Carnitine vs your gut bacteria




Human digestion and metabolism have a sneaky habit of complicating conventional nutrition wisdom.  It’s easy to identify some food component, extract it from the food, mix it in a test tube with cells or other chemicals, see what happens, and make some conclusion about potential health benefits.  Case in point: resveratrol: researchers examined the antioxidant activity of resveratrol, found in red wine in a test tube.  It seemed to do good things.  Conclusion: resveratrol is healthy; therefore the more the better.  An entire supplement industry is launched.

Not So Fast.  Turns out when a person actually consumes resveratrol, it may not be well absorbed into the blood or transported into cells.  And even then, it may be metabolized quickly to inactive compounds.

Carnitine is another case of conventional wisdom turned on its head.  Carnitine is made in the body, so strictly speaking it’s not a nutrient.  It’s also found in red meat and dairy foods.  Carnitine inside your body does help transport fats into cells, so supplement manufacturers tout it as a miracle fat burner.  The more the better, right?  But it turns out the carnitine you consume from food or supplements or energy drinks may take an unexpected path away from it’s role as a fatty acid transporter.  New research from the Cleveland Clinic shows that bacteria in the gut turn the carnitine we eat into a chemical called TMAO (trimethylamine N-oxide).  TMAO actually worsens atherosclerotic plaque formation.  So instead of absorbing all that supposedly fat-burning carnitine, you may be absorbing TMAO and increasing heart disease risk.

The researchers believe this finding explains a great deal about why elevated cholesterol alone isn’t always a good predictor of heart disease risk.  It also explains why eating a lot of red meat increases heart disease risk.  The study looked separately at vegans, meat eaters and vegetarians.  Not only do vegans have a lower intake of carnitine, but their plant-based diet sets up a population of gut bacteria that do not transform carnitine to TMAO.  Even when non-red-meat-eating subjects were challenged with a big dose of carnitine, they didn’t make TMAO, thanks to their very different gut bacteria.  Not only does eating red meat give you a big dose of carnitine, it encourages the type of gut bacteria that transform carnitine to TMAO.  Double whammy.

Think you’re OK if you don’t eat red meat?  Think again.  Red meat isn’t the only source of carnitine these days.  It’s being added to “energy” drinks and fat burning weight loss supplements, based on that simplistic conclusion that eating more carnitine will burn more fat.  As the Cleveland Clinic researchers note, some of these drinks have as much carnitine as a steak.  And habitual consumption of carnitine from any source will set up your gut bacteria to make TMAO.

At least it doesn’t have carnitine: The makers of Mountain Dew have devised a new marketing strategy.  Put a few drops of fruit juice in Mountain Dew, give it a catchy name — KickStart — and blast the message “real fruit juice” on the label.  Never mind that it’s only 5% real juice, or that the other 95% of the drink is added sugar or artificial sweeteners, flavorings and caffeine.

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