To get optimum nutrition you need to eat a good diet. But that is not enough. The best nutritional information is quite clear: it is not possible to get a truly nutritious diet from the foods you buy. Most of them have been showered with a variety of chemicals, which we then eat. Few of these have been properly tested to see what effect they have on us when consumed for a lifetime.
In addition, heat and light destroy many nutrients in foods, so that by the time we eat them, the level of nutrients is low. Then, there is the experiment in genetically modified (GM) foods, banned in some countries and by some supermarket chains. Clearly, our diet is worse than it was 100 years ago in many ways - yet more nutritional information is available.
Another problem of modern living is that animals and plants used for food have been interbred to just produce more food - often at the expense of quality and the health of the plant and animal. Healthy animals and plants produce better food.
Many experts will now tell you it is impossible to obtain all your nutrients from food - unless you eat huge amounts. This is why they recommend supplements. For example, the prestigious Nutrition Review showed some years ago that it was impossible to get sufficient vitamins from our food supplies.