Actually many factors can cause babies to cry at night, rickets is only one of the possible causes, according to Li.

A mother of a 14-month-old girl told the doctor that her baby was breastfed, but had a pillow bald ring. The woman wanted to know whether that was a sign of rickets.

But Li told the mother that rickets should be diagnosed with a combination of methods rather than the observation of any single symptom. "Pillow baldness is not necessarily related to rickets. It may also occur because babies' hair follicles are immature, so lying with their heads against pillows for extended periods of time impedes hair growth," she said.

Chinese mothers' fear of rickets stems from the fact that rickets was once very prevalent in China.

A national survey conducted from 1977 to 1983 showed that the prevalence of rickets among Chinese children up to 3 years old was 40.7 percent, and in some northern provinces, the rate exceeded 50 percent, said Ma Xiancai, a doctor at the Second Hospital Affiliated with Harbin Medical University in Harbin, northeastern Heilongjiang Province.

Over the years, rickets' prevalence in China has dropped significantly. A national survey conducted in 1990-96 showed that the national prevalence rate dropped to 26.7 percent.

Nonetheless, even today, the disease remains relatively common in some areas, especially among babies under one year old. A survey recently conducted by the Maternal and Child Health Care Station in Lanzhou, capital of northwest China's Gansu Province, indicated that one in five children up to the age of 3 still suffers from rickets.

While mothers do have a reason to worry about rickets, some of this paranoia stems from a misunderstanding, said Wang Danhua, Director of the Pediatrician Department at Peking Union Medical College Hospital.

That is because rickets is mostly caused by a lack of Vitamin D rather than calcium, Wang explained. Without Vitamin D, even if people receive enough calcium, they cannot absorb it.

Wang suggests that children under 2 years old take Vitamin D supplements. Vitamin D can also be obtained from exposure to sunlight and food.

Calcium deficiency phobia

China has become the largest calcium supplement market in the world. Not only infants are taking supplements, but also many adults, especially senior and middle-aged women.

Lai Jianqiang, a researcher in nutrition for children and women at the Chinese Center for Disease Control and Prevention, said that Chinese people mainly eat grain and vegetables, and consume a limited amount of milk and other dairy products, so their calcium intake is much lower than the dietary reference intake.

The Chinese dietary reference intake published by Chinese Nutrition Society in 2000 set the standard daily calcium intake for Chinese citizens at 800 mg. In 2004, a nutrition and health survey conducted by the Ministry of Health showed that the average daily calcium intake for Chinese citizens was 391 mg, less than half the recommended level.

"Nonetheless, there is no need to worry about insufficient calcium intake for babies whose diet is primarily milk, especially those up to 6 months old," Wang said.

The World Health Organization recommends 300 mg of calcium per day for babies up to six months old and 400 mg per day for those between 7 and 12 months old.

"Toddlers between 1 and 3 years old whose daily milk intake reaches 400 ml do not need calcium supplements either," said Lai.

However, a national survey on the nutrition and health of Chinese residents revealed that the average milk intake for urban children between 2 and 3 years old was no more than 140 ml per day, and that of rural children was even less, reported national broadcaster CCTV in 2008.

Yu Kang, a nutritionist at Peking Union Medical College Hospital, suggests those people who cannot get enough calcium from their current diet should first consider switching to a more calcium-rich diet rather than taking calcium supplements.

"Usually, people can get sufficient calcium from their diet," Yu said. "Calcium can de derived from a variety of food, such as milk, eggs, lean meat, soya bean products and green vegetables."

Of course, some people do need calcium supplements, such as infants whose mothers cannot breastfeed them and who have no access to formula milk, and people intolerant to calcium-rich food such as those who are lactose intolerant. In such cases, Yu said that one should consult doctors before taking calcium supplements.

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