Introduction

Although calcium deficiency is uncommon, dietary intakes of the nutrient below recommended levels might have health consequences over the long term. The following groups are among those most likely to need extra calcium.

Postmenopausal Women

Menopause leads to bone loss1 because decreases in estrogen production both increase bone resorption and decrease calcium absorption.2 3 Annual decreases in bone mass of 3%-5% per year frequently occur in the first years of menopause, but the decreases are typically less than 1% per year after age 65.4 Increased calcium intakes during menopause do not completely offset this bone loss.5 6

Hormone replacement therapy (HRT) with estrogen and progesterone helps increase calcium levels and prevent osteoporosis and fractures. Estrogen therapy restores postmenopausal bone remodeling to the same levels as at premenopause, leading to lower rates of bone loss,7 perhaps in part by increasing calcium absorption in the gut. However, because of the potential health risks associated with HRT use, several medical groups and professional societies recommend that postmenopausal women consider using medications, such as bisphosphonates, instead of HRT to prevent or treat osteoporosis.8 9 In addition, consuming adequate amounts of calcium in the diet might help slow the rate of bone loss in all women.

Amenorrheic Women and the Female Athlete Triad

Amenorrhea, the condition in which menstrual periods stop or fail to initiate in women of childbearing age, results from reduced circulating estrogen levels that, in turn, have a negative effect on calcium balance.10 Amenorrheic women with anorexia nervosa have decreased calcium absorption and higher urinary calcium excretion rates, as well as a lower rate of bone formation than healthy women.11 The "female athlete triad" refers to the combination of disordered eating, amenorrhea, and osteoporosis. Exercise-induced amenorrhea results in decreased bone mass.12 13 In female athletes and active women in the military, low bone-mineral density, menstrual irregularities, certain dietary patterns, and a history of prior stress factors are associated with an increased risk of future stress fractures.14 15 Such women should consume adequate amounts of calcium.

Individuals with Lactose Intolerance

Lactose intolerance refers to symptoms (such as bloating, flatulence, and diarrhea) that occur when one consumes more lactose, the naturally occurring sugar in milk, than the enzyme lactase produced by the small intestine can hydrolyze into its component monosaccharides, glucose and galactose.16 The symptoms vary, depending on the amount of lactose consumed, history of consumption of lactose-containing foods, and type of meal.17 18 19 20 Approximately 25% of U.S. adults have a limited ability to digest lactose, including 85% of Asians, 50% of African Americans, and 10% of Caucasians.21 22 23 Lactose-intolerant individuals are at risk of calcium inadequacy if they avoid dairy products.24 25 26

Depending on the degree of lactose intolerance, some people with this condition might be able to consume moderate amounts of lactose, such as that present in 8 ounces of milk or in two 8-ounce glasses taken at different meals.27 28 29 Other options to reduce symptoms include drinking milk with a meal, inducing some adaptation by regularly eating foods with lactose daily for 2-3 weeks, or eating aged cheeses (such as Cheddar and Swiss with little lactose), yogurt (whose live active cultures aid in lactose digestion), or lactose-reduced or lactose-free milk.30 31 32 To ensure adequate calcium intakes, lactose-intolerant individuals can also choose nondairy food sources of the nutrient or take a calcium supplement.

Vegetarians

Vegetarians might absorb less calcium than omnivores because they consume more plant products containing oxalic and phytic acids.33 On the other hand, some vegetarian diets contain less protein than typical omnivore diets, which reduces calcium excretion.34 Lacto-ovo vegetarians (who consume eggs and dairy) and nonvegetarians have similar calcium intakes.35 36 However, vegans, who eat no animal products, might not obtain sufficient calcium because of their avoidance of dairy foods.37 38 It is difficult to assess the impact of vegetarian diets on calcium status because of the wide variety of eating practices.

Related Links: What is Calcium? | What are some important links between calcium and my health? | What foods provide calcium? | How much calcium do I need? | What happens if I do not get enough calcium? | Do I need extra calcium? | Can calcium be harmful? | Does calcium interact with any medicines or supplements?

Disclaimer
Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.

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The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

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Footnotes

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