But we could have been doing much, much better. For the study found that the average American diet remains poor and that healthful-food disparities between various socioeconomic groups actually increased over the past 15 years.
“Policy initiatives are urgently needed to address other healthy eating components to maintain and accelerate improvements in diet — in particular, to reduce the large and growing disparities between socioeconomic groups that translate directly into greater differences in morbidity and mortality,” the study’s authors conclude.
For the study, the researchers used a measurement tool called the Alternative Healthy Eating Index (AHEI) to rate dietary data collected from more than 33,000 U.S. adults who participated in the National Health and Nutrition Examination Survey between 1999 and 2012. The AHEI is considered a strong predictor of people’s risk of developing a major chronic disease and dying prematurely.
The scale ranges from 0 (non-adherence to a healthful diet) to 110 (perfect adherence).
In general, the AHEI defines a healthful diet as one that is high in fruit, vegetables, whole grains, fish, nuts and plant sources of fat and low in red meat, carbohydrates and partially hydrogenated fats.
After analyzing all the data, the researchers found that the average American diet improved modestly but significantly between 1999 and 2012, rising from 39.9 to 48.2 on the AHEI scale.
That meant the average American diet was still well below the midpoint of the AHEI scale — in other words, it was still not very healthful — but it had at least become somewhat better.
Half of that improvement came from a reduction in the consumption of a single unhealthful food ingredient: trans fat. Other significant healthful changes were reductions in sugar-sweetened beverages and fruit juices and in red and processed meat. Less impressive were increases (very small ones) in the consumption of fruit, whole grains, nuts, legumes and polyunsatured fats.
The consumption of vegetables remained about the same (unfortunately), and sodium intake increased.
The impact on health
The researchers then used information from two long-running studies, the Nurses’ Health Study and Health Professionals Follow-Up Study, involving about 173,000 people, to determine how the quality of those dietary changes might have impacted the development of disease and early death.
They estimated that the changes prevented 1.1 million premature deaths between 1999 and 2012, including 1 in 10 heart disease-related deaths and 1 in 40 cancer deaths.
The changes also led to 8.6 percent fewer heart disease cases, 5.1 percent fewer strokes, 1.3 percent fewer cancer cases, and 12.6 percent fewer cases of type 2 diabetes over the 15 years of the study.
The data also revealed “persistent or widening gaps in dietary quality across socioeconomic groups.” Most notably, the quality of diet among blacks, while significantly improved, was still lower than other racial or ethnic groups.
“Groups with low socioeconomic status and non-Hispanic blacks generally had poor dietary quality,” the researchers write. “Current agricultural policy arrangements that channel taxpayer subsidies for row crops but do not support fruit and vegetable growers are at odds with a US food supply system designed to deliver an affordable and healthful diet for low-income populations. Also, populations with low socioeconomic status may have limited access to healthful food and lack enough nutrition knowledge to make healthy food choices.”
As the researchers point out, the drop in the consumption of unhealthful trans fat — the driving force behind the improvement in diet revealed in this study — came about as the result of government policies, most notably the 2006 requirement that trans fat be disclosed on nutrition labels. (Earlier this year, the Food and Drug Administration announced that it was giving processed food companies three years to eliminate trans fat from their products.)
“The role of government action in reducing trans fats has set a successful precedent,” the researchers stress.
Other policy initiatives are now “needed to insure future improvements,” they add.
An abstract of the study can be found on the website for Health Affairs.