Why is my Vitamin D low even if I am in the sun? - NL-060
Vitamin D keeps your bones and muscles healthy. And its role in boosting immunity and overall health is getting seriously acknowledged by the experts in recent years. The sunshine vitamin not only helps the body absorb calcium, a critical mineral required for bone growth and development, it influences many other important functions that make it an extremely important nutrient for your overall health. Vitamin D boosts natural immunity, regulates autoimmunity, supports heart health and maintains healthy cognitive functions. Maintaining healthy vitamin D levels are especially important for pregnant and breastfeeding women.
Exposing your skin to sunlight is a key step to getting the right amount of the vitamin D your body needs. Since vitamin D is a fat-soluble vitamin, you also need some kind of healthy fat for optimum digestion and absorption. While sensible sun exposure (15-20 minutes few times in a week) is the key to preventing vitamin D deficiency, you can still be deficient despite abundant sun exposure.
Sun exposure and low vitamin D status
You make vitamin D when your skin is exposed to sunlight. The UVB rays in the sunlight react with a type of cholesterol in the skin and convert it into pre-vitamin D3, which is then processed by the liver and kidneys to form calcitriol. This is the active form of vitamin D3 used by the body. A number of things can go wrong and disrupt this process.
Factors such as colour of your skin, latitude you are at, time of the day you go out and season can affect vitamin D production. For example, it is the UVB rays that trigger the production of vitamin D in the skin. These rays are strongest between 10.00 am to 4.00 pm. So getting exposure early morning may not help much. A word of caution though; do not expose yourself to UVB rays to the point of getting sunburn. That increases the risk of skin cancer, especially in people who are at a high risk or genetically predisposed. And a quick tip: check the length of your shadow when you are out in the sun. If your shadow is shorter than you are, your UVB exposure is high and you can make a good amount of vitamin D during this time. People with darker skin-tone need more sun exposure to make vitamin D than those with lighter skin.
There are many other factors that increase your risk of vitamin D deficiency, despite spending time in the sun. For example, the risk goes up with age. As you age, your skin becomes less effective in making vitamin D from the sunlight. In addition, the health of the liver and kidneys also take a hit with age, which impacts the processing and activation of vitamin D. Elderly people are also more likely to suffer from mobility issues mostly due to possible underlying health condition such as obesity, arthritis, depression, injuries and even muscle weakness that typically occurs with old age.
Another important reason that is often overlooked is "absorption". In some cases, the body is not able to properly use or absorb the active vitamin D that is available. It usually happens with age and in certain health conditions such as liver or kidney disorders, celiac disease, and Crohn's disease. Magnesium deficiency in the body also interferes with the proper absorption and utilization of vitamin D. Magnesium plays a very crucial role in converting vitamin D into calcitriol, which is the active and usable form. Magnesium activates enzymes that are involved in vitamin D metabolism in the liver and kidneys. Prolonged use of statins (drugs that are used to lower cholesterol levels in the body) also increases the risk of vitamin D deficiency.
Be aware that you can't get a boost in your plasma levels from sunlight blocked by glass, as the glass blocks the UVB rays required for vitamin D production. And remember that glass can't block UVA rays that can cause sun damage, premature skin ageing and skin cancer.
It is best to take a high quality liposomal vitamin D supplements to ensure higher absorption and bio-availability and better health outcomes, because even healthy sun exposure will not provide the Vitamin D your body requires.
1. Binkley et al. Low Vitamin D Status despite Abundant Sun Exposure. The Journal of Clinical Endocrinology & Metabolism. 2007
2. Uwitonze et al. Role of Magnesium in Vitamin D Activation and Function. The Journal of the American Osteopathic Association. 2018