Ingredients: The Strange Chemistry of What We Put in Us and on Us

Ingredients takes a popular scientific approach to analyzing what we eat. A good deal of the text analyzing the vexing question of why there is so much "garbage" out there about nutrition. It seems every day there is press coverage of some food being surprisingly healthy or unhealthy. This is often a result of the process of research. Subjects are often asked to recall what they had to eat and memories are not fully accurate. Even portions and exact contents may differ from person to person. There is also the matter of correlation. There are many different foods and lifestyle factors that contribute to overall health. A high fiber diet may be correlated with cancer simply because older people are more likely to be on a high fiber diet and have cancer. This does not mean that the diet causes cancer. The variables would need to be separated and controlled to get a more accurate picture.
Another problem is the nature of research. Publishing a study that says "chocolate doesn't protect against cancer" would not get much press coverage. However, one that found a connection would. Scientists are more likely to publish the novel findings. The nature of human populations and statistical flukes mean many of these findings could be found "significant" but not necessarily "real".
An ideal study would be tightly controlled. However, these are very difficult to do and may have ethical concerns. There have been some attempts. In one study, people brought groups of people into a hospital setting and fed some processed food and others unprocessed food. Then the diet was switched. The groups could eat as much as they wanted of each, and the food was set to be a somewhat similar caloric density. The participants claimed that each diet was equally tasty. However, those eating the processed food tended to eat more and gain more wait. This seems to say that processed food will cause us to gain weight. However, there could be other factors missed. If both tasted the same, why did they eat more of the processed food? Was there a "halo" effect involved? Was there something about the participants that made it less applicable?
All food contains chemicals. More processed foods often tend to be similar in structure. We need to eat chemicals to survive. Understanding what is best is a complex question. Simply avoiding one thing or another may be useful for one person, while detrimental to another. Food science is hard.