Background

Calcium is important for the normal development and maintenance of the skeleton, with over 99% of total body calcium found in bones and teeth [21]. The remainder of total body calcium is tightly regulated in blood, extracellular fluid, and muscle, where it plays a role in blood pressure regulation, muscle contraction, nerve transmission, and hormone secretion. Calcium homeostasis is maintained by parathyroid hormone, which increases blood calcium, and calcitonin, which lowers blood calcium. If blood calcium levels fall, parathyroid hormone is secreted, stimulating the release of calcium from bone. Chronic calcium deficiency, due to inadequate intake, will result in progressive loss of skeletal mass and osteoporosis.

During lactation, secretion of calcium into breast milk averages about 200 mg/day to accommodate the whole-body mineral accretion rate of the infant [22]. Although renal calcium excretion rates are lowered to meet the elevated calcium demands of lactation, the primary source of calcium secreted in breast milk appears to be from increased maternal bone resorption. The concentration of calcium in breast milk decreases after 3-6 months and thus, the greatest loss of bone mineral content occurs within the first

Table 18.3

Guidelines for Energy Control During Lactation

Diet

  • Eat a well balanced diet. Compare your typical daily food choices against the US Department of Agriculture Dietary Guidelines and MyPyramid, or dietary guidance from your country of origin, and make appropriate modifications [19, 20]. In the event that you need help making modifications, see your primary care physician or a clinical dietitian. A vitamin and/or mineral supplement may be necessary
  • Restricting dietary intake by 500 kcal/day is safe as is moderate weight loss
  • Reduce consumption of foods high in fat and simple sugars (e.g., sucrose, fructose)
  • Emphasize fruit and vegetable consumption
  • Emphasize foods high in calcium and vitamin D
  • If capable of becoming pregnant, then consume 400 mcg/day of folic acid for neural tube defect prevention

Exercise

  • Prepregnancy activities may be resumed gradually after medical clearance (usually around 4-6 weeks postpartum)
  • Gradually work up to 30 min of moderate exercise each day for most days of the week
  • An exercise regimen consisting of 45 min of moderate aerobic exercise 4 days/week (60-80% maximum heart rate) in combination with a 500 kcal/day diet restriction has been shown to promote postpartum weight loss and does not negatively affect breastfeeding
  • Avoid excessive fatigue and keep hydrated
  • Wear a bra that is supportive to your activity few months postpartum [22]. Serial measurements of bone density after 2-6 months of lactation have shown a decrease of 3-10% in bone mineral content of trabecular bone (sponge-like interior) in the lumbar spine, hip, femur, and distal radius, with smaller losses occurring with cortical bone (exterior shell) [22-24]. Loss of calcium from the maternal skeleton is not prevented by increased dietary calcium, even among women with low baseline calcium intakes [25-27]. Upon return of menses, and restoration of estrogen, maternal bone lost during lactation is restored within 3-6 months of cessation of breastfeeding [23, 24, 26, 28, 29]. Based on the majority of epidemiological studies, there is no adverse effect of lactation history on peak bone mass, bone density, or hip fracture risk [30]. Thus, the evidence suggests that the bone mineral changes that occur during and following lactation are a normal physiological response, and an increased requirement for calcium is not needed.
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