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Back to Bone Health and Osteoporosis

How Does Milk Product Consumption Affect Fracture Risk?

The relationship between milk product consumption and bone fracture risk has been examined in several studies, including a meta-analysis. Overall, the evidence suggests that milk product consumption is not associated with an increased risk of bone fracture, and may even decrease its risk.

Highlights

  • Milk and milk products, such as yogurt and cheese, appear to be either not associated with fracture risk or associated with a reduced risk, especially in women;
  • A similar relationship has been observed in men; however, the evidence is limited.

Synopsis

Although fracture risk is influenced by non-modifiable factors, such as age and sex, several lifestyle factors also play a role, namely diet, physical activity level and tobacco and alcohol use. Additionally, some chronic medical conditions and the long-term use of certain medications may increase fracture risk by weakening bones. Many variables, including genetic predisposition, may impact the effectiveness of interventions.

Milk contains many essential nutrients and bioactive compounds that promote bone mineralization, and has traditionally been associated with strong bones. Nonetheless, the impact of milk and milk products on fracture risk is not clear, and the mechanisms involved have yet to be fully elucidated.

Thus far, the sum of the evidence suggests that the intake of milk and milk products, such as yogurt and cheese, is either not associated with fracture risk or associated with a reduced risk.

The Evidence

A meta-analysis published in 2011 investigated the association between milk intake and hip fracture risk in adults aged 34 to 80 years. The analysis consisted of data from 7 prospective cohort studies (n = 270, 251), including the Health Professionals Follow-Up Study and the Swedish Mammography Study.1 

  • There was no significant association between milk intake and the risk of hip fracture in either men or women;
  • When excluding the Swedish study (an outlier), a 5% reduced risk of hip fracture per daily glass of milk was observed in women.

A prospective cohort study by Khan et al. investigated the long-term associations between dietary calcium intake and fractures in 41,514 adults aged 40 to 69 years from the Melbourne Collaborative Cohort Study.2

  • There was an inverse relationship between dietary calcium intake and fracture risk;
  • Adults with increased dairy consumption were less likely to have fractures after the age of 50.

Feskanich et al. conducted a prospective cohort study to examine whether adolescent milk consumption affects height attained and the risk of hip fracture in older adulthood. A cohort of 96,927 nurses and physicians, aged 21 to 103 years, from the Nurses' Health Study and the Health Professionals Follow-Up Study were followed for over 22 years.3

  • The consumption of milk or cheese during adolescence was not associated with fracture risk in older adulthood;      
  • In men, higher adolescent milk intake increased fracture risk by 9%, but the association became non-significant when adjusted for height.

In another prospective cohort study, 5,718 Caucasian adults aged 26 to 85 years from the Framingham Offspring Study were followed for 12 years to study the relationship between milk products and bone mineral density as well as hip fracture.4

  • There was a non-significant inverse relationship between milk intake, as well as that of yogurt, and hip fracture risk;
  • Participants in the highest tertile of fluid dairy intake (milk and yogurt combined) had a 60% lower risk of hip fracture than those in the lowest tertile.

A prospective cohort study by Michaëlsson et al. investigated whether high milk consumption is associated with mortality and fractures. This study followed 106,772 adults aged 29 to 79 years from the Swedish Mammography Cohort and the Cohort of Swedish Men for up to 20 years.5

  • Cheese and fermented milk products were inversely related to fracture rates, especially among women;
  • Women who consumed ≥3 glasses of milk per day had a 16% increased risk of fracture, including a 60% increased risk of hip fracture;
  • There was no association between fracture risk and any level of milk intake for men;
  • As stated by the authors, the results should be interpreted with caution as all confounding factors may not have been accounted for. Independent replication is warranted to confirm the findings.  

Two other prospective cohort studies investigated the relationship between milk product intake and hip fracture. Sahni et al. included 764 older Caucasian adults from the Framingham Offspring Study, whereas Benetou et al. included 29,122 adults from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Both studies found no association between the consumption of milk products and the risk of hip fracture.6,7

Data on 3,251 Caucasian women aged 20 to 90 years from the National Health and Nutrition Examination Survey (NHANES) III were used in a cross-sectional study. The relationship between bone health, including osteoporotic fracture, and childhood and adolescent milk intake was investigated.8

  • Among women aged ≥50 years, low milk intake during childhood, but not adolescence, was associated with a greater likelihood of lifetime and osteoporotic fractures;
  • Among women aged 20 to 49 years, childhood and adolescent milk intake did not appear to be associated with the incidence of lifetime fracture.

Potential Mechanisms

The potential mechanisms underlying the association between milk product intake and fracture risk are not entirely understood, but they are likely related to the role of milk and milk products in bone mineral density, a key risk factor for osteoporosis and fractures.

Calcium and vitamin D

Dietary calcium is needed to replace daily losses in order to maintain the structural strength of bones, and vitamin D plays an essential role in its absorption from the intestine.9

Other minerals: potassium, magnesium and phosphorus

Several of the minerals found in milk products may contribute to bone mineralization by promoting normal calcium metabolism (e.g., potassium, magnesium). The high Ca:Na and Ca:P ratios of milk may help protect bone calcium stores by reducing urine calcium losses, and potassium may also have a calcium-sparing effect.10,11

Protein

Milk protein intake has been associated with higher serum insulin-like growth factor-1 (IGF-1), which increases osteoblast activity and mediates bone mineralization, more so than other sources of protein.12

Milk protein digestion yields several components, such as lactose and phosphopeptides, which enhance the absorption of calcium from the gut.13

In vitro, whey protein has been shown to suppress osteoclast cells, which mediate bone resorption.14

Other dairy components

Probiotics found in fermented milk products synthesize vitamins, such as vitamin K and folate, which are involved in bone matrix formation and may stimulate calcium uptake.15

Conclusion

The sum of the evidence suggests that there is either no association or an inverse association between the consumption of milk and milk products and the risk of fractures in men and women. However, the research in men is more limited.

The majority of the research is based solely on milk. The association between total milk product consumption (i.e., milk, yogurt and cheese) and the risk of fractures is less clear and requires further research, but evidence suggests that yogurt and cheese may be protective.

More research is needed to better understand the relationship between total dairy intake during childhood and adolescence and fracture risk in adulthood.

References

  1. Bischoff-Ferrari HA et al. Milk intake and risk of hip fracture in men and women: a meta-analysis of prospective cohort studies. J Bone Miner Res 2011;26:833-839.
  2. Khan B et al. Higher dietary calcium intakes are associated with reduced risks of fractures, cardiovascular events, and mortality: a prospective cohort study of older men and women. J Bone Miner Res 2015;30:1758-1766.
  3. Feskanich D et al. Milk consumption during teenage years and risk of hip fractures in older adults. JAMA Pediatr 2014;168:54-60.
  4. Sahni S et al. Milk and yogurt consumption are linked with higher bone mineral density but not with hip fracture: the Framingham Offspring Study. Arch Osteoporos 2013;8:119.
  5. Michaëlsson K et al. Milk intake and risk of mortality and fractures in women and men: cohort studies. BMJ 2014;349:g6015.
  6. Sahni S et al. Protective association of milk intake on the risk of hip fracture: results from the Framingham Original Cohort. J Bone Miner Res 2014;29:1756-1762.
  7. Benetou V et al. Diet and hip fractures among elderly Europeans in the EPIC cohort. Eur J Clin Nutr 2011;65:132-139.
  8. Kalkwarf HJ et al. Milk intake during childhood and adolescence, adult bone density, and osteoporotic fractures in US women. Am J Clin Nutr 2003;77:257-265.
  9. Moore LL et al. Effects of average childhood dairy intake on adolescent bone health. J Pediatr 2008;153:667-673.
  10. Teucher B et al. Sodium and bone health: impact of moderately high and low salt intakes on calcium metabolism in postmenopausal women. J Bone Miner Res 2008;23:1477-1485.
  11. Kemi VE et al. Low calcium:phosphorus ratio in habitual diets affects serum parathyroid hormone concentration and calcium metabolism in healthy women with adequate calcium intake. 2010 Br J Nutr 2010;103:561-568.
  12. Darling AL et al. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr 2009;90:1674-1692.
  13. Toba Y et al. Milk basic protein: a novel protective function of milk against osteoporosis. Bone 2000;27:403-408.
  14. Takada Y et al. Whey protein suppresses the osteoclast-mediated bone resorption and osteoclast cell formation. Int Dairy J 1997;7:821-825.
  15. Scholz-Ahrens KE et al. Prebiotics, probiotics, and synbiotics affect mineral absorption, bone mineral content, and bone structure. J Nutr 2007;137:838S-846S.

Keywords: factures , bone health , calcium , vitamin D


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