Scientists can use different types of experiments to test hypotheses. The rickets experiment just described is called a laboratory experiment, as it was done in the confines of a lab. In the fields of nutrition and health, laboratory experiments are often conducted using animals, such as rats. Research conducted with humans is usually observational or experimental.
Observational Research
Observational research involves looking at factors in two or more groups of subjects to see if there is a relationship to a certain disease or another health outcome. For example, researchers might study rates of breast-feeding in infants with and without rickets, to see if breast-feeding influences the incidence of the disease.
One type of observational research is epidemiological research, which looks at populations of people. For example, scientists may look at people who live in
Experimental Research
Experimental research involves at least two groups of subjects. One group, the experimental group, is given a specific treatment, and another group, the control group, isn’t. For instance, after hypothesizing that vitamin D cures rickets, scientists would have randomly assigned children with rickets to two groups. They would have given the children in the experimental group a vitamin D supplement but would have given the children in the control group a substance, called a placebo that looked just like the vitamin D supplement but contained only sugar or some other nonnative ingredient. If neither of the two groups of subjects knew which substance they received, then they were “blind” to the treatment. If the scientists who were giving the placebo and the vitamin D supplement also couldn’t distinguish between the two treatments and didn’t know which group received which, this would be called a double-blind, placebo-controlled study.
The scientists would also have to make sure that all other significant factors were the same for both groups during the experiment. For example, since the scientists knew that sun exposure has a therapeutic effect on rickets, they couldn’t let the children in the control group go outside in the sunshine while keeping the children in the experimental group inside. The exposure to sunshine would change the outcome of he experiment. Similarly, they’d have to ensure that the children were eating exactly the same diet for the duration of the study.
A double-blind, placebo-controlled study is considered the “gold standard” of research, because all of the factors that might influence the study results are kept the same for the groups of subjects, and neither the subjects nor the researchers are biased, as they don’t know which group has received which treatment.
Although the results of many experiments fail to support the initial hypotheses, a great many discoveries are made. With continuing research, one discovery builds upon another.
Though it may seem frustrating when the findings of one research study dispute the results of another from just a few months before, even contradictory findings help advance scientific knowledge, in part because of the questions they raise. Why did the first study show one result and a second study something different? In tackling such questions, scientists continue to advance our understanding of the world around us, and within us. For example, scientists are asking intriguing research questions about nutritional genomics.
The feature box, “What Is Nutritional Genomics?” discusses this fascinating area of nutritional science.
A Hypothesis Can Lead to a Scientific Consensus
When a hypothesis is supported by research, the results are published in peer reviewed journals. Once a theory has been developed and supported by subsequent experiments, a consensus is reached in the scientific community.
Terms:
Peer-reviewed journal – A research journal in which fellow scientists (peers) review studies to assess if they are accurate and sound before they are published.
Laboratory experiment – A scientific experiment conducted in a laboratory. Some laboratory experiments involve animals.
Observational research – Research that involves looking at factors in two or more groups of subjects to see if there is a relationship to certain outcomes.
Epidemiological research – Research that looks at populations of people; it is often observational.
Experimental research – Research involving at least two groups of subjects.
Experimental group – The group given a specific treatment.
Control group – The group given a placebo.
Placebo – A sugar pill that has no impact on the individual’s health when ingested.
Double-blind placebo-controlled study – When the scientists and subjects in a research experiment can’t distinguish between the treatments given to the subjects and don’t know which group of subjects received which treatment.
