Does Birth Control Impact Bone Density?

Jenn is a 42-year-old female who came to pelvic floor physical therapy after experiencing urinary leakage. While going through her treatment plan of care, her mother fell and fractured her hip resulting in an osteoporosis diagnosis. Osteoporosis occurs when our bones become weaker over time and there is a higher chance of experiencing a bone break. Luckily, her mother recovered well, but the fracture caused Jenn to investigate osteoporosis further. She learned that osteoporosis risk increases in menopause due to lack of estrogen. As a long-time birth control user, Jenn started to wonder if this could impact her bone health and was concerned how it would impact her teenage daughter. 

The short answer to Jenn’s question of whether birth control impacts bone density is more research is needed to come to a conclusive answer. According to The National Osteoporosis Foundation, a 2016 statement based on the available research found there is not enough evidence regarding the negative effect of oral contraceptives on peak bone mass development but there is moderate evidence to support the detrimental effects of DMPA injections on peak bone mass.1 In other words, studies have found conflicting evidence on the use of combined oral contraceptives (estrogen and progestin) and whether it impacts bone density in adolescent girls. However, studies looking at the effect of low-dose estrogen oral contraceptives does raise concerns on the possibility that it can reduce the peak bone mass (think maximum strength of bones) achieved especially if used in the teenage years. DMPA or “depo” (depot medroxyprogesterone acetate) only has progestin and can cause reduced spine and hip bone density when used in adolescents that are developing. Bone loss in female adolescents who use DMPA is partly or fully reversible following discontinuation although recovery at the spine is faster than the hip.1 

It is possible that there is a difference between impacts on bone health at various ages and length of birth control use, but this is inconsistent in the research. For example, a study looked at 389 women who used oral contraceptives (OC) and 217 women who did not use oral contraceptive swith 50% of women aged 14-18 years old and 50% between 19-30 years old.2 There was no significant difference in bone mineral density (think thickness) in adolescent females regardless of OC duration use or estradiol dose. The bone density was lower with longer use in the spine and whole-body for women aged 19-30 years old. Bone density was lowest for the hip, spine, and whole-body when used for greater than 12 months. The results from this study indicated that long term use of oral contraceptives may negatively impact young adult women’s bone density while taking the medication.2 However, another study looked at 210 women who used oral contraceptive pills for at least 2 years with 200 nonusers in women aged 24-86 years old.3 There was no significant difference in bone mineral density between oral contraceptive users and nonusers.3 

It does appear that hormonal contraception among women 16-33 years old causes reduced B12 levels but very few women demonstrated a true deficiency outside of normal ranges over 3 years.4 It did not appear to negatively impact bone mineral density over the course of the study. However, postmenopausal women have shown an association between low B12 levels and low bone mineral density.4 

Overall, there is not enough research to fully answer Jenn’s question of whether birth control impacts bone density. It appears that birth control with both estrogen and progestin may or may not reduce bone mineral density although it does appear to reduce B12 levels. Progestin only hormonal birth control, like the “depo” shot, does lower bone mineral density. This may or may not be reversible. It is always smart to discuss the full benefits and side effects of any medication, including hormonal birth control, as well as alternative options with less possible side effects like Fertility Awareness Method. The choices we make should reflect our needs now but should also consider possible outcomes for our future selves. 

Written by Jordan Schmidt, PT, DPT

References

1. Weaver, C. M., Gordon, C. M., Janz, K. F., Kalkwarf, H. J., Lappe, J. M., Lewis, R., O'Karma, M., Wallace, T. C., & Zemel, B. S. (2016). The National Osteoporosis Foundation's position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations. Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA, 27(4), 1281–1386. https://doi.org/10.1007/s00198-015-3440-3
2. Scholes, D., Ichikawa, L., LaCroix, A. Z., Spangler, L., Beasley, J. M., Reed, S., & Ott, S. M. (2010). Oral contraceptive use and bone density in adolescent and young adult women. Contraception, 81(1), 35–40. https://doi.org/10.1016/j.contraception.2009.07.001
3. Allali, F., El Mansouri, L., Abourazzak, F.z, Ichchou, L., Khazzani, H., Bennani, L., Abouqal, R., & Hajjaj-Hassouni, N. (2009). The effect of past use of oral contraceptive on bone mineral density, bone biochemical markers and muscle strength in healthy pre and post menopausal women. BMC women's health, 9, 31. https://doi.org/10.1186/1472-6874-9-31
4. Berenson, A. B., & Rahman, M. (2012). Effect of hormonal contraceptives on vitamin B12 level and the association of the latter with bone mineral density. Contraception, 86(5), 481–487. https://doi.org/10.1016/j.contraception.2012.02.015