Why low vitamin D is a Hashimoto’s trigger
Every autoimmune disease has three things in common: a genetic component, a gut component, and one or more triggers. Low vitamin D is one of those triggers.
Here is the thing: you cannot feel low vitamin D. There is no obvious symptom that tells you your levels are off. That is why testing matters.
And most of us are low. Most Americans, most Australians, most Europeans are walking around with vitamin D levels lower than they should be.
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What vitamin D actually does in your body
Most of us grew up hearing that vitamin D is important for calcium and strong bones. That is true. But it does so much more.
Vitamin D works with vitamin K2 to make sure calcium goes where it needs to go, into your bones and not into your soft tissue. Your kidneys, bones, parathyroid, and intestines all work together using vitamin D to regulate calcium properly.
But here is what matters most for Hashimoto’s: vitamin D modulates the immune system. It is anti-inflammatory. It has been linked to autoimmune conditions including thyroiditis, type 1 diabetes, inflammatory bowel disease, lupus, and rheumatoid arthritis.
Vitamin D also supports blood pressure and muscle function. There is a lot of research on pubmed, which is just the Google of published research, connecting it to cancer prevention too.
One more thing that surprises a lot of people: vitamin D is actually a hormone, not a vitamin. Your body makes it when your skin is exposed to UVB rays from the sun. Because it is a hormone, it is part of your endocrine system. That means it communicates with other hormones and affects how your whole body functions.
How your body gets vitamin D and why it is probably not enough
Your skin makes vitamin D from sun exposure. But sun exposure does not guarantee good levels.
Early in my functional health education I heard a lecture from a doctor who practiced north of Chicago. He took care of a lot of snowbirds, people who live up north in the summer and move south for the winter. A lot of his patients spent winters in Florida. They would come back to his clinic in the spring tan, even leathery. He would test their vitamin D and a lot of them were very, very low. He realized that sun exposure does not guarantee a good vitamin D level.
Where you live matters too. There is a line that goes through Chicago. Everyone who lives north of that line cannot make enough vitamin D from the sun after the fall solstice. I live in Minnesota. I could be outside all day long and I still would not be making enough vitamin D through the winter. It is just part of living in the northern hemisphere.
Food sources are also limited. Milk is often cited, but milk does not naturally contain vitamin D. It is fortified. Foods that naturally contain vitamin D include oily fish, fish liver, and egg yolks. Most experts agree you cannot get enough from food alone.
Vitamin D is one of the nutrients that most experts recommend supplementing with, especially if you have Hashimoto’s or another autoimmune condition.
How to find out your vitamin D level
You need a lab test to know your number. The test is called 25-hydroxy vitamin D. You can just ask for a vitamin D test.
If your doctor will not order it, you have options now. Things have changed over the last decade or so. You used to have to go through your doctor for everything. Now you can advocate for your own health in even more ways.
Companies like Everlywell and Nutrisense send a lab kit right to your mail. You open it up, there is a little alcohol wipe, a little lancet. You poke your finger, put some drops of blood on the sample card, put it in the envelope, and mail it back. Within about two weeks you have your results in your email. That is what I did, because if it can come to me in the mail and I can do it in between homeschooling my boys, I am going to pick that one.
You can also get a link from a practitioner, order your own labs, go to a physical lab to get your blood drawn, and receive results by email. Some practitioners offer a consult to walk you through what your numbers mean. That is really valuable, because you do not want to just rely on Google. You are dealing with a lot of moving parts, and it is nice to have an expert in your corner helping you make sense of it.
For more on ordering your own labs, check out episode 39: Beyond TSH: how to get the thyroid labs you actually need.
What your vitamin D number means
This is where different experts have different opinions, and that is okay. Science is always evolving. When you know better, you can do better.
Here is the range of current guidance:
- National Institute of Health: 20-50 ng/mL is “generally considered adequate for bone and overall health in healthy individuals”
- Endocrine Society (the hormone experts): no longer have any recommended range. Instead, they tell “healthy adults under 75 to simply follow the Institute of Medicine/National Academies Dietary Reference Intakes rather than aiming for a blood-level target.”
- Independent Medical Alliance/Frontline Doctors: Optimal serum 25(OH)D levels (40-80 ng/mL) are essential for preventing infections, autoimmune diseases, and chronic conditions. The article, Understanding the Health Benefits of Vitamin D: Current Insights, goes on to say “From a disease prevention perspective, non-obese adults (~70 kg) require a daily intake of 5,000–7,000 IU to maintain optimal serum 25(OH)D levels.”
- The Institute for Functional Medicine’s vitamin D document lists optimal levels at 50-80 mg/mL and 80-100 ng/mL for patients with cancer.
In other words, there is no well-agreed upon optimal range. You are the CEO of your own health. Look at the research, look at the recommendations, talk with your doctor, factor in your risk factors, and figure out what is right for you.
For more on understanding your thyroid and hormone labs, check out episode 3: What do my thyroid labs mean?
Low vitamin D and Hashimoto’s: should you supplement?
The research says yes, for most people.
A study of over 130 studies said vitamin D supplementation can reduce autoimmune disease severity. A five-year study of over 25,000 people found that those who took vitamin D, or vitamin D with omega-3 fatty acids, had a significantly lower rate of autoimmune disease than people who took a placebo. The dose in that study was 2,000 IU of vitamin D every single day.
How much is right for you depends on several things:
- Your current lab level
- Your weight, which impacts how your body processes vitamin D
- How well you make vitamin D from sun exposure
- How much you are already supplementing
Work with your doctor or another practitioner who can look at all of those factors together.
One important note: when you supplement with vitamin D, pay attention to vitamin K2. Vitamin D and K2 work together to make sure calcium goes where it needs to go, into your bones and not your soft tissue. Look for a supplement that includes K2, or take it alongside your vitamin D.
For more on choosing the right supplement, check out episode 62: How to pick a vitamin D supplement.
This is one simple thing you can work on
There is a lot that can feel overwhelming when you have Hashimoto’s. When you first get diagnosed and start Googling, it can feel like you suddenly have a thousand things you need to do.
I do not want you to feel that way. Low vitamin D is just one tool in your toolkit. It is one trigger. And it is one simple thing you can work on.
Get your labs. Know your number. Work with someone who can help you interpret it and figure out whether supplementation makes sense for you.
Vitamin D sits on the immune side of Hashimoto’s. That matters because Hashimoto’s is two things happening at once, a thyroid problem and an immune problem, and knowing which side something belongs to is what keeps the list from feeling like a thousand things.
Hashimoto’s Decoded walks you through both systems so you can sort the rest of it the same way. Seven short chapters and a workbook. Under an hour, start to finish. $27.
