New data on the dietary intake of Americans over the past nearly 20 years shows that the intake of plant protein and soyfoods has significantly increased. However, whether the gains match expectations based on dietary guidelines issued during this time period is in question.
The report, which was published by researchers from the Harvard T. H. Chan School of Public Health and Tufts University, describes data from 9 consecutive cycles of the National Health and Nutrition Examination Survey (NHANES) administered from 1999 to 2016. Nearly 44,000 participants completed at least 1 valid dietary recall during the 9 cycles and were at least 20 years of age.
From 1999 to 2016, some notable demographic shifts occurred: the proportion of older adults (aged ≥65 years) increased from 18.0% to 21.1%; the proportion of younger adults (aged 20-34 years) decreased from 30.0% to 27.8%; the proportion who were non-Hispanic white declined from 69.8% to 64.4%; the percentage of other races/ethnicities increased from 4.6% to 9.6%; the proportion of respondents with at least some college education increased from 49.1% to 65.3%.
The estimated percentage of energy from total protein increased from 15.5% to 16.4% (P <0.001 for trend). The increases in the estimated total protein energy intake were associated with increases in estimated intake from both animal protein (10.2% to 10.6%; P <0 .001 for trend) and plant protein (5.38% to 5.76%; P <0.001 for trend). These data show that although plant protein intake did increase, the increase on an absolute basis was slightly less than the increase in animal protein (0.40 vs 0.38%). Therefore, the ratio of animal to plant protein consumption was essentially unchanged. In 1999-2000, animal protein accounted for 65.46% of total protein intake and in 2015-2016, it accounted for 64.79%. Americans are consuming more protein, but it is hard to conclude if the shift toward consumption of more plant protein is in line with what the Dietary Guidelines recommend.
The increases between 1999-2000 and 2015-2016 in estimated energy intake from plant protein were associated with increases in estimated protein intake from whole grains (from 0.38% to 0.50%), nuts (from 0.36% to 0.45%) and soy (from 0.12% to 0.19%). On a relative percent basis, the increase in soy was much larger than for nuts and whole gains (approximately 58% increase for soy and only 32% and 25% for whole grains and nuts, respectively). Interestingly, between 1999 and 2016, legume intake expressed as a percentage of energy increased only by about 10%, from 0.31 to 0.34%.
A closer look at the data provides insight into the increase in soy intake. Intake increased from 2001-2002 to 2002-2004 but then plateaued until 2015-2016 when it increased from 0.15% in 2013-2014 to 0.19%. It is difficult to speculate about whether the increase in soy intake will continue, although with the advent of so many new soy-based meat alternatives, there is ample opportunity for continued growth.
Finally, while the increased soy intake is welcomed news for those of us who believe soyfoods can positively contribute to overall health, some perspective is needed. The percentage of protein from refined grains for 2015-2016 is about 19 times greater than the protein from soyfoods. Clearly, there is a long way to go before soyfoods become a major contributor of protein to the U.S. diet.
References
Shan, Z., et al. (2019). “Trends in dietary carbohydrate, protein, and fat intake and diet quality among US adults, 1999-2016.” JAMA 322(12): 1178-1187.
