Vitamin D and Thyroid

Tina, HK BioTek Intern

What is Vitamin D?

Vitamin D is a fat-soluble vitamin naturally present in foods. When we are exposed to sunlight, the UV rays from sunlight interacts with the cholesterol cells in our skin and trigger Vitamin D synthesis. Vitamin D is known for its role in preserving bone health by regulating absorption of calcium and phosphorus in our body. However, researchers have discovered that low level of vitamin D may also have a role in non-skeletal disorders such as cardiovascular diseases and autoimmune disease including thyroid disease.

Vitamin D Deficiency and Thyroid Disease

Vitamin D deficiency is a global problem with a 9-70% prevalence in adults, and it is more common in Asian countries. Serum vitamin D level is found to have a negative correlation with thyroid stimulating hormone (TSH). TSH is secreted by pituitary gland to signal thyroid gland to produce more thyroid hormone. People with vitamin D deficiency may have a high TSH levels which usually indicates hypothyroidism. Hypothyroidism is a thyroid disease where underactive thyroid gland does not produce and release enough thyroid hormones. Under this condition, the pituitary gland will produce more TSH to compensate the low level of thyroid hormones, which explains the elevation of TSH. Besides, since thyroid hormones regulate metabolic processes, people suffer from hypothyroidism may experience low metabolism and difficult to lose weight.

Daily Vitamin D Requirements and Sources of Vitamin D

Knowing that Vitamin D deficiency can lead to bone health problems as well as thyroid disease, how much of Vitamin D should we eat to avoid insufficiency? The table below shows the Recommended Dietary Allowances for Vitamin D.

© Vitamin D and health-The missing vitamin in humans. Available from: https://doi.org/10.1016/j.pedneo.2019.04.007

Vitamin D deficiency is more common in elderly since vitamin D intake and the sun exposure is usually lower. Therefore, elderly is recommended to take more Vitamin D food as well as supplements.

Vitamin D is naturally rich in some food like flesh of the fatty fish such as trout, salmon, and tuna. Other food namely egg yolks, dairy products and mushrooms are also vitamin D sources. Including fortified breakfast cereals and orange juice in your diet can also increase vitamin D intake.

Sun exposure is equally important for our body to synthesize Vitamin D. It is recommended to have a daily sun exposure around 5-30 minutes between 10 a.m. and 4 p.m.

Dietary Vitamin D supplements contains either Vitamin D2 or Vitamin D3. Vitamin D3 supplements is preferable due to a stronger potency than vitamin D2. Current study demonstrated that vitamin D supplementation helps in prevention of several kinds of autoimmune diseases, and it is beneficial to hypothyroid patients by improving blood levels of thyroid stimulating hormones.

In short, vitamin D does not only take part in bone health, but also responsible for thyroid function. To prevent deficiency, we need to ensure to sufficient daily intake from food rich in vitamin D. Ensure adequate sun exposure is another way of avoiding vitamin D deficiency.

References:

1. Muscogiuri, G., Tirabassi, G., Bizzaro, G., Orio, F., Paschou, S. A., Vryonidou, A., ... & Colao, A. (2015). Vitamin D and thyroid disease: to D or not to D?. European journal of clinical nutrition, 69(3), 291-296. https://doi.org/10.1038/ejcn.2014.265

2. Talaei, A., Ghorbani, F., & Asemi, Z. (2018). The effects of Vitamin D supplementation on thyroid function in hypothyroid patients: A randomized, double-blind, placebo-controlled trial. Indian journal of endocrinology and metabolism, 22(5), 584.https://dx.doi.org/10.4103%2Fijem.IJEM_603_17

3. Mackawy, A. M. H., Al-Ayed, B. M., & Al-Rashidi, B. M. (2013). Vitamin D deficiency and its association with thyroid disease. International journal of health sciences, 7(3), 267. https://dx.doi.org/10.12816%2F0006054

4. Chang, Y. J., Hwu, C. M., Yeh, C. C., Wang, P. S., & Wang, S. W. (2014). Effects of subacute hypothyroidism on metabolism and growth-related molecules. Molecules, 19(8), 11178-11195. https://doi.org/10.3390/molecules190811178

5. Chang, S. W., & Lee, H. C. (2019). Vitamin D and health-The missing vitamin in humans. Pediatrics & Neonatology, 60(3), 237-244. https://doi.org/10.1016/j.pedneo.2019.04.007