Table 1.

Descriptions of commonly used methods to measure dietary intake in the U.S.

Method	Description and Examples	Demographic Information
Food Frequency Questionnaires (FFQs)	Relates dietary intake patterns to disease development over time and are designed to yield approximate intakes of broad food categories. Used commonly in prospective cohort studies.
	An example includes the Harvard T. H. Chan School of Public Health and the Brigham and Women’s Semi-quantitative Food Frequency Questionnaire [10] used in the Health Professional Follow-up Study and Nurses’ Health Study I and II cohorts [17].	At cohort initiation, the Health Professionals Follow-Up Study included n = 37,083 men aged 40 to 75 years, the Nurses’ Health Study I included n = 79,570 women aged 30 to 55 years, and the Nurses’ Health Study II included n = 87,504 women aged 25 to 42 years all with at least 20 years of follow-up data [17].
	Another example includes the National Cancer Institute Diet History Questionnaire II [11] used in the National Institute of Health American Association of Retired Persons (NIH-AARP) Diet and Health Study cohort [3].	At cohort initiation, the NIH-AARP Diet and Health Study included n = 536,969 men and women respondents aged 50 to 71 years from six U.S. states and two metropolitan areas with at least 16 years of follow-up data [3].
Food Disappearance Data	Estimates the amount of food in the food supply chain from production to retail outlets available for purchase; used to infer consumption.
	An example includes the United States Department of Agriculture, Economic Research Service (USDA-ERS) [9] which calculates summary estimates of per capita food and nutrient availability at the primary, retail and consumer levels based on total U.S. population 1.	Food availability estimates are developed by utilizing U.S. commodity market information to estimate the national food supply available to the population. The USDA-ERS uses sampling and statistical methods to calculate estimates.
Dietary Recalls	Measures participants’ recollection of food/beverage types and amounts consumed during the previous day; used to infer eating patterns.
	An example includes the 2013–2014 National Health and Nutrition Examination Survey Food Pattern Equivalency Database (NHANES, FPED) [12] which categorizes and quantifies equivalency (ounces per day 2) of dietary recall information from the NHANES into intake of broad food categories.	The 2013–2014 NHANES, FPED database included n = 9813 men and women in the U.S. aged 2 to 80 years. Dietary data were collected via two 24-h dietary recalls separated by at least 10 days. Interviews were conducted in-person or by phone using an automated multiple pass method and then statistically analyzed.

¹ Per capita availability reflects supply at the primary, retail and consumer levels. Loss at the consumer level is accounted for through adjustment and assumptions; more information about adjusting for loss is available at [9] ² In FFQ, 1 ounce ≈ 28 g.