5 Surprising Things You Might Not Know About Your Vitamin D Level

Vitamin D

You probably think of vitamin D as the “sunshine vitamin.” No wonder! The best natural source of vitamin D is exposing your skin to sunlight. When ultraviolet light hits your skin, specifically UVB rays, your skin converts a compound on your skin to a precursor to vitamin D. Your liver and kidneys then activate the vitamin D precursor.

Vitamin D has a variety of functions. It helps your body absorb calcium and it may play a role in immune health. Some studies suggest that getting sufficient vitamin D might lower the risk of some health problems, particularly autoimmune disease, like multiple sclerosis. At the very least, you don’t want your vitamin D level to be too low. Here are some surprising facts that you might now know about vitamin D.

Your Vitamin D Level Plays a Role in Sleep

You probably don’t think of vitamin D as playing a role in sleep, but it does. You’ve probably heard of melatonin, a hormone that sets your body’s circadian rhythms. During the day, the pineal gland in your brain secretes only small amounts of this sleep-inducing hormone. But as evening draws near, melatonin levels rise and sends your body the signal that it’s time to slumber. Preliminary studies show taking large amounts of vitamin D may suppress the release of melatonin and make it harder to sleep. In the study, subjects with multiple sclerosis averaged around 4,400 IU of vitamin D daily. In contrast, those who took a low dose of vitamin D (800 IU daily) did not experience a drop in melatonin release.

Other studies link levels of vitamin above the low 30s with a reduction in sleep quality. If you’re having sleep problems and taking vitamin D, talk to your physician about whether to cut back on your dose. Most sources recommend taking no more than 2,000 IU daily as a supplement unless you’re deficient. According to the Endocrine Society’s guidelines, 4,000 IU each day is the upper limit of what’s considered safe for an adult to take daily.

You Need a Source of Fat to Absorb It from Food

Most foods don’t contain substantial quantities of vitamin D. Exceptions are fatty fish, like wild-caught salmon, eggs, and foods fortified with vitamin D such as yogurt, breakfast cereals, milk, etc. Another source is mushrooms exposed to ultraviolet light. Wild-caught salmon and eggs naturally contain fat, so you will likely absorb most of the vitamin D from these foods. However, UV exposed mushrooms alone, despite containing vitamin D, contain little fat. Therefore, you should eat mushrooms with a source of fat like olive oil to absorb the vitamin D. But don’t count on food to supply your body’s vitamin D needs. Even the food sources listed above lack enough to meet your body’s vitamin D requirements unless you eat a lot of them.

Vitamin D Doesn’t Act Alone

To get the full benefits of vitamin D, your body needs other co-factors. One of the most important is vitamin K2, another fat-soluble vitamin. Vitamin D boosts calcium absorption from the gut, but vitamin K2 plays a key role in where calcium goes once you absorb it. Vitamin K2 ensures that calcium goes to the bones rather than sticking to the inside of the walls of arteries, a problem that could lead to cardiovascular disease. Because of vitamin K2’s ability to regulate where calcium goes, preliminary research suggests it may lower the risk of osteoporosis and heart disease, although more research is needed.

How can you get more of it? Vitamin K1 is abundant in leafy greens, but vitamin K2 is in meat, hard cheeses, and a fermented soy-based food called natto, an Asian delicacy. So, it’s not surprising that most people don’t get enough as sources are limited. Your gut can convert some of the vitamin K1 that you consume from leafy greens and other sources to vitamin K2, but the process isn’t very efficient. So, it’s best to get vitamin K2 directly rather than count on your body to convert vitamin

K1 to K2.

Magnesium, a mineral important for heart, muscle, and nerve function, also helps activate vitamin D and turn it into a form your body can use. Studies suggest that up to half of the population doesn’t get enough magnesium. The best sources are seeds, nuts, greens, and whole grains.

Getting More Vitamin D May Not Be Helpful for Preventing Bone Fractures

One reason people take vitamin D supplements is for bone health and the risk of falls and bone fractures, due to vitamin D’s role in calcium regulation. However, studies show taking a vitamin D supplement when you already have a sufficient level of vitamin D doesn’t offer additional benefits and may cause harm. In fact, one study in postmenopausal women found those with vitamin D levels of 32-38 ng/ml had the lowest risk of falls but falls increased when levels rose above 40 ng/ml. More isn’t better! On the plus side, research suggests that vitamin D may boost muscle mass in older people who have low blood levels of vitamin D. There seems to be a “sweet spot” for vitamin D. A level above 20 ng/ml but below 40 ng/ml appears to be ideal. In fact, vitamin D is one vitamin that you can be toxic at very high doses.

Some People Have a Harder Time Getting Enough Vitamin D

Since vitamin D isn’t abundant in most foods, getting enough through diet is a challenge. The best source is sun exposure, but this is hit or miss too since so many people wear sunscreen to reduce skin damage. Plus, a cloud day cuts UV light exposure in half and air pollution reduces it by 60%. In addition, people with dark skin need more sun exposure to produce enough vitamin D as they have more melanin in their skin. The elderly and those who are obese also are at higher risk of vitamin D deficiency. That’s why it’s important to periodically check a vitamin D level to make sure you’re not falling short.

The Bottom Line

Hopefully, you know a little more about vitamin D now. Yet, there’s still a lot we don’t know about the sunshine vitamin and the role it plays in health and disease. Hopefully, more research will give us a more precise understanding of its role in human health.



·                Consumer Lab. “Vitamin D Supplements Review”

·                The Journal of the American Osteopathic Association, March 2018, Vol. 118, 181-189.   doi:10.7556/jaoa.2018.037.

·                Healio.com. “Recommended upper limits for vitamin D, calcium associated with hypercalciuria”


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