We mean real food as opposed to processed food. Real food is fruits, vegetables, meats, dairy, seafood, nuts, seeds, whole grains and beans. Natural sweeteners, coffee, chocolate and wine count, too — just in moderation. Avoid food that is mass-produced, emulsified (where water and oil don’t separate) or shelf-stable. Eating real food leads to eating more nutrient-rich food without much effort. See What Real Food Looks Like for more information.
For example, while increased consumption of fruits and vegetables are related to decreases in mortality, cardiovascular diseases and cancers, supplementation with key factors found in fruits and vegetable, like antioxidants, vitamins, or minerals, do not help and some have been found to be harmful in some cases. In general as of 2016, robust clinical data is lacking, that shows that any kind of dietary supplementation does more good than harm for people who are healthy and eating a reasonable diet but there is clear data showing that dietary pattern and lifestyle choices are associated with health outcomes.