Chronic kidney disease (CKD) patients who consume a diet high in vegetables rather than meat may prevent the accumulation of toxic phosphorus levels, according to a study published online Dec. 23 in the Clinical Journal of the American Society of Nephrology.Sharon M. Moe, M.D., of the Indiana University School of Medicine in Indianapolis, and colleagues conducted a crossover trial in nine patients with a mean estimated glomerular filtration rate of 32 ml/min to compare vegetarian and meat diets containing equivalent nutrients prepared by clinical research staff.
The investigators found that one week of a vegetarian diet led to lower serum phosphorus levels, decreased phosphorus excretion in the urine, and reduced fibroblast growth factor-23 levels compared with a meat diet, despite equivalent protein and phosphorus concentrations in the two diets.
“In summary, this study demonstrates that the source of protein has a significant effect on phosphorus homeostasis in patients with CKD. Therefore, dietary counseling of patients with CKD must include information on not only the amount of phosphate but also the source of protein from which the phosphate derives,” the authors write.
Findings from a new study of 141 adults add to an ongoing medical debate over which patients with symptoms of celiac disease should go on a gluten-free diet. Published in ACS' Journal of Proteome Research, the study concludes that people currently diagnosed as “potential” celiac disease patients and not advised to follow a gluten-free diet may not be “potential” patients at all. Rather, the scientists found that these patients have the same distinctive metabolic fingerprint as patients with full-blown disease who do benefit from gluten-free diets.
In the study, Ivano Bertini and colleagues explain that celiac disease is an autoimmune digestive disorder characterized by the inability to digest a protein called gliadin, a component of gluten, which is found in wheat, rye, and barley. The condition causes diarrhea, bloating, and other symptoms in over 3 million people in the United States alone. Treatment is avoidance of foods containing gluten. But the disease is often undiagnosed or misdiagnosed. Definitive diagnosis involves biopsy of the small intestine, showing tissue damage. People with a positive blood test for the condition but no positive biopsy usually are diagnosed as “potential” celiac patients and may or may not be advised to follow a gluten-free diet.
The scientists used magnetic resonance metabolic profiling to analyze the biochemical markers in the blood and urine of 61 patients with celiac disease, 29 with potential celiac disease, and 51 healthy people. They found that those with potential disease largely shared the same profile as those with the confirmed disease and that the biochemical markers in both groups differed significantly from those of the healthy individuals. “Our results demonstrate that metabolic alterations may precede the development of small intestinal villous atrophy and provide a further rationale for early institution of gluten-free diet in patients with potential celiac disease, as recently suggested by prospective clinical studies,” the scientists conclude.
In an earlier investigation, the researchers had looked at the hormonal effects of diet cola ingestion on parathyroid hormone, calcium, phosphorus, insulin, alkaline phosphotase, and ghrelin.
The researchers thought that because of the phosphorus load, PTH would surge, but they found exactly the opposite, “which was that it comes down and sort of comes back to baseline; alkaline phosphatase increases also,” Larson said. “We thought, 'Well, that suggests there's some turnover of bone going on, and maybe there's some calcium being mobilized and it's going out in the urine and that might partially account for the fracture risk and decreased bone density that's being described.”
With results from that earlier study as the impetus, Larson and colleagues undertook the current study, for which they recruited 20 healthy women, ages 18 to 40.
Exclusion criteria were fracture within the prior six months, known bone disease or vitamin D deficiency, steroid or diuretic use, breast-feeding, and vitamin D supplementation above the current U.S. recommended daily allowance.
The participants were randomized to drink 24 ounces of either water or diet cola on two study days. Urine was collected for three hours after ingestion of the designated beverage and assayed for calcium, phosphorous, and creatinine using standard assays.
Data were analyzed on 16 participants; four were excluded because of lab error or failure to comply with the study protocol, the researchers said.
In addition to the higher calcium and phosphorus excretion, the investigators also found that normalized calcium and phosphorous excretion per gram of creatinine showed a trend in the same direction as total calcium and phosphorous per three hours. That figure did not achieve statistical significance, however.
Although the study was small, “it does look like there was a statistically significant rise in urine calcium,” said Larson. “The important part about that is that Diet Coke has no calcium content.”
Compared with milk, which also causes a rise in urine calcium but is replacing calcium at the same time, diet colas “would [create] an overall negative body calcium balance and that could partially explain why they appear to be bad for bones,” she said.
Although the study is too small to draw any firm conclusions, “certainly my personal practice among adolescent girls who tend to be concerned about their weight — and who drink diet beverages while they are in that critical period of bone formation — is to just try and counsel them to set habits of drinking calcium-containing beverages and maintaining adequate vitamin D,” said Larson.
Elizabeth Barrett-Connor, MD, of the University of California San Diego, called the study “fabulous.”
Barrett-Connor, who was not involved in the study, said that although it was a small and short-term trial, “it fits with all my preconceived ideas” about the nutritional problems with diet soda. “This [is new] but it just makes sense.”
The study was funded by the Walter Reed Department of Clinical Investigations.