Nutrition & Osteoporosis

Nutrition and Osteoporosis - Fact Sheet for Health Professionals

Nutrition has long been established as a key factor in building and maintaining bone strength. While calcium and vitamin D3 are crucial nutrients for bone health, energy, protein and other vitamins and minerals all play a role. Risk of osteoporosis is influenced not only by current dietary intake, but by life-long dietary habits. 

Body Mass Index
Low BMI (< 19) has been identified as a risk factor for osteoporosis. Frail older people, those with eating disorders and some athletes may have a low BMI and should be assessed for osteoporosis. Significant recent weight loss, particularly in older people, is also a cause for concern.

Nutritional screening
Nutritional screening tools can be used to identify those at risk who may require some intervention or referral to a dietitian. Tools include the Malnutrition Universal Screening Tool (MUST) devised by BAPEN. In older people there are many confounding factors which may contribute to poor nutritional status. These include difficulties eating (for e.g. badly fitting dentures, arthritis), poor appetite, loneliness, social isolation, difficulties accessing and preparing food and ill health. Identifying and managing any problems can have a significant impact on nutritional status. Older people should also be assessed for dehydration, as this can exacerbate dizziness and increase risk of falls and injury. 8 glasses of water daily will improve these symptoms, unless contraindicated by their doctor.

Dieting and weight loss
Bone loss has been shown to be accelerated three-fold during weight loss. This may increase risk of osteoporosis in dieters, particularly in those following restrictive diets. In addition, dieters may be excluding sources of calcium in the diet, such as dairy foods, in the belief that they are fattening. This is a worrying phenomenon in teenage girls, who may restrict milk at a time when 50% of bone mass is being laid down. Research has shown that teenage girls who consume adequate dairy foods do improve bone strength, but that this does not lead to weight gain. In fact, recent research is indicating that dairy foods may be beneficial for body weight. In an analysis of obesity and clinical trials of calcium intake, increased calcium from dairy products was consistently associated with a reduction in body weight, body fat and weight gain.

Dietary calcium
Calcium is necessary for bone health and the recommended intake (RDA) varies throughout life. According to the food safety authority of Ireland, the RDA is 800 mg/day for children, adults and older people, increasing to 1200 mg for teenagers, pregnant and lactating women. Unfortunately, one third of women in Ireland consume inadequate calcium. The National Children's Food Survey also found that 28% boys and 37% girls aged 5-12 have inadequate calcium intakes. The richest sources of calcium in the diet are yogurt milk and cheese. Three servings a day will help meet calcium needs of an adult or child, five servings are recommended during adolescence and pregnancy. Smaller amounts of calcium may be obtained from other food sources, such as green vegetables, bread and sardines. It should be noted however that the bioavailablility of calcium from non-dairy sources is lower. Calcium intake can be boosted by including dairy foods in a variety of ways such as in smoothies, hot chocolates, pizzas, cheese sauces, lasagne etc. For some, milks fortified with extra calcium and vitamin D can be useful.

Vitamin D
Recent research has confirmed that low vitamin D status (25 hydroxyvitamin D < 25nmol/l) is more prevalent than previously believed, in infants, adolescents, pregnant women and older people. Vitamin D is primarily produced by the action of UVB light on the skin, with a limited number of foods also providing vitamin D (oily fish, egg yolks, liver and fortified milks and margarines). Due to Ireland's latitude (and the use of sunscreens) production from UVB light is compromised. This, together with poor dietary intakes, has contributed to wide-spread sub-optimal vitamin D status. Dietary sources of vitamin should therefore be encouraged in all ages. Regular consumption of oily fish (salmon, sardines, mackerel, fresh tuna) will not only provide vitamin D, but also cardioprotective n3 fatty acids. Milks fortified with vitamin D are another useful source for at risk groups.

Special considerations
Particular attention should be paid to the calcium intakes of individuals at risk of osteoporosis due to conditions such as coeliac disease, malabsorption or inflammatory bowel disease. Those on long-term corticosteroids should also ensure a good calcium intake.

Calcium and vitamin D supplements
A recent Cochrane review of 38 clinical trials concluded that calcium and vitamin D supplements (given in combination) can reduce risk of fracture by 19%, being higher when given to residents in long-stay units. The women's health initiative reported that calcium and vitamin D supplementation result in a modest increase in bone density and a reduction in risk of hip fracture. Vitamin D given alone has not been found to reduce risk. Calcium and vitamin D supplements are routinely used for the treatment of osteoporosis, as an adjunct to a good dietary intake of calcium and vitamin D.

There is evidence that high alcohol intakes increase risk of osteoporosis, although different conclusions have been drawn regarding a safe level of intake. The Health Promotion Unit in Ireland recommends that women consume no more than 14 standard drinks per week, and men no more than 21 units. This advice has wide-reaching health benefits in addition to bone health. A high alcohol intake will also increase risk of falls and injury and should be a consideration when assessing falls risk.

It has been suggested that a high caffeine intake is a risk factor for osteoporosis, with some groups advising a consumption of no more than 4 cups of coffee a day. Caffeine is found in coffee, tea, cola-type drinks, energy drinks and chocolate. Consumption of fizzy drinks has been found to displace milk intake in teenagers and may contribute to sub-optimal bone development in this age group.

There is inconclusive evidence that soy has a beneficial effect on bone health. The available evidence does not support a recommendation for the use of soy for this purpose.

Other vitamins and minerals
Various research studies suggest a role for different vitamins and minerals in bone health. The evidence in some cases is inconsistent (e.g. vitamin A) or contradictory (e.g. vitamin C). There is stronger evidence for a role of certain micronutrients, for e.g. vitamin K. A low intake has been associated with low bone density and increased risk of fracture. However it should be noted that vitamin K may also be a marker for poor dietary intake overall.

Healthy eating advice
A healthy balanced diet will ensure that all nutrients necessary for bone health are provided in the diet. This can be achieved by following the principals of the food pyramid. Those at low risk of osteoporosis should be given general health and well being advice, including information on alcohol, caffeine, smoking, calcium and vitamin D. Those identified to be at high risk may need further assessment and dietary advice to improve nutritional status and reduce risk of fracture.