Calcium is the most abundant mineral in the human body. It is an essential element required for several life processes. Ninety-nine percent of the calcium in the human body is stored in the bones and teeth. The remaining one percent is found in the blood and other tissues.
Why should I be aware of this
Calcium is required for the formation and maintenance of skeleton and teeth. It is an important mineral component of bone. Bone is a dynamic tissue and undergoes continuous remodeling throughout life. There is constant resorption (breakdown of bone) and bone formation where calcium is deposited into the new bone. During normal growth, bone formation exceeds bone resorption. However, this balance changes as people age. There is greater bone formation than breakdown in childhood while during old age, the breakdown exceeds the formation of bone. As a result, the risk of osteoporosis ( porous, weak bones) increases in old age.
Calcium is also required for a number of other essential processes which include:
- normal contraction of muscles to make limbs move
- contraction of heart for normal function
- nervous activity like sending messages through the nervous system
- blood clotting
- secretion of hormones and enzymes
A constant level of calcium is maintained in body fluid and tissues so that these vital body processes function efficiently.
All about calcium
Calcium is present in both plant and animal foods. The richest source of calcium among animal foods is milk and milk products. These include cheese, yogurt, butter milk and other dairy products. A very good vegetable source of calcium is green leafy vegetables such as turnip greens, amaranth and drumstick leaves. Spinach is a very good source of calcium, however, it contains oxalic acid which combines with calcium and makes it less available to the body. There are several calcium-fortified food sources available, including fruit juices, fruit drinks, tofu and cereals. Most cereals and millets contain some amount of calcium and millet ragi is particularly rich in calcium.
Milk and calcium
Milk is a very good source of calcium which is in a form that can be easily absorbed by the body. It contains other nutrients like vitamin D which also help in the absorption of calcium. However, milk may not be the best source of calcium for people with lactose intolerance and can cause problems like flatulence, bloating and cramps. Many dairy products are high in saturated fats, and a high saturated fat intake is a risk factor for heart disease. For this reason, low-fat or fat-free milk will be a healthier option as a good source of calcium.
Conditions like inadequate calcium intake, decreased calcium absorption, and increased calcium loss in urine can decrease total calcium in the body. As a result, calcium is withdrawn from the bones since the calcium level in blood has to be maintained in order to carry out vital processes. Low levels of calcium in the blood may cause a condition called tetany which is characterized by muscle pain and spasms, tingling and/or numbness in the hands and feet.
Calcium deficiency in children can lead to improper bone mineralization resulting in a condition called rickets. Growth retardation and bone deformities are associated with rickets. On the other hand, in adults, calcium deficiency can lead to softening of the bones (osteomalacia) and osteoporosis (weak bones) in combination with other factors. Osteoporosis can be slowed down by doing regular exercise, especially weight-bearing and muscle strengthening exercise. Consuming enough calcium and adequate vitamin D will also ensure stronger bones.
Elevated blood levels of calcium lead to a condition called hypercalcemia. However, hypercalcemia from diet is very rare and occurs from calcium supplements or as a result of malignancy. Hypercalcemia can lead to unwanted accumulation of calcium in cells other than bone. Mild hypercalcemia may be without symptoms or may result in loss of appetite, nausea, vomiting, constipation, abdominal pain, dry mouth, thirst, and frequent urination. More severe hypercalcemia may result in confusion, delirium, coma, and if not treated, death. A Tolerable Upper Intake Level (UL) for calcium of 2,500 milligrams per day was established by the National Academy of Sciences in 1997.
What can I do?
In 1998, the Institute of Medicine at the National Academy of Sciences issued new Adequate Intake (AI) levels for calcium. An AI is set when there is insufficient scientific data available to establish a RDA. The recommendations are as follows:
- 14-18 years: 1300 mg/day
- 19-30 years: 1000 mg/day
- 31-50 years: 1000 mg/day
- 51+ years: 1200 mg/day
- Postmenopausal women not taking hormone replacement therapy: 1500 mg/day
- Pregnant and lactating women (younger than 18 years): 1300 mg/day
- Pregnant and lactating women (older than 18 years): 1000 mg/day
- Dietary Supplement Fact Sheet: Calcium
- Calcium & Milk
- Milk Matters
- What can high-calcium foods do for you?