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.

Is Coffee Good for You?

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CoffeeDrinking coffee will leave you dehydrated and geeked out on caffeine. For several decades we’ve been warned about America’s favorite beverage. Yet these dire warnings were largely based on assumptions rather than actual science. A growing body of evidence suggests your morning Cup O’ Joe may be good for you! Here’s a look at the latest research.

What’s in a Coffee Bean?

Coffee beans are actually seeds from coffee cherries. They are picked, dried, and roasted turning them from green to those familiar aromatic brown beans we know and love. It’s ironic that a beverage made from seeds has gotten such a bad rap. Green coffee beans are naturally rich in antioxidants including chlorogenic acids, compounds that are readily absorbed in the human body, have antibacterial and anti-inflammatory actions and are associated with many health benefits including a reduction in cardiovascular disease, type II diabetes and Alzheimer’s disease. Antioxidants protect plants from disease and pests. Some antioxidants also protect human cells from harm. Roasted coffee beans are loaded with antioxidants (contrary to popular belief, they are not destroyed during roasting) and scientists are slowly uncovering the metabolic fate of each type antioxidant as well as the potential health benefits associated with regular coffee intake.

Potential Health Benefits

A National Institutes of Health study published in 2012 found older adults who drank caffeinated or decaffeinated coffee were less likely to die from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections. Those who drank over 3 cups per day had a 10% lower risk of death compared to those who did not drink coffee. Though this study only showed an association between coffee consumption and a decreased risk of death, it provided some reassurance to people who couldn’t seem to give up their favorite beverage. Studies published over the past three years lend strength to the relationship between regular coffee intake and a decreased risk of certain diseases.

Heart Health
A study published in the British Medical Journal’s publication Heart, examined diet and artery health in over 25,000 Korean men and women. Those who drank 3 to 5 cups of coffee per day were 19% less likely to have the first signs of atherosclerosis,  plaque buildup on artery walls, compared to those who were not coffee drinkers. Lower intakes were not associated with a reduction in plaque buildup. Drawbacks to this study: diet was examined at one point in time and study subjects were asked to recall their coffee intake over the previous year (people generally don’t recall their food / drink intake with great accuracy). Also, keep in mind this study showed an association between coffee intake and artery health, it doesn’t prove that coffee reduces plaque buildup on artery walls or that it can prevent cardiovascular disease. More research is needed to understand how coffee intake could potentially support heart health.

Cancer
A recently published study found individuals previously treated for stage III colon cancer who were regular coffee drinkers, consuming at least 4 cups of caffeinated coffee per day, had a 42% lower risk of recurrence of colon cancer and 33% lower risk of dying from the disease. This study found an association between coffee intake and decreased risk of colon cancer recurrence.

Research on coffee intake and risk of various cancers is mixed with some showing it is protective and others suggesting it may increase risk. Keep in mind there are many potential factors that impact cancer risk and risk of cancer recurrence with a sedentary lifestyle, high body fat and alcohol intake strongly associated with increased risk of certain types of cancer. Fruit and vegetable intake is associated with a decreased risk of some types of cancers. As for your Cup O’ Joe, time and more research, will tell us how America’s favorite beverage fits in the picture.

Should You Increase Your Coffee Intake?

All of these studies on regular coffee consumption include higher intakes. No benefits are noted for lower intakes – one to two cups per day. Keep in mind that some people should avoid or be cautious with caffeine intake including kids, teens, people with anxiety disorders, glaucoma, heartburn or cardiovascular disease. Also, pregnant women should avoid higher intakes of caffeine – more than 3 cups of coffee per day (regular sizes cups). Now about the caffeine – regular intake of moderate amounts of caffeine will not dehydrate you.

If you drink coffee in moderation, enjoy it! Don’t increase your intake based on these studies or start drinking if you aren’t a regular coffee consumer. Future research will tell us more about the many naturally occurring compounds in coffee, their actions in the body and the potential link between coffee and disease risk.

References
Heart 10.1136/heartjnl-2014-306663
New Eng J Med 2012;366:1891-1904.
J Nutr 2008;138(12):2309-15.
Mol Nutr Food Res 2005;49:274–84.
J Agric Food Chem. 2006;54:8738–43.
Am J Epidemiol 2002;156:445–53.
Biol Pharm Bull 2006;29:2236–4
Pest Manag Sci 2003 Apr;59(4):459-64.
J Clin Oncol 2015 Aug 17. [Epub ahead of print]

 

 

Which Fat is Best for Heart Health?

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Butter

If you are more confused than ever about dietary fats, you’re not alone. Can a high fat diet help you lose body fat? Which fat is best for heart health – butter, coconut oil or vegetable oil?

What is Cholesterol & Why is it Essential?
Cholesterol is an essential component of all cell membranes and a precursor to hormones, vitamin D and bile acids (needed for the digestion of fat). It is so important that your body regulates cholesterol balance to ensure your cells receive a continuous supply of cholesterol.

How does High LDL Contribute to Cardiovascular Disease?

Though cholesterol is critical for life, low density lipoprotein cholesterol, LDL cholesterol, is considered a risk factor for heart disease because excess LDL can lead to an increase in plaque buildup in your arteries. Think of this process like a garden hose with gunk stuck in it. The gunk interferes with water flowing through the hose. If too much debris gets in there, no water will flow through.  Likewise, plaque in your arteries will decrease the amount of blood that moves through your arteries at one time and a complete blockage could lead to a heart attack or stroke.  Now, this is a simplistic view, especially considering LDL isn’t just one particle but instead, several that contain different amounts of cholesterol. Some research suggests that smaller, more dense LDL particles are more artery clogging. However, in addition to particle size, total number of LDL particles and oxidation of LDL contribute to the disease process.

As LDL particles travel through the bloodstream, excess LDL particles can stick to artery walls (particularly walls that are damaged due to smoking, high blood pressure and other insults). Trapped LDL becomes oxidized and sets off an inflammatory cascade resulting in the development of plaque (gunk) stuck to arteries – atherosclerosis.

Coronary Artery Disease

How Can I Lower my LDL Cholesterol?

Cholesterol in food has little effect on your blood cholesterol.

Years ago we were told to stay away from shrimp, eggs and other high cholesterol foods. Yet this advice wasn’t based on sound science – cholesterol in food has little effect on your blood cholesterol levels. So there is no need to take these nutrient-rich foods out of your diet. Shrimp is loaded with protein, and is a good source of iron plus it contains just 80 calories per serving. Eggs are also packed with nutrition – the whites are an excellent source of protein and the yellow color you see in the yolk is from antioxidants – plant compounds that protect plants from disease and protect your body from the damaging effects of free radicals, compounds that are essential but can cause damage as well.

Coconut Oil, Butter and Other Solid Fats are Not the Best Options

Man-made trans fats (partially hydrogenated oils) are the worst kind of fat you can eat. However, they should, finally, be making their way out of our food supply over the next few years. High levels of *saturated fat, the kind that is solid at room temperature like butter, increases HDL (the “good” cholesterol but not a target of therapy – doctors don’t focus on HDL levels because increasing HDL does not lower heart disease risk) and LDL cholesterol in the blood. In controlled diet experiments where saturated fat is replaced with polyunsaturated fat rich vegetable oils, risk of heart disease is reduced. Replacing saturated fat with monounsaturated fat, the kind found in olive oil, also lowers LDL but not to the extent that polyunsaturated fat does.

Coconut oil is popular and calorie for calorie it might be better for weight management than other fats. However, coconut oil raises our total, good and bad cholesterol levels. And therefore, it is not the best option for heart health.

Excess Carbohydrate Intake can Increase LDL

Overconsumption of carbohydrate-rich foods can also increase VLDL cholesterol (very low density lipoprotein). Foods with added sugars, in particular, are potent stimulators of VLDL production when the energy (calories) aren’t needed right away for energy or increasing glycogen stores (stored carbohydrate in your liver and muscle).

Best Fats for Your Heart

Nuts, seeds, avocados, olives and liquid oils are your bets for heart health. Oils with more polyunsaturated fat have a greater impact on LDL cholesterol than those rich in monounsaturated fat. Make sure you are choosing the right oil for the right cooking application. Many oils can’t stand high heat and they break down, damaging the structure (and function) of the oil.

Fatty Acids in Oils

Conclusion

Many factors contribute to high blood cholesterol levels, including genetics, overweight/obesity, inactivity, smoking, diabetes and age, making cholesterol management a multifactorial issue. Saturated fat increases LDL cholesterol but, as I’ll say over and over, we are all different and, people vary in their response to dietary saturated fat due to intrinsic differences in fat metabolism as well as other factors including obesity, insulin resistance and high triglycerides.

Replace fats that raise cholesterol with liquid oils, nuts, seeds, avocados, and olives. Consider your overall diet as well. Eat a plant-based diet including vegetables (non-starchy veggies as well as beans, lentils and peas), fruits, nuts, seeds and whole grains (oats, barley etc.). Consume fatty fish ( salmon, mackerel, herring, halibut, sardines etc.) at least two times per week. Limit your intake of foods with added sugars and refined starches as well as your alcohol consumption. 

* There are differences in specific saturated fatty acids and their effects on blood cholesterol. Therefore, some foods high in saturated fat do not raise LDL cholesterol. Also, oils have a different array of vitamins (primarily vitamin E) and plant-based compounds that may be beneficial for heart health.

Fatty acids composition of oils taken from the USDA Nutrient Database.