Vitamins are substances that your body needs to grow and develop normally. Vitamin D helps your body absorb calcium. Calcium is one of the main building blocks of bone. A lack of vitamin D can lead to bone diseases such as osteoporosis or rickets. Vitamin D also has a role in your nerve, muscle, and immune systems.
Many studies have shown that higher intake of vitamin D is associated with a lower risk of colorectal cancer.
You can get vitamin D in three ways: through your skin, from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. However, too much sun exposure can lead to skin aging and skin cancer, so many people try to get their vitamin D from other sources. Vitamin D-rich foods include egg yolks, saltwater fish, and liver. Some other foods, like milk and cereal, often have added vitamin D.
You can also take vitamin D supplements. Always check with your health care provider to see how much you should take.
The Institute of Medicine (IOM) of the National Academies has developed the following recommended daily intakes of vitamin D, assuming minimal sun exposure:
- For those between 1 and 70 years of age, including women who are pregnant or lactating, the recommended dietary allowance (RDA) is 15 micrograms (mg) per day. Because 1 mg is equal to 40 International Units (IU), this RDA can also be expressed as 600 IU per day.
- For those 71 years or older, the RDA is 20 mg per day (800 IU per day).
- For infants, the IOM could not determine an RDA due to a lack of data. However, the IOM set an Adequate Intake level of 10 mg per day (400 IU per day), which should provide sufficient vitamin D.
Be sure to follow any instructions on the supplement label but generally you will take the supplement daily with a meal.
Even though most people are unlikely to have high vitamin D intakes, it is important to remember that excessive intake of any nutrient, including vitamin D, can cause toxic effects. Too much vitamin D can be harmful because it increases calcium levels, which can lead to calcinosis (the deposit of calcium salts in soft tissues, such as the kidneys, heart, or lungs) and hypercalcemia (high blood levels of calcium).
Other potential side effects of too much vitamin D include fatigue, headache, loss of appetite, nausea, and others.