Red meat, gut bacteria and heart disease

Red meat intake has been associated with elevated risk of cardiovascular disease and cardiovascular death.1-5 For example, combined data from the Nurses’ Health Study and Health Professionals Follow-up study, comprising over 120,000 people, estimated that each serving (100 grams) of red meat raises the risk of cardiovascular death by 18 percent

Two widely accepted factors that are thought to link red meat to increased cardiovascular disease risk are the high saturated fat and heme iron contents of red meat. Saturated fats are known to elevate total and LDL cholesterol levels, and excess iron is associated with oxidative stress, which promotes atherosclerosis.6-9 However, scientists have theorized that these factors alone do not explain the contribution of red meat to cardiovascular risk.3 Additional properties of red meat are likely involved.

Fascinating research presents a new potential mechanism by which red meat may increase cardiovascular risk – by modulating the species of bacteria that populate our digestive tract!

We are learning that our intestinal flora interacts with the cells of the intestinal wall to exert profound effects on our health. Beneficial microbes produce vitamins, protect us against pathogenic microbes, promote healthy immune function, facilitate energy extraction from food, and break down fiber and resistant starch into beneficial short chain fatty acids, which protect us against colon cancer. Importantly, what we eat determines which species of bacteria thrive in our digestive tract. Healthful, fiber-rich plant foods provide an energy source (“prebiotics”) for beneficial bacteria to grow.10,11

Is the reverse true? Do unhealthy foods promote proliferation of unhealthy gut bacteria?

Carnitine is an amino acid involved in energy production, and it is abundant in animal products, especially red meat; there is little or no carnitine in plant foods, and the human body can produce adequate carnitine from other amino acids, lysine and methionine. Studying mice, the scientists found that carnitine was metabolized by intestinal bacteria, producing trimethylamine-N-oxide (TMAO), a substance previously shown to contribute to atherosclerotic plaque development by slowing the removal of cholesterol from the arterial wall. They then sought to confirm these findings with human subjects. When analyzing the blood levels of carnitine and TMAO in human subjects, they found that the combination of high carnitine and high TMAO was associated with increased likelihood of cardiovascular disease or cardiovascular events (heart attack and stroke). When they gave humans carnitine supplements, they interestingly found that omnivores produced far more TMAO in response to carnitine than vegans and vegetarians. In addition, the species of gut bacteria in omnivores were different from those in vegetarians and vegans. These results suggest that regularly eating carnitine-containing foods promotes the growth of gut bacteria that can metabolize carnitine into a heart disease-promoting substance.12-14  

Our overall dietary pattern determines the bacteria that live in our gastrointestinal tract, and this research indicates that eating red meat regularly promotes the growth of bacteria that produce harmful substances from the components of red meat. It also indicates that those of us that regularly consume a healthful diet of whole plant foods have a healthier microbial profile, and we are less susceptible to the disease-promoting effects of high-carnitine meats. Future studies will continue to uncover more of these intriguing links between diet, gut bacteria, and health. 

Carnitine content of animal foods:15

Food Carnitine (mg)
Beef steak (3 ounces) 81
Ground beef (3 ounces) 80
Pork (3 ounces) 24
Milk (whole; 1 cup) 8
Fish (cod; 3 ounces) 5
Chicken breast (3 ounces) 3
Cheese (1 ounce) 1

This research highlights an additional way that red meat likely increases heart disease risk, but certainly the high amount of carnitine in red meat does not exonerate fish, chicken, eggs and dairy products. We already have plentiful evidence that excessive consumption of animal products in general are associated with increased risk of death from all causes. Animal products overall are micronutrient-poor and calorically concentrated, void of phytochemicals and antioxidants, contain pro-inflammatory fats, increase cholesterol levels, promote weight gain, and most importantly elevate IGF-1 which increases heart disease and cancer risk.



1. Sinha R, Cross AJ, Graubard BI, et al: Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med 2009;169:562-571.
2. Bernstein AM, Sun Q, Hu FB, et al: Major dietary protein sources and risk of coronary heart disease in women. Circulation 2010;122:876-883.
3. Pan A, Sun Q, Bernstein AM, et al: Red Meat Consumption and Mortality: Results From 2 Prospective Cohort Studies. Arch Intern Med 2012.
4. Ascherio A, Willett WC, Rimm EB, et al: Dietary iron intake and risk of coronary disease among men. Circulation 1994;89:969-974.
5. Larsson SC, Virtamo J, Wolk A: Red meat consumption and risk of stroke in Swedish men. Am J Clin Nutr 2011.
6. Tholstrup T, Hjerpsted J, Raff M: Palm olein increases plasma cholesterol moderately compared with olive oil in healthy individuals. Am J Clin Nutr 2011;94:1426-1432.
7. de Oliveira Otto MC, Alonso A, Lee DH, et al: Dietary intakes of zinc and heme iron from red meat, but not from other sources, are associated with greater risk of metabolic syndrome and cardiovascular disease. J Nutr 2012;142:526-533.
8. Ahluwalia N, Genoux A, Ferrieres J, et al: Iron status is associated with carotid atherosclerotic plaques in middle-aged adults. J Nutr 2010;140:812-816.
9. Brewer GJ: Iron and copper toxicity in diseases of aging, particularly atherosclerosis and Alzheimer's disease. Exp Biol Med 2007;232:323-335.
10. Neish AS: Microbes in gastrointestinal health and disease. Gastroenterology 2009;136:65-80.
11. Backhed F: Host responses to the human microbiome. Nutr Rev 2012;70 Suppl 1:S14-17.
12. Koeth RA, Wang Z, Levison BS, et al: Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med 2013.
13. Wang Z, Klipfell E, Bennett BJ, et al: Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature 2011;472:57-63.
14. Woolston C: Red meat + wrong bacteria = bad news for hearts. 2013. Nature. Accessed April 12, 2013.

15. Linus Pauling Institute: Carnitine.

Salt: another public health hazard

Scientists have shown that sugary beverages may be responsible for 180,000 deaths per year, and the same group of scientists has reported an estimate of the number of deaths due to excess salt consumption.

High sodium intake is associated with poor health outcomes, including elevated blood pressure, heart attack and stroke (even in the absence of high blood pressure), kidney disease, ulcers, gastric cancer, osteoporosis, and autoimmune inflammation.1,2  Elevated blood pressure, a consequence of excess sodium intake, is a significant threat to one’s health, and its prevalence is rising. Hypertension is one of the leading causes of death in the U.S., contributes to heart attack and stroke risk, and is associated with dementia.3

Using data gathered from the World Health Organization, the average worldwide daily sodium intake was found to be more than double the American Heart Association’s recommended limit of 1500 mg/day. Average worldwide sodium intake was 3,950 mg, and American adults came in just under that average at 3,600 mg.  Most of the world – 119 of the 187 countries studied, or 88% of all adults – consumed more than 3,000 mg sodium a day. Out of the 187 countries, only one (Kenya) had an average sodium intake meeting the American Heart Association’s guideline of 1,500 mg a day. Excess sodium has clearly become a global issue.

With excess sodium consumption now common throughout the entire world, are more people dying from heart attacks and strokes?

Higher sodium intake is consistently associated with greater risk of heart attack, stroke, and cardiovascular death in healthy populations.1 The scientists gathered data on deaths in 50 different countries and concluded that 2.3 million deaths per year worldwide may be due to excess salt consumption, and 40% of those deaths occurred in individuals under the age of 70 – suggesting that excess sodium is needlessly cutting many lives short. They estimated that excess salt contributes to one in 10 deaths of American adults, and that 15 percent of all deaths from cardiovascular disease were a consequence of excess salt intake.4-6

Could reducing sodium intake really prevent some of these deaths?

Clinical trials have clearly shown that reducing sodium intake reduces blood pressure in both healthy and hypertensive subjects.1  Additional clinical trials have shown that cardiovascular events could be  reduced by 20% with sodium reduction.7 A publication in the New England Journal of Medicine used mathematical models to estimate that a 1200 mg reduction in daily sodium intake population-wide in the U.S. could result in 60,000 fewer cases of CHD, 32,000 fewer strokes, and 54,000 fewer heart attacks every year.8 The effort to reduce sodium intake is substantially worthwhile.

Added salt is ubiquitous in processed foods and restaurant meals, and is contributing to the rampant cardiovascular disease in the modern world. Since most of the added sodium in the American diet comes from these foods, it is simple to avoid added salt by preparing most of your meals at home.  Sodium is an essential mineral that becomes dangerous in excess; by consuming only the sodium present in natural foods, we get adequate but not disease-causing levels of sodium. 


1. Whelton PK, Appel LJ, Sacco RL, et al: Sodium, blood pressure, and cardiovascular disease: further evidence supporting the American Heart Association sodium reduction recommendations. Circulation 2012;126:2880-2889.
2. Tsugane S, Sasazuki S: Diet and the risk of gastric cancer: review of epidemiological evidence. Gastric Cancer 2007;10:75-83.
3. Murphy SL, Xu J, Kochanek KD: Deaths: Preliminary Data for 2010. Natl Vital Stat Rep 2012;60.
4. Phend C: Whole World Uses Too Much Salt, Study Finds. 2013. MedPage Today. Accessed
5. Armour S: High Salt Consumption Tied to 2.3 Million Heart Deaths. 2013. Bloomberg. Accessed
6. Gray N: High salt intake causes 2.3 million deaths per year. 2013. Food Navigator. Accessed
7. He FJ, MacGregor GA: Salt reduction lowers cardiovascular risk: meta-analysis of outcome trials. Lancet 2011;378:380-382.
8. Bibbins-Domingo K, Chertow GM, Coxson PG, et al: Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med 2010;362:590-599.