Is The Paleo Diet Bad For Your Heart?

Is The Paleo Diet Bad For Your Gut?

the paleo dietThere is a lot to like about the Paleo diet:

·       It is a whole food diet. Any diet that eliminates sodas, junk foods, and highly processed foods is an improvement over the American diet.

·       It includes lots of vegetables and some fruits.

·       It helps you lose weight, and any diet that results in weight loss improves your blood work – things like cholesterol, triglycerides, blood sugar control and more.

However, there are concerns the Paleo diet may not be healthy long term.

·       In part, that is because the diet is high in meat, red meat, and saturated fat.

·       Equally important, however, is what the diet eliminates – namely whole grains, legumes (beans), and dairy.

Those of you who have read my book, “Slaying The Food Myths”, know that I say: “We have 5 food groups for a reason”. This is particularly true for the plant food groups. That’s because each plant food group provides a unique blend of:

·       Vitamins and minerals. Those can be replaced with good multivitamin/multimineral supplement.

·       Phytonutrients. You can only get the full complement of health-promoting phytonutrients from a variety of foods from all 5 food groups.

·       Fiber. There are many kinds of fiber and they each play different roles in our intestine. You can only get all the health-promoting varieties of fiber by consuming fruits, vegetables, whole grains and legumes.

·       Gut bacteria. What we call fiber, our gut bacteria call food. Each of the plant food groups supports different populations of friendly gut bacteria.

Based on this reasoning, one might suspect that the Paleo diet might alter our gut bacteria in ways that could be bad for our health. Until recently, this sort of reasoning was just a theoretical concern. That’s because:

1)    We knew far too little about the health effects of different populations of bacteria. This is rapidly changing. Several recent studies have systematically investigated the connection between gut bacteria and health outcomes.

2)    We knew our diet influenced the bacteria populations found in our gut, but we had no understanding of how these changes might influence our health. This too is changing. The study (A Genoni et al, European Journal of Nutrition, https://doi.org/10.1007/s00394-019-02036-y) I discuss this week is an excellent example of recent studies linking diet, gut bacteria, and risk factors for disease.

How Was The Study Done?

can you believe clinical studies doctorThis study recruited 91 participants from Australia and New Zealand. It was a very well designed study in that:

·       The Paleo diet group (44 participants) was recruited based on self-proclaimed adherence to the Paleo diet (< 1 serving/day of grains and dairy products) for one year or more. This is important because short term effects of switching to a new diet are confounded by weight loss and other factors.

o   After analyzing the diets of the Paleo group, the investigators found it necessary to subdivide the group into Strict Paleo (< 1 serving/day of grains and dairy products) and Pseudo-Paleo (> 1 serving/day of grains and dairy).

·       The control group (47 participants) was recruited based on self-proclaimed adherence to a “healthy diet” for 1 year or more with no change in body weight (A healthy diet was defined as a whole food diet containing a variety of foods from all 5 food groups). This is important because far too many studies compare the diet they are promoting to an unhealthy diet with a lot of sugar and highly processed junk foods. These studies provide little useful information because almost anything is better than an unhealthy diet.

·       The participants completed a diet survey based on the frequency of consumption of various foods during the previous year. However, because diet surveys based on the recollection of participants can be inaccurate, the investigators used two rigorous tests to validate the accuracy of those diet surveys.

o   The first was a 3-day weighed dietary record (WDR). Simply put, this means that participants weighed and recorded all foods and beverages before they were eaten for 3 days. Two of those days were weekdays, and one was a weekend day.

o   Secondly, the investigators used blood, urine, and metabolic measures to independently determine protein and energy intake of each participant. Participants who were identified by these means as under reporting both protein and energy were considered unreliable dietary reporters and were excluded from the analysis.

o   It is very rare to find a study that goes to this length to validate the accuracy of the dietary data used in their analysis.

The participants also provided blood, urine and stool samples and completed a physical activity assessment.

What Were The Differences Between The Paleo Diet And The Healthy Control Diet?

Paleo FoodsOnly the Strict Paleo Diet group was faithfully following the Paleo diet. In addition, most of the results with the Pseudo Paleo Diet Group were intermediate between the other two diets. Therefore, to simplify my discussion of this study I will only compare the Strict Paleo Diet group, which I refer to as the Paleo Diet group, with the Healthy Diet control group.

The Paleo diet emphasizes fresh vegetables, especially green leafy vegetables, and discourages grains. Thus, it is no surprise that:

·       The Paleo Diet group ate 74% more vegetables and 3 times more leafy green vegetables than the Healthy Diet group.

·       The Paleo Diet group ate only 3% of the grains and 3% of the whole grains compared to the Healthy Diet group.

The Paleo diet encourages consumption of meat and eggs and discourages consumption of dairy and plant proteins. Thus, it is not surprising that:

·       The Paleo Diet group ate 3 times more red meat and 5 times more eggs than the Healthy Diet group.

·       The Paleo Diet group ate 10% of dairy foods compared to the Healthy Diet group.

·       The Paleo Diet group consumed two times more saturated fat and cholesterol than the Healthy Diet group.

The most interesting comparison between the two diets was the following:

·       Intake of total fiber, insoluble fiber, and soluble fiber was comparable on the two diets.

·       However, intake of resistant starch was 50% lower in the Paleo Diet group. This is significant because:

o   Resistant starch is a type of fiber found primarily in whole grains, legumes, potatoes, and yams (Potatoes and yams are also dietary “no nos” on most low-carb diets).

o   Resistant starch is an especially good food for certain species of healthy gut bacteria.

Is The Paleo Diet Bad For Your Gut?

Bas BacteriaBecause resistant starch affects gut bacteria, the study next looked at the effect of the two diets on the populations of gut bacteria. This is where the story starts to get interesting. When they looked at different groups of gut bacteria, they discovered that:

·       Bifidobacteria were much more abundant in the Healthy Diet group than in the Paleo Diet group, and the amount of Bifidobacteria in the gut was directly proportional to the amount of whole grains in the diet.

o   This is important because previous studies have suggested Bifidobacteria help maintain intestinal barrier integrity and protect against irritable bowel syndrome and obesity.

·       Roseburia were also much more abundant in the Healthy Diet group and proportional to the amount of whole grains in the diet.

o   This is important because previous studies have suggested Roseburia protect against inflammatory bowel diseases like Crohn’s disease and ulcerative colitis.

·       Hungatella were much more abundant in the Paleo Diet group and were inversely proportional to the amount of whole grains in the diet.

o   This is important because Hungatella metabolize carnitine and choline, which are found in meats (especially red meats), egg yolks, and high fat dairy, into a compound called trimethylamine or TMA. TMA is then further metabolized in the liver to trimethylamine-N-oxide, or TMAO.

o   TMAO is a bad player. It is positively associated with heart disease, stroke, kidney disease, diabetes, and Alzheimer’s disease. However, the evidence is strongest for heart disease. TMAO has been called an independent risk factor for cardiovascular death.

Because of this, the study looked at TMAO levels in the blood of the two diet groups. These results were concerning:

·       TMAO levels were 2.5-fold higher in the Paleo Diet group than in the Healthy Diet group.

·       As might be expected, TMAO levels were positively correlated with red meat intake and inversely proportional to whole grain intake.

Is The Paleo Diet Bad For Your Heart?

heart diseaseWhen you put all the evidence together you have a compelling argument that the Paleo diet is likely to increase the risk of heart disease. Let me summarize the data briefly:

1)    The Paleo diet discourages the consumption of whole grains.

2)    Whole grains are a major source of a dietary fiber called resistant starch.

3)    Because the Paleo diet is low in resistant starch, it causes a decrease in two healthy types of gut bacteria and an increase in a type of gut bacteria called Hungatella.

4)    Hungatella metabolize compounds found in meat, eggs, and dairy to a precursor of a chemical called TMAO. This study showed that TMAO levels were 2.4-fold higher in people consuming a Paleo diet.

5)    TMAO is associated with coronary artery disease and is considered an independent risk factor for cardiovascular death.

The authors of the study concluded: “Although the Paleo diet is promoted for improved gut health, results indicate long-term adherence is associated with different gut microbiota and increased TMAO. A variety of fiber components, including whole grain sources, may be required to maintain gut and cardiovascular health.”

Of course, studies like this are looking at associations. They are not definitive. What we need are long term studies looking at the effect of the Paleo diet on heart disease outcomes like heart attack and stroke. Until we have these studies my advice is:

·       Don’t accept claims that the Paleo diet is heart healthy. There are no long-term clinical studies to back up that claim.

·       Be aware that the Paleo diet affects your gut bacteria in ways that may be bad for your heart.

The more we learn about our gut bacteria, the more we appreciate the importance of including all 5 food groups in our diet, especially all the plant food groups.

Are Low Carb Diets Healthy?

low carb dietThe Paleo diet is not the only diet that is high in red meat and low in whole grains. The same is true for virtually all the popular low-carb diets. There are studies showing other low-carb diets also alter gut bacteria and raise TMAO levels, so there is a similar concern that they may also increase the risk of heart disease.

This is in addition to concerns about the high saturated fat consumption which increases the risk of heart disease and red meat consumption, which may increase the risk of certain cancers.

Finally, there are no studies showing that any low-carb diet is healthy long term, even the Atkins diet, which has been around for more than 50 years. Until we have long-term studies about the health consequences of low-carb diets, my advice is similar to that for the Paleo diet.

·       Don’t accept claims that low-carb diets are healthy. There are no long-term clinical studies to back up that claim.

·       Be aware that low-carb diets affect your gut bacteria in ways that may be bad for your health.

The Bottom Line

A recent study looked at the effect of the Paleo diet on an important risk factor for heart disease. Here is a brief summary of the data:

1)    The Paleo diet discourages the consumption of whole grains.

2)    Whole grains are a major source of a dietary fiber called resistant starch.

3)    Because the Paleo diet is low in resistant starch, it causes a decrease in two healthy types of gut bacteria and an increase in a type of gut bacteria called Hungatella.

4)    Hungatella metabolize compounds found in meat, eggs, and dairy to a precursor of a chemical called TMAO. This study showed that TMAO levels were 2.4-fold higher in people consuming a Paleo diet.

5)    TMAO is associated with coronary artery disease and is considered an independent risk factor for cardiovascular death.

Of course, studies like this are looking at associations. They are not definitive. What we need are long term studies looking at the effect of the Paleo diet on heart disease outcomes – like heart attack and stroke. Until we have these studies my advice is:

·       Don’t accept claims that the Paleo diet is heart healthy. There are no long-term clinical studies to back up that claim.

·       Be aware that the Paleo diet affects your gut bacteria in ways that may be bad for your heart.

·       Virtually all the popular low-carb diets discourage consumption of whole grains, so my advice for them is the same as for the Paleo diet.

The more we learn about our gut bacteria, the more we appreciate the importance of including all 5 food groups in our diet, especially all the plant food groups.

For more details on the study and what it means for you, 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

Can Gut Bacteria Make You Fat?

bacteria

bacteria

Gut Bacteria, Diet and Obesity

Author: Dr. Stephen Chaney

 

 

Can gut bacteria make you fat? It has been known for some time that the types of bacteria found in the intestines of obese people are different than those found in the intestines of lean individuals. But no one really knew the significance, if any, of that observation. Did obesity favor certain types of intestinal bacteria, or did certain types of intestinal bacteria favor obesity?

Obese individuals are often insulin resistant, and insulin resistance can cause higher sugar levels in the blood, urine and intestine. So it was easy to assume that obesity simply favored the growth of different types of bacteria in the intestine. However, recent studies have suggested that certain types of bacteria in our intestines may actually cause obesity.

Can Gut Bacteria Make You Fat?

For example, one study (Vijay-Kumar et al, Science, 328: 228-231, 2010) compared a strain of mice that are genetically predisposed to obesity with wild type (genetically lean) mice. They first looked at the intestinal bacteria. It turned out that the obese mice and lean mice had the same differences in intestinal bacteria that obese and lean humans have. And just like obese humans the obese mice ate more, displayed insulin resistance, and had elevated levels of triglycerides, cholesterol and blood sugar (They were pre-diabetic).

The investigators then decided to test the hypothesis that the particular bacterial strains found in the intestines of genetically obese mice might be causing their insulin resistance and obesity.

In the first experiment they killed off the intestinal bacteria in the genetically obese mice by putting high dose antibiotics in their food. Depleting the intestinal bacteria created some health problems for the mice, but it completely prevented the insulin resistance, overeating and obesity normally observed with this strain of mice.

In the second experiment they sterilized the intestines of the genetically lean mice and then colonized their intestines with intestinal bacteria from the genetically obese mice. When they did this, the genetically lean mice developed many of the characteristics of the genetically obese mice including insulin resistance, overeating, obesity and hyperglycemia.

insulin resistanceIn short, when their guts became colonized with bacteria from obese mice, the genetically lean mice became overweight and developed diabetes. Based on these experiments and other studies the scientists hypothesized that the wrong kinds of intestinal bacteria can make a significant contribution to insulin resistance, which in turn can lead to overeating and obesity. In short, they concluded that bad gut bacteria may make you fat.

The Battle of The Bacteria

In a second study (Walker et al, Science, 341: 1079-1089, 2013) the intestines of germ free mice were colonized with gut bacteria from lean and obese humans. The results were essentially the same as in the first study. That is, the mice who received gut bacteria from lean humans stayed lean and those who received gut bacteria from obese humans became obese.

But then the investigators asked two really interesting questions:

1) If you mixed the two types of bacteria, which one would win “the battle of the bacteria”?

For this experiment they took mice that had received gut bacteria from lean humans and mice that had received gut bacteria from obese humans and put them in the same cage. It turns out that since mice eat each other’s poop, they pick up each other’s intestinal bacteria. (No, I am not suggesting that you…)

The results of this experiment were (envelop please): The “lean” bacteria won out. They became the predominant bacteria in the intestines of all of the mice in the cage. Furthermore, none of the mice became obese – even the ones that had originally been inoculated with gut bacteria from obese humans.

2) Are the types of bacteria in the intestine influenced by diet?

In the previous experiment the mice were eating standard mouse chow – which is pretty healthy if you are a mouse. So the investigators decided to ask what would happen if they ate foods that were similar to really good and really bad human diets. They devised two types of diets for the mice – one that was high in fresh fruits & vegetable and low in fat (the good diet) and one that was high in fat and low in fresh fruits and vegetables (the bad diet).

On the good diet, the results were the same as in the previous experiment. On the bad diet the “lean” bacteria never grew in the intestines of the mice inoculated with bacteria from obese humans and those mice went on to become obese.

This study confirmed that the wrong kind of gut bacteria can cause obesity, but it also showed that diet can influence the type of bacteria that can grow in the intestine – something I talked about in an earlier issue of “Health Tips From the Professor”  Our Gut Bacteria Are What We Eat.

The Bottom Line

1) Does this mean that you should rush out and buy some probiotics (good bacteria) as part of your weight loss strategy? The simple answer is no. That would be premature. These studies were performed in mice. Although similar results have been reported in humans (for example, Jumpertz et al, Am. J. Clin. Nutr., 94: 58-65, 2011), those studies are very preliminary at present. In addition, genetics and diet obviously played a role in the results. In short, we are a long way from knowing to what extent intestinal bacteria might contribute to obesity in humans.

2) However, there are many very good reasons to make sure that you supply friendly bacteria to your intestinal track on a regular basis. For example, we know that bad bacteria in your intestine can compromise your immune system, convert foods that you eat to cancer causing chemicals, and cause chronic inflammation – which contributes to a number of major diseases.  Can gut bacteria make you fat?  We can’t yet say whether good bugs will help keep you slim, but we do know that they can help keep you healthy.

3) Finally, while we can’t yet say whether probiotic supplements can help you lose weight, it is becoming increasing clear that healthy diets (low fat, high fiber diets with lots of fresh fruits and vegetables) support the type of intestinal bacteria that can make you slim. This is yet one more reason why a healthy diet is so important if you want to stay slim and healthy.

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.

Our Gut Bacteria Are What We Eat

We Grow What We Eat

Author: Dr. Stephen Chaney

BacteriaThe subtitle of this week’s “Health Tips From the Professor” is “We Grow What We Eat”.

No, this is not about each of us starting a backyard garden and literally growing what we eat – although that would probably be a good idea for most of us. I’m actually talking about the bacteria that we “grow” in our intestine.

Most of you probably already know about the concept of “good” and “bad” intestinal bacteria.

Evidence suggests that the “bad” bacteria and yeast in our intestine can cause all sorts of adverse health effects:

  • There is mounting evidence that they can compromise our immune system.
  • There is also evidence that they can create a “leaky gut” (you can think of this as knocking holes in our intestinal wall that allow partially digested foods to enter the circulation where they can trigger inflammation and auto-immune responses).
  • There is some evidence that they can affect brain function and our moods.
  • They appear to convert the foods that we eat into cancer causing chemicals which can be absorbed into the bloodstream.
  • Studies in mice even suggest that they can make us fat.

The list goes on and on…

The “good bacteria” are thought to crowd out the “bad” bacteria and prevent many of the health problems they cause.

In case you’re thinking that it seems a bit far-fetched to think that our intestinal bacteria could affect our health, let me remind you that we have about 100 trillion bacteria in our intestine compared to about 10 trillion cells in our body. They outnumber us 10 to 1.

For years we have thought of “bad” bacteria and yeast as originating from undercooked, spoiled or poorly washed foods that we eat and the “good” bacteria as originating from foods like yogurt and probiotic supplements.

But most of us have not thought that the kinds of foods we choose to eat on a daily basis can affect the kinds of bacteria we “grow” in our intestine – until now. You’ve heard for years that “We are what we eat”. Well it now appears that we also “grow what we eat”. I’m referring to a recent study by G. D. Wu et al (Science, 334: 105-108, 2011).

Our Gut Bacteria Are What We Eat

I’m going to get a bit technical here (Don’t worry. There won’t be a quiz). Scientists refer to the population of bacteria in our intestines as our “microbiome”. Previous studies have shown that people from all over the world tend to have one of two distinct microbiomes (populations of bacteria) in their intestines – Bacteroides or Prevotella. [Again, don’t let the specialized scientific terminology scare you. These are just the names scientists have given to these two distinctive populations of intestinal bacteria].

What this study showed was that people who habitually consumed high-fat/low-fiber diets (diets containing predominantly animal protein and saturated fats) tended to have the Bacteroides bacteria in their intestine, while people who habitually consumed low-fat/high-fiber diets (diets that are primarily plant based and are high in carbohydrate and low in meat and dairy) tended to have the Prevotella bacteria in their intestine. And surprisingly this appears to be independent of sex, weight and nationality.

Is This Important?

The research defining these two distinct microbiomes (populations of intestinal bacteria) and showing that they are influenced by what we eat is very new. At this point in time we know relatively little about the health benefits and risks associated with the Bacteroides and Prevotella microbiomes.

For example:

  • Most of the studies on the health effects of “bad intestinal bacteria” were based on the identification of one or two “bad bacteria” in the gut – not on the hundreds of bacterial species found in the Bacteroides microbiome. So we can’t say for sure that the Bacteriodes microbiome found in people with diets high in animal protein and saturated fats will cause the same health problems as the “bad bacteria”. Nor do we know for sure how important a role the Bacteriodes microbiome plays in the health consequences of consuming that kind of diet.
  • Similarly, many of studies on the health benefits of “good intestinal bacteria” have been based on probiotic supplements containing one or two bacterial species – not the hundreds of bacterial species found in the Prevotella microbiome. So we can’t really say if probiotics or even the Prevotella microbiome will convey the same health benefits seen in populations who consume vegetarian diets.

However, now that do we know that we “grow what we eat” there are numerous studies ongoing to define the benefits and risks associated with each type of bacterial population.

For example, I shared a study with you recently which shows that the intestinal bacteria in people who eat a lot of animal protein convert carnitine (which is also found in meat) to a compound called TMAO, which may increase the risk of heart attacks, and that the conversion of carnitine to TMAO does not occur in people who consume a vegetarian diet ( see “Does Carnitine Increase Heart Disease Risk”)

Stay tuned! I’ll keep you updated as more information becomes available.

The Bottom Line:

Most of the studies I report on are ones that you can act on right away. This one is different. This study introduces a whole new concept – one that raises as many questions as it answers. This makes us ask those “what if” questions.

1)     Previous studies have shown that most people have one of two different kinds of microbiomes (populations of bacteria) in their intestines. This study showed that diets high in animal protein and fat favored one kind of intestinal microbiome, while diets low in fat and high in fiber from fruits & vegetables favored another type of intestinal microbiome.

2)     With a few exceptions we don’t know yet how important a role these intestinal microbiomes play in determining the health consequences of different diets. However, because our intestinal bacteria outnumber the cells in our body by 10:1, it is tempting to ask “What if?”

3)     We also don’t yet know the extent to which probiotics (either from foods or supplements) can overcome the effects of a bad diet on our intestinal microbiome, but it is tempting to ask “What if?”

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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