A two-part study that examined both mice and humans revealed a strong link between inorganic phosphate, a food additive that is prevalent in the "Western diet," and a lack of physical activity.
According to the latest statistics from the United States Department of Health and Human Services, less than 5 percent of the country's adult population engage in 30 minutes of physical activity every day.
Over 80 percent of U.S. adults do not follow the recommended guidelines for aerobic exercise and resistance training.
Also, only 1 in 3 people manage to exercise for the recommended amount every week.
Why are U.S. adults so sedentary? New research may now have found the culprit in a food additive present in meat, soda, and some processed foods: inorganic phosphate.
Scientists at the University of Texas (UT) Southwestern Medical Center in Dallas examined the link between inorganic phosphate and sedentarism in both mice and humans.
Phosphate contains phosphorus, an element that the body needs to "build and repair bones and teeth, help nerves function, and make muscles contract."
The researchers — led by Dr. Wanpen Vongpatanasin, a professor of medicine at UT Southwestern Medical Center — published their results in the journal Circulation.
Phosphate as a 'health risk'
Manufacturers add phosphate to food in order to keep it fresh for longer and to enhance its flavor. The additive is most likely to be present in "processed meat, ham, sausages, canned fish, baked goods, cola drinks, and other soft drinks."
Normally, kidneys control how much phosphate there is in the blood, and they help filter out the excess phosphate in the urine.
However, impaired kidneys may struggle to flush out excessive phosphate, which is why scientists have previously called the additive a "health risk" and called for labeling the amount of added phosphate in foods.
Some studies have also shown that inorganic phosphate correlates with a higher risk of mortality among people with kidney disease.
Meanwhile, newer studies have found that even in the general population, excess phosphate is linked with a higher risk of cardiovascular death as well as death from all causes.
How phosphate affects physical activity
For their study, Dr. Vongpatanasin and colleagues fed two groups of healthy mice similar diets; but, they gave one group of mice extra phosphate to a degree that is equivalent to that which U.S. adults consume.
Up to 25 percent of U.S. adults regularly consume between three and four times more phosphate than the recommended dose, say the researchers.
In the mouse experiment, 12 weeks of following a phosphate-enriched diet correlated with less time on the treadmill and lower cardiac fitness in the rodents.
The mice that consumed additional phosphate had an impaired fat-burning metabolism. Also, the researchers found that 5,000 genes that help process fat and aid cell metabolism were altered in these mice.
In the second part of the study, Dr. Vongpatanasin and team examined data on over 1,600 healthy people. The participants had worn fitness trackers for 7 days, which allowed the scientists to monitor their exercise levels.
They found that higher levels of phosphate in the blood correlated with more sedentarism and less time "spent in moderate to vigorous physical activity."
Dr. Vongpatanasin comments on the significance of the team's results, saying, "I think it might be about time for us to push the food industry to put this on labels so that we can see how much phosphate goes into our food."
"[B]ut this is just the beginning," notes Dr. Vongpatanasin, who concludes that more research is necessary to make this goal a reality.