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A recurring theme in vitamin D studies has been that low levels lead to adverse outcomes, but supplementation does little to reverse those outcomes.

Now another study has reinforced that theme: Calcium and vitamin D supplements -- at the official recommended-daily-allowance level -- had no impact on self-reported menopause-related symptoms for older women, according to , at the Kaiser Permanente Center for Health Research in Portland, Ore., and colleagues.

They looked at more than 34,000 women who took 1,000 mg of calcium per day plus 400 IU of vitamin D with an average follow-up of 5.7 years. Women in the calcium-vitamin D arm did not have a different number of symptoms at follow-up compared with women taking placebo (P=0.702), they reported in .

"Our study suggests that women should not rely on vitamin D and calcium supplements to relieve menopausal symptoms, but there are important caveats," said LeBlanc in an accompanying press release. "The average age of the women at the start of our study was 64, but the average age of menopause is 51, and it's around that time that the most severe symptoms usually occur."

She added that in order to study the effects of supplementation on the most severe menopausal symptoms, "we need to do a study in younger women."

Previous findings from the same trial showed that women on calcium-vitamin D combination improved their lipid profile compared with those on placebo; the same could not be said for reducing menopausal symptoms.

Data were taken from the Women's Health Initiative (WHI) trial from the mid 1990s until 2005. All of the women were ages 50-79 and were randomized into hormone therapy or dietary modification. From years 1-3, the participants also randomized into another two groups at 40 different sites. One of the groups took vitamin D and calcium supplements and one took placebo.

Menopausal symptoms were self-reported by the participants. In addition to the same number of symptoms, the supplement group also didn't have a significantly different level of sleep disturbance (adjusted P=0.909), emotional well-being (adjusted P=0.909), or energy or fatigue (adjusted P=0.909) versus the placebo group.

When researchers looked at individual symptoms, they still found no effect from the supplementation.

One possibility for a weak or nonexistent effect from supplementation is that the vitamin D supplements were at doses too low to make a significant difference, especially for women who were deficient. The dosage given in the study would have likely raised the mean serum 25(OH)D levels by about 4 ng/mL, according to the researchers, which might not have been enough to lead to a clinical difference. However, participants were allowed to take off-protocol supplements of up to 600 IU per day until 1999, then 1,000 IU after that.

Still, many advocates of vitamin D supplementation have argued that much higher regular doses, in the thousands of IU per day, are needed for prevention and/or treatment of conditions other than osteoporosis.

It's also possible that any potential benefits of vitamin D supplementation were offset by the calcium supplements, which have been linked to a higher likelihood of hot flashes in breast cancer survivors, the authors explained.

Data from larger, more decisive trials of vitamin D are set to be released in the next couple of years.

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