According to the 1929 Geneva Convention, captured troops were to receive the same housing and food as the country's own troops. Here are some excerpts from SECTION II - PRISONERS OF WAR CAMPS. (emphasis added)

Art. 10. Prisoners of war shall be lodged in buildings or huts which afford all possible safeguards as regards hygiene and salubrity. The premises must be entirely free from damp, and adequately heated and lighted. All precautions shall be taken against the danger of fire. As regards dormitories, their total area, minimum cubic air space, fittings and bedding material, the conditions shall be the same as for the depot troops of the detaining Power.
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Art. 11. The food ration of prisoners of war shall be equivalent in quantity and quality to that of the depot troops. Prisoners shall also be afforded the means of preparing for themselves such additional articles of food as they may possess. Sufficient drinking water shall be supplied to them. The use of tobacco shall be authorized. Prisoners may be employed in the kitchens. All collective disciplinary measures affecting food are prohibited.