Nutritional epidemiology is a branch of epidemiology that specifically focuses on the relationship between diet and disease.

Meta-analysis is a statistical technique used to combine the results of multiple studies, but it is not a primary method of data collection in nutritional epidemiology.

Cohort studies are often used in nutritional epidemiology to follow a group of people over time to determine the relationship between their diet and the development of disease.

In a cohort study, the primary outcome of interest is typically the incidence of disease, which is the number of new cases of disease that occur over a specified period of time.

Case-control studies are often used in nutritional epidemiology to identify risk factors for disease by comparing the dietary habits of people with a disease to those without the disease.

Vitamin C intake is not typically a primary focus of investigation in nutritional epidemiology, as it is not a major dietary risk factor for chronic diseases.

A positive association indicates that as the intake of a dietary factor increases, the risk of disease also increases.

An inverse association indicates that as the intake of a dietary factor increases, the risk of disease decreases.

A null association indicates that there is no significant relationship between intake of a particular dietary factor and the risk of disease.

A healthy dietary pattern is one that is rich in fruits, vegetables, whole grains, and lean protein, and low in saturated fat, trans fat, cholesterol, and sodium.

Processed meats, such as bacon, sausage, and hot dogs, are not part of a healthy dietary pattern and are associated with an increased risk of chronic diseases.

An unhealthy dietary pattern is one that is high in saturated fat, trans fat, cholesterol, and sodium, and low in fruits, vegetables, whole grains, and lean protein.

Fruits and vegetables are not part of an unhealthy dietary pattern and are associated with a lower risk of chronic diseases.

Dietary modification refers to the process of making changes to one's diet, such as increasing intake of fruits and vegetables or reducing intake of saturated fat, in order to improve health and reduce the risk of disease.

A randomized controlled trial is a type of dietary intervention in which participants are randomly assigned to either an intervention group, which receives the dietary intervention, or a control group, which does not receive the intervention.