When you eat a diverse diet of whole foods that have been prepared with traditional methods, your diet will naturally contain a healthy balance of nutrients, whether vitamins, minerals, proteins, carbohydrates, or fats. This is because humans normally seek out an extremely diverse diet. We forage for shellfish and kelp at the bottom of the ocean to birds and bees that nest high in trees. The average person has food from dozens of different plants and animals in their refrigerator at any moment. Not only will the nutrients in such a whole-foods diet be abundant, but traditional processing methods will make them available to your body, rather than leaving them locked up inside like a seed.
Dietary diversity both strengthens and protects us. Your body is designed to get rid of things it finds in excessive quantities in the diet, while holding on and increasing its absorption of foods that it is deficient in. A diverse diet gives your body a rich mix of nutrients. It also prevents you from taking in so much of any one food that you develop an overload of the nutrients that food has high levels of. There are also many nutrients and phytonutrients. People also tend to crave foods that contain nutrients they are deficient in. Salt-craving is a common phenomenon among all animals, including humans, and is just one example. If your diet is so limited that it doesn’t contain a food that is rich in a nutrient you are deficient in, how will your body respond? People today over-consume all kinds of unhealthy foods. Are they just looking for nutrients that they are deficient in? If they had foods in their diets that were rich in the nutrients that they are needing, maybe they would binge on these instead of junk food. Anecdotally, after cutting junk food out of my own diet and diversifying it with everything from seaweed to oatmeal, I have my own cravings for healthy food. Throughout the history of nutrition, this protective adaptation (to crave foods rich in nutrients we lack) has been described over and over again.
Dietary diversity is also something that requires us to travel, whether to the top of a tree or the other side of a continent. It requires humans to interact with one another and exchange goods and services (in this case, food). Food, particularly spices, have historically been so valuable that they have changed the course of world history with some frequency. The drive to diversify our diets has encouraged the mixing of cultures and human genetics. Our very identities and histories are wrapped up in our intrinsic craving for new, exotic foods. The modern epidemics are in part a reflection of a trend away from this kind of healthy curiosity and exploration.