Red Meat and Heart Health

Written by Dr. Steve Chaney on . Posted in Red Meat and Heart Health

Can Red Meat Be Part Of A Heart Healthy Diet?

Author: Dr. Stephen Chaney

 

What about red meat and heart health?

red meat and heart health studyIt is so confusing. One recent headline proclaimed “Plant-based foods decrease the risk of heart disease and cancer.”  Another headline read: “Including beef with the Mediterranean diet improves heart health.”  You are probably wondering which of these studies is correct. More importantly, you are probably wondering whether you should include more meat or less meat in your diet.

If you read the articles, you will find that the dueling headlines are deceptive. Both studies reached essentially the same conclusion. The first study (K.S. Petersen et al, Current Developments in Nutrition, 2017; 1:e001289 ) concluded that plant-based diets significantly decreased the risk of heart disease and diabetes. It also concluded that you can include small amounts of animal protein in a plant-based diet without losing its health benefits. The second study (L.E. O’Connor et al, American Journal of Clinical Nutrition, 108: 1-8, 2018 ) concluded that the Mediterranean diet, which is a primarily plant-based diet, significantly decreased the risk of heart disease and diabetes. It also concluded that you could include small amounts of lean, unprocessed red meat in the Mediterranean diet without losing its health benefits.

You might be wondering how it is possible to go from a study showing that small amounts of lean, unprocessed red meat did not reduce the heart-health benefits of the Mediterranean diet to a headline claiming: “Including Beef With A Mediterranean Diet Improves Heart Health.”  Did I mention that the study was funded by money from the beef industry and the headlines came from an online issue of Beef Magazine? That might explain it.

Let’s look at:

  • How the studies were designed.
  • The study results in detail.
  • What these studies mean for you.

 

How Were The Studies Done?

red meat heart health and heart diseaseStudy #1: The first study (K.S. Petersen et al, Current Developments in Nutrition, 2017; 1:e001289 ) was a systematic review of over 50 recent studies looking at the relative contribution of plant-based foods and animal products to healthy dietary patterns.

Study #2: The second study (L.E. O’Connor et al, American Journal of Clinical Nutrition, 108: 1-8, 2018 ) was, in the words of the authors, an investigator-blinded, randomized, crossover, controlled feeding trial. That is probably Greek to most of you, so let me explain.

  • A “controlled feeding study” is one in which subjects are given diets designed by dietitians to contain precise amounts of macronutrients and micronutrients. In this case, both diets were Mediterranean diets. One of the diets was the standard Mediterranean diet with 1 ounce/day of lean, processed red meat. This diet was referred to as Med-Control. The other diet was a version of the Mediterranean diet containing 2.47 ounces/day of red meat. It was referred to as Med-Red. (More about the design of these diets below). The diets were prepared for the subjects by the Indiana Clinical Research Center Bionutrition Facility at Purdue University. The subjects completed weekly menu check-off lists and met with staff weekly to monitor compliance.
  • A “crossover study” is one in which subjects are given one experimental diet, followed by a “washout period” when they consume their normal diet, followed by the second experimental diet. In this case both experimental diets were followed for 5 weeks and the washout period was 4 weeks. In this type of study each subject serves as their own control.
  • The term “randomized” simply means that some subjects consumed the Med-Control diet first and others consumed the Med-Red diet first.
  • The term “investigator-blinded” simply means the investigators did not know the order of the experimental diets each subject received. It is, of course, impossible to conduct a double-blind study when you are conducting a dietary intervention study, such as this one. The subjects know which diet they are consuming.

Other important features of the study were:

  • The study included 41 middle-aged (46±2 years), obese (BMI=30.5±0.6) adults from West Lafayette, Indiana.
  • Fasting blood samples were taken at entry into the study and during the last week of both experimental diets and the washout period. The investigators measured total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, ApoB, C-reactive protein, insulin, and blood glucose levels.
  • Blood pressure was also measured at the same times.

In interpreting the results of this study, it is important to know other features of the experimental diets. They are:

  • red meat heart health foodsOverall macronutrient composition was identical for the two diets. It was 40% carbohydrate, 22% protein, and 40% fat. In other words, it was nether low-carb nor low-fat. Instead it consisted of healthy carbs and healthy fats.
  • The differences between the two diets was almost entirely based on the relative amount of red meat and poultry in the diets. The Med-Control had more poultry and less red meat. The Med-Red had more red meat and less poultry.
  • The red meat was lean beef or pork tenderloin. The poultry was chicken or turkey breast (white meat with the skin removed prior to cooking). All meats were low in fat and cholesterol (˂10% total fat, ˂5% saturated fat, ˂95 mg cholesterol). In short, none of the subjects were eating juicy steaks and burgers or fried chicken.
  • Fish intake was the same on both diets (22% of protein intake) so that omega-3 intake was similar.
  • Nuts, seeds, and legumes (primarily soy) were the same on both diets (40% of protein intake). When you include grains and other plant protein sources, plant-based protein probably constituted almost 50% of total protein intake.
  • Both diets included the same amount of olive oil. The overall fat profile of the diet (7% saturated, 20% monounsaturated, and 13% polyunsaturated) was very healthy.
  • Both diets were rich in fruits and vegetables (4 servings/day of fruit and 7-8 servings/day of vegetables). This is much more than you would find in the typical American diet.
  • Both diets were composed primarily of whole grains. There was almost no sugar or refined grain in either diet. Again, this is very different from what most Americans eat.

 

Red Meat and Heart Health?

 

red meat and heart health dietsStudy #1: While the authors of this paper reviewed a variety of studies, I will focus on studies looking at the inclusion of red meat into otherwise healthy diets. For example, the authors reported on a recently published study looking at inclusion of 3 different levels (1 ounce/day, 4 ounces/day, and 5 ounces/day) of lean, red meat into the DASH diet, a diet specifically designed to reduce the risk of high blood pressure. That study showed:

  • Inclusion of up to 5 ounces/day of lean red meat did not reduce the effectiveness of the DASH diet at reducing heart disease risk factors. In fact, total and LDL cholesterol levels were slightly better than when red meat was limited to 1 ounce/day.
  • However, the authors noted that:
    • The DASH diet is already fairly high in animal protein. The increase in red meat consumption was achieved by replacing other animal protein sources in the diet.
    • These were very lean cuts of red meat. All 3 versions of the DASH diet were designed to limit saturated fat intake to ˂6% of total calories.
    • Plant protein was about 50% of total protein intake in all 3 diets.
    • All 3 diets eliminated “empty calorie” foods and provided lots of fruits and vegetables (8-10 servings/day).
    • All 3 diets included 4-5 cups of low fat dairy products.
  • The authors also noted that dietary intake was closely controlled in this study and that similar results might be difficult to achieve in a free-living setting. For example, they pointed out that previous studies have shown:
    • Higher meat consumption in the American population is associated with lower consumption of fruits, vegetables, legumes, nuts, seeds and soy products.

The authors concluded: “It is likely that consumption of animal products (excluding processed meats) at recommended amounts in the context of a dietary pattern that meets recommendations for fruits, vegetables, whole grains, nuts, seeds, and legumes, and does not exceed recommendations for added sugar, sodium, and saturated fat, may not adversely affect, and may benefit cardiometabolic risk [risk of heart disease and diabetes].”

The authors went on to say: “However, population adherence to these recommendations is markedly suboptimal. Therefore, improving intake patterns to align with dietary guidelines should be the focus of our efforts rather than engaging in debate about whether diets for cardiovascular disease prevention should be exclusively plant-based or include animal foods in recommended amounts.”

In case you think that was clear as mud, let me offer my translation: “Lean, unprocessed meat consumption does not increase the risk of heart disease or diabetes when consumed as part of an extremely healthy diet. However, the American diet is lousy. We should focus on eating a healthy diet rather than arguing about whether it should be completely plant-based or can include some meat.”

Study #2: This study found that:

  • red meat heart health vegetables fruitsTotal and LDL cholesterol decreased more with Med-Red Meat than with Med-Control. However, the authors noted that the Mediterranean diet has little effect on total and LDL cholesterol levels, so its effect on reducing heart disease risk must be due to other factors.
  • The other parameters (HDL cholesterol, ApoB, triglycerides, C-reactive protein, insulin and blood glucose levels) were essentially the same on the Med-Red and Med-Control diets. However, the Med-Control diet also had little effect on these parameters compared to the normal diet of the subjects in the study. That probably reflected the short duration (5 weeks) of the diet intervention phase. Much longer dietary interventions would be required to adequately assess the effectiveness of either the Mediterranean diet or the Mediterranean diet with red meat at reducing disease risk.
  • Once again, the Med-Red diet was a carefully controlled diet that featured:
    • Small amounts (2.5 ounces/day) of very lean (<10% fat, <5% saturated fat) red meat in place of very lean poultry with about 50% of the protein in the diet coming from plant sources.
    • Lots of fruits, vegetables, whole grains, nuts, seeds, legumes, omega-3-rich seafood, and olive oil.
    • Almost no sugar and refined carbs.
    • A very healthy fat profile (7% saturated, 20% monounsaturated, and 13% polyunsaturated fat).
  • In short, this diet was radically different from the typical American diet.

The authors concluded: “Adults who are overweight or obese can consume 2.5 ounces/day as lean and unprocessed beef and pork when adopting a Mediterranean Pattern to improve cardiometabolic disease [heart disease and diabetes] risk factors.”

The authors went on to say: “Our results support previous observational and experimental evidence which shows that unprocessed and/or lean red meat consumption does not increase the risk of developing cardiovascular [heart] disease…”

As discussed below, the second conclusion is not supported by the data. We need to remember that this study was funded by money from the beef industry.

What Does This Mean For You?

red meat heart health lean meatsThe beef industry and low carb enthusiasts are telling you that red meat consumption as part of a healthy diet is good for your heart. These claims are very misleading. That’s because most Americans assume that their diet is already healthy. In addition, some Americans are being misled into believing that low carb diets are healthy (As I document in my book, “Slaying The Food Myths” those claims are currently unproven). Finally, many Americans interpret these claims as telling them that the juicy steaks, burgers, and sausages they love are heart healthy. The reality is far different.

  • The studies the claims are based on looked at red meat consumption in the context of the heart healthy DASH and Mediterranean diets, not in the context of the typical American diet or low carb diets.
  • The only risk factors affected in most of the studies are total and LDL cholesterol, which have low reliability of predicting heart disease risk by themselves. Furthermore, they appear to have almost no effect on the heart healthy benefits of the Mediterranean diet. In addition, the studies have been too short (typically 5 weeks) to reliably assess the effect of red meat on other heart disease risk factors.
  • The effect of red meat on heart disease risk factors has been assessed in carefully controlled diets that feature:
    • Small amounts of very lean (<10% fat, <6% saturated fat), unprocessed red meat in place of very lean poultry with about 50% of the protein in the diet coming from plant sources.
    • Lots of fruits, vegetables, whole grains, nuts, seeds, legumes, omega-3-rich seafood, and vegetable oils.
    • Almost no sugar and refined carbs.
    • A very healthy fat profile (7% saturated, 20% monounsaturated, and 13% polyunsaturated fat).

The authors of one recent review accurately concluded: “It is likely that consumption of animal products (excluding processed meats) at recommended amounts in the context of a dietary pattern that meets recommendations for fruits, vegetables, whole grains, nuts, seeds, and legumes, and does not exceed recommendations for added sugar, sodium, and saturated fat, may not adversely affect, and may benefit cardiometabolic risk [risk of heart disease and diabetes]”.

How you extrapolate from that kind of conclusion to an unqualified claim that “Observational and experimental evidence shows that unprocessed and/or lean red meat consumption does not increase the risk of developing cardiovascular [heart] disease” is beyond me.

My summary would be: “Small amounts of lean, unprocessed meat do not appear to increase the risk of heart disease or diabetes when consumed as part of an extremely healthy plant-based diet. However, the American diet is lousy. Low carb diets leave out too many healthy foods. We should focus on eating a healthy diet [as defined above] rather than arguing about whether it should be low carb, low fat, completely plant-based or can include small amounts of lean, unprocessed meat.”

 

The Bottom Line

 

The beef industry and low carb enthusiasts are telling you that red meat consumption as part of a healthy diet is good for your heart. These claims are very misleading. That’s because most Americans assume that their diet is already healthy. In addition, some Americans are being misled into believing that low carb diets are healthy (As I document in my book, “Slaying The Food Myths” those claims are currently unproven). Finally, many Americans interpret these claims as telling them that the juicy steaks, burgers, and sausages they love are heart healthy. The reality is far different.

  • The studies the claims are based on looked at red meat consumption in the context of the heart healthy DASH and Mediterranean diets, not in the context of the typical American diet or low carb diets.
  • The only risk factors affected in most of the studies are total and LDL cholesterol, which have low reliability of predicting heart disease risk by themselves. In addition, they appear to have almost no effect on the heart healthy benefits of the Mediterranean diet. The studies have been too short (typically 5 weeks) to reliably assess the effect of red meat on other heart disease risk factors.
  • The effect of red meat on heart disease risk has been assessed in carefully controlled diets that feature:
    • Small amounts of very lean (<10% fat, <6% saturated fat), unprocessed red meat in place of very lean poultry with about 50% of the protein in the diet coming from plant sources.
    • Lots of fruits, vegetables, whole grains, nuts, seeds, legumes, omega-3-rich seafood, and vegetable oils.
    • Almost no sugar and refined carbs.
    • A very healthy fat profile (7% saturated, 20% monounsaturated, and 13% polyunsaturated fat).

The authors of one recent review accurately concluded: “It is likely that consumption of animal products (excluding processed meats) at recommended amounts in the context of a dietary pattern that meets recommendations for fruits, vegetables, whole grains, nuts, seeds, and legumes, and does not exceed recommendations for added sugar, sodium, and saturated fat, may not adversely affect, and may benefit cardiometabolic risk [risk of heart disease and diabetes].”

How you extrapolate from that kind of conclusion to an unqualified claim that “Observational and experimental evidence shows that unprocessed and/or lean red meat consumption does not increase the risk of developing cardiovascular [heart] disease” is beyond me.

My summary would be: “Small amounts of lean, unprocessed meat do not appear to increase the risk of heart disease or diabetes when consumed as part of an extremely healthy plant-based diet. However, the American diet is lousy. Low carb diets leave out too many healthy foods. We should focus on eating a healthy diet [as defined above] rather than arguing about whether it should be low carb, low fat, completely plant-based or can include small amounts of lean, unprocessed meat.”

For more details, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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  • Nancy

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    Oh boy – this is very interesting information. I appreciate your opinions and hope you will continue to share with us.

    Reply

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Is Our Microbiome Affected By Exercise?

Posted November 6, 2018 by Dr. Steve Chaney

Microbiome Mysteries

Author: Dr. Stephen Chaney

is our microbiome affected by exerciseIn a recent post,  What is Your Microbiome and Why is it Important,  of “Health Tips From The Professor” I outlined how our microbiome, especially the bacteria that reside in our intestine, influences our health. That influence can be either good or bad depending on which species of bacteria populate our gut. I also discussed how the species of bacteria that populate our gut are influenced by what we eat and, in turn, influence how the foods we eat are metabolized.

I shared that there is an association between obesity and the species of bacteria that inhabit our gut. At present, this is a “chicken and egg” conundrum. We don’t know whether obesity influences the species of bacteria that inhabit our gut, or whether certain species of gut bacteria cause us to become obese.

Previous studies have shown that there is also an association between exercise and the species of bacteria that inhabit our gut. In particular, exercise is associated with an increase in bacteria that metabolize fiber in our diets to short chain fatty acids such as butyrate. That is potentially important because butyrate is a primary food source for intestinal mucosal cells (the cells that line the intestine). Butyrate helps those cells maintain the integrity of the gut barrier (which helps prevent things like leaky gut syndrome). It also has an anti-inflammatory effect on the immune cells that reside in the gut.

However, associations don’t prove cause and effect. We don’t know whether the differences in gut bacteria were caused by differences in diet or leanness in populations who exercised regularly and those who did not. This is what the present study (JM Allen et al, Medicine & Science In Sports & Exercise, 50: 747-757, 2018 ) was designed to clarify.  Is our microbiome affected by exercise?

 

How Was The Study Designed?

is our microbiome affected by exercise studyThis study was performed at the University of Illinois. Thirty-two previously sedentary subjects (average age = 28) were recruited for the study. Twenty of them were women and 12 were men. Prior to starting the study, the participants filled out a 7-day dietary record. They were asked to follow the same diet throughout the 12-week study. In addition, a dietitian designed a 3-day food menu based on their 7-day recall for the participants to follow prior to each fecal collection to determine species of gut bacteria.

The study included a two-week baseline when their baseline gut bacteria population was measured, and participants were tested for fitness. This was followed by a 6-week exercise intervention consisting of three supervised 30 to 60-minute moderate to vigorous exercise sessions per week. The exercise was adapted to the participant’s initial fitness level, and both the intensity and duration of exercise increased over the 6-week exercise intervention. Following the exercise intervention, all participants were instructed to maintain their diet and refrain from exercise for another 6 weeks. This was referred to as the “washout period.”

VO2max (a measure of fitness) was determined at baseline and at the end of the exercise intervention. Stool samples for determination of gut bacteria and concentrations of short-chain fatty acids were taken at baseline, at the end of the exercise intervention, and again after the washout period.

In short, this study divided participants into lean and obese categories and held diet constant. The only variable was the exercise component.

 

Is Our Microbiome Affected By Exercise?

is our microbiome affected by exercise fitnessThe results of the study were as follows:

  • Fitness, as assessed by VO2max, increased for all the participants, and the increase in fitness was comparable for both lean and obese subjects.
  • Exercise induced a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise increased fecal concentrations of butyrate and other short-chain fatty acids in the lean subjects, but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production were largely reversed once exercise training ceased.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent of diet, and contingent on the sustainment of exercise.” [Note: To be clear, the exercise-induced changes in both gut bacteria and short-chain fatty acid production were independent of diet and contingent on the sustainment of exercise. However, only the production of short-chain fatty acids was dependent on obesity status.]

 

What Does This Study Mean For You?

is our microbiome affected by exercise gut bacteriaThere are two important take home lessons from this study.

  • With respect to our gut bacteria, I have consistently told you that microbiome research is an emerging science. This is a small study, so you should regard it as the beginning of our understanding of the effect of exercise on our microbiome rather than conclusive by itself. It is consistent with previous studies showing an association between exercise and a potentially beneficial shift in the population of gut bacteria.

The strength of the study is that it shows that exercise-induced changes in beneficial gut bacteria are probably independent of diet. However, it is the first study to look at the interaction between obesity, exercise and gut bacteria, so I would interpret those results with caution until they have been replicated in subsequent studies.

  • With respect to exercise, this may be yet another reason to add regular physical activity to your healthy lifestyle program. We already know that exercise is important for cardiovascular health. We also know that exercise increases lean muscle mass which increases metabolic rate and helps prevent obesity. There is also excellent evidence that exercise improves mood and helps prevent cognitive decline as we age.

Exercise is also associated with decreased risk of colon cancer and irritable bowel disease. This effect of exercise has not received much attention because the mechanism of this effect is unclear. This study shows that exercise increases the fecal concentrations of butyrate and other short-chain fatty acids. Perhaps, this provides the mechanism for the interaction between exercise and intestinal health.

 

The Bottom Line

A recent study has reported that:

  • Exercise induces a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise causes an increase in the number of gut bacteria that produce butyrate and other short-chain fatty acids that are beneficial for gut health.
  • These effects are independent of diet, but do not appear to be independent of obesity because they were seen in lean subjects but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production are largely reversed once exercise training ceases.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent on diet, and contingent on the sustainment of exercise.”

For more details and my interpretation of the data, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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