Consumption of raw and fried sardine (Clupea pilchardus) as protein source of diets: effects on iron metabolism in rats

The influence of fried fish consumption on dietary iron bioavailability in rats was studied. Sardines (Clupea pilchardus), raw and fried in olive oil, were used whole or defatted to prepare the samples. Five diets containing casein and the different samples as protein source were prepared. After in vitro digestion of the diets a greater proportion of soluble iron was found in the casein diet compared with the sardine diets. Five groups of rats were fed the diets over 28 days. Body weight and food intake were monitored weekly, and during days 21–28 an iron balance study was carried out. No significant differences were observed in food intake, body weight and protein efficiency ratio between groups. Absorbed and retained iron and apparent iron digestibility were higher in rats fed the sardine diets with respect to the control group, except in the whole fried sardine group. Metabolic efficiency and retention efficiency were increased in the four sardine groups. The frying process led to significant changes in the overall digestive and nutritive efficiency of dietary iron, which were different depending on whether the diets contained whole sardine or its protein. It was concluded that the consumption of sardines, whether raw or fried in olive oil, enhances dietary iron availability.