Calcium is one of the most abundant minerals in the body. As much as 99% of the calcium that is ingested is used to make up the skeletal system and teeth. Calcium strengthens the bone structure, and that provides a frame for the body to stay upright. Muscles and nerves then attach at several points in the skeleton to make purposeful motion possible. The 1% of ingested calcium that remains circulates in body fluids and plays a vital role in the contraction of muscles, clotting of blood, transmission of nerve impulses, maintenance of healthy blood pressure and secretion of hormones, among other things.
Because calcium plays such diverse and important roles, the body must ensure there is always an adequate supply. This is why bones store excess calcium and the body can dip into these stores during times of deficient intake. But sometimes when there is low intake of calcium over a period of time, the body just uses the reserves. This can eventually lead to calcium deficiencies which manifest after several years of deficient intake and are the cause of osteopenia (a condition where bone mineral density is lower than normal) and osteoporosis (a condition where bones become porous and are prone to spontaneous fractures).
The big C: Calcium does more than just strengthen bones.
Intake vs absorption
Several factors affect the absorption of calcium in the body, and it varies according to age. Growing children absorb as much as 50-60% of their daily calcium intake, pregnant women, 50% and adults for whom bone growth has stopped, just 30%. Bone density in later life depends entirely on whether peak bone density has been achieved by the late 20s, which is why a healthy calcium intake during adolescence is of critical importance. The stomach’s acid and vitamin D play a major role in absorbing calcium. Acid makes calcium soluble and easier to absorb and vitamin D helps in making the calcium-binding protein required to absorb it.
Adults absorb about 30% of the calcium they ingest. Vitamin D, stomach acid lactose and growth hormones enhance calcium absorption. A high-fibre diet does to a certain extent interfere with calcium absorption but the damage is minor. Aerated drinks inhibit calcium absorption the most because of the high levels of phosphorous they contain.
How much calcium do you need?
Adolescents need at least 1,300mg till the age of 18; from the ages of 19-50, recommendations are lowered to 1,000mg a day because one is now in the bone-maintaining stage rather than growth. The recommended daily allowance increases again to 1,200-1,500mg after 50 to make up for the natural losses of bone that occur in later life.
Estimating your daily calcium intake
Milk is the most abundant source of calcium, at 300mg per cup. Adults need 1,000-1,200mg per day, which makes an equivalent of 3 1/3-4 cups of milk. Let’s say the calcium in one cup of milk is assigned 1 point, then the goal is to attain 3-4 points a day. Give yourself a point each for a cup of milk or a cup of yogurt or 50g of cheese, or a cup of ice cream, a cup of paneer or tofu, calcium-rich vegetables such as cauliflower, mustard greens (sarson ka saag), broccoli or green beans, and one point for canned fish such as sardines or salmon with bones. Because a well-balanced diet (6-8 servings of complex grains such as wholewheat, bajra, brown rice, 2-3 servings of legumes, rajma, chana or chowli, 6-8 servings of 100g raw multicoloured vegetables and fruits, two handfuls of nuts and seeds such as almonds, pumpkin or sesame seeds and at least three fist-sized servings of protein such as paneer, poultry and fish and two servings of low- to medium-fat dairy, milk or yogurt) also contains a variety of foods that contain calcium, give yourself one point for that.
Two tablespoons of almonds give approximately 80mg of calcium, while two tablespoons of sesame seeds give 40mg. They are good sources of calcium for those who are lactose intolerant and cannot have milk. If you are taking supplements, then ensure you do not exceed 2,500mg of calcium from both dietary and supplemental sources. More than this could increase the risk of urinary stone formation, kidney dysfunction and in some cases where blood calcium levels reach above normal, calcium rigour, where muscles contract and cannot relax.
To further enhance bone health, avoid excessive alcohol intake and smoking. Both weaken bones and increase the chances of bone-related ailments. Hit the gym and engage in weight training at least three times a week to maximize bone health.
Madhuri Ruia is a nutritionist and Pilates expert. She runs InteGym in Mumbai, which advocates workouts with healthy diets.
Write to Madhuri at email@example.com