ONE OF THE highlights of the World Congress of Osteoporosis this year, held last month in Krakow, Poland, was the release of the Calcium Map by the International Osteoporosis Foundation (IOF) to map the calcium intake of countries across the globe. Not surprisingly, Northern Europe, North America and Australia-New Zealand figure right on top. Most of Asia, including China and India, hover at much lower levels. Data from India, which I presented, is largely based on NSSO survey figures analysed by Dr Kurpad’s group from St John’s hospital, Bengaluru, and suggests a mean intake of around 400 mg per day.
Calcium is like the bricks and mortar for our bones. Severe deficiency of calcium (and/or vitamin D which is essential for calcium absorption from the gut) in children results in rickets, a condition where the bones become soft and fracture easily. A similar condition in adults is called osteomalacia. Lower degrees of deficiency over prolonged periods can result in osteoporosis. The process starts very early in life. Researchers from Pune have shown that low calcium intake during pregnancy not only depletes the maternal skeleton, but may also result in a lower bone density in the offspring. Poor calcium and vitamin D intake during the adolescent growth spurt leads to a compromised ‘peak’ bone mass, which is usually achieved by the time we are twenty. We start losing bone at the age of 30. If we enter our thirties with low peak bone mass, we will be more prone to fractures in our old age. Calcium, vitamin D (and protein) intake are therefore critical throughout our life span to protect our bones. A low dietary calcium intake has a greater impact on Indians, since most urban Indians have varying degrees of vitamin D deficiency.
How much calcium is required by our body? The dietary calcium intake for adults recommended by the National Institute of Nutrition (NIN) is 600 mg daily, which is lower than that recommended by many Western countries; for the US, its 1,000 mg per day for adults between 18 and 50. Many experts feel that the Indian recommendations should be revised. Regardless, our average calcium intake seems to be lower than even NIN recommendations. Economically deprived sections of society have particularly low intake. In Delhi, calcium intake among schoolchildren of lower socio-economic groups was about 300 mg per day versus 700 mg per day for their more affluent counterparts.
The bulk of calcium in the diet comes from dairy sources. A 200 ml glass of milk contains about 240 mg of calcium; 100 gm of curd contains 83 mg; and 100 gm of paneer (cottage cheese) almost 500 mg. Thanks to the ‘white revolution’, India is now thelargest milk producing country in the world. As a result, the per capita availability of milk has increased to 337 ml per day; however, our liquid milk consumption is highly variable and lower in rural as compared to urban areas. There are also wide variations between states.
Although dairy products provide the bulk of calcium in our diet, lactose intolerance can be a limiting factor. Curd may be better tolerated by some. Others may obtain their calcium through non-dairy sources. Ragi, a cereal, is a rich source, containing almost 400 mg per 100 gm. Leaves rich in calcium include amaranth, colocasia, fenugreek and mustard. Nuts are also rich sources but the amount consumed is insignificant. Challenges remain. Phytates, present in large amounts in many cereals, can impair mineral absorption. Oxalates in leafy vegetables can have the same impact. Attempts have been made to increase the bioavailability of calcium by fermenting cereals or legumes.
Concerns about excess calcium intake are largely unproven. The increased risk of kidney stones is unconvincing, although people with kidney stones are advised to use calcium pills with caution. Controversies have also been raised about the adverse impact on heart disease—these come from countries that have high baseline calcium intake and not low intake like most of India and are not relevant in the Indian context.
It requires a multipronged approach to increase the calcium intake of Indians. Continuing emphasis on milk production and consumption, particularly in children and pregnant women, is the obvious first step. Non-dairy sources of calcium need to be encouraged. A study from Pune showed the feasibility of providing calcium fortified sweets (laddoos) in schools. Micronutrient rich powders have been used in countries like Bangladesh.Use of calcium supplements in particularly vulnerable groups like pregnant women and the elderly remains an important component of this strategy.
To build better bones and preserve them in our old age, we need to get our daily calcium fix—from womb to tomb.