Vitamin D plays an essential part in calcium absorption. When vitamin D stores are low, as they may be in as many 85 to 90 percent of women, according to nurse practitioner Marcelle Pick of Women to Women, the calcium you eat isn't well absorbed from the intestines. If you don't get enough vitamin D, all the calcium supplements in the world won't improve your bone density. Since women are at higher risk for osteoporosis, or low bone density, getting enough vitamin D throughout life becomes crucial to preventing bone loss after menopause.
Sources
Vitamin D comes from two sources, sun exposure and dietary intake. Few foods contain vitamin D. Fortified milk, yogurt, margarine, cereal and orange juice, fish such as salmon, tuna and mackerel and cod liver oil all supply vitamin D. Sun exposure activates vitamin D synthesis in the skin, but the time of year, latitude and duration of sun exposure all affect the amount of vitamin D absorbed. Between five and 30 minutes twice a week between 10 a.m. and 3 p.m. is generally adequate, at least in the spring, summer and fall, the Office of Dietary Supplements reports. Men in general have a higher intake of vitamin D than women, and older women have lower intakes than younger women, according to the ODS.
Dosage
Vitamin D dosage recommendations have recently been revised upward. The new recommendations for women are 600 International Units, or IU, daily from age 14 through age 70, and 800 IU daily for those over age 70. Vitamin D intake is also expressed in micrograms; the doses in mcg equals 15 mcg from 14 to 70 and 20 mcg for those over 70. The upper dosage limit for safe intake is 4,000 mg. Take amounts greater than the recommended daily dose only on the advice of your medical practitioner, since vitamin D can be toxic at high doses.
Types
There are two forms of vitamin D supplements, ergocalciferol, or D-2 and cholecalciferol, called D-3. While both appear to have the same benefit at nutritional levels, in high doses D-3 appears to have more potency, the ODS advises. The Harvard School of Public Health recommends taking supplements that contain D-3, stating that this form is three to four times more potent than D-2.
Overdose
Too much vitamin D can have toxic side effects. Excess vitamin D can cause appetite loss, excessive urination and heart arrhythmias. Vitamin D excess can also lead to excess calcium absorption, or hypercalcemia. Calcium deposits can build up in the heart, blood vessels and kidneys, damaging the organs. High vitamin D levels don't normally occur from sun exposure or from dietary intake, but rather from over-supplementation. Women should follow their medical practitioner's guidance on the ideal dosage for their needs.
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