Vitamin D is an essential fat-soluble vitamin which means it’s crucial for our survival. It is absorbed with the fats from the food we eat, and is then stored in our body’s fat tissue and liver. Compared to other vitamins, vitamin D is unique because it’s both a nutrient we eat and a hormone our bodies make with the help of the sun’s rays. Synthesis of vitamin D from the sun has given it the nickname “sunshine vitamin.” According to the National Institutes of Health, 35% of adults in the United States are deficient in vitamin D. However, getting enough of the sunshine vitamin to support all the benefits that it provides doesn’t have to be complicated.
Benefits of Vitamin D
- Bone Health - Vitamin D regulates the absorption of calcium and phosphorus. A vitamin D deficiency can lead to osteoporosis (brittle bones) or osteomalacia (soft bones).
- Immunity and Inflammation – By reducing inflammation and inhibiting cell damage, vitamin D plays defense when it comes to keeping our body healthy.
- Mental Health – Studies have shown that low levels may contribute to schizophrenia, depression, and seasonal affective disorder.
- Heart Health – Although a direct link has yet to be formed, studies point to a vitamin D deficiency as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease, strokes, and high blood pressure.
- Diabetes – Low levels of vitamin D are associated with higher levels of insulin resistance.
- Cancer – Higher levels of vitamin D are associated with a lower risk for prostate and breast cancers.
Vitamin D from Food
It isn’t surprising that so many people are deficient in vitamin D as food sources are limited - especially if you don’t eat fish. Fortunately, some foods are fortified, which means that vitamin D has been added during processing. For consuming enough vitamin D, it’s important to note that the Recommended Daily Allowance (RDA) assumes minimal sun exposure. The vitamin D recommendation for adults is 800 IU/day (20 mcg/day). Here are some foods that are good sources of vitamin D:
- Fatty Fish (salmon, sardines, herring, mackerel, tuna)
- Skim milk or soy milk (fortified)
- Cheese (fortified)
- Breakfast cereals (fortified)
- Low Fat or Fat Free Yogurt (fortified)
- Orange Juice (fortified)
Vitamin D Synthesis from Sunlight
For all latitudes of the United States, there’s a seasonal variation in our vitamin D levels. The peak is in September and the low is in March. Fortunately, with vitamin D being a fat-soluble vitamin, it can stay in our body for 1-2 months. To maintain healthy blood levels, the World Health Organization (WHO) recommends 5 to 15 minutes of sun exposure 2 to 3 times a week. You’ll want to make sure your forearms, hands or lower legs are uncovered and without sunscreen. People with darker skin may need a little more time in the sun due to having more melanin that reduces vitamin D synthesis. Of course, too much time outdoors can lead to skin damage or skin cancer.
Avoiding a Deficiency
Vitamin D deficiency can happen for many reasons, such as not getting enough sunlight or not eating enough foods containing vitamin D. Also, people with lactose intolerance, gastrointestinal issues, or who follow a vegan diet may be at increased risk for a deficiency. To know your level, you must request a vitamin D test from your doctor. Once you know your level, compare it to this chart adapted from the National Institutes of Health.
Serum 25-Hydroxyvitamin D [25(OH)D] Concentrations and Health
|Less than 30||Associated with vitamin D deficiency, which can lead to rickets in infants and children and osteomalacia in adults|
|30 to less than 50||Generally considered inadequate for bone and overall health in healthy individuals|
|≥50||Generally considered adequate for bone and overall health in healthy individuals|
|>125||Linked to potential adverse effects, particularly at >150 nmol/L (>60 ng/mL)|
Getting Enough Vitamin D
Consult with your medical doctor or registered dietitian to ensure you’re taking in adequate levels of vitamin D. They can assist with a treatment plan based on lab tests, diet, and lifestyle factors. If a supplement is warranted, it’s important to note the upper limit for vitamin D is 4000 IU (100 mcg/day). Dosages greater than this can cause gastrointestinal issues, bone and kidney problems, and increased triglycerides. When choosing a vitamin D supplement, choose D3 over D2 because D3 is more effective in raising blood plasma levels.
In general, it’s best to get most of our nutrients from food, but vitamin D may be an exception to this rule with more than 1 in 3 adults being deficient. This is especially true for those that don’t get regular sunlight or eat fish or foods fortified with vitamin D. With this said, simple changes in our lifestyle can alleviate the need to supplement – like getting a little more sun exposure and/or including foods that are good sources of vitamin D.
To your vitamin D health,