Inflammation is a risk factor for many chronic diseases, including cardiovascular disease (CVD), and the role of nutrition in inflammation is gaining scientific attention.
Recommendations to reduce red meat consumption, in example, are frequently based, in part, on old studies showing that red meat negatively affects inflammation - despite the fact that more recent studies have not supported this.
"The role of diet, including red meat, on inflammation and disease risk has not been adequately studied, which can lead to public health recommendations that are not based on strong evidence," said Dr Alexis Wood, associate professor of paediatrics - nutrition at the USDA/ARS Children's Nutrition Research Center at Baylor College of Medicine and Texas Children's Hospital.
"Our team sought to take a closer look by using metabolite data in the blood, which can provide a more direct link between diet and health."
Wood and her colleagues analysed cross-sectional data from around 4,000 older persons who took part in the Multi-Ethnic Study of Atherosclerosis (MESA), and their findings were just published in The American Journal of Clinical Nutrition.
Cross-sectional data is a useful source of evidence on how nutrition impacts health since it involves data collected from free-living people without seeking to modify their normal lifestyle.
As a result, it may be easier to adapt the findings of such investigations in non-research situations.
In addition to self-reported food intake and many indicators, researchers evaluated a variety of dietary intake metabolites in blood.
Plasma metabolites can aid in the detection of the effects of dietary intake as it is metabolised, digested, and absorbed.
Researchers found that when adjusted for body mass index (BMI), intake of unprocessed and processed red meat (beef, pork or lamb) was not directly associated with any markers of inflammation, suggesting that body weight, not red meat, may be the driver of increased systemic inflammation.
Of particular interest was the lack of a link between red meat intake and C-reactive protein (CRP), the major inflammatory risk marker of chronic disease.
"Our analysis adds to the growing body of evidence that indicates the importance of measuring plasma markers, such as metabolites, to track diet and disease risk associations, versus relying on self-reported dietary intake alone," Wood said.
"Our analysis does not support previous observational research associations linking red meat intake and inflammation."
Because observational studies cannot indicate cause and effect, randomized controlled trials (RCTs) where individuals are randomly assigned to consume a dietary factor of interest or not consume it, are needed as an additional line of evidence to adequately understand if red meat does not alter inflammation.
Several RCTs have demonstrated that lean unprocessed beef can be enjoyed in heart-healthy dietary patterns.
"We have reached a stage where more studies are needed before we can make recommendations to limit red meat consumption for reducing inflammation if we want to base dietary recommendations on the most up-to-date evidence," Wood said.
"Red meat is popular, accessible and palatable - and its place in our diet has deep cultural roots. Given this, recommendations about reducing consumption should be supported by strong scientific evidence, which doesn't yet exist."