Exposure to the sun gives us easy access to one of the most important vitamins for overall health. Unfortunately, with our modern fear of skin cancer, a growing number of folks—over a billion people worldwide—are shying away from the sun. With an increasingly processed diet as well, many of us are not getting nearly enough of this crucial vitamin. Yet, with growing research pointing to the benefits of vitamin D to human health, keeping up your levels is key to maintaining good health.
One of the best-known functions of vitamin D is helping the body absorb and utilize calcium (as well as phosphate, magnesium, and zinc), making it essential for developing strong bones and protecting you from osteoporosis as you age. But it does so much more. At least 1,000 different genes, governing nearly every tissue in the body—including several in the neuromuscular and immune systems—are thought to be regulated by 1,25-dihydroxyvitamin D, or D3, the active form. It also plays a key role in preventing a host of health problems—such as heart disease, depression, autoimmune disorders, viral infections, and even cancer. It’s also involved in regulating cell growth, supporting immune function, and reducing inflammation. It may even affect how easily you develop cavities.
Low Vitamin D & Deficiency: A Growing Epidemic
Despite how easy this nutrient is to acquire, a growing number of people have low vitamin D levels. Over 40% of adults in the US are deficient, and that number has remained consistent for almost 20 years. This deficiency is associated with decreased bone health, viral infections, and chronic illnesses, including some cancers, multiple sclerosis, diabetes, and heart disease.
9 Most Common Symptoms of Low Vitamin D
- Blood-sugar issues
- Bone softening (low bone density) or fractures
- Joint pain (particularly in the back and knees)
- Low immunity
- Mood changes and irritability
- Muscle cramps and weakness
- Weight gain
Age and skin color are some of the leading factors that can affect your body’s ability to produce adequate levels. Many cases of deficiency occur in those living in areas of higher latitudes or who simply spend way too much time indoors. Additionally, deficiencies in minerals, especially magnesium, can further contribute to low levels.
Also of concern is that as we get older, our ability to produce vitamin D in our skin decreases by 50%, making it even more important to increase either the time we spend in the sun and/or the amount we get from our diet or supplements. An age-related general reduction in kidney function negatively impacts the conversion of 25OH D to the active form, further decreasing our usable levels. Regardless of your age, ensuring that your kidneys, liver, and gut are all functioning optimally can help ensure your body can produce decent levels.
Magnesium: A Codependent Relationship
Like most aspects of the human body, there are multiple moving parts and interconnected systems to consider. Like every functional medicine practitioner will tell you, health doesn’t exist in a vacuum. Magnesium and vitamin D have a symbiotic relationship. For example, adequate levels of 1,25(OH)2D are required to maximize magnesium absorption, however, reduced levels of magnesium can hinder the conversion of D to its active form.
Magnesium itself plays a huge role in bone health, lowering your risk of osteoporosis, and heart health. Unfortunately, with industrialized agriculture and poor soil quality, the magnesium content in our food today is estimated at only 25% to 80% of pre-1950 levels! With our love of processed foods, as many as three-quarters of folks in the U.S. are magnesium-deficient.
Maintaining ideal levels of magnesium is extremely important for ensuring your vitamin D levels remain in the ideal range and making sure what you do have can do its job. The magnesium RDA for adults is 310-420 mg (depending on age and gender). While you can supplement to help maintain healthy levels, plenty of foods contain decent levels of magnesium. Some of the best dietary choices include leafy greens and fish, such as:
- 1 cup cooked spinach, 157 mg
- 1 oz pumpkin seeds, 156 mg
- 1 cup cooked beet greens, 98 mg
- 3 oz cooked halibut, 90 mg
- 1 cup cooked artichoke, 71 mg
Sun and Supplements
Hands down, spending time in the sun is the best way to increase vitamin D levels. There’s no danger of levels getting too high, not to mention the other health benefits of being outside. To produce enough vitamin D to avoid becoming deficient, we should be spending at least 15-20 minutes per day in the sun, with enough bare skin exposed. It’s important that this time is spent sans sunscreens, which block ultraviolet B waves (UVBs) and severely limit the skin’s ability to produce vitamin D.
How much vitamin D your body can produce depends on factors like your health status, age, skin color, season, and where you live. Because of this, there are instances when you may need to supplement to maintain a healthy level. Folks living in cities like Hartford, CT and Medford, OR can’t produce vitamin D from sun exposure from November through February. If you live in Canada or Alaska you can’t produce decent levels for about half the year. Thanks to air pollution absorbing UVB radiation, living in big cities like Los Angeles can also negatively impact your ability to produce vitamin D from sunlight.
If you do decide to supplement, it’s important to attain a baseline reading and regularly test your levels every couple months. This will help you understand how much you should be taking. Unfortunately, suggested limits vary and there’s no uniform recommendation for dosages. The Institute of Medicine suggests a safe upper limit of 4,000 IU per day, the Vitamin D Council recommends 5,000 IU per day, and the Endocrine Society Practice Guidelines states amounts as high as 10,000 IU per day are safe.
While rare, vitamin D toxicity can happen, but typically only by over-supplementing, not from diet or sun exposure. Studies indicate that blood levels above 100 ng/mL are excessive and above 150 ng/mL is considered toxic. This same study also shows that an average daily intake of 10,000 to 15,000 IU per day is “not associated with deranged calcium or phosphate metabolism or toxicity.”
It’s also a good idea to take vitamin K2 alongside vitamin D supplements. Studies have suggested that high doses of vitamin D may cause calcium to build up in blood vessels, and vitamin K may help prevent that from happening.
If you suspect you are deficient in vitamin D, or if you want to find out where you levels are, ask your doctor for a 25(OH)D test (also called 25-hydroxy vitamin D). This test is currently the most accurate way to measure the level in your body. You can also order your own test from folks like Ulta Lab Tests. Remember: Most health insurance carriers don’t classify these tests as “medically necessary”, and as a result won’t cover these tests under their preventive care benefits.
The DMinder app, available for free in the App Store and Google Play, can be extremely helpful in tracking your vitamin D levels. It helps you gauge the best time to be in the sun for maximum production based on your location, body type, skin exposure, and time of day. It will also warn you when you need to get out of the sun before you burn, as well as keep a running estimate of your level. I’ve found it to be a handy tool to keep track of estimated levels between tests.
There’s no question that sustaining a healthy vitamin D level is key in maintaining optimum health. While there are certainly instances where supplementation is appropriate, be sure to test your levels first to get a baseline, then work with your doctor if necessary to move your levels into a healthy range. And don’t forget that when it comes to vitamin D, the sun is your best friend.