Genetics are a major determinant for strong bones and account for 60 to 80% of the variation in peak bone mass, i.e. the maximum bone density. Nutrition and exercise also play important roles in the development of the bones while growing (children) and in the bone tissue maintenance phase for adults and elderly people. Health authorities agree that calcium, protein and phosphorus from, among others, milk support the development and maintenance of the bones mass.
Bones consist of a protein matrix, which is filled with calcium phosphate and other minerals, such as sodium, magnesium, potassium and zinc. Bone tissue is continuously broken down (bone resorption) and built up (bone formation) for recovery after minor ‘damage’ and in order to adapt the bone strength to the exerted load. Bone formation exceeds bone resorption from birth up to the age of about 30 years. During this period, the bone density increases, resulting in a peak bone mass. About 95% of the adult skeleton has already been developed by the end of adolescence. The adolescence period goes with fast bone growth and about 40-60% of the adult bone tissue is developed in this period of life. Girls experience this peak moment at the age of about 12.5 years and boys when they are about 14.0 years old. From the age of 50, bone resorption starts exceeding bone formation, resulting in a decrease of the bone mineral density. With women this process goes faster due to hormonal changes. At the age of 80, the peak bone mass in women will have decreased by an average of 40-45%, whereas for men the decrease is about 30%.
Genetics accounts for 60 to 80% of the variation in peak bone mass. Factors such as exercise and a healthy and varied diet with sufficient amounts of calcium, vitamin D and protein are important for bone health. Hormones (gender and growth hormones), ethnicity, gender, use of medicines, BMI, smoking and use of alcohol could also influence the bone mass.
Calcium is an important building block for the bones. As 99% of the calcium in the body is stored in the bones. Next to calcium, protein, phosphorus, zinc, magnesium, and the vitamins K and D contribute to the maintenance of normal bones. These nutrients are part of the bone matrix, or in the case of vitamin D contribute to the absorption of calcium and phosphorus.
Around a decade ago a number of scientific publications stated that increased protein intake may have an adverse effect on bone health as a result of an increased amount of calcium in the urine (hypercalciuria) and a decline of calcium in the bones. However, this is not confirmed by more recent scientific research. Only in the case of a very high protein intake, in combination with a low calcium intake, there could be an adverse effect on bone health. In practice this almost never occur when dairy is part of the diet. It is known that excessive consumption of caffeine, carbonated drinks, alcohol and salt can have an adverse effect on the body’s calcium balance.
Milk naturally contains protein, calcium and phosphorus. These nutrients contribute to the maintenance of bone mass. This is also seen in a recent literature review of intervention and observational studies. The researchers conclude that dairy is associated with an increase in bone mass development in children and adolescents (2-19 years old). According to the researchers, this association is found due to the amount of calcium and phosphorus naturally present in milk.
Figure Bone mass during life (women)
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