I’ve also been told that I must increase my intake of vitamin D. Should I take a separate vitamin D supplement, or can I get enough through eating the right foods?
Calcium alone won’t make strong bones. You must also have enough vitamin D, which is an important but somewhat unusual kind of vitamin. First, it’s the only vitamin that can be made by your body when you are out in the sun. And second, liver and kidney enzymes convert vitamin D into a hormone (calcitriol) so that it can aid in strengthening bone. Vitamin D also aids in the absorption of calcium from the intestines so that blood levels stay normal. Vitamin D has two roles in bone health: It is a substance that helps maintain healthy calcium levels in the blood, and it also actually helps to make strong bones and teeth.
The amount of vitamin D that you need varies by age. Children and young adults up to age 25 need 400 international units (IU), as do pregnant and lactating women. Adults between the ages of 25 and 50 only need 200 IU. Adults between the ages of 51 and 70 require 400 IU. And if you’re over 70, you need 600 IU of vitamin D. Many clinicians now recommend 600– 1000 IU for all adults, especially older individuals who are particularly frail.
Most people don’t get enough sunlight to produce an adequate amount of vitamin D, and sun exposure is usually discouraged due to the risks of skin cancer. Therefore, you need supplements or fortified foods to meet the RDA for your age group. The best known vitamin D-fortified food is milk, which contains 100 IU per 8 ounces. But margarine, cereals, canned salmon, and orange juice can also be fortified with vitamin D.
It’s hard to determine how much sunshine you need to make enough vitamin D. Time estimates differ for warm versus cold weather because sun rays in the cold weather aren’t strong enough to trigger the body’s vitamin D-making mechanism. Older individuals do not absorb sun well enough to make an adequate sup-ply of vitamin D. Dermatologists are getting into the debate about vitamin D deficiency, as they have long been concerned about unprotected sun exposure and its associated risk of skin cancer. If you wear sunblock regularly, as is recommended by most dermatologists, the sunblock will block your body’s ability to make vitamin D. If you are a person of color, you may require longer sun exposure, because Black men and women and probably other persons of color tend to produce less vitamin D than do Whites during the same amount of sun exposure. Because determining how much sun exposure is needed to get adequate vitamin D is so unreliable and because unprotected sun exposure remains controversial among members of the scientific community, it really shouldn’t be counted toward your total for vitamin D.
As it relates to bones, vitamin D deficiency can cause fractures, leg pain, and deformities such as bowing of the legs. Severe vitamin D deficiency causes rickets in children and osteomalacia (softening of the bones) in adults.
Vitamin D has not only demonstrated its value for bone health, but a new study of 50,000 men showed that higher levels of vitamin D were associated with a 30% decrease in overall cancer risk, not just colon and prostate cancers. Taking vitamin D supplements has been associated with reducing the risk of multiple sclerosis and diabetes. Vitamin D deficiency has been linked to chronic fatigue, poorer cognitive function among older adults, fibromyalgia, and other problems. Also, pre-menopausal women who consume more than 500 IU of vitamin D may reduce their risk of breast cancer.
Vitamin D also benefits muscles. Older people who have higher levels of vitamin D can get up from a chair and walk better, leading researchers to believe that vitamin D can help reduce falls and fractures. So get-ting the optimal amount of vitamin D is particularly important for those whose fracture risk is increased due to osteopenia or osteoporosis. Some researchers have found that 800 IU of vitamin D provides the maximum amount of benefit in terms of fractures and falls. This dosage is usually prescribed for older frail adults but more and more clinicians are recommend-ing a daily intake of 600 to 1000 IU for all adults.
For those taking long-term steroids or who have glucocorticoid-induced osteoporosis (GIO), it is advisable to take either supplements of 800 IU of vitamin D per day or an activated form of vitamin D called alfacalcidiol (1 microgram/day) or calcitriol (0.5 microgram/day). For healthy individuals, a multivitamin containing the RDA of vitamin D for your age group should be enough to meet your daily requirement. You should not exceed 2000 IU through diet or supplements per day. The exception to this is once-a-week Fosamax Plus D, a prescription medication for osteoporosis, which also contains 2800 IU of vitamin D. Although you would be taking 2800 IU in 1 day, the dosage is absorbed by your body over the course of 7 days (see Question 56). Be aware that many calcium preparations also contain varying amounts of vitamin D.
Because vitamin D has been associated with several health benefits, many clinicians are now evaluating blood levels of vitamin D to identify people who may not be getting enough of this important vitamin. This is especially important for people at risk for bone loss and those who already have osteoporosis or osteopenia. The total blood level of vitamin D (total serum 25-OHD) includes both vitamin D made in the body and vitamin D absorbed from foods or supplements.
Normal levels of total vitamin D in the blood are above 30 ng/mL. If your level is between 20 and 30 ng/mL, this suggests insufficient vitamin D intake, while a level below 20 ng/mL shows vitamin D deficiency. If your level is below 30 ng/mL, your clinician will likely recommend supplements; the specific type and amount depend on how low your blood level is.