- 19 - 50 years: 600 IU (recommended dietary allowance)
- 70 years and older: 800 IU (recommended dietary allowance)
- Pregnant and breastfeeding females: 600 IU (recommended dietary allowance)
April 3, 2016
Are You Getting These Nutrients? - Part 7
Lower-than-optimal blood levels of vitamin D is becoming more common. It is thought this may be because people are spending less time outside (especially in winter and in areas far from the equator) and wearing more sunscreen. It is difficult to get enough in the diet. Very important for our bones, but is turning up as a factor in many aspects of health.
Low-carb sources include salmon, tuna, eggs, yogurt, and liver.
Vitamin D is a fat-soluble vitamin that plays a role in many important body functions. It is best known for working with calcium in your body to help build and maintain strong bones. Vitamin D is also involved in regulating the immune system and cells, where it may help prevent cancer.
Your body stores vitamin D and can make it when your skin is exposed to sunlight. Vitamin D is also found in some foods, mostly ones like milk that have been fortified with vitamin D. There are two forms of vitamin D: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Some research suggests that cholecalciferol is better at raising levels of vitamin D in the blood.
In children, a vitamin D deficiency can cause rickets, a disease that results in soft, weak bones. In adults, many people may not be getting enough vitamin D, especially those who live in northern areas (like the northern half of the U.S.) and the elderly. People with dark skin do not absorb sunlight as easily as those with light skin, so their risk of low vitamin D is even higher. One study of childbearing women in the Northern U.S. found that 54% of African-American women and 42% of white women had low levels of vitamin D.
That’s important because researchers are beginning to find that low levels of vitamin D may be linked to other diseases, including breast and colon cancer, prostate cancer, high blood pressure, depression, and obesity. The evidence doesn’t prove that too little vitamin D causes these conditions, but that people with higher levels of vitamin D are less likely to get these diseases.
Your body make vitamin D when your skin is exposed to the sun. The color of your skin affects the production of vitamin D. A fair-skinned person may need only about 45 minutes of sunlight a week to get enough vitamin D, while a person with dark skin may need up to 3 hours.
Clouds, smog, clothing, sunscreen, and window glass all reduce the amount of sunlight that actually reaches the skin. In northern areas, it is hard to get enough vitamin D from sunlight during the winter, so people living there may need to take vitamin D supplements. In the U.S., people who live above a line running from Los Angeles to South Carolina may not get enough vitamin D in winter.
Vitamin D is included in many multivitamins. It can be found alone as softgel capsules, tablets, and liquid in over-the-counter strengths from 50 - 1,000 IU. Higher doses are also available, but it is best to ask your doctor what the safest, most effective dose for you would be. For those who have trouble digesting fat, vitamin D injections are also available by prescription.
Recommended dietary allowances for vitamin D are listed below. Seniors and people who don’t get exposed to much sunlight may need to take supplements. Seniors may be at risk of developing vitamin D deficiency because, as we age, the body does not make as much vitamin D from sunlight, and it has a harder time converting vitamin D into a form it can use.
If you are concerned about your vitamin D levels, ask your doctor whether you should take a supplement, and how much.
Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable doctor.
Taking too much vitamin D can cause several side effects. However, scientists don’t all agree on how much is too much.
Side effects may include - being very thirsty, metal taste in mouth, poor appetite, weight loss, bone pain, tiredness, sore eyes, itchy skin, vomiting, diarrhea, constipation, a frequent need to urinate, and muscle problems.
You cannot get too much vitamin D from sunlight, and it would be very hard to get too much from food. Generally, too much vitamin D is a result of taking supplements in too high a dose.
People with the following conditions should be careful when considering taking vitamin D supplements - high blood calcium or phosphorus levels, heart problems, kidney disease, sarcoidosis, and tuberculosis.