Calcium

Calcium is one of the essential nutrients necessary for healthy bone development. Adequate calcium intake is necessary for the attainment of peak bone mass in the late teens (i.e the highest level of bone strength which occurs at completion of growth) and therefore strong healthy bones, which will sustain the effects of ageing on the skeleton. It is important to have a well balanced diet with adequate amounts of dairy products, which are the primary source of foods rich in calcium.

Not only is calcium important to bones, it is also important for the function of various organs within the body and a certain amount of calcium circulates within the blood. If blood calcium levels fall as may occur with inadequate calcium intake in the diet, the body will compensate for this by drawing calcium out of bones and putting it into the blood. Calcium is also excreted by the body daily. Hence it is important to have an adequate daily calcium intake through the diet so that bone mineral strength is not compromised.

Calcium Requirements Through Life

There are critical times in life when it is vital to ensure that calcium intake through food and/or supplements is adequate and meets the recommended requirements for age and sex.
Recommended daily calcium intake

Childhood and adolescence

During childhood and adolescence, when the skeleton is actively growing it is essential that calcium intake meets the requirements of the growing skeleton. It is during this growth phase that the foundations for the attainment (achievement) of peak bone mass are laid.

Peak bone mass is achieved in your early 20's. It represents a stage when bone has achieved its maximum density and occurs when growth has been completed. Peak bone mass generally represents a time when the bones are at their ‘strongest’. The higher the peak bone mass, the greater protection the skeleton has against the effects of ageing.

It is important to realize that the peak bone mass achieved varies from one individual to the next. It primarily reflects what has occurred during growth and development in childhood and adolescence and also hereditary factors. Hence an individual who has had adequate intake of calcium, plenty of exercise and not been subjected to any sex hormone deficiencies (i.e. interruption to menstrual periods) during childhood and adolescence will likely achieve a high peak bone mass as compared to the individual who has not had favourable circumstances for bone development during childhood and adolescence.

20s-40s

Between the ages of 20-35 years bone gain and loss is quite stable. It is important to maintain a healthy lifestyle during these years for good bone health.

From the mid 30s onwards bone loss starts to increase more than bone gain. It is part of the normal ageing process that bones lose their mineral (calcium) and collagen (protein) content. For women this process of bone loss is also accelerated further at the time of menopause. Thus if an individual starts with a high peak bone mass, their skeleton will withstand the effects of the age related bone loss better than the individual who has a low peak bone mass and who will be more likely to develop osteoporosis at a latter stage.

Midlife - 50's to 65

Midlife and beyond is a time when calcium requirements are also high. When women go through menopause, there is a rapid loss of bone that is primarily due to oestrogen deficiency and this process may last from 4 – 8 years after menopause.⁴

It is also known that women generally start to lose bone even in the years leading up to menopause due to the fact that oestrogen levels are already starting to drop even though menstrual periods may still be occurring.⁵

The gastrointestinal system also becomes less efficient at absorbing calcium from food and it is believed that this process is due to the loss of oestrogen. The kidney also becomes less efficient in conserving calcium. This creates a state of potential calcium loss in the blood, and the body compensates for this by drawing calcium out of the bones.⁴

Thus not only do the bones become weaker because of oestrogen deficiency at menopause, they also lose more calcium. Hence the way to reduce the loss of calcium from the bones is to increase the intake of calcium from food.

Older years - over 65

In the years beyond menopause the rate of bone loss as a consequence of oestrogen deficiency slows down. However, there is still a requirement for high intake of calcium through the diet so as to offset the process of calcium being drawn from the bones in order to compensate for inefficient calcium absorption from the gastrointestinal system and kidney.⁴ 

Pregnant and breastfeeding women

Pregnant women and breastfeeding women need to ensure that they have adequate calcium intake. In pregnancy, especially in the third trimester of pregnancy, calcium requirements are increased, in order to meet the requirements for bone mineralization in the foetal skeleton. Women who breastfeed also have high requirements for calcium in order to allow for milk production. Normal pregnancy and breastfeeding is associated with a certain amount of bone mineral loss, which generally recovers 6 – 12 months after the cessation of pregnancy and/or breast feeding.³

Calcium Counter

Daily calcium requirements need not come necessarily from dairy products. If you choose alternative calcium sources, note carefully the quantity of calcium found within the particular food source. 

Other dietary factors

Overall it is important to have a well balanced diet.

Protein intake is important for bone development as it provides the necessary building blocks in bone.

However, it has been found that diets that are very high in protein, salt, caffeine and phosphorus may adversely affects the body’s calcium balance, although this affect may not be that significant in an individual with an adequate calcium intake.^13,14

Content updated February 20, 2006