchgate.net/publication/19439136_Effect_of_low_zinc_intakes_on_basal_metabolic_rate_thyroid_hormones_and_protein_utilization_in_adult_men
[x] Betsy A, Binitha M, Sarita S. Zinc Deficiency Associated with Hypothyroidism: An Overlooked Cause of Severe Alopecia. International Journal of Trichology. 2013;5(1):40-42. doi:10.4103/0974-7753.114714. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3746228/
[xi] Maylor EA, Simpson EE, Secker DL, et al. Effects of zinc supplementation on cognitive function in healthy middle-aged and older adults: the ZENITH study. British Journal of Nutrition 2006 Oct;96(4):752-60 https://www.ncbi.nlm.nih.gov/pubmed/17010236
[xii] Mott DD, Dingledine R. Unraveling the role of zinc in memory. Proceedings of the National Academy of Sciences of the United States of America February 2011, vol. 108 no. 8, 3103-3104. Doi: 10.1073/pnas.1100323108 http://www.pnas.org/content/108/8/3103.full
[xiii] Yang Y, Jing X-P, Zhang S-P, et al. High Dose Zinc Supplementation Induces Hippocampal Zinc Deficiency and Memory Impairment with Inhibition of BDNF Signaling. Yan R, ed. PLoS ONE. 2013;8(1):e55384. doi:10.1371/journal.pone.0055384. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3561272/
[xiv] Aihara K, Nishi Y, Hatano S, et al. Zinc, copper, manganese, and selenium metabolism in thyroid disease. American Journal of Clinical Nutrition July 1984, vol. 40 no. 1, 26-35 http://ajcn.nutrition.org/content/40/1/26
[xviii] De Vito P, Incerpi S, Pedersen JZ, et al. Thyroid hormones as modulators of immune activities at cellular level. Thyroid 2011 Aug;21(8):879-90. Doi: 10.1089/thy.2010.0429 https://www.ncbi.nlm.nih.gov/pubmed/21745103
[xix] Prasad AS. Zinc in Human Health: Effect of Zinc on Immune Cells. Molecular Medicine. 2008;14(5-6):353-357. doi:10.2119/2008-00033.Prasad. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2277319/
[xx] Prasad AS. Zinc: role in immunity, oxidative stress, and chronic inflammation. Current Opinion in Clinical Nutrition and Metabolic Care 2009 Nov;12(6):646-52. Doi: 10.1097/MCO.0b013e3283312956 https://www.ncbi.nlm.nih.gov/pubmed/19710611
[xxi] Zinc, National Institutes of Health https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/