Calcium plays a vital role within the body and has numerous essential functions.
Calcium and bones
Bone is formed from a complex matrix of proteins within which calcium and other minerals are laid down (deposited).
Calcium, phosphate and magnesium are the most important and abundant minerals in bone, with calcium and phosphate combining together in the crystalline complex; hydroxyapatite [Ca10(PO4)6 (OH)2].
This complex provides the hard and rigid structure of bone which is essential to its function in supporting soft tissues and as a store of calcium for other body functions.
Calcium is essential for bone development and an adequate intake during childhood and adolescence is essential. If we lack calcium in our diet, our bones may not reach their genetic potential and peak bone mass. Peak bone mass is the stage when our bones are strongest and is usually reached at 30-35 years of age.
Bones grow at different rates throughout our lives, with maximal growth for length occurring soon after birth and continuing for the first year of life. In the second year the growth rate is half that of the first year and only a third thereafter, until a dramatic increase in bone growth, known as the pre-pubertal growth spurt.
This pre-pubertal growth spurt occurs in females at 10 years and 12 year old males. The teenage years therefore represent an important time for bone growth and development and this is reflected in the highest calcium requirements of our lifetime.
We only have a once in a life time opportunity to develop bone. Approximately 30% of all mineral deposited in our bones throughout life, occurs during adolescence and 90% of our adult skeleton is formed by the age of 18 and even earlier in girls.
Up until we achieve our peak bone mass we continue to make new bone on a daily basis but we also lose bone (bone resorption). Up until 35 years the rate of bone formation is greater than bone loss, so our bones get stronger. At the age of about 35, the opposite occurs and we unfortunately lose bone at a faster rate than we make it.
Therefore, the more calcium and minerals deposited in bone during childhood and adolescence, the stronger the bones we develop will be. A greater bone mass is associated with a lower the rate of bone loss with ageing, and a reduced risk of fracture and osteoporosis. The risk of fracture and osteoporosis in later life are lower in people who develop stronger bones during life.
For more information see section on bones.
Osteoporosis describes a condition in which low bone mass and deterioration of the bone tissue results in fragile bones which are more susceptible to fracture.
As mentioned earlier, we naturally lose some bone as we grow older but some people may experience more severe bone loss than others.
Osteoporosis can affect all the bones in the body, but fractures to bones in the wrist, spine and hip are most common. While many factors such as physical activity, body shape and diet play a role in osteoporosis, postmenopausal women are often at particular risk.
From the mid 40’s onwards, up to 1% of bone can be lost each year, however rapid loss occurs in the first few years after the menopause due to the lack of oestrogen.
Osteoporosis is however a disease not confined to women. Although 1 in 3 women in the UK currently suffer from osteoporosis, 1 in 12 men also suffer. Also 1 in 2 women and 1 in 5 men in the UK will suffer a fracture after the age of 50 years.
There are two types of osteoporosis-primary and secondary.
Primary osteoporosis includes postmenopausal and age-related osteoporosis where the amount of bone falls below a critical level and bones become vulnerable to fracture and break under circumstances where a healthy bone would not. Primary osteoporosis can be further classified as type 1 (early onset or postmenopausal osteoporosis) or type 2 (senile osteoporosis).
Secondary osteoporosis arises in response to an underlying condition or therapeutic treatment e.g. long term corticosteroid therapy, rheumatoid disease, chronic liver disease or intestinal malabsorption which all affect bone mineralization and strength.
For more information why not visit The National Osteoporosis Society website.
Calcium and teeth
Teeth are composed of three types of hard tissue: enamel, dentine and cementum. Calcium and phosphate exist as hydroxyapatite in both dentine and enamel.
Before birth, tooth mineralization begins and is complete by the first year of life. Diet has a big influence on teeth after they have erupted and calcium plays an important role in maintaining the mineral composition of teeth.
Tooth demineralization and remineralisation are dependent on a number of dietary factors and also the pH (level of acidity) in the mouth. Sugars consumed in the diet are fermented by plaque bacteria, and generate acid which lowers the pH at the tooth surface. This promotes demineralisation and therefore loss of calcium and phosphate from the hydroxyapatite in enamel, which increases the risk of dental caries.
However, when calcium and phosphate levels increase, the degree of acidity required for demineralisation to occur also increases. This means that the greater the amount of calcium and phosphate present in the saliva and plaque surrounding teeth, the lower the risk of tooth decay and the development of dental caries.
Consumption of calcium containing foods, such as milk and cheese, can help protect against dental caries as they increase the concentration of calcium in plaque and also contain other protective nutrients. Foods that are protective towards teeth are known as anti-cariogenic or cariostatic foods.
Certain other foods, for example sugary foods and drinks, can reduce the concentration of calcium in plaque and increase the risk of decay. These foods are known as acidic or cariogenic foods.
For more information on teeth and dental health see the section on teeth or why not visit the British Dental Health Foundation website?
The remaining 1% of calcium in our bodies is present in fluids and the cells of soft tissue and plays a role in blood clotting, nerve function, maintenance and function of cells, activation of enzyme reactions and hormone secretion.
Calcium and diseases
The role of calcium in the body has also been linked to prevention of several diseases. New and emerging evidence has shown calcium to have a role in the prevention of breast and colon cancers, cardiovascular disease, type 2 diabetes and reduction in obesity and improved weight management.
Calcium and cancer
There is considerable evidence to suggest that calcium has a protective effect on risk of both colorectal and breast cancer with increased intakes.
A recent study of 45,000 Swedish men reported that men who drank 1.5 glasses of milk per day or more, had 35% lower risk of the disease than those who had a low milk intake of less than 2 glasses per week.
Additionally a study of over 40,000 Norwegian women found that those who drank milk as children and continued to do so as adults, had a lower risk of developing breast cancer.
Dairy products which are good calcium providers offer even greater protection than just calcium alone, due to beneficial interactions of calcium with other dairy nutrients.
The presence of a naturally occurring fat in dairy products known as Conjugated Linoleic Acid (CLA) in addition to calcium, has also being linked with reducing the risk of colorectal cancer.
For more information see section on cancer.
Calcium and cardiovascular disease
An association between calcium and cardiovascular mortality has long been established, with people living in areas with hard water, high in calcium and magnesium, less prone to the disease.
Epidemiological studies have also shown higher intakes of calcium to be linked to a reduced risk of cardiovascular disease. More specifically, studies have shown that high calcium intakes may reduce high levels of bad cholesterol in the blood, and increase low levels of good cholesterol both of which are known risk factors for cardiovascular disease. In addition, it is also thought that calcium may bind harmful fats together in the gut and prevent their absorption, which in turn prevents levels in the blood increasing.
Consumption of dairy products provides calcium and a recent study in Welsh men found that those who drank the most milk had fewer heart attacks than those who had little or no milk in their diets.
Calcium also plays an important role in muscle contraction (including the heart muscle) and lowering blood pressure which are both important for good cardiovascular health.
Any reduction in blood pressure, modest or significant, can reduce the rates of mortality and morbidity from stroke and coronary heart disease.
While calcium supplementation reduces both systolic and diastolic blood pressure in both people with high and low blood pressure, low-fat dairy products also play a role in blood pressure reduction.
The Dietary Approaches to Stop Hypertension Diet (DASH Diet) which combines fruit and vegetables, low-fat dairy and a low-salt diet, results in a greater reduction in blood pressure than just a fruit and vegetable diet alone.
Maternal calcium intakes during pregnancy are also thought to play a role in determining the likelihood of high blood pressure in our offspring in later life. Increased intakes during pregnancy are thought to be linked to healthy blood pressure in the resulting baby, in childhood and later life.
For more information see sections on blood pressure and cardiovascular disease.
Calcium and type-2 diabetes
Type 2 diabetes is a condition in which the amount of sugar (or glucose) in the blood remains too high because the body cannot use it properly. This condition if poorly controlled is associated with many health problems including blindness, damage to blood vessels, increased risk of cardiovascular disease and many more.
Although a specific connection with calcium is as yet unfound, consumption of calcium providing dairy foods has been associated with a reduced risk of developing type-2 diabetes.
A recent study of more than 37,000 middle aged women found that those with the highest intakes of dairy had a reduced risk of type 2 diabetes.
The strongest association was found with low fat dairy products.
Similarly a study of men in 2005 found a reduced risk of type 2 diabetes with increased consumption of low fat dairy, interestingly, every extra portion of dairy consumed was associated with increasingly lower risk.
It is thought that this effect is due to the combined effects of many beneficial nutrients found within dairy foods including calcium, but the exact mechanisms involved are still unclear at present.
For more information see section on diabetes.
Calcium, obesity and weight management
The role of calcium in weight management has been established in recent years as higher calcium intakes have been associated with reduced bodyweight and body fat.
Studies have shown that consumption of calcium providing dairy foods as part of a calorie controlled diet is associated with increased weight loss, particularly form the abdomen. This is particularly beneficial since excess fat around the trunk region of the body is associated with greater risks to health.
In addition, studies have also found that those who consume milk and dairy foods are likely to be slimmer than those who do not!
Evidence for an anti-obesity effect for calcium and in particular calcium from dairy products is accumulating rapidly but the precise mechanism by which calcium affects body weight remains unknown. It is likely that calcium plays an important role in combination with the beneficial effects of other nutrients in dairy. As yet no definitive mechanism has been established, but this area of research is gaining enormous attention.
For more information see section on obesity.