The Benefits of Vitamin D for Your Thyroid - Dr. Izabella Wentz, PharmD (2024)

This time of year, I like to focus on immune support for my family. In previous years, I used to start in January, but thanks to preschool and kindergarten, I now focus on immune support in October. 🙂

I love taking reishi, S. boulardii and astragalus for overall immune health and to support secretory IgA levels, our own first line of defense in our respiratory and digestive tracts. We are also drinking bone broth and taking vitamin D.

Do you ever feel worse in the winter than you do in the summer? A deficiency in vitamin D and a certain spectrum of light may hold the key to feeling better.

Autoimmune conditions are more likely to cluster in regions farther from the equator, and scientists have suggested that one of the potential reasons for this may be due to inadequate vitamin D levels, as vitamin D is primarily absorbed via sunshine on skin that is free of sunscreen.[1]

Although those who live in warm climates are more likely to be absorbing enough of the sunshine vitamin, I often find that even people who live in warm climates such as Southern California, Florida, and Arizona, are vitamin D deficient at similar rates to people living in Wisconsin or Minnesota!

This is because our absorption of the vitamin from food sources is minimal, and is often further compromised by digestive enzyme deficiencies and gut conditions that lead to malabsorption of nutrients (such as infections and bacterial overgrowth).

As a result, vitamin D is one of the most under-recognized deficiencies in our society, and an estimated 85 percent of Americans may be deficient in it.[2]

Vitamin D affects about 3,000 to 30,000 genes in our bodies. You may know that it’s necessary for helping our body to absorb calcium and strengthen our bones, but it also plays an important role in our immune system health, keeping its delicate balance in check. Vitamin D may prevent and modulate autoimmunity, while a deficiency in vitamin D is associated with improper immune function.[3]

Many diseases have also been connected to low vitamin D levels, including heart disease, autoimmune disease, depression, and recently, thyroid conditions, including Hashimoto’s.[4]

Optimizing your levels of this important nutrient may be a key part of the puzzle of restoring your health.

In this article, you’ll discover:

The role of vitamin D within the body
The link between vitamin D deficiency and thyroid conditions
How to test for vitamin D deficiency
Lifestyle tips and supplements to boost your vitamin D levels

What is Vitamin D?

Vitamin D is an essential nutrient and a precursor hormone that plays an important role in many biochemical functions within the body. The body produces vitamin D from cholesterol, when our skin is exposed to sunlight. Vitamin D is also found in certain foods, such as fatty fish and fortified dairy products. However, it is very difficult to get adequate amounts through diet alone.

Vitamin D has several important functions within the body, including the regulation of calcium and phosphorus absorption for bone and tooth growth.

This vitamin has also been shown to reduce one’s risk of developing multiple sclerosis (MS) and heart disease.[5] It plays an important role in regulating mood and preventing depression as well. In fact, researchers behind a 2013 meta-analysis observed that, statistically, people with low vitamin D were at a much greater risk of depression.[6] Another study found vitamin D receptors in the same areas of the brain associated with depression, and concluded that vitamin D plays an important role in brain function and mental health.[7]

Of note, vitamin D can also support the immune system. (In fact, there are vitamin D receptors and activating enzymes on the surfaces of all white blood cells!) By enhancing the pathogen-fighting effects of monocytes and macrophages — white blood cells that are important parts of immune defense — and decreasing inflammation, vitamin D can help reduce the likelihood of contracting viruses, such as the seasonal flu.[8]

An analysis of 10,933 trial participants, yielded the first definitive evidence that vitamin D does protect against respiratory infections. The results of the analysis revealed that, in trial participants, daily or weekly supplementation halved the risk of acute respiratory infection in people with the lowest baseline vitamin D levels (below 25 nmol/L). However, people with higher baseline vitamin D levels also benefited, although the effect was more modest (10 percent risk reduction). Overall, vitamin D supplementation was shown to be helpful in reducing the risk of acute respiratory infection.

The role of vitamin D in the health of the human body has been well described by researchers and the medical community alike. Recent studies have shown that serum vitamin D levels can be directly correlated with human life expectancy.[9] Dr. William Grant, Ph.D., a vitamin D expert, has proposed that raising the optimal serum vitamin D level would prevent 30 percent of cancer deaths each year.

While it is estimated that 1 billion people worldwide have low levels of vitamin D, most don’t realize that they’re deficient, as symptoms are often subtle. Indications that you may have a vitamin D deficiency include:

Fatigue
Bone aches
Back pain
Muscle pain and weakness
Stress fractures (especially in your legs, pelvis, and hips)
Frequent illness or infections
Depression
Impaired wound healing
Osteoporosis
Hair loss

Additionally, in those with Hashimoto’s, elevated thyroid antibodies may be a sign of a vitamin D deficiency.

Vitamin D and Autoimmune Thyroid Conditions

Numerous studies have connected low vitamin D levels to various autoimmune conditions. For example, a deficiency in vitamin D has been correlated with higher rates of type 1 diabetes.[10] In Finland, the incidence of type 1 diabetes in Finnish children increased when the daily recommended dosage of vitamin D was reduced from 4000-5000 IU in 1964, to 400 IU in 1992. Yet, incidences of diabetes in children have been decreasing since 2006, the year Finland decided to fortify all dietary milk products with vitamin D3.

Vitamin D may be beneficial in balancing the immune system through supporting the production of T-regulatory cells, and suppressing the Epstein-Barr virus, a virus that has been tied to numerous autoimmune conditions, including Hashimoto’s.[11] Research has also shown that vitamin D actively prevents the development of autoimmunity in animal models.[12]

Vitamin D and Endocrine Health

Along with reducing antibodies and being beneficial to thyroid health, vitamin D has been shown to be helpful for women’s endocrine systems. One study found that women with normal vitamin D levels were found to have lower rates of endocrine and reproductive system conditions such as oligomenorrhea (infrequent periods), amenorrhea (missing periods), and other menstrual cycle irregularities.[19]

Furthermore, vitamin D has also been shown to inhibit uterine fibroid growth through its role in cell growth of uterine tissue.[20]

Who’s at Risk for Deficiency?

As skin cancer awareness and the use of sunscreen has become more widespread, most people are not getting adequate amounts of vitamin D through skin absorption. In fact, a clinical review published in The Journal of the American Osteopathic Association found that nearly 1 billion people worldwide may have insufficient levels of vitamin D related to sunscreen use.[21] The study also found that vitamin D deficiency can be more prevalent in certain populations due to differences in skin pigmentation. For example, 95 percent of African American adults may have vitamin D deficiency.

Furthermore, those living in northern climates are especially at risk for vitamin D deficiency in the colder months, when the body is covered up.

However, even those living in warm countries may be at risk for low vitamin D levels. According to a Spanish study, although Spain receives sufficient sunlight radiation, it is difficult for its population to attain the recommended daily dose of vitamin D in the winter, as sunlight exposure is affected by Spain’s northern latitude.[22] The study also noted that absorption could depend on the time of day and the position of the sun. At 10 am, almost 10 hours would be required to get enough vitamin D — but most people do not get 10 hours of sunshine — and if they did, that would be excessive exposure!

Additionally, those with pancreatic enzyme deficiency may be at risk for vitamin D deficiency.[23] If you are deficient in pancreatic enzymes, you will not be properly digesting and absorbing fats. As such, the body will not be able to optimally absorb and utilize fat-soluble vitamins such as vitamin D.

Testing for Vitamin D Deficiency

You may be wondering, how much vitamin D does your body need?

It’s interesting to note that according to some all-cause mortality studies, patients with vitamin D levels between 30-40 ng/mL had the lowest rate of dying.[24] Levels under 30 ng/mL and over 50 ng/mL had a greater association with dying, so it appears to be beneficial to have vitamin D levels in the mid-range.

That said, I am often suspicious of all-cause mortality studies because “all-cause mortality” means dying of any cause, and there are often a number of uncontrolled variables. For example, vitamin D will not protect you from dying in a car accident, nor prevent an armed assassin from showing up at your door.

While the conventional reference ranges define vitamin D deficiency as under 30 ng/mL, I have found that vitamin D levels should be between 60 and 80 ng/mL for optimal thyroid receptor and immune system function.

There are two common forms of vitamin D:

Vitamin D2 (ergocalciferol) – This form is found in some fortified foods and certain supplements.
Vitamin D3 (cholecalciferol) – This is the most biologically active form and is found in some high-quality supplements.

Vitamin D2 and D3 can both be converted by the liver and the kidney into the active form 1,25-dihydroxyvitamin D.

There are two available tests to check your vitamin D levels: 1,25 (OH)D (which checks for the active form of vitamin D) and 25(OH)D (which checks for both D2 and D3). The 25(OH)D (25-hydroxyvitamin D) test is preferred, as it tests for both vitamin D2 and D3 levels and more accurately reflects one’s vitamin D status.

In my experience of performing case reviews for people with Hashimoto’s, vitamin D is the most common deficiency, followed by ferritin. However, as vitamin D excess can be problematic, I always recommend testing for these nutrients before supplementing.

If you have Hashimoto’s and have not had your vitamin D levels checked, I recommend testing as soon as possible. When supplementing, I recommend testing every 3-6 months to ensure you are getting adequate amounts, and then testing again in the winter season.

How to Get Your Vitamin D

Studies are now suggesting that much higher doses of vitamin D than the original recommended daily allowance of 400 IU per day should be taken. In fact, some studies show that 25(OH)D levels under 75 nmol/L may be too low for safety, and are associated with higher all-cause mortality.[25] Moreover, one study found that a daily intake of 6201 IU was needed to achieve the Endocrine Society’s recommendation of serum 25(OH)D values at 75 nmol/L.

Furthermore, I believe that vitamin D is especially important for people who have had a prior Epstein-Barr infection, as the CD8+ T cells that fight the virus are vitamin D dependent.

So how can we get adequate amounts of vitamin D?

Vitamin D can be produced in the skin when exposed to sunlight, or it can be ingested from foods and supplements.

1. Get Outside

One of the best ways to restore optimal vitamin D levels is through sun exposure. (As a bonus, sunlight has natural immune modulating benefits, and can also lift your mood.)

You could say that boosting your vitamin D levels can be a “walk in the park.” 🙂 Vitamin D advocates recommend 15 minutes of unexposed skin, without sunscreen, around noon.

Perhaps you can consider going for a walk during lunchtime? If you are fair-skinned and not used to the sun, you may need to start slower. Be careful not to overexpose yourself, to prevent getting a sunburn.

However, some health care professionals suggest that in cases of severe deficiency, getting adequate vitamin D levels would require you to spend four to six hours exposed on a sunny beach… for seven days straight. Sounds awful, right? However, many of us simply can’t get to the beach and live in climates that do not provide us with adequate amounts of sun exposure yearound, so we’ll need to look for alternate sources of vitamin D.

Please note that people with darker skin tones may actually need more light, due to having more melanin in their skin. Studies have shown that people with darker skin require more sun exposure to achieve adequate vitamin D levels, versus light-skinned people.[26] Some sources say they need as much as six times more sun to get enough vitamin D![27]

I generally recommend beach vacations for those of us living in Northern climates this time of year, but this isn’t always realistic for many! As such, we have to get sunshine when we can, as well as really focus on food and supplements.

2. Food Pharmacology

We can get vitamin D from dietary sources, including wild salmon (which contains 800 IU of D3 per 3.5 oz), cod liver oil (700 IU per teaspoon), fish, fortified dairy products and orange juice, and eggs.

However, the amount of vitamin D we absorb from food is limited, and people with fat malabsorption, food sensitivities, and other digestive issues common in Hashimoto’s, may be further impaired in their ability to absorb nutrients. Additionally, dairy, eggs and sugary drinks can be problematic for people with Hashimoto’s and blood sugar issues, so I don’t recommend relying on these foods for adequate vitamin D. This is why supplementation can be incredibly helpful, and why I recommend vitamin D supplements for most people with Hashimoto’s.

3. Supplements

My recommendation for those who can’t get out in the sun, is to take an oral vitamin D3 supplement.

As the recommended daily allowance of 400 IU of vitamin D has been shown to be inadequate for most people, I generally recommend 5,000 IU per day as a starting point for my clients with Hashimoto’s. Taking your vitamin D supplements with a meal can be helpful in increasing its absorption by 30-50 percent.[28]

However, I also recommend monitoring vitamin D levels to ensure that levels are within the optimal range (60 to 80 ng/mL for optimal thyroid receptor and immune system function).

In some cases, practitioners may utilize doses as high as 20,000 IU to get to the goal, but I would not recommend doing this on your own, as vitamin D is a fat-soluble vitamin and can build up. (If you’re looking for a practitioner to help you on your journey, you can download my list of recommended clinicians, here.)

Please note: Some people with Hashimoto’s may also be deficient in vitamin K, especially when they have issues with fat malabsorption. Vitamin K deficiency is not routinely tested, but symptoms may include easy bruising, excess bleeding, and heavy menstrual periods.[29]

Supplementing with vitamin D when one is deficient in vitamin K can have a negative impact on our arteries. Vitamin D supplements liberate calcium from our bodies, and in the case of vitamin K deficiency, the calcium may go to our arteries instead of our bones. Adequate vitamin K can prevent arterial calcification and encourage more calcium into the bones, which is beneficial in osteoporosis, a common condition seen in people with Hashimoto’s. As such, I recommend taking vitamin D with or without added vitamin K, depending on your individual needs.

The vitamin D supplements I recommend include:

Pure Encapsulations Vitamin D 5000 IU (without Vitamin K) — you can also purchase this through Fullscript. If you don’t have a Fullscript account, you can sign up with my credentials here.
Designs for Health Vitamin D Supreme (with Vitamin K*) — you can also purchase this through Fullscript. If you don’t have a Fullscript account, you can sign up with my credentials here.

*Please note, soybean peptone is used as a raw material in the fermentation process for the vitamin K2. The finished vitamin K2 is tested for contamination of soy protein and contains less than 10 ppm (parts per million). If you do not tolerate soy, you may want to opt for the Pure Encapsulations version, without vitamin K, instead.

Additionally, vitamin K supplements are generally safe and well tolerated, but if you take blood thinning medications like warfarin, speak to your doctor or pharmacist before starting a supplement that contains vitamin K.

Blue Light Therapy – Another Winter Tool

If you find yourself feeling worse in the winter than you do in the summer (and especially if you have the winter blues), vitamin D may help, but you would likely have the best outcomes if you combined it with blue light therapy.

A recent study published in Scientific Report suggests that exposure to sunlight may be beneficial to our immune system, via mechanisms that are separate from vitamin D.[30] The researchers noted that blue light, in particular, which is produced naturally by the sun, may activate key immune cells and boost immune function. In their study, blue light exposure triggered the synthesis of hydrogen peroxide, which inactivated pathways that signaled an increase of motility of the T cells (which play a role in mounting an immune response against infections), in both mouse and human T lymphocytes.

Blue light is known to reach the second layer of the skin, where there is a higher concentration of T lymphocytes compared to those found in the bloodstream. The study, therefore, suggests that there could be a separate pathway through which sunlight — specifically blue light exposure — may boost the immune system.

Blue light therapy devices have also been studied in seasonal affective disorder (SAD), aka “the winter blues”, with great success.[31]

I like this blue light therapy device to reap the benefits of blue light exposure anytime, from the comfort of my home, without having to wait for the weatherman to announce a sunny day. It’s also great to have around during the winter. While I recommend using it for about 15 minutes a day, you can set the timer according to your needs. This light therapy can also be really helpful if you have trouble waking up in the mornings. I recommend keeping it at your bedside and turning it on when you wake up, or keeping it in your bathroom and turning it on while you get ready. The little blue light therapy device has helped me through many dark winters in Chicago, cloudy days in Amsterdam, and long Colorado winters.

A Word of Caution…

Some research has shown an interesting link between levels of two different forms of vitamin D (1,25-D and 25-D), autoimmunity, and thyroid health.

Research suggests that elevated levels of 1,25-D (the active form of vitamin D) may be linked to promoting autoimmune processes. A ratio of elevated levels of the 1,25-D form, and low levels of the 25-D form, is a result of inflammatory processes of the immune system, and further maintains an inflamed autoimmune response.

The high 1,25-D:low 25-D ratio is associated with changes in the VDR gene, which is responsible for producing vitamin D receptors (VDR).[32] Changes in how the VDR gene is expressed can lead to the dysfunction of vitamin D receptors — this may be how the inflammatory processes are maintained.

The 1,25-D form specifically has an affinity for thyroid nuclear receptors. Thus, elevated levels of this form of vitamin D can create dysregulation of thyroid hormone production by affecting T3 hormone activity through thyroid nuclear receptor activity.

Supplementing without testing for vitamin D levels (both 1,25-D and 25-D forms) can contribute to the detrimental high 1,25-D:low 25-D ratio, which then can be harmful to the thyroid. Those who are deficient in vitamin D may find benefit from supplementing with high quality vitamin D3.

However, as previously mentioned, excess vitamin D can be toxic… and may contribute further to the inflammatory (and thyroid damaging) high 1,25-D:low 25-D ratio. Thus, I always recommend getting one’s vitamin D levels tested and continuing to consistently monitor levels to ensure vitamin D levels are not too high.

The Takeaway

Vitamin D has been helpful in my recovery, and I’ve found that exposure to sunshine, vitamin D supplements, and blue light therapy are strategies that consistently make my clients and readers feel better. In my survey of 2232 people with Hashimoto’s, 67 percent of my readers reported their fatigue improved and said they felt significantly better after taking a vitamin D supplement. Improvements in mood, pain reduction, as well as a reduction in antibody titers, are also things I see time and time again.

Because of the prevalence of vitamin D deficiency in Hashimoto’s, and due to its known connection to autoimmune disease in general, I’ve recommended vitamin D testing and supplementing to my readers and clients since 2013. I have noticed that those who are struggling most with thyroid symptoms often have vitamin D deficiency; and those who feel their best and/or who are in remission from Hashimoto’s tend to have vitamin D levels between 60-80 ng/mL. While it’s not a magic bullet, optimizing vitamin D levels can be a really simple and inexpensive way to feel better and optimize the immune system.

I’d love to hear from you! How much sunshine do you get in your part of the world? Do you take a vitamin D supplement?

As always, I wish you the best on your journey to better health.

P.S. I love interacting with my readers on social media, and I encourage you to join my Facebook, Instagram, TikTok, and Pinterest community pages to stay on top of thyroid health updates and meet others who are following similar health journeys. For recipes, a FREE Thyroid Diet start guide, notifications about upcoming events, and the Nutrient Depletions and Digestion chapter from my first book for free, be sure to sign up for my email list!

If you’re curious about other vitamin deficiencies and symptoms related to them, you can download my FREE Supplements to Subdue Symptoms eBook below!

References

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Note: Originally published in October 2016, this article has been revised and updated for accuracy and thoroughness.