Ranked: your protein shelf, worst to best for the chemical your gut makes from steak

Your gut bugs turn steak into a heart chemical

You cut into a steak. Your body pulls out protein and iron. Down in the colon, a crew of bacteria grabs something else.

They take a compound called carnitine and turn it into a molecule called TMA. Your liver then flips TMA into TMAO. And TMAO keeps showing up in the blood of people with clogged arteries.

So one dinner feeds you and feeds a tiny factory. One diet study put a number on that factory.

And a few of those 113 people went far past three times.

113 adults ate three set diets — the beef month tripled one number

Hazen's team handed 113 healthy adults their meals. Every person did a month of red meat, a month of white meat and a month with no meat, with a washout break between.

Blood and urine told the same story. TMAO tripled on the beef plan, and a handful of people climbed more than ten-fold. Drop the red meat and the number sank back over the following month.

The kidneys joined in too. On beef weeks they flushed TMAO out less well. So why did one person triple while the next one shot up ten times higher?

Eating meat daily staffs up the crew that does the dirty step

The same lab ran a second test. Fifteen meat eaters and nine vegetarians and vegans swallowed one 250 mg dose of carnitine, tagged so it could be tracked. The meat eaters made more than 20 times as much TMAO.

Both groups handled the first step fine. Bugs turn carnitine into a middle molecule with a long name, gamma-butyrobetaine. The whole gap sat in step two, where that middle molecule becomes TMA. In the meat eaters, step two ran up to ten times busier.

Think of it as hiring. Send carnitine down there every day and the bugs that do step two multiply. Which points at the one ingredient placing the orders.

Carnitine: up to 122 mg sits in one 3-ounce steak

Carnitine lives in muscle, and red muscle holds the most. That's why beef leads the shelf. Three ounces of cooked steak carries 42 to 122 mg by the NIH's own table. Ground beef lands at 65 to 74.

After that the drop is steep. A cup of whole milk holds 8 mg. Cod sits at 3 to 5, chicken breast at 2 to 4, two slices of whole-wheat bread at 0.2.

And the heaviest hit on any shelf isn't meat. Fat-burner pills sell L-carnitine by the gram, 500 to 2,000 mg a serving. That's a dozen steaks in one gulp, handed straight to the crew. So where does the rest of your shopping land?

Ranked: your protein shelf, most carnitine to least

Cooked 3-ounce servings, unless marked. Smaller number, less fuel for the TMA crew.

Nobody has to give up beef. Move it down the week and the crew thins out on its own. And there's one cheap thing to pour over the steak you keep.

Dress the beef in cold-pressed olive oil and balsamic

Hazen's lab hunted for a way to jam step two. They found a compound called DMB. The bugs stay alive — DMB blocks the tool they use to make TMA.

DMB turns up in cold-pressed extra virgin olive oil, balsamic vinegar and grape seed oil. In mice bred to clog their arteries, it pulled TMAO down and kept plaque from piling up. Mice, not people yet… though olive oil on your steak costs you nothing either way.

Two beef dinners moved. One bottle on the table. That's the whole job.