Eating patterns shift over time
in response to changes in relative food prices
and income levels, exposure to new cuisines and
food products, and evolving dietary advice. It
is difficult to know exactly how eating patterns
are changing because time series data on actual
consumption by Americans are lacking. Although
extensive food expenditure data are regularly
collected, good intentions in the grocery store
do not always equate to what is eaten. Surveys
may undercount some foods, such as when consumers
“forget” their extra helpings and
snacks. In addition, most consumer surveys of
dietary intake cover only one or a few years of
consumption and many are not nationally representative.
So how do we track consumption patterns over time?
ERS has been calculating the amount of food commodities
available for consumption for decades. ERS’s
data system has continued to expand and now consists
of three data series. Users can download spreadsheets
from all three data series. The Food Availability
data series can also be accessed via the custom
query feature to develop tables or charts for
specific food groups, individual commodities,
and years.
The first series, the core Food
Availability data, is the only time series data
on the amount of food available for consumption
in the U.S. It is a continuous series extending
back to 1909 for many commodities. The data are
calculated for each food or commodity (e.g., beef,
low-fat milk, and fresh broccoli) as the sum of
annual production, beginning stocks, and imports
minus exports, ending stocks, and nonfood uses.
Per capita estimates are calculated by dividing
the total annual food supply of a commodity by
the U.S. population that year. Although the series
does not directly measure actual quantities ingested,
it provides an indication of whether Americans,
on average, are consuming more or less of various
foods over time. For example, in 2005, per capita
apple availability reached 46 pounds, 45 percent
above the 1970 level. These 46 pounds include
fresh apples as well as apples used for juice
and other processed products. The availability
data do not account for spoilage and waste in
the marketing system and at home. Thus, the data
typically overstate actual consumption.
Loss-Adjusted
Food Availability |
In the mid-1990s, ERS developed
methods to adjust the availability data for spoilage
and other losses and to convert the data to food
servings for comparison with Federal dietary recommendations.
For each commodity or food, this second series—the
Loss-Adjusted Food Availability data—subtracts
the estimated amount of food lost due to spoilage
and other factors at three stages. These losses
vary by commodity. For example, loss at all levels
for fresh apples totals an estimated 39 percent,
while total loss for cheddar cheese is estimated
at 18 percent. Efforts to refine the loss adjustments
are under way.
Next, the loss-adjusted data are converted from
pounds per capita per year into daily per capita
food intake in two forms—food servings (as
identified in USDA’s MyPyramid Food Guidance
System) and calories per person per day. Per capita
servings for individual commodities are estimated
and aggregated to determine total daily servings
for each food group. Calories are likewise aggregated.
These estimates are then compared with recommendations
for the U.S. population.
The third series, the Nutrient
Availability data, is compiled by USDA’s
Center for Nutrition Policy and Promotion (CNPP)
using the Food Availability data. This historical
data series estimates the amounts per capita per
day of food energy (calories), as well as 27 nutrients
and dietary components (i.e., protein, carbohydrates,
fats, vitamins, and minerals) in the Nation’s
food supply. Such information lets nutritionists
and others know which food groups are supplying
which nutrients. For example, vegetables contributed
27 percent and fruit 11 percent of the potassium
in food available for consumption in 2004.
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