Calcium Needs During Lactation

by Judith B. Roepke, Ph.D., R.D.

Conventional wisdom says that women should drink lots of extra milk while nursing so they will have enough calcium to produce milk for their babies. But recent research has shown that new mothers, like all women, need plenty of milk, but they don't benefit from more milk than other women who are not nursing.¹

All Women Need Sufficient Calcium
All women should get at least 1000 mg of calcium a day - the equivalent of about three glasses of milk - and women 18 or younger need 1300 mg of calcium to keep their bones strong. But, surprisingly, breastfeeding mothers don't need to drink a lot more milk than their non-nursing friends. This is because a nursing mother's body adapts in elegant ways to ensure that her baby gets calcium-rich milk.

Nursing Alters Calcium Absorption
During the early stages of nursing, mothers actually lose bone. The mother's extra calcium needs are handled by the body in two ways. Less calcium is excreted in her urine, and a hormone called parathyroid-related peptide (PTHr-P) apparently plays a role in pulling calcium out of the woman's bones and getting it into her blood. High levels of calcium in the blood keeps the excess calcium - for example, all those extra glasses of milk a nursing mother might drink - from being absorbed. Nursing mothers also have low levels of estrogen, which normally stimulates women's bodies to absorb calcium.

Once a woman stops nursing or menstruation begins, her estrogen levels rise and calcium begins to be absorbed normally again. It is in this period that the bone is rebuilt. Research indicates that a woman's bones are restored to normal within 6 months to a year after menstruation starts or she weans her child. ² It is reassuring that the process of producing breastmilk may reduce the risk of bone disease.

Breastfeeding May Help to Prevent Osteoporosis
The process that occurs in the bones during nursing is thought to help protect women from developing osteoporosis later in life. Research has shown that women who breastfed had a considerably lower incidence of hip fractures in later years. One study even found that the more months a woman spent breastfeeding, the lower her risk was for a hip fracture later in life.³Osteoporosis is a disorder that affects both men and women, but primarily women in the later years. Bone is an active tissue that is remolded constantly as older bone is gradually removed and replaced by new bone. With aging, the process of forming new bone seems to be slower than the removal of older bone. This results in a decrease of bone mass. The so-called trabecular bone is generally most affected. This is mesh-like bone within the marrow that acts as a grid, and provides strength to the other bone. When this bone mass is decreased the bone is weakened and fractures can occur even without falling. Women with low bone mass most often end up breaking their hips or vertebrae. The resulting pain and disability can be life threatening.

Adequate Calcium and Being Active is the Best Prevention
There are probably many causes of osteoporosis, but it occurs more frequently in women who are petite and have been sedentary. Smoking and excessive alcohol use are often related as well. However, scientists and health professionals still have much to learn about this condition. Why do some women lead very healthy lifestyles and still develop osteoporosis, for example?

Some factors that we cannot modify, such as one's genetic make up, affect the risk of osteoporosis. We also know that men are at lower risk for the disease because they generally have a greater bone mass than women of similar weight. In addition, women who are heavy tend to have greater bone mass than those who are slim, although being overweight is a risk factor for a host of other problems including heart disease and diabetes.

Current knowledge suggests that an active lifestyle and a good lifelong calcium intake are the best ways to prevent osteoporosis.

The lesson here is that all women need plenty of calcium throughout their lives, not just when pregnant and breastfeeding. It's easy enough for women to get the required 1000 mg. of calcium daily. A combination of milk, cheese, yogurt and green leafy vegetables like broccoli and kale can provide the required 1000 mg needed. Women who don't care for milk can boost their calcium intake with enriched orange juice, soymilk, enriched soy products and calcium supplements. When buying a calcium supplement, choose simple calcium carbonate, which is 40% calcium, because researchers have found that calcium from these forms is better absorbed than some mixtures.⁴

¹ Institute of Medicine, Dietary Reference Intakes: Phosphorous, magnesium, Vitamin D, fluoride. National academy Press, Washington DC 1997
² Kent GN et al., J bone Mineral Research 1990; 5: 361- 369.
³ Cummings RG and RJ Klineberg, Int J Epidemiology 1993; 22:684-691
⁴ Whitney, EN and Rolfes SR, Understanding Nutrition, 8^th ed., 1999, West/Wadsworth Publishing Co, CA pp . 400-401.