Whether or not you give much thought to your thyroid, it is an integral part of your hormone system and its health is important; the thyroid gland is an endocrine gland located in the front of the neck which stores and produces hormones that affect the function of virtually every organ in our body. Thyroid hormone (Triiodothyronine or T3) regulates our metabolic rate and is associated with modest changes in body weight and energy levels. So, when it comes to nutrients that play a role in healthy thyroid function, people normally think of iodine and selenium. Iodine is a key constituent of thyroxine (T4) and tri-iodothyronine (T3), and selenium is a required cofactor for the de-iodinase enzyme that converts T4 into the more potent T3- see- important! Ok, so that may be a lot of info, but stay with me. Because there’s another nutrient that’s important for a healthy thyroid- Vitamin A.
Most people think of carrots (and then I think of Bugs Bunny) when vitamin A is mentioned because of its key role in eye health. But vitamin A is also a major player in the immune and reproductive systems, and in thyroid function as well.
It seems that insufficient vitamin A may depress thyroid function and a deficiency in A could cause problems further up in the pituitary gland, according to some animal models. From the Thyroid Nation article, “Vitamin A insufficiency increases pituitary synthesis and secretion of thyroid-stimulating hormone (TSH), increases the size of the thyroid gland, and reduces uptake of iodine by the thyroid gland. Vitamin A given alone, even in the absence of increased iodine, has demonstrated a positive impact on thyroid function and gland size.
Vitamin A supplementation was also shown to:
- Reduce serum TSH levels and increase T3 in premenopausal women (ages 17-50), including a group of obese women, who are at increased risk for subclinical hypothyroidism.
- For children with goiter (living in areas where iodine deficiency disorders are prevalent) the greater the severity of vitamin A deficiency, the greater their thyroid gland volume and the higher their TSH levels. Compared to placebo, supplemental vitamin A significantly reduced median TSH and the rate of goiter.
- In rats with concurrent deficiencies in both iodine and vitamin A, vit A repletion alone was effective in reducing thyroid gland size and hyperstimulation.
But, this isn’t a one size fits all vitamin solution because high doses of vitamin A may actually decrease thyroid function. There must be a balance; hyperthyroid patients have been treated successfully with high doses of A, resulting in decreased symptoms of an overactive thyroid and a decreased metabolic rate. Too little causes problems, but too much can also be harmful and that depends on the individual patient’s pituitary and thyroid status.
It is rare that the thyroid gland, itself, isn’t working. A sluggish thyroid usually has more to do with chronic, long-term stress- which comes to it as feedback from the adrenals, pituitary, and hypothalamus. It is possible then that for patients who don’t have those issues, that there may be nutrient insufficiencies at play. It’s even possible for those who consume a whole-foods diet and avoid processed foods (like me) to be low in iodine and selenium- particularly if they avoid iodized salt and don’t eat dairy, shellfish, or seaweed.
But try not to worry too much. Normally, those truly deficient in vitamin A, live in developing nations more so than industrialized ones. While people vary in their ability to convert plant precursor carotenes into true vitamin A, this shouldn’t be an issue for those on omnivorous diets, although it may be problematic for vegetarians and vegans, especially if their plant-based diet is low in fat (good fats aren’t bad, not all fat is equal).
And lastly, as if the too much vs. too little issue wasn’t enough, studies show that sluggish thyroid function may impair the conversion of carotenes into true vitamin A; rat studies showed a hypothyroid state resulted in lower conversion of carotenes to vitamin A, but an overactive thyroid led to an accumulation of greater vitamin A stores- this information will likely help identify dietary recommendations for hypo- and hyper-thyroid patients.
Pay attention to your vitamin A status and if you are having thyroid issues, ask your doctor to check your levels.
Source: Thyroid Nation
