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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Calcium
Who may need extra calcium to prevent a deficiency?
Post-Menopausal Women
Menopause often leads to increases in bone loss with the most rapid rates of bone loss occurring during the first five years after menopause [64]. Drops in estrogen production after menopause result in increased bone resorption, and decreased calcium absorption [12,65,66].
Annual decreases in bone mass of 3-5% per year are often seen during the years immediately following menopause, with decreases less than 1% per year seen after age 65 [67]. Two studies are in agreement that increased calcium intakes during menopause will not completely offset menopause bone loss [68,69].
Hormone therapy (HT), previously known as hormone replacement therapy (HRT), with sex hormones such as estrogen and progesterone, helps to prevent osteoporosis and fractures. However, some medical groups and professional societies such as the American College of Obstetricians and Gynecologists, The North American Menopause Society and The American Society for Bone and Mineral Research recommend that postmenopausal women consider using other agents such as bisphosphonates (medication used to slow or stop bone-resorption) because of potential health risks of HT if combination HT (estrogen and progestin) is solely being administered to prevent or treat osteoporosis [70-72]. Postmenopausal women using combination HT to reduce bone loss should consult with their physician about the risks and benefits of estrogen therapy for their health.
Estrogen therapy works to restore postmenopausal bone remodeling levels back to those of premenopause, leading to a lower rate of bone loss [65]. Estrogen appears to interact with supplemental calcium by increasing calcium absorption in the gut. However, including adequate amounts of calcium in the diet may help slow the rate of bone loss for all women.
Amenorrheic Women and the Female Athlete Triad
Amenorrhea is the condition when menstrual periods stop or fail to initiate in women who are of childbearing age. Secondary amenorrhea is the absence of three or more consecutive menstrual cycles after menarche occurs (first menstrual period). The secondary type of amenorrhea can be induced by exercise in athletes and is referred to as "athletic amenorrhea". Potential causes of athletic amenorrhea include low body weight and low percent body fat, rapid weight loss, sudden onset of vigorous exercise, disordered eating and stress [73]. Amenorrhea results from decreases in circulating estrogen, which then negatively affect calcium balance [2]. Studies comparing healthy women with normal menstrual cycles to amenorrheic women with anorexia nervosa (a type of disordered eating) found decreased levels of calcium absorption, a higher urinary calcium excretion, and a lower rate of bone formation in women with anorexia [74].
The condition "female athlete triad" refers to the combination of disordered eating, amenorrhea, and osteoporosis. Exercise-induced amenorrhea has been shown to result in decreases in bone mass [75,76]. In female athletes, low bone mineral density, menstrual irregularities, dietary factors, and a history of prior stress fractures are associated with an increased risk of future stress fractures [77]. Stress fractures can severely impact health and cause financial burden, especially in physically active females such women in the military [78]. Thus, it is important for amenorrheic women to maintain the recommended Adequate Intake for calcium.
Lactose Intolerant Individuals
Lactose maldigestion (or "lactase non-persistence") describes the inability of an individual to completely digest lactose, the naturally occurring sugar in milk. Lactose intolerance refers to the symptoms that occur when the amount of lactose exceeds the ability of an individual's digestive tract to break down lactose. In the US, approximately 25% of all adults have a limited ability to digest lactose. Lactose maldigestion varies by ethnicity, with a prevalence of 85% in Asians, 50% in African Americans, and 10% in Caucasians [79-81].
Symptoms of lactose intolerance include bloating, flatulence, and diarrhea after consuming large amounts of lactose (such as the amount in 1 quart of milk) [82]. Lactose maldigesters may be at risk for calcium deficiency, not due to an inability to absorb calcium, but rather from the avoidance of dairy products [2,83,84]. Although some lactose maldigesters avoid dairy products, others are able to consume moderate amounts of lactose, such as the amount in an 8-oz glass of milk. Some individuals may be able to consume two 8-oz glasses of milk a day if they do so at different meals [85-87].
Symptoms of lactose intolerance vary from individual to individual depending on the amount of lactose consumed, history of previous consumption of foods with lactose and the type of meal with which the lactose is consumed [88-91]. Drinking milk with a meal helps reduce symptoms of lactose intolerance substantially. In addition, regularly eating foods (e.g. daily for 2-3 weeks) with lactose (such as milk) can help the body adapt to the lactose and thus reduce symptoms of lactose intolerance [88,90,92]. Other dietary options for lactose maldigesters include choosing aged cheeses (such as Cheddar and Swiss) which contain little lactose, yogurt which contains live active cultures that aid in lactose digestion, or lactose reduced and lactose free milk.
If an individual is a lactose maldigester and chooses to avoid dairy products, it is important for them to include non-dairy sources of calcium in their daily diet (see Table 2 for a listing of selected food sources of calcium) or consider taking a calcium supplement to help meet their recommended calcium needs.
Vegetarians
There are several types of vegetarian eating practices. Individuals may choose to include some animal products (ovo-vegetarian, lacto-vegetarian, lacto-ovo vegetarian, pesco-vegetarian) or no animal products (vegan) in their diet. Calcium intakes between lacto-ovo-vegetarians (those who consume eggs and dairy products) and non-vegetarians have been shown to be similar [93,94]. Calcium absorption may be reduced in vegetarians because they eat more plant foods containing oxalic and phytic acids, compounds which interfere with calcium absorption [2]. However, vegetarian diets that contain less protein may reduce calcium excretion [1]. Yet, vegans may be at increased risk for inadequate intake of calcium because of their lack of consumption of dairy products [95]. Therefore, it is important for vegans to include adequate amounts of non-dairy sources of calcium in their daily diet (see Table 2) or consider taking a calcium supplement to meet their recommended calcium intake. Furthermore, while early studies found vegetarian diets to be beneficial for bone health, more recent studies have found no benefits or even the opposite effect [96].
What is the recommended intake for calcium?
Helping hints for meeting your calcium needs
What affects calcium absorption and excretion?
Calcium's role in health and disease prevention
When can a calcium deficiency occur?
Is there a health risk of too much calcium?
