The media loves excitement, but our progress in Nutritional Science is incremental, and progress is only made through research. The only source of valid Nutrition information is scientific research . Most facts we have about nutrition have been established by careful experiments, conducted by capable scientists, under carefully controlled conditions. Many of these facts have been verified by numerous experiments, repeated many times, by several groups of scientists. At least four kinds of scientific research can lead to facts about nutrition.
Case studies are careful examinations of events taking place in individuals.
From these individual observations, experimental hypotheses are derived, and many of these are subsequently tested by more complex and controlled experiments. For example, spina bifida, a birth defect, occurred in the babies of many women who had insufficient intakes of folic acid, a vitamin, during pregnancy. These case studies led to controlled experiments that proved that folic acid deficiencies caused birth defects, and established that fact by scientific means. Collection of data from examination of many individuals with a common characteristic, such as nationality, age, sex or food intake pattern, that reveals a correlation between some variables. For example, children born in the USA to families of Japanese people who have immigrated to the USA from Japan are usually several inches taller than similar children born to Japanese parents and raised in Japan.