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Osteoporosis

This article was originally written in 1997 by Kathryn Orlinsky.

 

 

 

The risk of osteoporosis is not increased by extended breastfeeding. On the contrary, long-term breastfeeding may be beneficial to our bones.

There were two different kinds of studies about bone density. In the first set, researchers examined the density of women's bones over time as they nursed their babies. For example, they asked how a woman's bone density was affected by nursing for six months and compared that value with those obtained at parturition (birth), and six months after weaning. In the second set of studies, researchers determined what the influence of pregnancy and breastfeeding was on bone density later in life.

In all cases, bone densities were found to be less, and sometimes significantly less than baseline levels after six months of nursing.6,10 This turned out to be merely a temporary dip in bone density. The same studies showed that bone densities were increasing and sometimes back to baseline levels by twelve months postpartum. This increase in bone density occurred even when women were still nursing and/or pregnant.5

Increased bone turnover

We tend to think of bones as being static entities. Nothing could be further than the truth. Our bones are really factories, manufacturing our blood cells within their marrow. In addition, the bone structure itself is constantly being renewed as old bone is metabolized and new bone is formed. The rate of turnover can be found by determining the concentration of certain marker chemicals.

Several researchers found that these markers for bone turnover; urinary hydroxyproline for bone resorption, and serum osteocalcin for bone formation, were dramatically increased during the first six months of breastfeeding.4,11 Upon weaning, bone resorption decreased while high rates of bone formation were retained, resulting in a net gain of bone. 4

There is another life stage during which bone turnover is markedly increased. This is the period following menopause. Osteoporatic women who are in menopause have much in common with amenorrheic breastfeeding women. In the months before lactating women resume ovulating, they and their menopausal counterparts both have low estrogen, high prolactin, high serum calcium, high hydroxyproline and high parathyroid hormone (PTH) levels. Both types of women are losing bone mass at this time. However, in lactating women, this loss is later reversed.

Another difference, which may explain the reversibility of the bone loss, is that unlike women in menopause, breastfeeding women do not lose calcium in their urine. Researchers found that "urinary Ca [calcium] excretion declines rapidly in early lactation, with a further decline as lactation proceeds." This conservation was sustained throughout the six month postweaning period.4 It is unclear what differentiates osteoporatic women from lactating women. PTH and PTH-related peptide have both been implicated,4,11 as has progesterone.

Although in some studies, women who had breastfed for six months or less did not always regain their baseline bone densities by six months after weaning, in other studies, women who breastfed for a year suffered no loss in bone density. This difference may depend on when the bone density is tested. Some women may recover bone density more quickly than others.

Long term studies

What happens when women breastfeed for several years? None of the studies were continued long enough to answer this question. Hopefully, these studies will be continued so that the answers will be found one day. In the meantime, we must turn to the second set of studies to understand what happens later in life.

When researchers asked women about past practices, bearing and breastfeeding many children did not show up as risk factors for osteoporosis.8 On the contrary, one study found not breastfeeding children to be a risk factor.2 Another study found that "breastfeeding for more than eight months was associated with greater mineral at some sites."7 In a third study, women with a history of lactation had higher lumbar bone densities than women who had not breastfed.3 Even when women had breastfed for 22 months, their bone mineral densities did not differ from women who had not breastfed at all.9 The number of pregnancies had no affect on bone density.1,7

These data together suggest that breastfeeding is at least neutral, if not beneficial to women. The short-term studies indicate that bone density is on the way up by one year after giving birth, even if the mother is still nursing. The long-term studies show that breastfeeding is not a risk factor for osteoporosis, regardless of the number of children or length of time each had nursed. Further studies may even indicate that extended breastfeeding is beneficial to women's bones.

 

  1. Bererhi H, Kolhoff N, Constable A and Nielsen SP. 1996. Br. J. Obstet. Gynecol. 103(8):818-821.
  2. Blaauw R, Albertse EC, Beneke T, Lombard CJ, Laubscher R and FS Hough. 1994. South African Med. J. 84(6):328-332.
  3. Feldblum PJ, Zhang J, Rich LE, Fortney JA and RV Talmage. 1992. Epidemiology. 3(6):527-531.
  4. Kent GN, Price RI, Gutteridge DH, Smith M, Allen JR, Bhagat CI, Barnes MP, Hickling CJ, Retallack RW, Wilson SG, Devlin RD, Davies C and A St. John. 1990. J of Bone and Mineral Research. 5(4):361-369.
  5. Laskey MA and A Prentice. 1997. Lancet. 349(9064):1518-1519.
  6. Lopez JM, Gonzalez G, Reyes V, Campino C and S Diaz. 1996. Osteoporosis International. 6(2):153-159.
  7. Melton LJ 3rd, Bryant SC, Wahner HW, O'Fallon WM, Malkasian GD, Judd HL and BL Riggs. 1993. Osteoporosis Int. 3(2):76-83.
  8. Parazzini F, Tavani A, Ricci E and C La Vecchia. Menstrual and reproductive factors and hip fractures in post menopausal women. 1996. Maturitas. 24(3):191-196.
  9. Sinigaglia L, Varenna M, Binelli L, Gallazzi M, Calori G and R Ranza. 1996. J Reprod Med. 41(6):439-443.
  10. Specker BL, Tsang RC, and ML Ho. 1991. Obstet Gynecol. 78(1):56-62.
  11. Zinaman MJ, Albertson BD, Hickey M, Simon JA and TP Tomai. 1990. Fertility and Sterility. 54(3):465-469.

 

 

 


 

 
 

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