The research team warned that while many people already know that too much dietary phosphate stiffens blood vessels, enlarges the heart and can be bad for bones, their new data suggests that where the phosphates come from has an impact on these risks.
Writing in the American Journal of Clinical Nutrition, the research team set out to distinguish the association of food sources of organic phosphorus and inorganic phosphate additives on serum phosphorus concentration after noting that previous research had not fully investigated whether sources of phosphate ion food had any impact on levels.
"The study suggests people should be more aware of what they eat," said the study’s lead author Linda Moore of Houston Methodist Hospital.
"The Institute of Medicine recommends 700 milligrams of phosphate per day and we think that's a good number,” said Moore. “What we were seeing in this study was twice the consumption of that amount for a lot of people.”
“Too much phosphate is concerning to people who are healthy - but it is of special concern to people who already have kidney damage or chronic renal disease,” she added.
Moore and her colleagues used data from the National Health and Nutrition Examination Survey (NHANES) survey between 2003 and 2006 to perform a cross-sectional analysis of 24-hour food recall data from 7,895 adult participants.
The team then categorised phosphorus content of foods as organic or inorganic before testing for correlations of serum phosphorus to clinical and dietary intake variables using multiple regression analysis.
After controlling for body-mass index, kidney function, sex, race, and other factors, the team found that the most significant increases in blood phosphate levels occurred in people who ate dairy foods and cereal/grain-based foods that contain artificially added phosphates.
A less pronounced but significant increase in blood phosphate levels occurred in people who ate dairy foods without artificially added phosphates, they added.
“This analysis shows that dairy products and cereals/grains having inorganic phosphate additives significantly increase serum phosphorus concentration, despite being consumed less frequently than foods without phosphate additives,” concluded Moore and her colleagues.
Source: American Journal of Clinical Nutrition
Published online, open access, doi: 10.3945/ajcn.114.102715
“Association of dietary phosphate and serum phosphorus concentration by levels of kidney function”
Authors: Linda W Moore, et al