Table of Contents
- 1 Role of vitamin A
- 2 Vitamin A and the Thyroid
- 3 How much vitamin A to consume?
- 4 Conclusion
- 5 References
Vitamins are considered essential nutrients. They work together with minerals and other important nutrients to support our overall health and wellbeing.
Vitamins perform hundreds of functions thus explaining why a deficiency in some of these micronutrients causes a number of side effects.
In previous articles, we discussed the role of different vitamins in thyroid health and briefly mentioned vitamin A, but in this post, we’re going to take a closer look at the influence of this particular micronutrient on thyroid function.
Role of vitamin A
Vitamin A belongs to the group of fat-soluble vitamins meaning in order to be digested in a human body it requires dietary fats, lipids, or oils. The vitamin is involved in the immune function, reproduction, vision, and cellular communication.
In addition, vitamin A supports cell growth and differentiation thus playing an essential role in normal function and maintenance of heart, kidneys, lungs, and other organs.
It’s important to mention that vitamin A also functions as an antioxidant that neutralizes free radicals and prevents oxidative stress and damage it would cause. In fact, antioxidant properties of this micronutrient are the biggest reason why many anti-aging products contain it in their formula.
While many benefits of vitamin A are well-known, its role in thyroid function isn’t overly discussed.
Let’s change that!
Vitamin A and the Thyroid
Two most common conditions affecting the butterfly-shaped gland are hyper- and hypothyroidism. Hypothyroidism is a common condition indicated by underactive thyroid gland or insufficient production of T3 and T4 hormones while hyperthyroidism is characterized by overproduction of these hormones.
Many vitamins and minerals are involved in thyroid function and hypo- or hyperthyroidism indirectly or directly, and vitamin A is one of them.
Thyroid hormones vital for beta-carotene conversion
The precursor of vitamin A is called beta-carotene which is also a pigment that gives carrots their vibrant orange color. Beta-carotene is a potent antioxidant that our body needs to remain healthy. Basically, the body converts beta-carotene into vitamin A.
The conversion and absorption of this compound take 6 to 7 hours after ingestion. About 1/3 of beta-carotene in food is converted to vitamin A. This is where your thyroid steps in. Thyroxine or T4 hormone stimulates the conversion of beta-carotene into a usable nutrient.
Without proper function of the thyroid, the body can’t get sufficient amount of vitamin A. This explains why some hypothyroid patients are deficient in this micronutrient. Not only can inadequate thyroid function lead to vitamin A deficiency, but insufficient intake of this micronutrient can contribute to hypothyroidism.
Vitamin A may prevent hypothyroidism
As seen above, thyroid hormone T4 is important for conversion of beta-carotene into vitamin A and insufficient consumption of this micronutrient could lead to hypothyroidism. Therefore, it is easy to conclude that vitamin
A supplementation (or sufficient consumption) prevents this common thyroid disorder. Although data on this subject is limited due to lack of studies, current evidence confirms the importance of vitamin A in the prevention of hypothyroidism.
Morely J.E. et al investigated the relationship of thyroid hormones with vitamin A and zinc nutritional status in 62 clinically stable patients with hepatic and gastrointestinal disorders. Results showed that vitamin A therapy in patients with documented deficiency in this micronutrient produced an increase in T3 and T4.
Scientists also discovered that supplementation in persons with sufficient vitamin A levels produced a transient decrease in T3 and T4 after one week, but thyroid function restored to normal after the second week.
In other words, the study found a causal relationship between the pathogenesis of impaired metabolism of vitamin A and decline in T3 levels.
The association of inadequate vitamin A metabolism and lower T3 could be due to the impaired enzymatic conversion of T4 to T3 or through interference with the entry of T4 into tissues.
Farhangi M. A. et al explored the influence of vitamin A supplementation on thyroid function of obese women. For this purpose, they enrolled 84 healthy women ages 17-50. Of these, 56 women were obese and they were divided into two groups where they either received vitamin A supplement or placebo. Non-obese women received vitamin A only.
Then, scientists measured TSH, T3, T4, RBP (retinol-binding protein), and other parameters at the onset of the study and four months later.
Supplementation with vitamin A caused a significant decrease in TSH in both obese and non-obese ladies. Levels of T3 increased, but right after the treatment when supplementation was over T4 levels dropped.
These findings led to a conclusion that regular supplementation with vitamin A reduces the risk of hypothyroidism in premenopausal women.
Vitamin A supplementation may prevent goiter
Zimmermann et al. carried out a study to inspect effects of vitamin A deficiency and supplementation on thyroid function in goitrous children and made interesting discoveries. Vitamin A deficiency was a strong predictor of greater thyroid volume and a higher concentration of TSH and thyroglobulin.
In iodine deficiency disorder (IDD) supplementation with vitamin A improves iodine efficacy and reduces goiter rates. Goiter is swelling in the neck resulting from enlarged thyroid gland it can be a consequence of both hyper- and hypothyroidism. A vast majority of goiter cases are caused by iodine deficiency.
Speaking of iodine deficiency, Brossaud J. et al explained that derivatives of Vitamin A called retinoids interfere with iodine metabolism and deficiency in vitamin A aggravates thyroid function caused by iodine-deficient diets.
Symptoms of vitamin A deficiency include:
- Poor eye health
- Dry, scaly skin
- Thickening of the skin
- Respiratory infections due to weakened immune system
Inflammation can be defined as a process wherein the white blood cells and substances they produce protect us from invaders, bacteria, and other potential dangers. Basically, inflammation is the body’s way to defend itself and promote wound healing. That said, chronic or persistent inflammation is an underlying cause of numerous health problems including those affecting thyroid.
Savas E. et al found significant changes in the levels of inflammation markers in patients with hypothyroidism, hyperthyroidism, autoimmune, and non-autoimmune disorders affecting the gland. Therefore, scientists concluded that inflammation plays a vital role in the pathogenesis of thyroid dysfunctions regardless of the type of condition affecting the gland.
A growing body of evidence confirms that vitamin A has a role as an anti-inflammatory agent and supplementation with this micronutrient is beneficial in a number of inflammatory conditions. What’s more, vitamin A deficiency can induce inflammation and aggravates existing inflammatory state.
Bearing in mind that thyroid disorders are associated with inflammation and vitamin A ameliorates it, we witness yet another potential effect of this important micronutrient for thyroid health and function.
Thyroid hormones play a significant role in reactive oxygen species (ROS) production due to their potential to speed up basal metabolism and change respiratory rate in mitochondria, Villanueva I. et al explained. In addition, thyroid hormones also affect the cell antioxidant mechanisms in different ways.
As a result, they create a situation whose outcome is difficult to predict. The relationship between thyroid hormones and oxidative stress is complicated, but the generally accepted fact is that hyperthyroidism induces oxidative stress while hypothyroidism results in mild oxidative stress.
Since thyroid hormones play a role in modulation of oxidative stress and imbalance between free radicals and antioxidants can lead to oxidative damage, vitamin A can be of huge help in providing equilibrium between the two. Studies show that vitamin A has potent antioxidant effects .
Stronger immune system
The immune system is our body’s defense system that comprises of many biological structures and processes to ward off diseases, infections, among other things. It turns out that thyroid is important for immune system function.
For example, exposure to synthetic or natural antigens (foreign substances which induce an immune response) leads to a drop in circulating thyroid hormones. While the reason for immune-modulating effects of those stimuli on thyroid hormone levels is unclear, Klein J.R. concluded they involve some type of acute immunological stress.
De Vito P. et al report that hyperthyroidism decreases pro-inflammatory activities of monocytes and macrophages, types of cells involved in the immune system. On the other hand, enhancement of phagocytosis and elevated levels of ROS tend to occur in hypothyroidism. Phagocytosis is the process wherein cells called phagocytes engulf or ingest other cells or particles.
The same study reports that in hypothyroidism we witness the expression of pro-inflammatory molecules. Thyroid hormones contribute to different aspects of both innate and adaptive immune responses. Although the relationship between immune cells and thyroid hormones T3 and T4 is complex, they may modulate immune responses through both non-genomic and genomic mechanisms.
What are adaptive and innate immune responses, you wonder? Innate immunity is a term that refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in the body. Basically, it is the body’s natural immunity present at birth. On the other hand, adaptive or acquired immunity is the specific defense mechanism that saves us from infections.
Thyroid function and strength of immune system go hand in hand. If thyroid doesn’t work properly, it may weaken the immunity and vice versa. Fortunately, vitamin A is well-known for its amazing potential to address immune system function.
Stephensen C.B. writes that incidence and prevalence of infectious diseases are higher in populations where availability and intake of vitamin A are low. As stated, deficiency in vitamin A disrupts “innate immunity by hindering normal regeneration of mucosal barriers damaged by infection and by diminishing function of macrophages and natural killer cells.”
How much vitamin A to consume?
As seen throughout this post, vitamin A is important for thyroid function and your overall health for that matter.
In order to avoid deficiency and ensure proper functioning of the thyroid, immune system etc. you need to consume sufficient amounts of vitamin A.
Recommended daily intake of vitamin A for adult men is 900mg while women need 700mcg. Pregnant women need 770mcg vitamin A while lactating mothers need 1300mcg1. If you have some thyroid disorder, it’s useful to consult your doctor about vitamin A, particularly when considering using supplements.
Remember, vitamin A deficiency is bad but it doesn’t mean we need to consume too much. In fact, excessive intake of this vitamin can cause toxicity. Supplements usually deliver the right amount you need during the day, but the importance of consulting a physician should not be underestimated.
Food sources of vitamin A
Fortunately, we can obtain sufficient amount of vitamin A through diet alone. To make it happen, it is important to enrich your menu with a well-balanced diet that includes a plethora of fruits and vegetables, among other things. Here are some food sources rich in vitamin A:
- Beef liver
- Romaine lettuce
- Sweet potato
- Winter squash
Vitamin A is an important micronutrient we need for eye health, strong immune system, but it’s also vital for thyroid function too.
Proper thyroid function and vitamin A levels go hand in hand as this gland is responsible for the conversion of beta-carotene to vitamin A.
Sufficient levels of this vitamin prevent hypothyroidism, alleviate inflammation, reduce oxidative stress, and prevent the growth of goiter.
 Vitamin A, National Institutes of Health https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
 Morely JE, Russell RM, Reed A, et al. The interrelationship of thyroid hormones with vitamin A and zinc nutritional status in patients with chronic hepatic and gastrointestinal disorders. American Journal of Clinical Nutrition 1981 Aug;34(8):1489-1495. Doi: 10.1093/ajcn/34.8.1489 https://academic.oup.com/ajcn/article/34/8/1489/4812462
 Farhangi MA, Keshavarz SE, Eshraghian M, et al. The effect of vitamin A supplementation on thyroid function in premenopausal women. Journal of the American College of Nutrition 2012 Aug;31(4):268-274. Doi: 10.1080/07315724.2012.10720431 http://www.tandfonline.com/doi/abs/10.1080/07315724.2012.10720431?scroll=top&needAccess=true&journalCode=uacn20
 Zimmermann MB, Wegmuller R, Zeder C, et al. The effects of vitamin A deficiency and vitamin A supplementation on thyroid function in goitrous children. Journal of Clinical Endocrinology and Metabolism 2004 Nov;89(11):5441-7. Doi: 10.1210/jc.2004-0862 https://www.ncbi.nlm.nih.gov/pubmed/15531495
 Brossaud J, Pallet V, Corcuff JB. Vitamin A, endocrine tissues and hormones: interplay and interactions. Endocrine Connections 2017 Jul;6(7):121-130. Doi: 10.1530/EC-17-0101 http://www.endocrineconnections.com/content/6/7/R121
 Vitamin A Deficiency Clinical Presentation, Medscape https://emedicine.medscape.com/article/126004-clinical
 Savas E, Sahin AZ, Aksoy SN, et al. Serum levels of inflammatory markers in patients with thyroid dysfunction and their association with autoimmunity status. International Journal of Clinical and Experimental Medicine 2016 Feb;9(2):4485-4490. http://www.ijcem.com/files/ijcem0012422.pdf
 Villanueva I, Alva-Sanchez C, Pacheco-Rosado J. The role of thyroid hormones as inductors of oxidative stress and neurodegenration. Oxidative Medicine and Cellular Longevity 2013 Nov. Doi: 10.1155/2013/218145 https://www.hindawi.com/journals/omcl/2013/218145/
 Palace VP, Khaper N, Qin Q, Singal PK. Antioxidant potentials of vitamin A and carotenoids and their relevance to heart disease. Free Radical Biology and Medicine 1999 Mar;26(5-6):746-61 https://www.ncbi.nlm.nih.gov/pubmed/10218665
 Klein JR. The Immune System as a Regulator of Thyroid Hormone Activity. Experimental biology and medicine (Maywood, NJ). 2006;231(3):229-236. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2768616/
 De Vito P, Incerpi S, Pedersen JZ, et al. Thyroid hormones as modulators of immune activities at the cellular level. Thyroid 2011 Aug;21(8):879-90. Doi: 10.1089/thy.2010.0429 https://www.ncbi.nlm.nih.gov/pubmed/21745103