Severe vitamin D deficiency is rare in the United States. It can cause a disease known as osteomalacia where the bones become soft. In children, this is known as rickets. These are both different conditions from osteoporosis.
National Osteoporosis Foundation Recommendations for Vitamin DNOF recommends that adults under age 50 get 400-800 International Units (IU) of vitamin D every day, and that adults age 50 and older get 800-1,000 IU of vitamin D every day. Some people need more vitamin D.
There are two types of vitamin D supplements. They are vitamin D2 and vitamin D3. Previous research suggested that vitamin D3 was a better choice than vitamin D2. However, more recent studies show that vitamin D3 and vitamin D2 are equally good for bone health. Vitamin D3 is also called cholecalciferol. Vitamin D2 is also called ergocalciferol.
Experts disagree on the safe upper limit for vitamin D. In the past, experts said that people should not get more than 2,000 IU of vitamin D per day. Because of recent studies, some experts now say that a much higher amount is safe. It is difficult to get too much vitamin D unless a person is taking a prescription dose (usual dose 50,000 IUs once a week). In that case, healthcare providers can easily monitor a patient’s vitamin D level with a blood test to make sure they aren’t getting too much of the vitamin. Problems associated with getting too much vitamin D are very rare.
Sources of Vitamin DThere are three ways to get vitamin D:
- Supplements and medications
SunlightYour skin makes vitamin D from the ultra-violet light (UVB rays) in sunlight. Your body is able to store the vitamin and use it later. The amount of vitamin D your skin makes depends on time of day, season, latitude, skin pigmentation and other factors. Depending on where you live, vitamin D production may decrease or be completely absent during the winter. It is difficult to measure the amount of vitamin D that your skin makes.
People with fair skin make more vitamin D than people with darker skin. People who live in higher latitudes such as New York, instead of lower latitudes such as Florida, may get less vitamin D from sunlight. Window glass and air pollution also decrease the amount of vitamin D that your skin can make.
People who are housebound and do not get outside in the sun are unable to make vitamin D. As adults age, the ability to make vitamin D also decreases. Because of concerns about skin cancer, many people stay out of the sun, cover up with clothing and use either sunscreen or sunblock to protect their skin. Probably the most important factor which limits the ability of the skin to make vitamin D is the use of sunscreen and sunblock. Even an SPF (sun protection factor) of 8 reduces the production of vitamin D by 95 percent. These products help protect the skin from the harmful effects of the sun. Because of the cancer risk from staying in the sun, many people need to get vitamin D from other sources.
FoodVitamin D is naturally available in only a few foods. It is very difficult to get all the vitamin D you need from food. Foods that have vitamin D include fatty fish (examples are mackerel, salmon and tuna). Vitamin D is also added to milk and to some brands of other dairy products, orange juice, soymilk and cereals.
Check the food label to see if vitamin D has been added to a particular product. One eight ounce serving of milk usually has 25% of the daily value (DV) of vitamin D. The DV is based on a total daily intake of 400 IUs of vitamin D. Therefore a serving of milk with 25% of the DV of vitamin D contains 100 IUs of the vitamin.
Supplements and MedicationsMany people do not get enough vitamin D. These individuals should consider taking a supplement. Before adding a vitamin D supplement, check whether any supplements, multivitamins or medications you already take contain vitamin D. You can also estimate the amount of vitamin D that you get from foods.
Subtract the total amount of vitamin D you are already getting each day from the total amount you need to get each day. For example, a 55 year old woman who gets 400 IUs of vitamin D from her calcium supplement should take between 400 and 600 additional IUs of vitamin D to meet the 800-1,000 IUs of vitamin D that is recommended for her age.
Vitamin D supplements can be taken with or without food. While your body needs vitamin D to absorb calcium, you do not need to take vitamin D at the same time as a calcium supplement. If you need help choosing a vitamin D supplement, ask your healthcare provider or pharmacist to recommend one.
People Who May Not Get Enough Vitamin DIn the U.S. today, many people do not get enough vitamin D. People most likely at risk for not getting enough vitamin D include:
- older adults
- people who spend little time in the sun
- people living in nursing homes or other institutions
- people with certain medical conditions such as serious diseases of the nervous or digestive systems
- people with very dark skin
- obese or very overweight people
How to find out if you’re getting enough vitamin DYou can find out if you’re getting enough vitamin D for your body’s needs by having a simple blood test that checks your vitamin D level.
Discuss with your healthcare provider whether you should have this test done. It measures 25-hydroxyvitamin D, which is also written as 25(OH)D. This test should not be confused with a test for 1,25-dihydroxy-vitamin D.
To protect your bone health, most experts agree you need one of the following levels of 25(OH)D:
- 75 nmol/L or higher
- 30 ng/mL or higher
In general, we can make the following recommendations, assuming you are in good health.
Calcium citrate (not calcium carbonate): 1000mg per day
Calcium carbonate will not be absorbed if you are taking medications to reduce stomach acid. The carbonate needs stomach acid to be broken down and absorbed.
Vitamin D3: 2000 units per day. There seems to no disadvantage and there may even be a benefit to more vitamin D.
Vitamin C: 500mg per day.
From the National Osteoporosis Foundation.