Vitamin D has long been known to help the body absorb calcium and phosphorus (which are critical for bone health). And in recent years, vitamin D has frequently been in the news as researchers have learned more about its role in supporting a healthy immune system, reducing cancer cell growth, and controlling infections and reducing inflammation. Research into these benefits continues.
Because our T cells — our body’s infection fighters — rely on vitamin D to do their work, the vitamin plays an important role in helping us stay healthy and fend off viruses (like the common cold or the flu).
The recommended dietary allowance (RDA) of vitamin D for most adults is 600 international units (IU) a day. For people older than 70, That goes up to 800 IU a day.
Vitamin D occurs naturally in many foods and is frequently added to others. Foods that are high in vitamin D include fatty fish such as salmon, fish oil, egg yolks, butter, and liver. Foods that are frequently fortified with vitamin D are breakfast cereals and milk products.
Most adults do not get enough vitamin D from their diets; however, exposure to sunlight can make up the rest. (Our bodies can make vitamin D when we are exposed to sunlight — you may have even heard vitamin D called “the sunshine vitamin.”) So for the majority of adults, vitamin D deficiency is not a concern. However, some people — for instance, people who follow a vegan diet, who have dark skin, or who live far from the equator — may have lower levels of vitamin D due to their diets, a lack of sun exposure, or other factors.
Common signs of vitamin D deficiency include:
• Fatigue, tiredness
• Catching colds or viruses frequently
• Bone or back pain
• Hair loss
• Slow wound healing
If you are experiencing any of those symptoms, talk with a healthcare provider.
Vitamin D deficiency has been linked to several health conditions, such as:
• Osteoporosis or osteopenia (bone softening)
• Muscle weakness
• Bone fractures
• Weakened immune system
• Cardiovascular disease
Some people are more at risk for vitamin D deficiency than others.
• Breastfed infants always need supplemental vitamin D
• Older adults may need supplemental vitamin D, because as we age our skin loses the ability to make vitamin D from sunlight.
• People with limited sun exposure may be at higher risk. If you are homebound or always wear long sleeves, robes, or face coverings, you may not be getting enough vitamin D from the sun. People who live in climates with limited sunlight or who live far from the equator may also be at risk, if only seasonally.
• People with dark skin may be at risk, because melanin, the pigment that darkens skin, can reduce the skin’s ability to make vitamin D.
• People with limited fat absorption are at increased risk. Vitamin D is fat soluble, so if you have a medical condition or take a medication that limits fat absorption, you may not be absorbing the vitamin D your body needs. Similarly, if you have undergone a gastric sleeve or bypass procedure, the smaller surface area of the stomach's absorption sites means you may need supplemental vitamin D.
• People who follow a vegan diet (or who avoid foods rich in vitamin D — which are mostly animal-based — for other reasons).
If you or someone you care about falls into an at-risk group, you may want to discuss vitamin D supplementation with a healthcare provider. With routine blood work, they’ll be able to tell you if you’re deficient and recommend actions that will help you get your vitamin D level where it needs to be. This may mean more foods that are rich in vitamin D, more sunlight exposure, or supplements.
There are two forms of vitamin D; D2 and D3. D2 is called ergocalciferol; D3 is called cholecalciferol. D2 is found only in plants and is typically cheaper to produce in supplement form. D3 comes from animal sources (and is the form of the vitamin our bodies make when exposed to sunlight). Compared with D2, D3 is used more effectively in the body once it has been metabolized by the liver. D3 may even stay in the body longer, helping your body retain more of what it needs. Vitamin D2 is a better choice for people who are following a vegan lifestyle.
If a vitamin D supplement isn't for you, you may still get some vitamin D from a daily multivitamin. (For more on supplements, read “Do You Need a Daily Supplement?”)
Before starting any supplement or making drastic changes to your diet, be sure to talk to your healthcare provider — some supplements may interact badly with medications you’re taking.
Carbon Health’s expert providers are always ready to talk nutrition! We offer in-person and virtual appointments, so you can schedule an appointment in the way that works best for you. Our seamless, personalized care is designed to support you in reaching all your health goals.