Foods which promote long life, virtuosity, immunity and resistance to disease, enhance joy and love for all, which has good nutrition and taste, are easy to swallow or eat, provide poise and stability to heart (eliminate anxiety and excitement), offered with love, such foods are dear to Satwik people.

(The foods that are) Bitter, citric, salty, excessively spicy, hot, dry and roasted, are the foods loved by Rajasik. These tend to create excitement, pain, grief, dismay and disease.
Note that these Shlokes were written about 5, 000 years ago. Even in those times, healthy foods were identified. Foods that render psychological imbalance were also identified, which science has yet to discover. Most importantly, see the similarity of human tastes, habits and foods which has not changed in the past 5000-6000 years. These categories of satwik, rajasik and tamasik foods still exist, and their definitions are still the same. Some people like fried, roasted and spicy foods which is not healthy, yet some prefer boiled with no or little salt, which is considered healthy. How could the Rishis discover the effects of foods so long ago, without the knowledge of modern medical science? Think! their ways and research, was it not scientific?

Foods that are stale (cooked more than three hours ago), tasteless, smelly, rotten or junk refuse and untouchable foods (referring to dead meats) are liked by the Tamasik.
Food builds human bodies. Like any other medicine, vitamin, fruits and vegetables, foods directly affect one's physical and psychological health. Non-vegetarian foods are said to increase excitement and reduce self-control. People tend to be more arrogant and reactive. Fruits and vegetables contribute to benign demeanour and enhance analytical capacity of mind. Psychological benefits from fruits and vegetables are far superior to non-vegetarian foods. Nature is witness to it as all meat-eating animals are dangerous and aggressive while plants eating animals are relatively gentle. Foods have its effect, but external moderation and  education subside natural instinct. Satwik foods provide broader consciousness, enhance tolerance and empathy. Effect of Tamasik foods are opposite. Meat and stale food are indicator of human selfishness, and should not be eaten to avoid other ill-effects. While non-vegetarian foods are good source of protein and vitamin, but can be replaced by milk, beans, seeds and lentils.
Often people argue that milk is not vegetarian and non-vegetarian. True, but here the idea of vegetarianism emerges from the compassion and equality among souls including animals. Killing animals is human selfishness, not an eco-system. If humans can learn to survive without killing animals, then why not? Such solutions were invented by Rishis thousands of years ago on the Indian plateau. Milking domestic cows and pets does not deprive their calves of the milk. It is produced in surplus quantity. Domesticated animals allow being milked as they realize the loving behaviour received from their caretakers. Here, it's worth quoting that some people declare it unethical to use animals for human needs, such as bullock carts etc. This is not true because like human labours are engaged to their physical strength and human minds are employed to work in offices, just the same way animals are utilized for their physical capacities within their limits. This is good for their health as well just the way exercising is good for us. In return, they get, love, care, food and safety from wild animals. Such cooperative living was developed thousands of years ago, for mutual benefits, and with love for animals, who lived with humans as one family.