Osteoporosis is associated with a number of lifestyle factors, including nutritional intake, vitamin D status, physical activity, smoking and alcohol consumption. International guidelines recommend healthy lifestyle choices to reduce risks associated with osteoporosis.1,2
To help maintain optimum bone health, the Australian recommended dietary intake (RDI) is 1300 mg per day for women older than 50 years of age, 1000 mg per day for men 50–70 years of age, and 1300 mg per day for men older than 70 years of age.3 The Australian adult population does not meet RDIs for calcium. In 2011–2012, the average daily intake for people 51–70 years of age was 781 mg for males and 741 mg for females, with intakes lower in people older than 70 years of age.4 With ageing, absorption of calcium becomes less effective.5,6
The richest sources of dietary calcium are dairy foods – milk, cheese and yoghurt. At least three serves of dairy food per day is recommended.3 High-fat soft cheeses should be avoided, and low-fat milks and yogurts chosen over regular varieties. Other calcium-rich foods include firm tofu (check label), almonds, sesame seeds, tinned fish, some green leafy vegetables, dried figs and calcium fortified soy milk.7 Patients who cannot achieve adequate calcium intake through diet alone may require supplementation.3 Guidelines for Australian recommended dietary intakes are listed in ‘Resources and further information’ earlier.
The evidence for the relationship between dietary calcium intake and fracture risk is contradictory; much is confounded by different methods of assessing calcium intake and the problems inherent in the self-reporting of calcium intake. A 19-year prospective cohort study of over 61,000 older Swedish women found that dietary intakes below 700 mg per day are associated with increased risk of fracture, including hip fracture, but higher intakes of dietary calcium only marginally reduce fracture risk.8 The rate of self-reported fractures in a five-year prospective study of approximately 35,000 British men and women was substantially increased in women with a dietary calcium intake of less than 525 mg per day. Fracture rates decreased with each quintile of increasing calcium intake, up to at least 1200 mg per day.9 Several meta-analyses (MAs)10,11,12 have concluded that dietary calcium has no effect on fracture risk, and a recent systematic review of 44 cohort studies found no association between dietary calcium intake in people older than 50 years of age and risk of fracture.13 In general, the inadequate design and imprecision of studies into the effects of dietary calcium on fracture risk precludes the drawing of robust conclusions, and MAs have reported considerable heterogeneity.
The importance of adequate calcium intake throughout life for the building and maintenance of the skeleton is supported by Australian and New Zealand guidelines.14
Vitamin D has an important role in maintaining bone health by promoting the absorption of calcium. Although some vitamin D can be acquired through diet (fatty fish, egg yolks, liver, irradiated mushrooms), the primary source for those residing in Australia is exposure to sunlight. Ultraviolet (UV) radiation from the sun has both beneficial and harmful effects on human health. A balance is required between excessive sun exposure, which increases the risk of skin cancer, and enough exposure to maintain adequate vitamin D levels. In Australia, the current recommendation for people with moderately fair skin is exposure of approximately 15% of the body (ie hands, face and arms) for 5–10 minutes, on most days of the week in summer before 10.00 am or after 3.00 pm (standard time).15 Exposure in winter should be 7–30 minutes, in the middle of the day. Exposure time depends on latitude and skin tone, with lower latitudes and darker skins requiring the longest exposures, as well as body fat level (obesity is associated with less synthesis of vitamin D).16,17 Clinicians should refer to recent national guidelines on seasonal sun exposure according to latitude and UV index.18
Additionally, after the age of 70, the skin is less efficient or incapable in some individuals of synthesising adequate amounts of vitamin D.19 Vitamin D supplements may be needed in order to maintain adequate levels.
Low body mass index (BMI) is an established risk factor for fracture. An MA of almost 60,000 participants in 12 prospective population-based cohorts worldwide found that the risk of any type of fracture increased significantly with lower BMI, largely independent of age and sex.20 When compared with a BMI of 25, a BMI of 20 was associated with a two-fold increased risk of hip fracture, independent of BMD. The association between high BMI and fracture risk is more complex. An MA of approximately 400,000 women from 25 prospective cohorts worldwide21 suggests that at a population level, high BMI (>35 kg/m2) is protective for all types of minimal trauma fracture, except humeral fracture. When adjusted for BMD however, obesity slightly increases the risk of all fractures. Weight fluctuation also appears to influence fracture risk. Post hoc analysis of data from over 120,000 women taking part in the Women’s Health Initiative (WHI) observational study and clinical trials demonstrated that both weight gain and weight loss are associated with increased fracture incidence.22 Women who lost more than 5% of their baseline body weight over three years increased their risk of hip fracture by 65%, compared to those who maintained stable weight for three years. Significantly higher rates of spinal fracture were also seen in this group. A 5% weight gain over three years was associated with higher incidence of upper- and lower-limb fractures.22 The relationship between body weight and fracture risk is complex. Guidance related to weight control should balance an individual’s current comorbidity status and/or comorbidity risk associated with overweight and obesity, such as type 2 diabetes and cardiovascular disease, with their risk of osteoporotic fracture. In particular, the increased risk of falls and fracture associated with frailty (of which weight loss is a component) in older individuals should be considered.
Smoking is a well-recognised risk factor for osteoporosis. An MA of over 59,000 men and women in 10 prospective cohort studies found that current smoking is significantly associated with increased risk of any fracture, compared to non-smokers (relative risk [RR]: 1.25, 95% confidence interval [CI]: 1.15–1.36). The highest risk was seen for hip fracture.23 A past history of smoking was also associated with significantly increased fracture risk in this analysis. The risk was lower than for current smoking, indicating that risk is attenuated with cessation of smoking. Although smokers tend to be thinner than non-smokers, low BMD could only account for 23% of smoking-related hip fractures in this study, indicating a potential direct effect of cigarette smoke toxins on bone metabolism.23
Excessive alcohol intake is also associated with increased fracture risk. A recent systematic review and MA of 22 observational studies suggests a significantly increased risk of fracture in men consuming alcohol daily or consuming more than 10 drinks per week (RR: 1.28, CI: 1.08–1.53).24 An analysis of three prospective cohorts (approximately 6000 men and 11,000 women) also found a significant increase in hip-fracture risk with alcohol intake, although no increased risk was seen in men and women consuming two units or less daily.25 Risk was only marginally lower in women compared to men. These observations were independent of BMD.25 General practitioners should consult recent Royal Australian College of General Practitioners (RACGP) guidelines that outline preventive-health strategies and smoking-cessation interventions.26,27,28