Did you know that 46.1 percent of Americans are deficient in Vitamin D?  Today, the primary sources of dietary vitamin D are fortified processed foods and meat products. And according to health.gov dietary guidelines, Americans are consuming more protein-based foods, processed foods, saturated fats, and grains than needed. If this is true, why are we so deficient in vitamin D? Americans are eating the foods that provide us with adequate levels of dietary vitamin D, yet deficiency affects almost half of our population!
Has your physician ever told you that you have low vitamin D, and then said you should eat more fortified grains (cereals) and more fortified dairy products and meat products such as fish, eggs, and red meat? If so, you probably left thinking that your vitamin D levels would be “fixed” by following these instructions. But you may be surprised to learn that vitamin D consumption, absorption, and utilization are all different processes. As a result, it’s important to take a holistic viewpoint on why our national levels are so low despite sun exposure and eating fortified foods.
Now, it’s worth noting that when patients come to me with questions about vitamin D, they’re often related to bone health. For sure, vitamin D is essential to bone health—probably one of the most important nutrients when it comes to strong, healthy bones. However, vitamin D health benefits extend well beyond the skeleton; the vitamin does other good things for the body, too, particularly in its D3 form. And that’s why it’s crucial to make sure you have sufficient vitamin D3 levels. But before we dive into vitamin D3 health benefits and more, let’s learn a bit more about vitamin D: what it is, where it comes from, and how it differs from vitamin D3.
Vitamin D is a fat-soluble vitamin. The truth is that vitamin D isn’t overly present in food, though fatty fish, egg yolks, and some plant-based foods such as mushrooms offer some vitamin D.  You can get the health benefits of vitamin D3 by taking vitamin D supplements, and your body does produce vitamin D in response to UV rays from the sun. 
There are several forms of vitamin D—vitamin D 1 (calciferol), vitamin D2 (ergocalciferol), and vitamin D3 (cholecalciferol). The active form your body can use is vitamin D3.
It’s important to note that the amounts of vitamin D in your body don’t result directly from your vitamin D intake. Vitamin D can be manufactured in your skin, or it can be consumed as vitamin D2 and D3 from your food or a supplement. However, before it can be metabolized and utilized for action, it must cross through your liver where it becomes vitamin D 25OH (commonly measured in your regular lab work).
And the process does not stop there! It then moves on to your kidneys, which transform it into vitamin D 1,25 OH. This actually goes on to have a massive impact on your body’s biochemistry. Unfortunately, this impact won’t happen if you totally cover your skin with sunscreen, though. So, what does this mean? It means your best option is to spend the 15 to 20 minutes in the sun before you apply sunscreen. 
You must have a strong liver, strong kidneys, and solid gut health to be able to activate and use vitamin D properly. If these organs can’t healthy and doing their jobs, your body cannot convert the vitamin D it intakes to a metabolically active vitamin D. In other words, going out in the sun for 15 minutes each day may not be enough to get the vitamin D3 health benefits your body needs. Instead, it only provides you with the backbone for further activation and utilization of this amazing vitamin. 
There’s also a link between low vitamin D levels and stress. As you may recall, cholesterol is the backbone for creating cortisol and other hormones, yet it is also involved in manufacturing vitamin D. Often, I find in clinical practice that the body will defer to creating more cortisol over producing vitamin D as part of the sympathetic response. Remember, that in order to complete your everyday repair functions, your body must be at rest—not “running from a bear.”
Alternatively, researchers have been actively trying to draw clear and concrete associations between vitamin D levels and cortisol, as well as to other endocrine disorders, such as PCOS, type 2 diabetes, autoimmune thyroid diseases (such as Hashimoto’s and Graves’), and Addison’s disease.  So, here’s yet another reason to lower the stress in your life—in the name of vitamin D!
Vitamin D3 health benefits are plenty. Here are a few of the top benefits.
Vitamin D contains significant antioxidant impact—improving cellular function and repairing DNA. In addition, it’s been shown to help prevent the progression of numerous diseases or medical conditions, such as obesity, type 2 diabetes, high blood pressure, pregnancy complications, dementia, osteoporosis, autoimmune diseases, certain cancers, and systemic inflammatory diseases. In fact, low vitamin D levels have been linked to each of the above-mentioned conditions. 
Vitamin D is involved in the pathway of creating glutathione, your body’s most powerful antioxidant, which is critical for detoxification and slowing the aging process. It does this by helping with cell growth and fighting inflammation.  In fact, a 2008 study determined that vitamin D “is now one of the most essential vitamins” for anti-aging. 
Vitamin D3 supports bone health by boosting your gut absorption of the mineral calcium. When there is vitamin D deficiency, the body can only absorb 10 to 15 percent of dietary calcium compared to 30 to 40 percent when the body’s vitamin D levels are on par. Vitamin D and calcium work together to help prevent osteoporosis, a disease that involves bone thinning and leads to fractures and problems with the spine.  It’s important to note here that calcium, via vitamin D-assisted absorption, is not the only mineral involved in strengthening bones. Other minerals, such as magnesium, boron, strontium, and manganese, just to name a few, are also incredibly important!
Vitamin D deficiency also puts people at increased risk of developing soft bones, a condition called osteomalacia. 
In addition, recent research suggests that in addition to the intestines, where they bind to vitamin D and help with calcium absorption, there may be vitamin D receptors in other organs of the body as well. Adding to the list of vitamin D3 health benefits, there seem to be vitamin D receptors in the heart, muscles, endocrine glands, blood vessels, and prostate—where the vitamin appears to do good things. 
In addition, some studies suggest vitamin D may also help protect against high blood pressure, and several autoimmune diseases, including multiple sclerosis, psoriasis, and rheumatoid arthritis. [13, 14, 15, 16]
According to most medical advice, vitamin D levels should be between 50 and 80 ng/mL. In my patients, I screen for both vitamin D3 and vitamin D2 levels, so we can see if it’s converting properly. If you have a high level of D2 and a low level of D3, you know the problem is in the conversion. In this case, adding more sun exposure won’t always help because the issue lies with the liver, gut, or kidney. 
First, realize you’re not alone. Many Americans are deficient in vitamin D. People who live in cold, northern climates and those with darker skin are at higher risk for being vitamin D deficient. However, I can tell you from experience that the majority of my patients in sunny Arizona are also deficient, leading me to believe that the issue involves more than simple sun exposure.
Vitamin D3 deficiency symptoms include muscle pain, fatigue, and depression.  Other signs include experiencing regular illness (such as the common cold or flu), exacerbation of autoimmune disease symptoms, osteopenia, and more. If these symptoms arise, it’s time to look at levels of both vitamin D2 and vitamin D3 in addition to assessing your stress hormones, inflammatory markers, current symptoms, and overall health picture. If both levels are low, you can try a few more minutes of sunlight per day. If D2 levels are high and D3 levels are low, you can try vitamin D supplements and work with your provider to look into what might be going on with your kidneys, liver, or gut.
The recommended dietary allowance (RDA) of vitamin D for maintenance differs depending on the age group. Here’s the breakdown: 
0-12 months: 400 IU
1-23 years: 600 IU
14-70: 600 IU
70 and above: 800 IU
Please keep in mind that this doesn’t account for deficiencies. Every healthcare provider has different protocols for restoring vitamin D levels through supplementation. Recommendations can range from 400 IU to 5,000 IU daily or weekly to higher doses such as 10,000 IU to 50,000 IU for a certain length of time. It is possible to take too much vitamin D; therefore, you should always work directly with your medical provider to determine the exact dose for you and length of treatment.
If you’re not able to meet the RDA, you can add vitamin D supplements. Look for supplements that contain vitamin D3 (cholecalciferol). Side effects from supplements are rare in proper dosages. If an overdose occurs, symptoms may include dizziness, cough, difficulty swallowing, hives, fast heart rate, skin rash, puffiness in the face, chest tightness, or unusual fatigue. Rarely, vitamin D3 supplements can cause hypercalcemia (too much calcium in the blood).