Types of Scientific Studies
There are various types of scientific studies on humans that can be used to provide supporting evidence for a particular hypothesis. These include epidemiological studies, interventional clinical trials, and randomized clinical trials. Valuable nutrition knowledge also is obtained from animal studies and cellular and molecular biology research.
Table 1.4 Types of Scientific Studies
| Type | Description | Example | Notes |
| Epidemiological | Observational study of populations around the world and the impact of nutrition on health. | Diets with a high consumption of saturated fat are associated with an increased risk of heart attacks. | Does not determine cause-and-effect relationships. |
| Intervention Clinical Trials | Scientific investigations where a variable is changed between groups. | Testing the effect of different diets on blood pressure. One group consumes an American diet, group 2 eats a diet rich in fruits and vegetables, and group 3 eats a combination of groups 1 and 2. | If done correctly, it does determine cause-and-effect relationships. |
| Randomized Clinical Trials | Participants are assigned by chance to separate groups that compare different treatments. Neither the researchers nor the participants can choose which group a participant is assigned. | Testing the effect of calcium supplements on women with osteoporosis. Participants are given a pill daily of a placebo or calcium supplement. Neither the participant nor the researcher know what group the participant is in. | Considered the “gold” standard for scientific studies. |
| Animal and Cellular Biology | Studies are conducted on animals or on cells. | Testing the effects of a new blood pressure drug on guinea pigs or on the lipid membrane of a cell. | Less expensive than human trials. Study is not on whole humans so it may be not applicable. |
Nutrition Assessment
Nutritional assessment is the interpretation of anthropometric, biochemical (laboratory), clinical and dietary data to determine whether a person or groups of people are well nourished or malnourished (overnourished or undernourished).
Nutritional assessment can be done using the ABCD methods. These refer to the following:
- A. Anthropometry
- B. Biochemical methods
- C. Clinical methods
- D. Dietary methods
Anthropometry methods of assessing nutritional status
The word anthropometry comes from two words: Anthropo means ‘human’ and metry means ‘measurement’. The different measurements taken to assess growth and body composition are presented below.
To assess growth, several different measurements including length, height, weight, head circumference, mid-arm circumference, skin-fold thickness, head/chest ratio, and hip/waist ratio can be used. Height and weight measurements are essential in children to evaluate physical growth. As an additional resource, the NHANES Anthropometry Procedures Manual (revised January 2004) can be viewed here https://www.cdc.gov/nchs/data/nhanes/nhanes_03_04/B