Long-term study shows U.S. consumption of minerals varies

Writing in BMC Nutrition​, researchers from Harbin Medical University in China tracked NHANES data taken from 48,223 participants between 1999 to March 2020 and discovered that although some nutritional improvements were made through diet, consumption of minerals was inconsistent across supplement, food and beverage groups. They also found that the intake of minerals and their food sources varied across sociodemographic groups, though this narrowed over time.  

“Although some improvements were observed, important challenges, such as overconsumption of sodium and under-consumption of potassium, calcium and magnesium, still remained among U.S. adults,” the researchers wrote. “Moreover, the proportion of adults meeting recommended dietary allowances for iron, potassium, zinc and copper significantly decreased.”

Suboptimal diet ​

Minerals play an important role in a variety of biological functions, such as cognition, development, immune response and thyroid function, and less than ideal levels of minerals can increase chronic disease risk. The bioavailability of minerals is an important factor that can vary depending on the type of food sources, which has implications for overall health.

The last few decades have shown that a suboptimal diet is a leading factor for chronic diseases, disability and death. It also has proven to have a global economic burden, though improvements in diets have broad economic and health benefits.  

The researchers noted that recent data indicate that the chronic diseases morbidity and mortality rate have stalled or deteriorated among U.S. adults, despite that macronutrient composition and overall dietary quality improved in the past decade.

During this time, studies have focused on trends in energy, macronutrients, micronutrients and other items such as sugar-sweetened beverages and ultra-processed food consumed by U.S. adults.

“However, previous studies about trends in minerals intake focused on only a few minerals, or used older data, or neglected sources,” the researchers wrote. “Furthermore, potential differences among population subgroups have not been evaluated. Thus, it is essential to evaluate time trends in minerals intake and their sources in overall population and population subgroups among U.S. adults to discover prevalent, worsening or potentially improving dietary problems.”

Study details​

The NHANES study included participants aged 20 years or older who were not pregnant or had extreme energy intake (< 500 or > 3,500 kcal/day for women, and < 800 or > 4,200 kcal/day for men).

Over two nonconsecutive days, the researchers collected dietary information about what foods and beverages participants consumed in the prior 24-hour period. The estimated minerals intake from food and beverage was calculated as well as the mean of minerals obtained through 24-hour recalls.

As for dietary supplement data, participants told researchers whether they used any prescription or non-prescription supplements in the past 30 days. They also provided the bottles of each supplement product or name, the frequency or duration of use and the type of formulation.

Dietary supplement-based minerals, which provided a large proportion of the minerals, decreased dramatically. Zinc-based supplements decreased from 18.06% to 14.00% during the study period. Copper supplementation declined from 16.27% to 9.22% and iron from 13.01% to 7.75%. Similar results appeared for calcium (from 11.75% to 9.04%), magnesium (from 8.57% to 6.07%), phosphorus (from 1.86% to 0.40%), potassium (from 0.83% to 0.51%) and selenium (from 7.81% to 6.67%).

The major food sources studied (defined by the U.S. Department of Agriculture) included: milk and milk products, meat, poultry, fish and mixtures, eggs, legumes, nuts and seeds, grain products, fruits, vegetables, fats, oils and salad dressings, and sugar, sweeteners and beverages.

Meat consumption remained stable, and the estimated percentage of calcium, phosphorus, potassium, sodium and selenium from meats significantly increased. Iron, magnesium, phosphorus, potassium, sodium, zinc and copper from grains also remarkably increased.

The story was different for fruits and vegetables as minerals from this category declined over time. The estimated percentage of magnesium from vegetables and fruits significantly decreased; potassium from vegetables and fruits also markedly decreased; copper from vegetables declined.

Sodium intake either increased or remained stable across all subgroups during the 21 years of study. Processed, packaged and prepared foods contributed to higher levels of sodium consumption.

“Due to the difference in study periods and methods for estimating minerals intake, it is hard to directly compare our results with previous studies,” the researchers wrote. “But our results confirmed previous findings that intake of iron, copper and zinc decreased, and intake of magnesium and calcium increased in 1999-March 2020. Moreover, we also observed the percentage of participants meeting recommended dietary allowances of calcium and magnesium increased during the study periods.”

Socioeconomic status and cultural differences also played a role in macro- and micronutrient consumption, although some of those differences have diminished over time.

“White, higher socioeconomic status participants had a higher iron intake, but had a greater decrease in iron intake,” according to the study authors. “Inversely, Black, lower socioeconomic status participants had a lower calcium intake, but had a greater increase in calcium intake. Previous studies reported closing gaps in dietary habits or dietary quality across different socioeconomic, racial or chronic diseases subpopulations, which were consistent with our findings to some extent.”

The researchers suggested the federally funded food assistance programs for lower income families could close the gap in income-related disparity regarding minerals consumption. They also proposed that economic growth and cultural integration have changed dietary habits across various subpopulations.  

Source: BMC Nutrition​
doi: 10.1186/s12937-024-00950-4​
“​National trends in nine key minerals intake (quantity and source) among U.S. adults, 1999 to March 2020”
Authors: Xuemin Yan et al.