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Educate your patients on the importance of 3-A-Day of Dairy: Here's
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tool (PDF: 618k) to show families how to get their 3-A-Day of Dairy
every day for stronger bones.
Developed in conjunction with The American Academy of Family
Physicians, The American Academy of Pediatrics, The American Dietetic
Association, and The National Medical Association.
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Dairy Council Digest Archives
DAIRY'S BENEFICIAL ROLE IN WOMEN'S HEALTH
Volume 77, Number 2 Mar/Apr 2006
Dairy and Diseases/Disorders Affecting Women
Osteoporosis. Osteoporosis is a major public health threat for an estimated 44 million Americans (15). In the United States, 10 million individuals over the age of 50 years are estimated to already have the disease and almost 34 million have low bone mass, placing them at increased risk for osteoporosis (16). Of the 10 million Americans estimated to have osteoporosis, 80% are women (15). One in two women (one in four men) over age 50 will have an osteoporosis-related fracture within their lifetime.
To reduce the risk of osteoporosis, lifestyle changes, including intake of a nutritionally balanced diet containing foods rich in calcium and vitamin D (e.g., dairy foods such as milk, cheese, and yogurt) and regular exercise (particularly weight-bearing or resistance exercise) are recommended (2,6,15,16). Calcium and vitamin D are the nutrients most important for bone health (2,16). Unfortunately, many women fail to consume sufficient amounts of these nutrients (3).
Numerous studies in women indicate that increasing consumption of dairy foods or dairy food nutrients (e.g., calcium, vitamin D, protein) helps to maximize peak bone mass and reduce bone loss and the incidence of osteoporosis (17-24). Researchers recently found that hip and spine bone loss associated with oral contraceptive use was reduced in women using oral contraceptives who consumed dairy products containing at least 1,000 mg of calcium per day (18). Use of oral contraceptives without adequate calcium intake may prevent young women from reaching peak bone mass and increase their risk of osteoporosis in later life. In this one-year study, 154 women aged 18 to 30 years (oral contraceptive users and non-users) with low dietary calcium intakes (<800 mg/day) were randomized to one of three diet intervention groups: control (<800 mg calcium/day), medium dairy (1,000 to 1,100 mg calcium/day), or high dairy (1,200 to 1,300 mg calcium/day) (18). At the end of the year, women consuming the medium or high dairy diets had significantly higher bone mineral density in their hips and spines compared to the low dairy group. Oral contraceptive users consuming low calcium diets lost bone at both spine and hip sites compared to non-users, but this loss was prevented with the medium or high dairy intakes (18). Findings of this study suggest that women taking oral contraceptives should consume dairy products at levels necessary to achieve recommended intakes of calcium to optimize their bone health (18).
Health professionals should encourage women to consume 3 servings of fat-free or low-fat dairy products (i.e., milk, cheese, or yogurt) a day, which can improve the overall nutritional quality of their diets and help prevent diseases such as osteoporosis.
In a cross-sectional study of 108 Japanese female nursing students aged 19 to 25 years, low calcium intake and mild hyperparathyroidism (partly explained by low vitamin D nutrition and low calcium and protein intakes) were identified as important independent predictors of low bone mineral density (21). In another cross-sectional study of 963 Norwegian women aged 19 to 35 years, low milk intake was associated with low forearm bone mineral density, whereas milk drinkers had significantly higher bone mineral density at the wrist and forearm (22).
A meta-analysis of 15 randomized controlled trials of the effect of calcium for the prevention of postmenopausal osteoporosis found that increasing calcium intake reduced bone loss by approximately 2% after two or more years and led to a significant (~23%) reduction in the risk of spine fractures (20).
In 29 postmenopausal women whose diets were typically low in calcium (<600 mg/day), intake of three servings/day of fruit-flavored yogurt instead of a non-nutritious sweet snack for seven to ten days significantly reduced a urinary marker (i.e., N-telopeptide) for bone resorption (14). The addition of yogurt to the diet also improved the nutrient quality of the women’s diets (14). Studies in Chinese postmenopausal women have demonstrated that age-related bone loss is reduced and bone mineral density is increased in those who increased their milk intake (23,24).
In addition to calcium, other nutrients in dairy foods such as vitamin D and protein are also important for bone health. Adequate vitamin D status is essential to maximize skeletal health throughout life (4,16,25). Vitamin D can be obtained through synthesis in the skin following exposure to sunlight and by consuming vitamin D-containing foods such as vitamin D-fortified dairy foods (e.g., milk, some cheeses and yogurts). Few foods are naturally rich in vitamin D. For this reason, virtually all milk in the U.S. is voluntarily fortified with vitamin D to a level of 100 I.U. per one cup serving (4).
Emerging science indicates that overweight or obese women may enhance their weight loss efforts by consuming 3 servings of milk, cheese, or yogurt a day incorporated in a calorie-reduced weight loss diet.
Recent findings from national surveys reveal that many women fail to consume sufficient vitamin D and/or have poor vitamin D status (26,27). One study reported that females aged 14 to 50 years were about half as likely as their male counterparts to meet vitamin D recommendations from food sources (26). This study found that the dairy group was the largest food source of calcium and vitamin D (26).
Poor vitamin D status results in decreased intestinal calcium absorption and can lead to secondary hyperparathyroidism, increased bone loss, osteomalacia, and increased risk of fractures (4). A meta-analysis of 25 randomized controlled trials of vitamin D and bone density and fractures in postmenopausal women found that vitamin D decreased vertebral and possibly non-vertebral fractures (28). Increased intake of calcium and vitamin D has been shown to be effective in reducing bone loss, fracture incidence, and falls in older women (21,29-31).
Protein is another nutrient in dairy foods that favorably affects bone health and helps to prevent osteoporosis, particularly in women who meet their calcium and vitamin D requirements (32,33). Several epidemiological studies in women demonstrate a positive association between protein intake and bone health (34-37). In a cross-sectional study of 489 postmenopausal women, higher bone mineral density in the spine, midradius, and total body was found in those who consumed a high protein diet (72 grams/day or 20% of calories) and at least 400 mg calcium/day compared to women who consumed diets lower in protein (37). Other nutrients in dairy foods such as phosphorus and potassium have been demonstrated to improve bone health in women (38,39).
A report from the North American Menopause Society (NAMS) emphasizes the important role of calcium both before and after menopause to reduce the risk of diseases such as osteoporosis (40). The NAMS states that dairy products are among the best sources of calcium due to their high calcium content, high calcium bioavailability, and low cost relative to their total nutritional value (40). Dairy foods are also important sources of other key nutrients for bone health such as vitamin D, protein, phosphorus, and potassium (7-9).
Overweight and Obesity. Among U.S. women aged 20 years and over, 61.1% are overweight or obese (41). Overweight and obesity are associated with a number of diseases affecting women such as heart disease, type 2 diabetes, and some cancers (e.g., endometrial, colon, postmenopausal breast) (42).
More women (43.6%) than men (28.8%) attempt to lose weight (42). Unfortunately, many women trying to lose weight fail to follow the recommended strategy of reducing calorie intakes and increasing physical activity (43). Evidence indicates that eliminating certain food groups (e.g., dairy foods) from the diet in an effort to lose weight may be harmful to women’s health and counterproductive to their weight loss efforts. Because weight loss or calorie restriction is associated with adverse effects on bone health, higher calcium intakes than currently recommended may be needed for overweight women on calorie-reduced diets to protect their bones (44,45).
Emerging scientific research indicates that overweight or obese women may be able to enhance their weight loss efforts by consuming 3 servings of dairy products such as milk, cheese, or yogurt each day as part of a reduced calorie weight loss diet (46-49). In young adult women ages 18 to 31 years enrolled in a two-year exercise program, calcium from dairy foods was associated with lower body weight and body fat in those consuming fewer than 1,900 calories per day, but not in those whose intake of calories was higher (46). In this study, higher calorie intakes appeared to obscure any beneficial effect of calcium on body weight. In a reevaluation of five clinical studies originally designed to measure bone health and including 780 women, researchers found that a higher intake of calcium, particularly from dairy foods, was associated with a lower body mass index and body weight (48). In a subsequent reevaluation of the same data, it was estimated that increasing calcium intakes to recommended levels may reduce the prevalence of overweight and obesity in women by 60 to 80% (49).
Although more research is needed, intake of recommended daily servings of dairy foods may help women reduce their risk of premenstrual syndrome, stroke, metabolic syndrome, kidney stones, and other diseases or disorders.
As reviewed in a previous Digest (50), several randomized clinical trials which included overweight or obese women following reduced calorie diets (i.e., 500 calorie deficit) demonstrated that increasing consumption of dairy foods (i.e., milk, cheese, and/or yogurt) to 3 servings/day enhanced body weight and body fat losses, reduced central (trunk) obesity, and minimized loss of lean body tissue compared to the same degree of energy restriction while consuming little or no dairy. Consuming 3 servings of dairy foods a day may also help improve body composition during weight maintenance (51). It is important to note that the beneficial effect of dietary calcium or dairy product intake on body weight or body fat appears to occur only under specific circumstances such as reduced calorie intake, or only for specific individuals such as those who are obese or overweight (52).
Among the several mechanisms suggested to explain dairy’s beneficial effect on body fat metabolism is the ability of dietary calcium to increase fat oxidation (53). In a recent clinical trial in 19 normal weight women ages 18 to 30 years, researchers found that women who consumed 3 servings of dairy foods each day over the course of a year burned more fat and calories from a meal than did women who consumed a low calcium (<800 mg/day or 1 to 2 servings of dairy/day) diet (53).
Premenstrual Syndrome. A diet rich in dairy foods or dairy food nutrients may be beneficial in alleviating symptoms and preventing premenstrual syndrome (PMS), a condition occurring in about 8% to 20% of women of childbearing age (54). Results of clinical trials indicate that increasing calcium intake by about 1,000 mg to 1,300 mg/day substantially alleviates PMS symptoms (55-58). Further, studies show that intake of milk, cheese, and yogurt is associated with fewer PMS symptoms (55,56,59). In addition to reducing PMS symptoms, calcium and vitamin D in foods may help prevent PMS from developing in the first place (54). In a recent case-control investigation, researchers compared the diets and supplement use of 1,057 women aged 27 to 44 years who reported developing PMS over the course of 10 years with that in 1,968 women who reported no or minimal PMS symptoms during the same period (54). High calcium and vitamin D intake from food (but not supplements) – equivalent to about 4 servings of fat-free or low-fat milk or low-fat yogurt – was associated with a significantly lower risk of PMS compared to intake of one serving or less a day (54).
Metabolic Syndrome. Metabolic syndrome, a risk factor for coronary heart disease and type 2 diabetes, is a clustering of three or more of the following metabolic abnormalities: abnormal lipid profiles, high blood pressure, obesity, and abnormal glucose metabolism. An analysis of data from more than 10,000 middle-aged and older U.S. women participating in the Women’s Health Study found that higher intakes of calcium (total, dietary, supplemental) and dairy products were associated with a lower prevalence of metabolic syndrome (65). The highest versus the lowest calcium intake from foods was associated with a lower prevalence of metabolic syndrome than calcium from supplements (65). Also, in overweight younger women aged 18 to 30 years, increased dairy consumption was shown to be associated with reduced incidence of metabolic syndrome (66).
Women can be positive role models for their families by consuming milk and other dairy foods themselves and by making these foods readily available at meals and as snacks.
Other Potential Benefits. Consuming dairy products has additional potential benefits for women. A high intake of calcium-rich foods may reduce women’s risk of developing kidney stones (67,68). According to an eight-year prospective study of more than 96,000 women aged 27 to 44 years participating in the Nurses’ Health Study II, women with the highest (1,129 mg/day or more) versus lowest (626 mg/day or less) intakes of dietary calcium had a significantly reduced risk for kidney stones (67). In contrast to dietary calcium, supplemental calcium intake was associated with increased risk of kidney stones. The researchers speculate that high dietary calcium inhibits the intestinal absorption and urinary excretion of oxalate, thus decreasing the formation of calcium oxalate stones, the most common type (67).
Fermented dairy products or dairy products containing probiotics (i.e., live microorganisms that confer a health benefit) may help protect against urinary tract infections in women, according to a case-control study that evaluated dietary and other risk factors for urinary tract infections (69). Women who consumed fermented milk products such as yogurt and certain cheeses three or more times a week had a 79% lower incidence of urinary tract infections compared to those who ate these dairy foods once a week or less (69).
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