Vitamin D – Your Big Questions Answered
Vitamin D is certainly a hot topic, in both the functional medicine space and increasingly in the popular media. Dr. Fauci himself has acknowledged that he uses vitamin D3 daily and he also recommends taking it in a recent interview with actress Jennifer Gardner.
Vitamin D benefits include proper gene expression, growth, bone strength and immunity. It’s because of this immune system function that vitamin D is increasingly being studied for its therapeutic and preventative use in both chronic and infectious disease, including COVID-19.
I often get questions about vitamin D, including how much to take, what form and what the most optimal levels are in the body. I’ll cover all of these, and more, in the article you are about to read.
In this article, you will learn more about:
- Vitamin D biochemistry
- The main roles of vitamin D in the body and related conditions
- Vitamin D deficiency
- The connection between vitamin D and COVID-19
- Vitamin D testing
- Optimal vitamin D levels
- Vitamin D supplementation
Let’s get started!
What Is Vitamin D3?
Vitamin D is a fat-soluble vitamin that acts much like a hormone in the body. In the presence of sunlight, your skin makes vitamin D from 7-dehydrocholestrol. (Source 1) You read that right; cholesterol is the precursor to vitamin D, just like it is for cortisol, estrogen, progesterone, testosterone and other steroid hormones.
Vitamin D3, or cholecalciferol, is the final and active form produced in the skin (this is also the most popular supplemental form). Vitamin D3 is converted to 25-hydroxy vitamin D in the liver to make the most abundant form of vitamin D that circulates in the blood. This is also the form that is most often measured in a vitamin D blood test. 25-hydroxy vitamin D is activated to 1,25 dihydroxy vitamin D in the kidneys. It’s this active form that binds to vitamin D receptors (VDR) in every cell, which signals for the expression of hundreds of genes. (Source 1)
Vitamin D is obtained, in smaller amounts through food and absorbs into circulation in the presence of fat. Vitamin D works in synergy with magnesium, vitamin K, vitamin A among other nutrients. This is why micronutrient deficiencies may impact vitamin D levels and function.
What Does Vitamin D Do? Vitamin D3 Benefits
Vitamin D plays many crucial roles in the body and supports the health of every cell. Of course, we often first think about vitamin D’s role in calcium balance and bone health. Vitamin D is required for the absorption of calcium and phosphorus in the small intestine. These are the two most abundant minerals in the body and make up a large portion of bone structure. In those with vitamin D deficiency, only a maximum of 10 to 15 percent of dietary calcium is absorbed compared to 30 to 40 percent in those with better vitamin D status. (Source 2)
The role of vitamin D for bone health benefits is so critical that severe vitamin D deficiency causes rickets in children and osteomalacia in adults, both characterized by a softening and weakening of the bones. In addition, vitamin D deficiency contributes to osteoporosis. (Source 2)
Vitamin D is also important for cell differentiation. Vitamin D supports new cells in becoming specialized. This may be one reason that vitamin D helps to prevent cancer (Source 3) and is important during pregnancy and other times of growth.
In addition, vitamin D is an important immune system modulator. Vitamin D regulates the immune system and supports innate immunity, which is the first line of defense against pathogens. (Source 4). Innate immunity involves direct action taken by our immune cells against an infectious agent like a bacteria or a virus. Acquired immunity, by contrast, is learned immunity which involves making specific antibodies targeting the specific invader.
Vitamin D may have other important roles in the body such as blood pressure regulation, insulin secretion and more. Many of the mechanistic vitamin D studies are in animals, but we have a growing number of human studies and clinical trials showing vitamin D is supportive in a variety of health issues and disease, including:
- Asthma (Source 5, 6)
- Respiratory tract infections (Source 5, 7)
- Bone fractures (Source 8)
- Breast cancer (Source 9, 10)
- All-cause mortality (Source 11)
These are the areas with the most robust, strongest evidence in the research literature, but compelling arguments may also be made for the role of vitamin D in autoimmune disease, diabetes and cardiovascular disease. A recently published German study estimated that supplementing vitamin D3 in the 50+ year old population could cut cancer related mortality by 13% or 30,000 lives. (Source 12)
And, you may have seen headlines about the relationship between vitamin D and coronavirus disease 2019, COVID-19.
Vitamin D3 Deficiency And COVID-19
Vitamin D deficiency is a widespread problem, both globally and domestically. Vitamin D deficiency is defined as blood levels of 25 hydroxy vitamin D below 30 ng/mL. (Source 13)
Deficiencies are so prevalent because we aren’t consuming enough vitamin D3 foods. Our ancestors regularly ate organ meats such as liver, fish eggs and other rich sources that are much more rare in our modern diet. In addition, because of modern life lived indoors, geographic location, skin pigmentation, the use of sunscreen or other factors, we miss the UV exposure needed for the body to synthesize vitamin D in the skin.
As discussed above, we already know that vitamin D status and supplementation is helpful for shortening respiratory tract infections. This is likely because of the important role it plays in immunity and why it is getting so much attention in terms of COVID-19.
A recent article in the Journal of the American Medical Association looked at the relationship between vitamin D status and COVID-19. The study found that vitamin D deficiency (defined as below 20 ng/mL in this study) was associated with an increased COVID-19 risk and calls for randomized controlled trials to further study this relationship. (Source 14)
Similarly, a study in Switzerland found low vitamin D levels were associated with positive COVID-19 tests and those with negative tests often had better vitamin D levels. (Source 15)
In a study looking at data from European countries including Spain, Italy and Switzerland, researchers found a correlation between low vitamin D levels and COVID-19 risk, complications and mortality. It’s also important to note that vitamin D levels tend to be lower in the elderly, who are also more vulnerable to complications and death from COVID-19. (Source 16)
The Vitamin D Test And Optimal Levels
With vitamin D levels seemingly so important for both acute and chronic disease, let’s talk a little about testing and the ideal blood levels.
A typical vitamin D3 test blood test will look at 25 hydroxy vitamin D. This is both the most common test and the most useful clinically since this is the main form of circulating vitamin D in the body. This is also the form you’ll find in micronutrient testing, such as NutraEval. But, your doctor can order a direct vitamin D3 level at almost any lab nationwide, so if you have not had one done yet, here’s a call to action: call your doctor and ask for this simple blood test.
The lab range on most tests you see will have 30 ng/mL as the lower limit. While this may be the lowest level needed for calcium absorption and to prevent vitamin D3 deficiency symptoms, it may not be high enough to optimize all of the important roles vitamin D plays in the body, disease prevention and immune support. Many functional medicine doctors recommend blood levels of at least 40 nmol/L, with recommendations often exceeding that for certain individuals. In functional medicine, we are interested in optimizing the health of each individual, not just obtaining the minimum.
Vitamin D3 Supplements
Supplementation may be the most effective and fastest way to raise vitamin D levels in the ideal range. It is important to first have a vitamin deficiency test and see where your blood levels are. Then, your individual vitamin D3 dosage can be tailored to your current levels and goal. It is helpful to work with a functional medicine provider throughout this process so levels can be rechecked and supplements adjusted.
I often get the question: How much vitamin D3 should I take daily? The answer is incredibly individual and is ideally based on testing. You’ll find most multivitamins only provide the RDA (recommended daily allowance) of 600 IU (International Units) per day, which might not be high enough for many individuals.
Core Med Science’s Liposomal Multivitamin contains 1000 IU of liposomal vitamin D3 in a combination with vitamin K2 which helps vitamin D3 exert it’s functions properly. This dosage may be enough for maintaining optimal levels, but for those of you who need to raise their blood levels significantly an additional supplement might be required.
Those with severe deficiency might be prescribed Vitamin D3 50,000 IU to be taken weekly for a certain amount of time. This may seem like a large number, but to put in perspective our bodies generate 15,000-20,000 IU of vitamin D3 by being outside in sunshine for about 20 minutes.
The new trend in the USA is to list vitamin D3 dosages in micrograms (mcg) instead of IU. You will see updated labels on supplements list both in “mcg” and “IU. If you only see mcg, the conversion for vitamin D3 is 10 mcg = 400 IU.
The Institute for Functional Medicine recommends taking 5000 IU (125 mcg) per day in the absence of blood test results and with the goal of achieving blood levels between 50 and 80 ng/mL. (Source 16) As you can see, there are a wide range of acceptable dosages and most are tolerated without vitamin D3 side effects.
In rare cases of too much supplementation or sustained high levels of vitamin D in the blood, the body can absorb too much calcium, which can be dangerous. Please work with a qualified practitioner to properly identify your needs.
Tips For Supplementing With Vitamin D
Ready to start your vitamin D supplement? Here are some tips to consider:
- Take vitamin D with fat. Since vitamin D is fat soluble, it’s important to take it along with a meal containing fat, MCT or olive oil or PC Complex.
- Take vitamin D in the morning. It intuitively makes sense to take vitamin D in the morning or when the sun is high to mimic the vitamin D we get from the sun. Some report vitamin D provides energy and when taken at night may disrupt sleep.
- Choose vitamin D3 instead of vitamin D2. Vitamin D2 is the form made by plants and in the war of vitamin D2 vs D3, D3 wins. Vitamin D3 has been shown to raise blood serum levels of 25 hydroxy vitamin D better than D2. (Source 18)
- Add in K2. Whereas vitamin D3 helps absorb calcium, vitamin K2 helps to direct that calcium to the bones and is another common vitamin deficiency. You can take a vitamin D3 K2 supplement or check to make sure your multivitamin contains K2 (in addition to K1).
- Don’t forget food. Fatty fish and liver are a couple of the best dietary sources of vitamin D. Be sure to choose high quality sources.
- Don’t forget sunlight. During the summer months, try to get some mid-day sun exposure on most days. You don’t want to burn, so be sure to adjust the amount of time you spend in the sun, arms and legs exposed and without sunscreen, per your individual tolerance and needs.
The best vitamin D3 supplement will really depend on your individual levels, lifestyle and the optimal blood level for you, given your health history and goals. Vitamin D is certainly a unique nutrient and one to have on your radar, especially now, as it may provide some very safe protection against COVID-19 infection and associated outcomes.
While we might all have individual needs, most of us will benefit from more vitamin D in our lives. Be sure to request a blood test from your provider if you haven’t had one recently and discuss with them the best strategy for optimizing your levels. Your bones, immune system and genetic expression will thank you!
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