Milk: How much is too much?
While calcium in dairy lowers osteoporosis risk, overdosing on milk may raise the risk of prostate and ovarian cancershealth Updated: Feb 24, 2018 18:56 IST
How much calcium does an adult need? Conflicting advice on recommended daily allowances across countries makes decisions tougher than watching Canada’s Prime Minister Justin Trudeau smile his way through repeated political gaffes.
The RDA for calcium differs widely across nations. The Indian Council of Medical Research’s (ICMR) report on the Nutritional Requirements and RDA for Indians puts the upper value of calcium for adults at 600 mg/d – roughly two glasses of milk, the country’s most bellowed source of calcium - and 800 mg/dl for 10-18 year olds. Since maximum bone mass is built till the age of 20 years, optimising calcium absorption through adolescence and early adulthood can prevent osteoporosis.
Just 200ml (one glass of milk or a large bowl of yoghurt) is enough to meet an adult’s daily calcium need, the rest comes from legumes, beans, cereal and vegetables that are part of traditional Indian diets, according to ICMR.
The UK’s RDA for calcium is similar to India’s, with the NHS recommending people 19-64 years old have 700 mg of calcium. The US recommendations are almost double that of India’s, with the USDA fixing the RDA for calcium at 1,000 mg until the age of 50; and 1,200 mg per day after that. In milk terms, 1,200 mg is about four glasses of milk a day.
Apart from milk, yoghurt, cheese and other dairy foods, calcium is found in soya and dried beans, shellfish and bony fish, cabbage, okra, broccoli, nuts, cereals like ragi, and green leafy vegetables, such as mustard and turnip greens. The bioavailability of calcium in spinach is poor because it contains oxalic acid, which combines with the calcium to form calcium oxalate, a chemical salt that makes the calcium less available to the body.
Depending too much on unpackaged milk brings with it risk of adulteration. India’s exchequer gained Rs 809,702 last year in penalties from people fined and convicted for adulterating and misbranding milk. Of the 2,123 milk samples tested in 2016-17, 466 were found to be adulterated or misbranded, which means they did not meet the required amounts of lactose, fat, protein and trace minerals recommended by the Food Safety and Standards Act.
GLASS OF GOOD
Milk is fortified with vitamins A and D, close to four in five Indians are deficit in the latter. This essential vitamin is synthesised by the skin on exposure to direct sunlight, but many people miss out on it because of increasing time spent indoors, under shade outdoors, or covered under clothes.
Vitamin D helps maintain normal blood levels of calcium and phosphorus that build bones. It also helps in calcium assimilation, which prevents osteoporosis or brittle bone disease in later life. It also has a role in lowering blood pressure to lower heart attack and stroke risk.
High levels of retinol (vitamin A) can cause toxicity, paradoxically weaken bones, so people who also have multivitamins must look for those that have replaced retinol with beta-cartotene, which doesn’t harm bones.
While calcium in dairy lowers osteoporosis risk, overdosing on milk may raise the risk of prostate and ovarian cancers. High levels of galactose, a sugar released when lactose is digested, have been linked to ovarian damage and ovarian cancer. A pooled analysis of 12 studies in the US, which included more than 500,000 women, concluded that women who drank three glasses of milk a day had a “modestly higher risk of ovarian cancer”, compared to women who drank milk the least.
FOR MEN TOO
Milk also ups the chances of men developing prostate cancer. Men who drank two or more glasses of milk a day were almost twice as likely to develop advanced prostate cancer as those who didn’t drink milk at all, found a Harvard study, which linked the increased cancer risk to calcium, and not dairy products.
Building bones is not just about eating right. Regular exercise, especially weight-bearing exercise, is an essential part of building and maintaining strong bones and muscle mass that brings down fracture risk associated with ageing. People over 60 who are agile – measured by their ability to get up from a chair without support – are less likely to have fractures. Strong and flexible muscles help support bones, which lowers fracture risk from falls.
A glass of milk or a bowl of yoghurt is doable, but those who are lactose intolerant or need to take a supplement, must get one that includes vitamin D and limits calcium intake to 500 mg of a day, unless they are osteoporotic.
First Published: Feb 24, 2018 18:56 IST