Achieving a healthy diet is popularly misperceived as being attainable by eating 'healthy foods'. Many people falsely believe that there are 'good' and 'bad' foods they develop bad diets because they think that abundant eating of foods they consider 'healthy' will create a healthy diet. However, this is far from the truth. The consumption of nothing but substances that are deemed healthy, such as an "all-grain diet" or a diet consisting only of pasta or other health-foods, would most likely result in deficiencies because important nutrients (like protein-based foods) would be missed. Foods such as grains, fish, corn, etc. are healthy when consumed with a balanced diet, because in combination they supply us with all of the required nutrients. The most important aspect of any diet is maintaining a healthy intake and balance of foods.

The balance of micronutrients gained from meat, vegetables, and other foods is what makes diets healthy, not only consuming 'healthy' foods. For instance, milk, cheese, and other dairy products are known to have a relatively high fat content. Removing such dairy products from a diet may lower fat ingestion, but it will also negatively affect the intake of calcium and riboflavin that such foods offer.

Detrimental eating habits

In specific individuals, ingesting foods containing natural allergens (e.g. peanuts, shellfood) or drug-induced triggers (e.g. tyramine for a person taking an MAO inhibitor) may be life-threatening.

Some foods have low nutritional value, and if consumed on a regular basis will contribute to the decline of human health. This has been demonstrated by various epidemiological studies that have determined that foods such as processed and fast foods are linked to diabetes and various heart problems.

When improperly cut or prepared, a small number of foods (such as fugu) can result in death.

The ingredient usually cited as being most crucial to good health, water, has even been known to result in death when consumed in extraordinary quantities.