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 Taking vitamin D or calcium in supplement form had no benefit in the
large study of U.S. nurses, the study team writes in American
Journal of Clinical Nutrition, and there may be other substances in
dairy foods that also contribute to their apparent protective
effect.
“Early menopause can have substantial health impacts for women. It
increases their risk of cardiovascular disease and early cognitive
decline and osteoporosis,” lead author Alexandra Purdue-Smithe told
Reuters Health.
In addition, as women are delaying having kids into their later
reproductive years, having early menopause can have a substantial
impact on their ability to conceive as they wish, which can have
psychological and financial consequences, said Purdue-Smithe, an
epidemiologist with the School of Public Health and Health Sciences
at the University of Massachusetts Amherst.
“Given that (early menopause) affects roughly 10 percent of women in
the U.S. and other Western populations, it felt like a worthwhile
problem to start investigating and seeing if there are any
potentially modifiable risk factors for it,” she said.
Menopause, when a woman stops menstruating and her levels of
hormones like estrogen decline, typically happens between the ages
of 45 and 55. Menopause before age 45 is considered “early.”
Vitamin D may be involved in some of the hormonal mechanisms of
early menopause, but little is known about how dietary vitamin D and
calcium affect the risk, Purdue-Smithe and her colleagues write.
They analyzed data from the Nurses' Health Study II, a long-term
study of more than 100,000 U.S. registered nurses who were 25 to 42
years old in 1989 when they began answering health questionnaires
every two years.
The questionnaires were designed to assess the nurses’ lifestyles,
behaviors and overall health. Questions about diet were asked five
times over 20 years. Researchers followed the participants until
2011, by which time 2,041 women experienced early menopause.
“The women who consumed the most vitamin D from food sources had a
17 percent lower risk of having early menopause as compared to women
who consumed the least,” Purdue-Smithe said. The researchers found
this association only with dairy sources of vitamin D, like milk,
not with non-dairy sources like oily fish.
Women who consumed the most calcium from food sources were also
about 13 percent less likely to experience early menopause compared
to women who consumed the least calcium, and once again, only dairy
foods seemed to provide a benefit..
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“Our next direction is to look at actual individual dairy foods and
see if there's something else going on with dairy itself,” Purdue-Smithe
said.
The study team also found that taking high doses of calcium in
supplement form was associated with a higher risk of early
menopause. But the researchers speculate that these women might have
been diagnosed with osteoporosis or other conditions that are also
risk factors for early menopause.
“Most of what is known about the relationship between calcium and
Vitamin D and women’s issues is related to bone health," said Sandra
Arevalo, a dietitian and director of the Nutrition Services and
Community Outreach for Community Pediatrics at Montefiore Medical
Center in New York.
Lack of Vitamin D and calcium in a woman’s diet, mainly as age
progresses, increases her risk of low bone mineral density,
osteoporosis and bone fractures, said Arevalo, who wasn’t involved
in the study.
The top 10 food sources of calcium are low-fat yogurt, low-fat
cheese, sardines, calcium-fortified soy milk, calcium-fortified
orange juice, salmon, calcium fortified ready-to-eat cereal,
turnips, kale and bok choi, she noted in an email.
The top 10 sources of Vitamin D are cod liver oil, swordfish,
salmon, tuna fish, vitamin D fortified orange juice, low-fat vitamin
D-fortified milk, yogurt, fortified margarine, sardines and liver,
Arevalo said.
SOURCE: http://bit.ly/2qRLWPa American Journal of Clinical
Nutrition, online May 10, 2017
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