Janis C. Kelly
Women with a high dietary acid load — typically associated with eating lots of protein but few vegetables — had a 56% higher risk for type 2 diabetes than women in the lowest quartile for dietary acid load, in a new analysis of the Étude epidémiologique auprès des femmes de la Mutuelle Générale de l"Education Nationale — European Prospective Investigation into Cancer and Nutrition (E3N-EPIC) study.
"A diet rich in animal protein may favor net acid intake, while most fruits and vegetables form alkaline precursors that neutralize the acidity. Contrary to what is generally believed, most fruits — even lemons and oranges — actually reduce dietary acid load once the body has processed them," say the authors, led by Guy Fagherazzi, PhD, from Gustave Roussy Institute in Villejuif, France, in a press release.
The fact that the association between both potential renal acid load and net endogenous acid production scores and risk for incident type 2 diabetes "persisted after adjustment for dietary patterns, meat consumption, and intake of fruit, vegetables, coffee, and sweetened beverages suggests that dietary acids may play a specific role in promoting the development of type 2 diabetes, irrespective of the foods or drinks that provide the acidic or alkaline components," the researchers add.
They report their findings in their study published online November 11 in Diabetologia.
First Demonstration that High Acid Load Is Linked to T2D
Dr. Fagherazzi and colleagues prospectively examined the association between dietary acid load and development of diabetes using data from 66,485 women from the E3N-EPIC cohort followed for incident type 2 diabetes over 14 years.
Subjects in E3N, the French component of the EPIC study, returned questionnaires on health-related information, including a validated 208-item diet history ("structured according to the French meal pattern") every 2 to 3 years. The researchers used a claims database to identify subjects who were reimbursed for a diabetes drug. The analysis included a total of 3496 incident diabetes cases, which the authors assume are mostly type 2 diabetes because the age range of study subjects was 46 to 60 years.
The dietary information was used to estimate the potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores for each subject.
Multivariate adjustments were made for age, years of education, smoking status, physical activity, hypertension, hypercholesterolemia, family history of diabetes, alcohol intake, omega-3 fatty-acid intake, carbohydrate intake, energy from fat and protein, coffee, and dietary patterns. Dietary components were classified as "Western" (rich in animal products and other acidogenic foods) or "healthy" (criteria not defined).
At baseline, women with higher PRAL scores (higher dietary acid load) were younger than those with low PRAL scores, less physically active, less likely to be treated for hypercholesterolemia, more likely to have a family history of diabetes, and more likely to report a "Western" dietary pattern. High-PRAL diets also included more meat, fish, cheese, bread, and soft drinks, particularly artificially sweetened beverages. Low-PRAL diets included more dairy products, fruit, vegetables, and coffee.
Women in the top quartile for PRAL had a 56% increased risk of developing type 2 diabetes compared with the bottom quartile. Women of normal weight (body mass index [BMI] 25 kg/m2 or lower) had the highest increased risk (96% for top quartile vs bottom), while overweight women (BMI 25 kg/m2 or higher) had only a 28% increased risk (top quartile vs bottom).
The NEAP score provided similar findings.
"We have demonstrated for the first time in a large prospective study that dietary acid load was positively associated with type 2 diabetes risk, independently of other known risk factors for diabetes," the researchers say.
However, they acknowledge that further research is required on the underlying mechanisms and that the results need to be validated in other populations; if they are replicated, this "may lead to promotion of diets with a low acid load for the prevention of diabetes," they conclude.
Hard to Control for Confounders; Eat a Balanced Diet
Naim M. Maalouf, MD, from the University of Texas Southwestern Medical Center, Dallas, who was not involved in this research, told Medscape Medical News:"Their data show that people who eat diets higher in acid content (more meat and fewer vegetables and fruits) are more likely to develop diabetes. There are already data published that show a relationship between greater meat intake and diabetes, so the only thing this study adds is that it shows a link between "potential acid" (a marker of meat-fruits/vegetables) and diabetes."
It suggests "that it is the acid itself that leads to diabetes, but the people on a higher acid diet were very different from people on low acid diet at baseline. They were slightly heavier, less likely to exercise, more likely to have a family history of diabetes, more likely to consume salt, etc, so it is difficult to prove causality," said Dr. Maalouf, who herself has studied the metabolic basis for low urinary pH in type 2 diabetes [Clin J Am Soc Nephrol. 2010;5:1277-1281].
"I am not totally convinced that the acidogenic diet itself led to diabetes based on this study alone, because of the potential confounders. One would have to specifically try to neutralize the acid and see what happens to diabetes risk, although this is difficult to do clinically. So at this point, I would tell my patient to continue to eat a balanced diet, keeping their meat portion size small, and to eat their salad and fruits with their steaks," Dr. Maalouf concluded.
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