Following protests from international scientists and Greenpeace about breaches of medical ethics and scientific good practice, the Chinese government has denied that any experiments have been conducted to feed GM Golden Rice to children in the country (see article below).

But it seems the authors of a study published in the August edition of The American Journal of Clinical Nutrition, are under the impression that they did in fact conduct the experiments in question:
http://www.ncbi.nlm.nih.gov/pubmed/22854406

A major ethical and scientific problem with the study, assuming it did happen, is that Golden Rice does not appear to have undergone toxicological tests on animals before being fed to children.
http://www.i-sis.org.uk/SPUCTGM.php
This would be a required safeguard in the field of pharmaceuticals, where human clinical trials can only take place if the animal trials did not show problems.
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China denies Greenpeace GM rice test claims
China Daily USA
1 Sept 2012
http://usa.chinadaily.com.cn/china/2012-09/01/content_15726699.htm

CHANGSHA – Government officials in central China's Hunan Province on Saturday denied claims that children in the area were being used as guinea pigs in US-backed research on the effects of consuming genetically-modified (GM) rice.

The response was prompted by a Greenpeace article saying that the environmental protection group had discovered a study backed by the U.S. Department of Agriculture involving feeding genetically modified Golden Rice to a group of 24 children, aged between six and eight, in Hunan.

The study, published in the August edition of The American Journal of Clinical Nutrition, claimed that Golden Rice, genetically engineered to be rich in carotene, is effective at providing vitamin A to children.

A spokesman for Hengyang City, where the study was allegedly conducted, said the government has formed an investigation team to probe the claim, but initial findings indicated that there had been no such research project.

The spokesman said there was instead a study on the transformation of carotene in vegetables to vitamin A in children's bodies. The study, commissioned to its Hunan branch by the Chinese Center for Disease Control and Prevention (CDC) in 2008, selected 68 primary school children in Hengyang's Hengnan County for the experiment.

"The food given to the children did not involve GM rice or other GM food," the spokesman said. "Parents were notified of the experiment in advance."

Hunan CDC officials said that the food for the experiment was all locally purchased and all results were submitted to the China CDC immediately after the experiment concluded.

The government spokesman said the CDC study had not involved any American institute.

GM food is controversial as there is still no consensus on whether or not it is harmful for the human body. The State Council of China introduced a regulation as early as 2001 to ensure the safety of genetically modified food, with strict provisions on its research, testing, production and marketing.