Mediterranean diet with lean beef shows no spike in heart-risk indicator: Study
A new analysis out of Penn State is pushing back on the long-standing belief that beef automatically spells trouble for the heart. The research team, writing in the Journal of the American Heart Association, tracked how different diets affected trimethylamine N-oxide – TMAO – a blood marker often linked to cardiovascular disease.
Their conclusion was more measured than expected. When participants ate modest portions of lean beef within a Mediterranean-style diet, TMAO levels did not climb.
TMAO forms when the body breaks down certain animal foods, beef included, so the researchers wanted to see exactly how portion size and diet quality changed the equation.
Kristina Petersen, who teaches nutritional sciences at Penn State and oversaw the work, said the team wanted “to better understand the relationship between lean beef consumption and TMAO levels in the context of a healthy, Mediterranean style diet.”
Four diets, one group and a lot of controlled meals
The data came from an earlier controlled feeding study involving 30 adults. Every person cycled through four separate four-week diets, with a week’s break between each round. One diet reflected the typical American pattern – higher in saturated fat and lower in olive oil, fruit and vegetables. It included 2.5 ounces of regular, non-lean beef each day.
The other three phases followed a Mediterranean framework. Participants ate more plants, more olive oil and either 0.5 ounces, 2.5 ounces or 5.5 ounces of lean or extra-lean beef daily. Because everyone ate every diet, differences in results were not due to one group simply being healthier than another.
When participants ate the Mediterranean versions with either 0.5 or 2.5 ounces of lean beef, TMAO levels stayed lower than in the American diet phase. Higher-beef Mediterranean rounds – or the American diet – did not show meaningful differences from one another. Petersen said the takeaway was simple: diet quality mattered more than the sheer amount of beef.
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What does it mean for people who still want red meat?
Lead author Zachary DiMattia said the study used 2.5 ounces of lean beef because it lines up with what Americans typically eat each day. “This study suggests that, in the context of a healthy dietary pattern, people may be able to include similar amounts of lean beef without increasing their TMAO levels,” he said.
The team also tracked gut-microbiome changes. All three Mediterranean diets improved diversity compared to the American one, though more research is needed to explain how that ties into TMAO.
Petersen cautioned against reading the findings as permission to binge on red meat or switch to processed beef. She stressed that the study looked at lean, unprocessed cuts and relatively young participants, so more work is needed in older adults or people at higher risk.
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FAQs:
Does lean beef raise TMAO levels?
The study found no increase when lean beef was eaten in moderation within a Mediterranean diet.
How much beef did participants eat?
Daily portions ranged from 0.5 to 5.5 ounces depending on the diet phase.
Did the American diet show higher risk?
TMAO levels were higher on the American diet than on Mediterranean diets with small lean-beef portions.
What type of beef was used?
All beef in the study was unprocessed, and Mediterranean phases used lean or extra-lean cuts.
Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.
