Final answer:
The statement is false; foods generally contain a combination of both saturated and unsaturated fatty acids in varying proportions, depending on the food source.
Step-by-step explanation:
The statement that foods contain only one type of fatty acid, either saturated or unsaturated, but never both is false. Dietary fats typically consist of a mixture of both saturated and unsaturated fatty acids, which include monounsaturated and polyunsaturated types. Foods are often characterized by the predominant type of fatty acids they contain.
For instance, animal products like meats and whole milk are rich in saturated fats, while plant-based oils and fish usually provide higher amounts of unsaturated fats. Both types are important for health, with unsaturated fats being recommended in larger quantities due to their beneficial effects on cholesterol levels and heart health.