Researchers studying the effects of fatty diets on puppies say their results could help further understanding of how these fats contribute to ageing and development of human diseases such as atherosclerosis and cancer.
Scientists at Purdue University in the US fed one group of dogs a highly-oxidised lipid diet and another group with a moderate level of this fat type. Both had reduced growth, bone formation and immune function, said John Turek, Purdue professor of basic sciences.
"We know that eating diets high in oxidised fat contributes to atherosclerosis and other diseases in people," said Turek, "but we don't know the long-term effects of foods high in oxidised lipids fed during the growth stage. Will organ and tissue growth be compromised? Will children develop geriatric diseases at an earlier point in their lives?"
Results showing that dogs on a moderate oxidised fat diet also exhibited some of the same effects as those eating meals containing high oxidised lipids were unexpected, Turek said. This finding has major significance for studies on overall health in both people and animals, the researchers report in the January issue of The Journal of Nutritional Biochemistry.
They added that fats, oils and processed foods without added antioxidants can contain oxidised lipids. In addition, frying food adds more of this type of fat. With people eating more convenience and fast-food, often prepared by frying, the level of oxidised fat in the modern diet has escalated alarmingly in recent years.
The process that forms oxidised lipids also occurs in the body's metabolic processes. Free radicals, a component of lipid oxidation, damages proteins, other lipids, DNA and cells, thereby causing disease. This is why foods, such as fresh fruits and vegetables, which are low in oxidised lipids and high in antioxidants, are important, according to the team.
Though researchers have linked oxidised fat to several human diseases, most of the research was done in rodents. The Purdue team suggested that young, growing dogs might give a better picture of how oxidised lipids affect humans, especially children during critical stages of development and growth. In the early months of life, dogs grow rapidly, adding considerable bone and lean body mass, which is more comparable to humans in rapid growth phases, such as puberty.
The 24 dogs, all two months old, were divided into three groups. One group ate a low-oxidised fat diet, one a diet with a moderate level of oxidised fat, and one a high oxidised fat diet. They were all kept on their assigned feeding regimen for 16 weeks. Other than the oxidation level of the fat, their diets were identical and contained all the other nutrients necessary for a healthy dog.
In the puppies, researchers found that those consuming highly oxidised fat gained less weight and had less body fat than those that ate moderate- and low-oxidised fat diets. The coonhounds on the diet high in oxidised fat also had decreased immune function and less vitamin E, an antioxidant that helps counteract the effects of free radicals. In addition, bone formation rate was reduced.
"Our study shows the need to control the amount of oxidised fats in food for both humans and companion animals so that we can ensure proper growth and optimum health," Turek said.
The oxidised lipid research is one of the ongoing projects by members of the Center for Enhancing Foods to Protect Health, a collaboration between Purdue and the Indiana University School of Medicine. The Iams Company Research and Development Fund funded the research.