Calcium is by far the most abundant major mineral in our body. Not surprisingly, it plays many critical roles in maintaining overall function and health. One of the primary functions of calcium is to provide structure to our bones and teeth. We cannot survive for long if our blood calcium level rises above or falls below a very narrow range; therefore our body maintains the appropriate blood calcium levels at all cost. When we do not consume enough calcium in our diet, a process called resorption occurs. Osteoclasts, which are cells that erode the bones by secreting enzymes and acids that dig into grooves into the bone matrix. Then comes the formation process where new bone is formed through the action of cells called osteoblasts. In young healthy adults, the processes of bone resorption and formation are equal, so that just as much bone is broken down as is built, maintaining bone mass. Around 40 years of age, bone resorption begins to occur more rapidly than bone formation, and this imbalance results in an overall loss in bone density. Because this affects the vertebrae of the spine, we also tend to lose height as we age.
Calcium is also critical for the normal transmission for nerve impulses. Calcium flows into nerve cells and stimulates the release of molecules called neurotransmitters, which transfer the nerve impulses from one nerve cell to another. Without adequate calcium, our nerves’ ability to transmit messages is inhibited. Not surprisingly, when blood calcium levels fall dangerously low, a person can experience convulsions. Another role of calcium is to assist muscle contraction, maintain healthy blood pressure, the initiation of blood clotting, and the regulation of various hormones and enzymes.
There is no RDA (only an adequate intake) value for calcium, but values for adults over age 50, pre-teens and teens have the highest requirement. Many people of all ages fail to consume enough calcium to maintain bone health. The bioavailability or calcium depends on many factors. Vitamin D which I will discuss briefly increases the absorption of calcium from the intestines.
Calcium supplements maybe be required for vegans and people who avoid dairy products. Others who may need them are small or inactive people who eat less to maintain and healthy weight, and older adults who need more calcium than they can obtain in their diets
Vitamin D which is different from other nutrients because it does not always need to come from our diet. This is because our body can synthesize vitamin d using energy from exposure to the sunlight. However when we do not get enough sunlight, we must consume vitamin d in our diet.
There have been studies that suggest a vitamin D deficiency may play a role in cardiovascular disease, multiple sclerosis, and rheumatoid arthritis (IFIC Foundation, 2007). But if your exposure to sun is adequate, then you do not need to consume vitamin d in your diet. Individuals living in sunny, climates may synthesize enough vitamin d from the sun to meet their needs throughout the year – as long as they spend time outdoors. However vitamin d synthesis from the sun is not possible during winter months for people living in places located at latitude of more than 40 degrees North or more than 40 degrees South. This is because at these latitudes in the winter the sun never rises high enough in the sky to provide the direct sunlight needed. Calgary is said to have more hours of sunshine than any other Canadian city; however at 51 degrees north latitude, the sun’s ultraviolet rays are not strong enough to produce sufficient vitamin d in the skin of many people. Thus, Canadians cannot rely on exposure for vitamin D synthesis from October to April, and an adequate intake from diet or supplements becomes essential during those months.
In conclusion, of the many nutrients that help maintain bone health, calcium and vitamin D have received the most attention for their role in the prevention of osteoporosis. Research studies conducted with older adults have shown that taking calcium and vitamin D supplements reduce bone loss and fracture risk. If people do not consume enough of these nutrients over time, their bone density is lower and they have a higher risk for bone fractures. For more info you can see my web resources.
1) Osteoporosis Canada – http://www.osteoporosis.ca
2) Medline Plus Information – http://www.nlm.nih.gov/medlineplus
3) Janice Thompson, Melinda Manore, Judy Sheeshka – Nutrition: A functional approach
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