N° 94 | November 2014

Dietary intake of carotenoid may reduce risk of hip fracture in lean men

Osteoporosis is an epidemic problem affecting both elderly men and women worldwide. Although the prevalence of osteoporosis is higher in women than in men, men experience greater comorbidity and mortality after hip fracture than women.

Leanness has been established as an independent risk factor of hip fracture. Recently, several observational studies have reported that low body mass index (BMI) could be related to increased oxidative stress, particularly, in men. Experimental and epidemiologic data suggest that carotenoids in vegetables and fruits may benefit bone health due to their antioxidant properties. This study examined the relationship between dietary total and specific carotenoids, as well as vegetables and fruits, and risk of hip fracture among middle-aged to elderly Singapore Chinese.

Study design

Data was used from a prospective cohort of Chinese men and women in Singapore. The study followed up 63,000 middleaged to elderly participants for hip fracture incidence from 1993 through 2010. Cox proportional hazards model was used to estimate relative risk after adjustment for age, dialect group, body mass index, level of education, daily total energy intake, smoking status, physical activity, dietary intake of calcium, soy isofl avones, and vitamin B6, menopausal status for women, use of hormone replacement therapy for women, and medical history of diabetes and stroke.

Results

It was found that dietary intake of vegetables was signifi cantly associated with reduced hip fracture risk in men. Similarly, dietary intake of total carotenoids, α, β-carotene and lutein/zeaxanthin were inversely associated with hip fracture risk in men (P<0.05). Compared to men in the lowest quartile intake, men in the highest quartile had statistically significant lower risk of hip fracture by 26% to 39%. Interestingly, the greatest protective effects of vegetables and carotenoids were found in men with body mass index < 20kg/m2. However, no association was observed between dietary intake of carotenoids or vegetables/fruits and hip fracture risk among women.

Plausible explanation of the results

It is proposed that the benefits of carotenoids on bone might be via their counteractive effects against oxidative stress, which has been shown to play a possible etiologic role in age-related bone loss and consequent osteoporotic fractures by increasing osteoclastogenesis and stimulating osteoclastic differentiation through the receptor activator of NF-kB ligand (RANKL) expression and signaling mechanism. Furthermore, low BMI has been associated with increased oxidative damage indexed by 8 - hydroxy - 20-deoxyguanosine particularly in men; the molecule 8 - hydroxy - 20 - deoxyguanosine is a reliable biomarker for the measurement of systemic oxidative stress. Following this, it is speculated that lean men possibly have higher oxidative stress in bones leading to hip fracture, and the antioxidant effects of carotenoids may counteract this mechanism of osteoporosis related to leanness. In addition to the high carotenoid content in vegetables, another possible mechanism for the benefi cial effects on bones includes the alkaline nature of vegetables. In particular, potassium in vegetables may neutralize excess metabolic acid to maintain an acid - base homeostasis and to promote calcium balance in bones.

Conclusion

Findings from the study demonstrated increased dietary intake of vegetables or carotenoids from fruits and vegetables may reduce risk of hip fracture in men. The apparent protective effect was observed particularly among lean men with body mass index less than 20 kg/m2. This is potentially due to the antioxidant effects of carotenoids, which may counteract the mechanism of osteoporosis related to leanness. Take home message

Besides maintaining a healthy lifestyle, a balanced diet with increased consumption of carotenoid-enriched vegetable and fruits, such as carrots, sweet potatoes, green leafy vegetables, cantaloupe and papaya, may benefit bone health, especially in lean men.

Based on: Dai Z, Wang R, Ang LW, Low YL, Yuan JM, Koh WP. Protective effects of dietary carotenoids on risk of hip fracture in men: the Singapore Chinese Health Study. J Bone Miner Res. 2014;29(2):408-17

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