Cambodian cuisine is an umbrella term for the cuisines of all ethnic groups in Cambodia, whereas Khmer cuisine (; ) refers specifically to the more than thousand years old culinary tradition of the Khmer people. Over centuries, Cambodian cuisine has incorporated elements of Indian, Chinese and due to some of these heavily shared influences and mutual interaction, it especially has many similarities with the neighbouring Thai, Vietnamese and Lao cuisines. Khmer cuisine can be classified into peasant, elite and royal cuisine, although the difference between the royal and popular cuisine is not as pronounced as in the case of Thailand and Laos. The royal and elite dishes use more varied and higher quality ingredients, and contain more meat, while the peasant food is made from simpler and more accessible ingredients. History Because of Cambodia's geographic location, rice and fish, especially freshwater fish, are the two most important sources of nutrients in the Cambodian diet. Rice is a staple food generally eaten at every meal. It is believed to have been cultivated in the territory of Cambodia since 5,000 to 2,000 B.C. The advanced hydraulic engineering developed during the Khmer Empire allowed the Khmer to harvest rice and other crops three to four times a year. According to the International Rice Research Institute, there are approximately 2,000 rice varieties indigenous to Cambodia bred over the centuries by the Cambodian rice farmers. One of them – "Malys Angkor" (, ) – has been regarded the world's best rice. Many spices in Khmer cuisine were introduced by the Indian merchants around the 2nd century. The Indian influence on cuisine among other aspects of Khmer culture was already noted by a Chinese visitor around 400 AD. The trace of Indianization can be seen in the coconut-based curries (, ), as well as boiled red and white sweets. The Chinese began arriving in Khmer Empire in the 13th century, bringing their cuisine with them, from which Cambodian cuisine adopted an extensive use of noodles and stir frying. From the 9th to the 15th century the culinary influence of the growing Khmer Empire spread beyond the borders of modern-day Cambodia into what is now Thailand, Laos, Vietnam, and Indonesia. The Khmer palace food developed into a refined royal cuisine and through the Khmer royal cooks brought to the Ayutthaya Kingdom strongly influenced the Thai royal cuisine. The original Khmer palace recipes were modified in the Ayutthaya