Scientific disciplines are on a spectrum of certainty, with none being completely certain. This link is a good presentation of what science isn’t:
The most certain scientific disciplines are the so-called “Hard” sciences, such as chemistry, physics and biology. The least certain sciences are the so-called “Soft” sciences, such as the social sciences, which include such disciplines as sociology, psychology, economics and politics. Depending on its use of scientific methods, history can fall on different points somewhere between the “Hard” and “Soft” sciences. Where does nutrition and medical science fall?
Nutrition and medical science also falls somewhere between the “Hard” and “Soft” sciences. There are elements of the “Hard” sciences through its reliance on biology and chemistry. However, since medical science is involved with living organisms in general, and humans in particular, evaluation of the effects of many foods, treatments and procedures can have significant variability. A common complaint of lay people when nutrition or medical science changes its opinion based on new evidence is to discredit science generally. It is important to understand the information I have presented above so that one’s view of science is consistent with reality.
Below is a link to a recent article about recent findings in the area of nutrition to point out the reality of nutrition science: