Most of the calcium in our body is in the skeleton and a tooth; the rest is stored in tissues or blood. Calcium is essential for healthy teeth and bones. It also plays a crucial role in other body systems, such as the health and function of nerve and muscle tissue.
Good sources of calcium include dairy products and calcium-fortified products such as soy milkand breakfast cereals. People in different life stages need different amounts of calcium. Young children, teenagers and older women have a greater need for this mineral.
It is much better to get calcium from foods that calcium supplements.
What is calcium?
Calcium plays a role in:
- Strengthening bones and teeth
- Regulation of muscle functions, such as contraction and relaxation
- Regulation of heart function
- Blood clotting
- Transmission of nerve messages
Calcium deficiency can weaken bones. If your body realizes that calcium circulating in blood is not enough, hormones are used to reduce the amount spent by the kidneys in urine. If the calcium that comes from diet is not sufficient, it is taken from the bones.
If your dietary intake of calcium is constantly low, the body will eventually lose bone density.
Calcium needs vary throughout life
The recommended daily intake of calcium is different for people of different ages and stages of life:
Babies 0-6 months: approx. 210 mg (if breastfed) and approximately 350 mg (if bottle-fed)
Infants 7-12 months: 270 mg
Children 1-3 years: 500 mg
Children 4-8 years: 700 mg
Children 9-11 years: 1,000 mg
Adolescents 12-18 years: (including pregnant and lactating women) 1,300 mg
Women 19-50: (including pregnant and lactating women) 1,000 mg
Women 50-70: 1,300 mg
Men 19-70: 1,000 mg
Adults over 70 years: 1,300 mg
Calcium in foods
Good food sources of calcium include:
Milk and dairy products: milk, yogurt, cheese and butter.
Green leafy vegetables: broccoli, cabbage, Chinese cabbage and spinach. A cup of cooked spinach contains 100 mg, although only five per cent of this can be absorbed. This is due to the high concentration of oxalate in spinach, a compound that reduces the absorption of calcium. By contrast, a cup of broccoli cooked contains approximately 45 mg of calcium, but absorption of broccoli is much higher at about 50-60 percent.
Soy and tofu: tofu (depending on type) and soy beverages fortified with calcium.
Fish: sardines and salmon (with bones). Half a cup of canned salmon contains 402mg of calcium.
Nuts and seeds: Brazil nuts, almonds and sesame seed paste. Fifteen almonds contain about 40 mg of calcium.
Calcium-fortified foods: including breakfast cereals, fruit juices and bread.
It is much better to get calcium from foods (which also provide other nutrients) than calcium supplements. If you have trouble eating enough calcium-rich foods, you may need to consider a calcium supplement, especially if you are at risk of developing osteoporosis. It's a good idea to talk with your doctor or other professional who can guide you. If you take calcium supplements, make sure you don’t take more than the recommended amount on the package. Excess calcium can cause gastrointestinal disorders, such as bloating and constipation.
Lifestyles that can affect bone strength
Some of the factors that can reduce the calcium in the bones and lower bone density (weak bones) include:
- Diets high in salt
- More than six cups a day of caffeinated drinks
- Excessive alcohol consumption
- Very low body weight
- Very high fiber doses (greater than 50 g per day, from wheat bran)
- Low levels of physical activity
- Low levels of vitamin D, people who rarely leave home or completely cover their bodies when they are out have a higher risk