Vitamin D is a water-soluble vitamin that helps maintain calcium levels and bone metabolism for keeping your bone and teeth healthy. To get enough vitamin D, look for certain foods, dietary supplements, or carefully planned sun exposure to increase vitamin D levels.
Milk fortified with vitamin D in the early 1930s was effective in eliminating rickets in the world. However, there is still no consensus regarding whether vitamin D deficiency increases the risk of certain types of cancer, cardiovascular disease, type 2 diabetes, autoimmune disease, osteoporosis and even cognitive impairment.
Many conflicting recent studies are now suggesting that vitamin D deficiency may be linked to these conditions.
What Is the Role of Vitamin D?
Vitamin D is one among many vitamins our bodies need for good health. The benefits of vitamin D include:
- You need vitamin D for your bones to grow strong and protects you from various conditions, such as rickets. Rickets is a disease that causes children to have brittle bones and weak muscles. Osteomalacia is a condition where soft bones develop and have a higher fracture risk.
- Calcium and Vitamin D help build healthy bones and keep them strong and healthy. If you have weak bones, this could lead to osteoporosis, which can have the risk of fractures. Once either taken orally or from sunlight exposure, vitamin D is then converted into its active form. The absorption of calcium is best when taken in an active form.
- Parathyroid glands communicate with the kidneys, gut, and bones to regulate the level of calcium in the blood. As long as there is enough calcium absorption in the body and enough vitamin D, dietary calcium is used by the body for bone health. If calcium supplements are inadequate, or if vitamin D levels are low, the parathyroids will “borrow” calcium from the bones to maintain the blood calcium level within the normal range.
What Are the Sources of Vitamin D?
There are various ways to get vitamin D. Examples of these to include:
- Exposure to sunlight. Usually, 15-20 minutes three times per week is enough.
- Through eating the right foods and by taking a daily supplement.
What is an Association Between Vitamin D and Sunlight?
Sunlight has many health benefits. Vitamin D is produced by your body when your skin is exposed directly to sunlight. The amount of vitamin D your skin makes depends on factors such as:
- The season: This factor depends on where you live. The UV-B light does reach the earth for six months out of the year in areas such as Cleveland, Ohio because of the ozone layer and the position of the sun.
- The time of day when the sun's rays are at their strongest is between 10 a.m and 3 p.m., which is known as "the golden hour."
- The amount of cloudiness and air pollution.
- Cities near the equator tend to have higher UV light levels. It is the ultraviolet B (UV-B) light in sunlight that causes our skin to produce vitamin D.
- Melanin is a brownish-black pigment found in the eyes, hair, and skin. Skin color depends on melanin, which causes the skin to tan. Darker skin requires more sun exposure to get enough vitamin D from the sun.
What is the Relationship Between Vitamin D Supplementation and Your Diet?
Vitamin D doesn't occur naturally in many foods. That’s one reason why certain foods have added Vitamin D. Newer food labels show the amount of Vitamin D contained in a particular product.
It may be difficult for vegans or people with lactose intolerance to get sufficient vitamin D from foods alone, so they may choose to take supplements instead. Eating a variety of healthy foods is always important. The daily intake of different foods that have vitamin D is shown in the table below.
|Swordfish, cooked, 3 ounces
|Oily fish like salmon or other fatty fish, cooked, 3 ounces
|Tuna, canned in water, drained, 3 ounces
|Orange juice fortified with vitamin D, 1 cup
|Milk with vitamin D-fortified, 1 cup
|Yogurt, fortified with 20% of the daily value of vitamin D, 6 ounces
|Sardines, canned in oil, drained, 2 sardines
|Beef liver, cooked, 3 ounces
|Egg yolk, 1 large
|Cod Liver Oil
How Much Vitamin D Do You Need?
The amount of vitamin D needed daily varies by age and body weight. The following chart shows the often-cites recommendations. These are general recommendations. Your doctor may adjust your vitamin D intake based on your blood levels.
If you have osteopenia or osteoporosis, you may have a severe deficiency. The number of vitamin supplements can be customized for each individual, based on their results. Many older people may benefit from taking a daily dose of vitamin D supplement containing between 800 to 2000 IU dietary intake per day for healthy bones, which can be obtained with no prescription. Speak with your doctor about getting adequate vitamin D.
|People by age
|Recommended dietary allowance (IU/day)
|Upper-level intake (IU/day)
|Infants 0-6 months*
|Infants 6-12 months*
|Children 1-3 years old
|Children 4-8 years old
|People 9-70 years old
|People over 70 years old
|Females 14-50 years old, pregnant/lactating
What Causes Vitamin D Insufficiency?
Vitamin D deficiency can occur if you have this health condition:
- Cystic fibrosis (CF), Crohn's disease (CD), Inflammatory bowel disease, and celiac disease (CD): These autoimmune diseases can affect your intestines' ability to absorb vitamin D.
- Bariatric surgery that decreases the size of the stomach or bypasses parts of the small intestine makes it very difficult to ingest sufficient quantities of certain nutrients and vitamins. These people need to be carefully monitored and need to continue taking vitamin D and other supplements for life.
- A vegan diet: If you follow a strictly vegan diet, you may not be consuming enough vitamin D because most of the naturally occurring sources are animal-based.
- If you don't get enough sun, you may be at risk of vitamin D deficiency. Vitamin D deficiency during the winter is more likely because there is less sunlight.
- Darker Skin: Melanin reduces the skin's capacity to produce vitamin D in response to sun exposure. Older adults with dark skin are at high risk for vitamin D deficiency.
- Obesity: A BMI above 30 is associated with low Vitamin D levels. Fat cells store vitamin D so that it can't be released into the bloodstream. Vitamin D deficiency is more common among obese people. Obesity may require you to take larger doses of vitamin D to reach and maintain normal D levels.
- Live and Chronic Kidney Disease: These diseases reduce the ability of the body to convert vitamin D into its active form. Vitamin D deficiency results from a lack of this enzyme. Your body cannot convert vitamin D into its active form. With age, our kidneys become less efficient at converting vitamin D to its active (or usable) form, thus increasing our risk of vitamin D deficiency.
Other Factors Can Cause Vitamin D Deficiency.
- As we get older, our skin becomes less able to produce vitamin D.
- People who are homebound or who rarely go outdoors (such as nursing home residents) cannot use sunshine vitamin as a source of vitamin D.
- Dark-skinned people tend to be less able to produce vitamin D than fair-skinned people.
- Human milk only contains small amounts of vitamin D. Infants who are only breastfed are at Irish of not having enough vitamin D. Infant formula often includes only a small amount of D.
Medications Can Cause Vitamin D Deficiencies.
These medications include:
- Cholesterol-lowering drugs
- Seizure-control drugs
- A tuberculosis drug
- A weight-loss drug
Tell your doctor about any vitamins or supplements or alternative health products you take.
Signs and Symptoms of Vitamin D Deficiency
It's important to get enough vitamin D for strong bones and teeth. Vitamin D deficiency rickets in children is where their bones are weak and soft and can cause skeletal deformity (bowed legs). Vitamin D deficiency can lead to osteoporosis, which is when the bones become brittle and break easily. It makes it much more likely for osteoporotic fractures.
Vitamin D leads to the prevention of rickets, which manifests itself in children as incorrect growth patterns, muscle weakness, joint pain, and bone deformity. Children who are deficient in vitamin D can also have muscle weakness, sore and painful muscles.
Vitamin D deficiency symptoms include:
- Bone pain
- Muscle weakness, muscle aches, or muscle cramps.
- depressive symptoms
- loss of appetite
Tests for Vitamin D Deficiency
The best way to measure how much Vitamin D is in your body is by screening for vitamin D serum level, taking a 25-hydroxy blood test. For healthy people, a level of 20 ng/mL to 50 ng/mL of vitamin D is considered adequate. A level below 12 ng/mL indicates a deficiency of vitamin D.
Your doctor can order a simple blood test to check your vitamin D levels. There are two types, but the most common form of vitamin D is the 25-hydroxyvitamin D, which is known as 25(OH). You don't need to fast or otherwise prep for this kind of test.
Treatment for Vitamin D Deficiency
Vitamin D treatment involves getting more dietary vitamin D and supplements. There is no consensus on the level of vitamin D needed for optimal health, but a concentration of fewer than twenty nanograms per milliliter is generally considered vitamin D deficient and requires treatment.
The guidelines from the Institute of Medicine now recommend that everyone ages 1-70 take 600 international units (IU) and that adults older than age 70 take 800 IU of vitamin D to optimize bone health. The safe upper limit for vitamin D has been raised to 4,000 IUs. Doctors may prescribe up to 4,000 IU to treat a vitamin D deficiency.
If you don't get enough sunlight or take care to cover your skin when outdoors, you should speak to your physician about supplemental vitamin D, particularly if you have risks for vitamin D deficiency.
How Can I Prevent Vitamin D Deficiency?
The goals of treating or preventing vitamin D inadequacy are the same—to achieve and maintain an adequate level of vitamin D in the body. Your doctor will tell you whether or not you need to take vitamin D supplements. If so, they'll tell you how much you should take, too. You may also want to consider:
Eating foods that contain vitamin D is one way to get enough vitamin D. Remember that foods alone usually don’t provide enough vitamin D for optimal health.
It's unclear exactly how much sunlight exposure is needed to get enough vitamin D. 10 to 15 minutes a couple of times a week to the skin is probably all that's needed. You might need more sunlight (especially in early spring or late fall) if:
- You are older
- You have a darker skin color
- You live in the northern climate and are lack exposure to sunlight
Inadequate sun exposure prevent vitamin D from being produced by the skin. However, you should be aware that too much sunlight can increase the risk of skin cancer and age your skin. That is why taking a daily dose of a healthy vitamin is far safer than trying to get enough sun exposure.