 |
 |
|
 |
|
|
PREVENTATIVE STRATEGIES
Prevention is based on two objectives, which take into account the time course of bone mass during a subject's life time (see insert 2):
- Optimising the gain in bone mass during growth : according to epidemiologic studies, a 10% increase in peak bone mass reduces the subsequent risk of osteoporotic fracture by 50%. Two recent nutritional interventional studies demonstrate that it is possible to alter the pathway of bone development in children and teenagers, and especially that this effect is sustained several years after the discontinuation of such an intervention.
- Maintaining bone mass and then limiting bone loss: even though such bone loss is a normal event related to aging, osteoporosis results from an excessively negative balance between bone loss and new bone formation, with fracture being a complication.
Prevention of osteoporosis is based mainly on hormone replacement therapy in post-menopausal women, performance of regular physical activity and nutritional measures.
NUTRITIONAL PREVENTION
A consensus exists in that the main nutrients which participate in nutritional prevention of osteoporosis are calcium, vitamin D and proteins, key elements to bone metabolism.
Calcium
The purpose of calcium homeostasis is aimed at maintaining constant serum calcium levels. Bone contains nearly 99% of body calcium, i.e., 1000-1200 grams in adults. It acts as the body's calcium stores. In the event of a calcium deficiency, constant serum calcium levels are maintained at the expense of the bone pool. This finding emphasises the importance of building an optimal bone mass and of adequate calcium intake throughout life.
In children and teenagers, several nutritional interventional studies using calcium phosphate or milk have demonstrated that optimisation of calcium intake promotes bone mass gain. The most favourable period may be the time before puberty maturation. Retrospective studies suggest that bone mineral density in adults is correlated with calcium intake in childhood.
In the years following the menopause, calcium cannot obviously compensate for oestrogen deficiency. Conversely, it potentiates the effect of hormone replacement therapy: bone mass is better protected if therapy is administered in combination with a high calcium diet.
Later in life, calcium inhibits bone loss all the more so in that spontaneous intake of calcium is low. When used in combination with vitamin D, it significantly reduces the risk of bone fracture.
Actually, French dietary surveys demonstrate that calcium intake is very inadequate, especially in women: 50% of teenagers and 75% of subjects over 50 years of age ingest less than two thirds of nutritional recommendations (see insert 3), a level considered as “critical”.
In practice, dairy products are the foods which have the highest amounts of calcium, in a highly bioavailable form; 300 mg of calcium are found in 250 ml of milk (whole milk, skim milk or fat-free milk) or two yoghurts, or also in 30 g of Swiss cheese 40 g of Cantal cheese or 300 g cottage cheese. Thus, it is recommended to ingest three or four dairy products daily. Fruits and vegetables, cereals and drinking water supplement these intakes.
Vitamin D
Vitamin D in large part determines the intestinal absorption of calcium. It is provided by food in the diet (in fish liver oil, oily fish, egg yolk, butter, liver and whole milk dairy products) and especially in the skin, under the effect of ultraviolet radiation. Vitamin D deficiency is relatively common, even in young subjects. Thus in a survey conducted on teenagers in the Paris area, 24% presented with low serum 25OH-vitamin D levels at the end of the winter period. Studies conducted in Europe on adults show that 36% of men and 47% of women on average had a vitamin D deficiency, with this percentage rising to 60% in subjects over 75 years of age and 90% of those confined to an institution. Interventional studies have demonstrated the positive effects of the calcium-vitamin D combination on bone mass and the incidence of bone fractures, even in the very elderly. Supplementation with vitamin D of milk and fresh dairy products routinely ingested, which has been authorised in France for over one year, should contribute to improved vitamin D status in the French population. An improvement in serum vitamin D levels, even though minor, has been observed in certain countries (US, Canada), where this measure has been applied for several years.
In the elderly, exposure to sunlight and dietary intake, which generally are inadequate, provide the rationale for drug supplementation.
Proteins
Inadequate protein intake has a negative effect on bone status. During growth, it can induce demineralisation, as illustrated by the case of young girls with anorexia nervosa. In older adults it is a risk factor for bone fracture: inadequate protein intake accelerates bone loss and enhances sarcopenia (significant loss of muscle mass), which itself promotes falls. Normalization of protein intake in subjects with a fracture of the upper extremity of the neck of the femur limits contro-lateral bone loss and improves muscular performance. In particular proteins act by stimulating hepatic synthesis of a growth factor, IGF-1.
Conversely, it is generally considered that an excess amount of proteins produces urinary excretion of calcium via acidosis. In fact, recent studies have shown that proteins have no harmful effect when calcium intake is adequate.
In practice, the risk of protein deficiency mainly involves the elderly, who should be encouraged to ingest protein with high nutritional quality, ie., meat, fish or eggs, at least once a day, and one dairy product at each meal. Proteins from vegetables provide the supplement. In patients with a "small appetite", the nutritional density of the diet can be increased without altering the size of portions by incorporating for example, powdered milk in coffee or chocolate milk, and in mashed potatoes and desserts; by adding grated cheese and egg to soups and cheese-topped baked vegetable or by adding beaten egg whites into vegetable mousse or fruit.
Other nutrients
Chronic alcoholism is a risk factor for osteoporosis due to the toxicity of alcohol for bone forming cells and malnutrition. It is also a risk factor for bone fracture as a result of a propensity to falls. Excess sodium can negate the calcium balance by increasing calciuria, but the benefit of restricted sodium intake has not been demonstrated. Some epidemiological studies suggest that vitamin K, vitamin C or phyto-oestrogens (which exist in some vegetables such as soya bean), may have a protective effect on bone. Since little data is available, and in particular interventional studies are lacking, it is not possible to make recommendations.
A consensus exists in that the main nutrients which participate in nutritional prevention of osteoporosis are calcium, vitamin D and proteins, key elements to bone metabolism.
Calcium
The purpose of calcium homeostasis is aimed at maintaining constant serum calcium levels. Bone contains nearly 99% of body calcium, i.e., 1000-1200 grams in adults. It acts as the body's calcium stores. In the event of a calcium deficiency, constant serum calcium levels are maintained at the expense of the bone pool. This finding emphasises the importance of building an optimal bone mass and of adequate calcium intake throughout life.
In children and teenagers, several nutritional interventional studies using calcium phosphate or milk have demonstrated that optimisation of calcium intake promotes bone mass gain. The most favourable period may be the time before puberty maturation. Retrospective studies suggest that bone mineral density in adults is correlated with calcium intake in childhood.
In the years following the menopause, calcium cannot obviously compensate for oestrogen deficiency. Conversely, it potentiates the effect of hormone replacement therapy: bone mass is better protected if therapy is administered in combination with a high calcium diet.
Later in life, calcium inhibits bone loss all the more so in that spontaneous intake of calcium is low. When used in combination with vitamin D, it significantly reduces the risk of bone fracture.
Actually, French dietary surveys demonstrate that calcium intake is very inadequate, especially in women: 50% of teenagers and 75% of subjects over 50 years of age ingest less than two thirds of nutritional recommendations (see insert 3), a level considered as “critical”.
In practice, dairy products are the foods which have the highest amounts of calcium, in a highly bioavailable form; 300 mg of calcium are found in 250 ml of milk (whole milk, skim milk or fat-free milk) or two yoghurts, or also in 30 g of Swiss cheese 40 g of Cantal cheese or 300 g cottage cheese. Thus, it is recommended to ingest three or four dairy products daily. Fruits and vegetables, cereals and drinking water supplement these intakes.
Vitamin D
Vitamin D in large part determines the intestinal absorption of calcium. It is provided by food in the diet (in fish liver oil, oily fish, egg yolk, butter, liver and whole milk dairy products) and especially in the skin, under the effect of ultraviolet radiation. Vitamin D deficiency is relatively common, even in young subjects. Thus in a survey conducted on teenagers in the Paris area, 24% presented with low serum 25OH-vitamin D levels at the end of the winter period. Studies conducted in Europe on adults show that 36% of men and 47% of women on average had a vitamin D deficiency, with this percentage rising to 60% in subjects over 75 years of age and 90% of those confined to an institution. Interventional studies have demonstrated the positive effects of the calcium-vitamin D combination on bone mass and the incidence of bone fractures, even in the very elderly. Supplementation with vitamin D of milk and fresh dairy products routinely ingested, which has been authorised in France for over one year, should contribute to improved vitamin D status in the French population. An improvement in serum vitamin D levels, even though minor, has been observed in certain countries (US, Canada), where this measure has been applied for several years.
In the elderly, exposure to sunlight and dietary intake, which generally are inadequate, provide the rationale for drug supplementation.
Proteins
Inadequate protein intake has a negative effect on bone status. During growth, it can induce demineralisation, as illustrated by the case of young girls with anorexia nervosa. In older adults it is a risk factor for bone fracture: inadequate protein intake accelerates bone loss and enhances sarcopenia (significant loss of muscle mass), which itself promotes falls. Normalization of protein intake in subjects with a fracture of the upper extremity of the neck of the femur limits contro-lateral bone loss and improves muscular performance. In particular proteins act by stimulating hepatic synthesis of a growth factor, IGF-1.
Conversely, it is generally considered that an excess amount of proteins produces urinary excretion of calcium via acidosis. In fact, recent studies have shown that proteins have no harmful effect when calcium intake is adequate.
In practice, the risk of protein deficiency mainly involves the elderly, who should be encouraged to ingest protein with high nutritional quality, ie., meat, fish or eggs, at least once a day, and one dairy product at each meal. Proteins from vegetables provide the supplement. In patients with a "small appetite", the nutritional density of the diet can be increased without altering the size of portions by incorporating for example, powdered milk in coffee or chocolate milk, and in mashed potatoes and desserts; by adding grated cheese and egg to soups and cheese-topped baked vegetable or by adding beaten egg whites into vegetable mousse or fruit.
Other nutrients
Chronic alcoholism is a risk factor for osteoporosis due to the toxicity of alcohol for bone forming cells and malnutrition. It is also a risk factor for bone fracture as a result of a propensity to falls. Excess sodium can negate the calcium balance by increasing calciuria, but the benefit of restricted sodium intake has not been demonstrated. Some epidemiological studies suggest that vitamin K, vitamin C or phyto-oestrogens (which exist in some vegetables such as soya bean), may have a protective effect on bone. Since little data is available, and in particular interventional studies are lacking, it is not possible to make recommendations.
CONCLUSION
It has long been considered that the only effective measure to fight osteoporosis and its complications was hormone replacement therapy (HRT). Without casting doubt on its usefulness, this approach has been radically transformed during the last ten years as a result of a large number of studies showing that certain environmental factors, including nutrition, can affect the course and outcome of bone stores throughout life.
Marie-Claude Bertière, MD.
Hôpital Bichat, AP-HP, Paris
Insert 1:
|
Insert 2:
|
French nutritional recommendations for calcium and vitamin D (AFSSA 2001)
Bibliography
- AFSSA-CNERNA-CNRS ; Apports conseillés pour la population française, 3ème édition ; Tec et Doc, 2001
- Bonjour J.-P., Amman P., Chevalley T., Bertière M.-C., Rizzoli R. Nutrients and osteoporosis : is calcium enough ? Sciences des aliments 2002; 22:409-414
- Chapuy M.-C., Arlot ME, Duboeuf F., Brun J., Crouzet B ., Arnaud S., Delmas P., Meunier P.-J. Vitamin D3 and calcium to prevent hip fracture in elderly women. N. Engl. J. Med 1992; 327: 1637-42
- Kalkwarf H.J., Khoury J.C., Lamphear B.P. Milk intake during childhood and adolescence, adult bone density and osteoporotic fractures in US women Am. J. Clin. Nut 2003; 77:257-65
- Wosje KS, Specker BL Role of calcium in bone health during childhood Nutrition reviews 2000; 58:253-68
Our Network
Danone Institutes are not-for-profit entities which link scientists involved in human nutrition with health and education professionals. They support nutrition research programs and provide diet and nutritional information including: information on eating behaviors, dietary guidelines, nutrition events and nutrition organizations. The Institutes focus particularly on, Nutrition and child development, early childhood nutrition and childhood obesity prevention.