Is TMAO from Fish, Meat and Eggs Harmful?

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In another confusing nutrition story that should be titled “is there anything left for us to eat?” recent research threw a curveball. Fish, a staple of the Mediterranean diet, as well as meat and eggs may be doing more harm than good thanks to a compound called trimethylamine-N-oxide (TMAO). TMAO is found in fish and produced in the body after eating meat and eggs. TMAO is linked to greater risk for heart attack, stroke and death; yet the research isn’t crystal clear. Is it time to give up fish meat and eggs or ignore the recent media headlines?

This post will cover:

  • TMAO: More than a Gut Reaction—What gives us higher TMAO levels?
  • TMAO and health?
  • The bottom line

TMAO: More than a Gut Reaction

Blood levels of TMAO are ~ 50 times higher after eating fish compared to eggs or beef. The human body absorbs intact TMAO like the kind found in fish, easily. However, the human body’s production of TMAO, after eating foods containing the essential nutrient choline (found in eggs and meat) and the compound l-carnitine (found in meat and pork and in much smaller quantities in chicken breast and dairy products), depends on the makeup of bacteria in your gut, kidney functioning and genetics.

In one study, regular meat eaters produced more TMAO than a vegetarian did after eating steak (which contains ~ 180 mg of l-carnitine). After wiping out their gut bacteria with antibiotics, the carnivores didn’t produce any TMAO after consuming 250 mg l-carnitine. The makeup of gut bacteria in the habitual meat eaters was presumably responsible for greater TMAO production compared to the vegetarian, yet this was a small study and we don’t know anything else about the participants’ diet. Was it the meat that altered gut bacteria or something else in their diet? After all, a steady diet of red meat may mean double cheeseburgers on white bread with regular servings of French fries and soda on the side. This isn’t exactly the diet you want for promoting good bacteria in your gut.

Another study found blood levels of TMAO were greater in those with a less diverse makeup of microbes and greater amounts of a less healthy type of bacteria (firmicutes), compared to one that is healthy (bacteroidetes). A diet higher in saturated fat will promote this environment.

While bacteria seem to influence TMAO production from l-carnitine, l-carnitine also influences the makeup of gut bacteria. A study in mice found those with their gut bacteria wiped out thanks to antibiotics produced a different makeup of bacteria in the gut after consuming l-carnitine while also doubling the risk of plaque buildup in their arteries.

Higher TMAO levels come from:

  • Eating fish
  • Less diverse array of gut bacteria and increased levels of bad versus good bacteria
  • Consuming l-carnitine (mouse study)

TMAO and Health

A few human studies found higher blood levels of TMAO were associated with greater risk for heart disease. However, all research isn’t pointing in the same direction. One study in over 300 patients found blood TMAO levels were not associated with heart attack or heart disease over the course of eight years, following the initial test for TMAO. However, TMAO levels were higher in those with diabetes, patients with metabolic syndrome and those with declining kidney functioning. Another study examined over 800 people between the age of 33 and 55 and found blood TMAO levels were not associated with clogged arteries, insulin resistance (this comes before type 2 diabetes) and inflammatory markers or negative changes in blood lipids suggesting TMAO levels might not contribute significantly to the progression of clogged arteries. However, this study shows TMAO levels were significantly lower than in previous research, showing an association between TMAO and heart disease.

TMAO is considered a risk factor for cardiovascular disease. In those with type 2 diabetes, higher TMAO levels are associated with greater risk for death, heart attack, heart failure and unstable angina (chest pain). Also, higher levels of circulating TMAO are associated with higher risk of death in those with chronic kidney disease and greater risk of certain cancers. Yet, there are several confounding factors. Fish is the primary culprit for higher acute circulating TMAO levels, yet fish-based diets are associated with reduced risk for heart disease. Also, levels of TMAO are dependent upon disease state and the makeup of gut bacteria. Therefore, at this time it isn’t entirely clear which came first – does TMAO cause disease or does TMAO increase due to disease?

The Bottom Line

The story on TMAO isn’t crystal clear, so there’s no reason to avoid fish, meat and eggs in an effort to decrease TMAO levels. All three of these foods are good sources of several nutrients important for health. Though processed red meats are linked to higher risk of colorectal and stomach cancers, when cooked appropriately (lower, moist heat for example) red meat can fit into a healthy diet and deliver important nutrients including iron, zinc and vitamin B12. Eggs are an economical source of protein and contain many nutrients and compounds that contribute to health including two antioxidants important for eyesight.

Though there is no reason to completely avoid these foods, you can alter your diet to help diversify gut bacteria and also increase the amount of good versus bad bacteria. Probiotic rich foods such as yogurt and kefir with live and active cultures, miso soup, tempeh and other fermented foods contain good bacteria. Fiber-rich plant foods (fruits, vegetables, legumes) are important food sources for bacteria to thrive in your body.

Disclosure: this post was sponsored by USFRA. All views are my own and backed by research.

References
Koeth RA, Wang Z, Levison BS et al. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med 2013 Apr 7.

Cho CE, Caudill MA. Trimethylamine-N-Oxide: Friend, Foe, or Simply Caught in the Cross-Fire? Trends Endocrinol Metab 2016 Nov 4. [Epub ahead of print]

Cho CE, Taesuwan S, Malsheva OV, Bender E, Tulchinsky NF, Yan J, Sutter JL, Caudill MA. Trimethylamine-N-oxide (TMAO) response to animal source foods varies among healthy young men and is influenced by their gut microbiota composition: A randomized controlled trial. Mol Nutr Food Res 2016 Jul 5.

Carnitine. Health Professional Fact Sheet, NIH. https://ods.od.nih.gov/factsheets/Carnitine-HealthProfessional/

Mueller DM, Allenspach M, Othman A, Saely CH, Muendlein A, Vonbank A, Drexel H, von Eckardstein A. Plasma levels of trimethylamine-N-oxide are confounded by impaired kidney function and poor metabolic control.Atherosclerosis 2015;243(2):638-44.

Meyer KA, Benton TZ, Bennett BJ, Jacobs DR Jr., Lloyd-Jones DM, Gross MD, Carr JJ, Gordon-Larsen P, Zeisel SH. Microbiota-Dependent Metabolite Trimethylamine N-Oxide and Coronary Artery Calcium in the Coronary Artery Risk Development in Young Adults Study (CARDIA). J Am Heart Assoc. 2016 Oct 21;5(10). pii: e003970.

What You Need to Know about Pork

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If visions of mistreated animals injected with a continuous supply of hormones and antibiotics leave you feeling confused and terrified about your food choices—this post is for you. I’m cutting through many myths about how pork is produced, so you can rest assured you are making the right choices. For this post I interviewed Wanda Patsche, a pig farmer from Minnesota.

Aren’t big farms owned by big agriculture companies?
Wanda: Family farmers own 97% of pig farms. Some farms are big some are small.

What are the greatest misperceptions consumers have about pigs?
Wanda: Many people think modern farms are less humane compared to small farms; niche farms, pasture raised. Actually, the opposite is true. With modern farms barns are designed so you can handle the pigs better; pigs have a social hierarchy where they fight with each other. Modern farms are specifically created to easily control this fighting by having pigs in individual pens. This means less stress for the pigs, plus the buildings are temperature controlled with fresh air. Pigs are given clean water and clean feed. The barns are pressure washed and sanitized between groups of pigs (when pigs move out and prior to new pigs coming in). Plus, pig farmers work closely with their veterinarians. Farms that have more pigs mean the famers continually grind feed because they have more mouths to feed. Continually grinding feed means the pigs get fresh feed. Their diets are designed for health and growth.

What you need to know about porkIs hormone-free pork better?
Wanda: No pigs are given hormones. Farmers are not allowed to give pigs hormones. Therefore, any pork labeled “hormone-free” has been given this label to try and make customers think it is better than other pork. However, there is no difference, all pork is free from added hormones.

Are there any antibiotics in my pork?
Wanda: Antibiotic-free is another labeling term to try to persuade customers to choose chose a specific pork product. All meat is free of antibiotics. If a pig is given an antibiotic, all traces of the antibiotic must leave the body—called the withdrawal period—before the pig is sent to off for pork production.

What do you think is driving these perceptions?
Wanda: In the U.S., less than 2% of people are farmers. Many people don’t know farmers, and they are 2 – 4 generations removed from farmers. If you’ve never been to a farm or know people who farm it is easier to believe the myths that circulate on the internet.

Tell us a little more about advances in pork production and the safeguards in place to ensure pork is safe.
Wanda: Forty years ago, pigs were all outside. They had clean air but many hazards including sunburn and the greater likelihood of getting worms (and therefore the vets would have to treat them with medicine for worms). Now, with the introduction of indoor facilities and individual pins, pigs are less stressed which keeps them healthier. Stress = greater likelihood of sickness.

In addition, antibiotics are used less, and there is a comprehensive vaccination program in place to keep pigs healthy. On farms that do not use antibiotics to treat animals when sick, the animals must be pulled away from the other pigs to prevent the illness from spreading.

Animal scientists are currently conducting studies examining ways to keep animals healthy including the use of essential oils, probiotics, and enzymes. Healthier pigs mean even fewer antibiotics are used.

Antibiotics are the last resort and only used when necessary.

Pigs are grouped together based on age. This is helpful as immune system functioning differs by age. This is just another step to keep pigs as healthy as possible.

Aren’t farms more concerned about quantity vs. quality?
Wanda: No. Every day I wake up and think, “what can I do to ensure my pigs are as healthy as possible?” Pig farmers get more money for higher quality meat. So, every pig farmer has an added incentive to produce healthy, high quality pigs. Lower quality pork goes to a secondary market for ground pork, pepperoni and similar process products. Farmers get considerably less money for lower quality pork.

Are there any concerns that consumers should have about pork?
Wanda: The biggest concern for consumers is how pork is handled and cooked. According to the USDA pork should be cooked to 145°F internally. Ground pork should be cooked to 160°F. It can be pink in the middle as long as these internal temperatures are reached.

What are the best cuts of pork?
Wanda: pork is 16% leaner than it was 20 years ago due to the way animals are fed and genetics. Pork tenderloin is just as lean as chicken breast. An easy way to remember this: loin = lean.

This post was sponsored by USFRA, all views are mine and Wanda’s.