Which Foods Affect Stroke Risk?

Why Is Diet And Stroke Risk So Confusing?

strokeOne day we are told vegetarian diets reduce our stroke risk. The next day we are told they increase stroke risk. It’s the same with red meat, dairy, and eggs. We keep getting mixed messages. It’s enough to make your head spin. Why is diet and stroke risk so confusing?

Part of the problem is that there are two distinct types of stroke. The technical names for them are ischemic stroke and hemorrhagic stroke.

An ischemic stroke occurs when an artery in the brain becomes blocked, shutting off blood flow and damaging part of the brain. This is usually caused by the gradual buildup of fatty deposits and cholesterol plaques in the arteries. When a blood clot forms and lodges in one of the narrowed arteries leading to the brain, an ischemic stroke occurs.

  • Ischemic strokes account for 87% of all strokes.
  • Ischemic strokes are associated with obesity, elevated cholesterol, diabetes, high blood pressure, and smoking.

A hemorrhagic stroke occurs when a weakened blood vessel bursts and bleeds into the surrounding region of the brain. Because our brains are surrounded by a protective skull, that blood has nowhere to go. Pressure from the buildup of blood damages brain cells in the vicinity of the bleed.

  • Hemorrhagic strokes account for only for only 15% of strokes but are responsible for 40% of stroke deaths.
  • The most common cause of a hemorrhagic stroke is the localized enlargement of a blood vessel due to chronic high blood pressure. This weakens the wall of the blood vessel, making it prone to rupturing.

Part of the confusion about diet and stroke risk is because many earlier studies did not distinguish between the two types of stroke.

  • If the studies just measured the incidence of stroke, the data were dominated by ischemic strokes (87% of strokes are ischemic).
  • However, if the studies focused on stroke deaths, hemorrhagic stroke made a larger contribution to the data set (40% of stroke deaths are hemorrhagic).

Fortunately, recent studies have started to focus on the effect of diet on ischemic and hemorrhagic strokes separately. However, many of those studies have been too small to accurately assess the effects of diet on hemorrhagic stroke.

The latest study (TYN Tong et al, European Heart Journal, ehaa007, published February 24, 2020) is one of the largest studies to look at the effect of diet on both kinds of stroke. It has enough patients in the hemorrhagic group to get an accurate estimate of the effect of diet on hemorrhagic stroke.

How Was The Study Done?

Clinical StudyThis study analyzed data on diet and stroke from 418,329 participants in the EPIC (European Prospective Investigation into Cancer and Nutrition). Although the study has cancer in the title, it actually investigated the effect of nutrition on multiple diseases (Presumably, the study title was chosen because EPIC is a more appealing acronym than EPID (European Prospective Investigation into Diseases and Nutrition)).

The participants were recruited from 9 European countries (Denmark, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden, and the UK). The average age of participants was 50, and they were followed for an average of 12.7 years.

At the beginning of the study participants completed country-specific dietary and lifestyle questionnaires.

The dietary assessment was a food frequency questionnaire that asked participants about their dietary intake for the year prior to enrollment in the study. The food frequency data were used to estimate daily intake of red meat, processed meat, poultry, fish, dairy products, eggs, grains, fruits, vegetables, legumes, nuts, seeds, and dietary fiber (It measured total fiber and fiber from grains, fruits and vegetables individually).

The outcome measured was the incidence of ischemic and hemorrhagic strokes during the 12.7-year follow-up.

Which Foods Affect Stroke Risk?

Heart Healthy DietFor ischemic stroke:

  • Each 200 gram/day increase in consumption of fruits and vegetables decreased ischemic stroke risk by 13% (200 grams roughly corresponds to one large apple or one large orange without the skin).
  • Each 10 gram/day increase in consumption of fiber decreased ischemic stroke risk by 23%. Most of this decreased stroke risk was due to fiber from whole grains, fruits, and vegetables.
    • Each 4 gram/day increase in fiber from whole grains decreased ischemic stroke risk by 10%.
    • Each 4 gram/day increase in fiber from fruits and vegetables decreased ischemic stroke risk by 12%.
  • Dairy foods decreased ischemic stroke risk with the following breakdown:
    • Each cup of milk decreased ischemic stroke risk by 5%.
    • Each half cup of yogurt decreased ischemic stroke risk by 9%.
    • Each ounce of cheese decreased ischemic stroke risk by 12%.
  • Each 50 grams/day (2 ounces) of red meat increased ischemic stroke risk by 14%.
    • However, red meat was only half as likely to increase risk of ischemic stroke when the diet was also rich in fruits, vegetables, whole grains, and legumes.

For hemorrhagic stroke:

  • Each 20 gram/day increase in consumption of eggs increased hemorrhagic stroke risk by 25% (20 grams roughly corresponds to about 1/2 of a small egg or 1/3 of a jumbo egg).
  • This study did not measure the effect of salt intake on hemorrhagic stroke risk.

No other foods measured in this study had a significant effect on hemorrhagic stroke risk.

high blood pressureHowever, hemorrhagic stroke is highly associated with high blood pressure. When we look at the influence of foods on high blood pressure, here are the Harvard School of Medicine recommendations for keeping blood pressure low:

  • Eat more fish, nuts and beans in place of high-fat meats.
  • Choose fruits and vegetables instead of sugary, salty snacks and desserts.
  • Select whole grains rather than refined grains.Eat fruit instead of drinking fruit juice.
  • Use unsaturated fats like olive, canola, soybean, peanut, corn or safflower oils instead of butter, coconut oil, or palm-kernel oil.
  • Use herbs, spices, vinegar, and other low-sodium flavorings instead of salt; Choose low-sodium foods whenever possible.

Why Is Diet And Stroke Risk So Confusing?

egg confusionAs I mentioned at the start of this article, part of the reason that the headlines about diet and stroke risk are so confusing is:

  • Many studies did not distinguish between the two types of stroke.
  • Other studies were too small to reliably estimate the effect of food on hemorrhagic stroke risk.

However, there are still some unexplained inconsistencies among recently published studies. It is these inconsistencies I would like to address. For example:

1) In a recent issue of Health Tips From the Professor I reported on a major study (500,000 people followed for 8.9 years) in China. That study came to the opposite conclusion about eggs and risk of hemorrhagic than the EPIC study I discussed above. It found:

  • People consuming one egg per day had a 26% decrease in hemorrhagic stroke risk and a 28% decrease in hemorrhagic stroke deaths compared to people who never or rarely consumed eggs.

In other words, the two studies came to opposite conclusions. In the China study eggs decreased risk of hemorrhagic stroke. In the European study (EPIC) eggs increased risk of hemorrhagic stroke. The reason for this discrepancy is not clear, but one can speculate it might be explained by differences in the underlying diets of the two countries:

  • In China the diet is primarily plant-based. The addition of an egg/day may provide needed protein, fat, and cholesterol (Some cholesterol is essential. We just overdo it in this country).
  • In Europe the diet is already high in protein, saturated fat, and cholesterol. Getting more of them from eggs may not be such a good thing.

In short, if your diet is primarily plant-based, the addition of an egg/day may be a good thing. However, if your diet is already high in meat, saturated fat, and cholesterol, the addition of an egg/day may not be a good thing.

Vegan Foods2) In another recent issue of Health Tips From the Professor I reported on the EPIC-Oxford study that claimed vegetarians had 20% increased risk of hemorrhagic stroke compared to meat eaters.

Interestingly, the EPIC-Oxford study represented a very small portion (~10%) of the overall EPIC study and differed from the rest of the EPIC study in two important ways.

  • It looked at the effect of diets rather than foods on stroke risk.
  • Oxford was the only one of the 22 research centers involved in the EPIC study to invite people following a vegetarian diet to enroll in the study, so it had a much higher proportion of vegetarians than other centers that participated in the study.

The current study did not find any evidence that fruits, vegetables, nuts, seeds, beans, or whole grains influenced the risk of hemorrhagic stroke. In other words, in this much larger data set there was no evidence that the foods associated with a vegetarian diet increased hemorrhagic stroke risk.

However, most of the participants in larger EPIC study were also eating meats. They were not following a pure vegetarian diet.

As I said previously, “If the data on hemorrhagic stroke risk in the EPIC-Oxford study are true, it suggests it may not be a good idea to completely eliminate meat from our diet. However, you don’t need to add much meat to a vegetarian diet. The fish eaters in this study were consuming 1.4 ounces of fish per day. That was enough to eliminate the increased risk of hemorrhagic stroke.”

What Does This Mean For You?

Questioning WomanFor ischemic stroke (blockage of blood flow to the brain), which is the most common form of stroke, the data are clear cut:

  • Fruits, vegetables, whole grains and dairy foods are good for you. (Your mother was right.)
  • Red meat is not so good for you. However, the bad effect of red meat on ischemic stroke risk can be reduced by including plenty of fruits, vegetables, and whole grains in your diet.
  • These conclusions are consistent with multiple previous studies, and the mechanisms of these effects are well established.

For hemorrhagic stroke (bleeding from a weakened blood vessel in the brain) the data are not as clear cut.

  • If you are consuming a primarily plant-based diet, eggs appear to reduce your risk of hemorrhagic stroke.
  • If you are consuming a diet with lots of meat, saturated fat, and cholesterol, adding eggs may increase your risk of hemorrhagic stroke.
  • A vegetarian diet may increase your risk of hemorrhagic stroke. But you don’t need to add much meat to a vegetarian diet. Consuming 1.4 ounces of fish per day appears to be enough to eliminate the increased risk of hemorrhagic stroke.
  • The mechanisms of these effects of food on hemorrhagic stroke are unclear, so these conclusions may be modified by subsequent studies.

In terms of an overall take-home lesson on diet and stroke risk, my advice is: “A primarily plant-based diet is a good idea, but you don’t need to become a vegan purist. Nor do you want to follow fad diets that eliminate whole food groups. We have 5 food groups for a reason. Eliminating any of them may not be a good idea.”

The Bottom Line

A recent study examined the effect of various foods on the risk of the two major forms of stroke.

For ischemic stroke (blockage of blood flow to the brain), which is the most common form of stroke, the data are clear cut:

  • Fruits, vegetables, whole grains and dairy foods are good for you. (Your mother was right.)
  • Red meat is not so good for you. However, the bad effect of red meat on ischemic stroke risk can be reduced by including plenty of fruits, vegetables, and whole grains in your diet.
  • These conclusions are consistent with multiple previous studies, and the mechanisms of these effects are well established.

For hemorrhagic stroke (bleeding from a weakened blood vessel in the brain) the data are not as clear cut.

  • If you are consuming a primarily plant-based diet, eggs appear to reduce your risk of hemorrhagic stroke.
  • If you are consuming a diet with lots of meat, saturated fat, and cholesterol, adding eggs may increase your risk of hemorrhagic stroke.
  • A vegetarian diet may increase your risk of hemorrhagic stroke. But you don’t need to add much meat to a vegetarian diet. Consuming 1.4 ounces of fish per day appears to be enough to eliminate the increased risk of hemorrhagic stroke.
  • The mechanisms of these effects of food on hemorrhagic stroke are unclear, so these conclusions may be modified by subsequent studies.

In terms of an overall take-home lesson on diet and stroke risk, my advice is: “A primarily plant-based diet is a good idea, but you don’t need to become a vegan purist. Nor do you want to follow fad diets that eliminate whole food groups. We have 5 food groups for a reason. Eliminating any of them may not be a good idea.”

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.

 

Is The Impossible Burger Healthy For You?

Is The Impossible Burger Healthy For the Planet?

Vegan BurgerAmericans love their meat. In 2018 we averaged over 200 pounds of meat per person. If we just focus on beef, we eat about 54 pounds per year. That’s equivalent to four quarter pounders a week!

But we are also getting the message that too much meat, especially red meat, may be bad for us. Nearly 40% of us are trying to eat a more plant-based diet.

The problem is that we love the convenience of fast food restaurants, and we love our burgers. Plus, in the past the meatless burgers on the market were, in a word, disappointing. Their taste and texture left something to be desired. You really needed to be committed to a plant-based diet to eat them in place of a regular burger.

That all changed a few years ago with the introduction of the and new generation of meatless burgers – the Impossible Burger and the Beyond Burger. They had the taste and texture of a real burger, but they were completely plant-based. What wasn’t to like?

  • Both companies claimed that their meatless burgers were healthier for the planet than regular burgers. For example, Impossible Food’s mission statement is: “Animal agriculture occupies almost half the land on earth, consumes a quarter of our freshwater, and destroys our ecosystems. So, we’re doing something about it: We’re making meat using plants, so that we never have to use animals again”.
  • Neither company claims their burgers are healthier for you. However, because their burgers are plant-based, the almost universal assumption has been that they are healthier than regular burgers.

Since their introduction they have taken the world by storm. You can find them in almost every supermarket and in many of your favorite fast food restaurants. Now that they are omnipresent, it is perhaps time to step back and take a closer look at this new generation of meatless burgers. In this article, I will ask two questions:

  • Are they healthier for you than regular burgers?
  • Are they healthier for the planet than regular burgers?

For the sake of simplicity, I will focus on the Impossible Burger with occasional comparisons with the Beyond Burger. It is beyond the scope of this article to compare these burgers with the many other meatless burgers that are now starting to flood the marketplace.

What’s In The Impossible Burger?

  • When we think of a burger, the first thing we think of is protein. The Impossible Burger gets its protein from soy, while the Beyond Burger gets its protein from peas.

Coconut OilHowever, soy and pea protein don’t give you the mouth feel, flavor, red color, and texture of a beef burger.

  • The mouth feel of a burger comes from its saturated fat. Both the Impossible Burger and Beyond Burger use coconut oil as their source of saturated fat.
    • Coconut oil has gained a reputation as a “healthier” saturated fat. However, as I have discussed in my book, “Slaying The Food Myths”, we have no long term studies on the health effects of diets high in coconut oil. We don’t really know whether it is healthier than other saturated fats.
  • The taste and color of a beef burger come from its heme content. Heme does not occur in the parts of plants we eat. However, heme is involved in nitrogen fixation, so it is found in the roots of some legumes.
    • The Impossible Burger has genetically engineered yeast to produce a type of heme called leghemoglobin that is found in soy roots. The Beyond Burger uses beet juice extract and annatto for the color and unspecified “natural flavor” for the flavor.
  • To get the texture of a beef burger, both the Impossible Burger and the Beyond Burger use maltodextrin, modified food starch, and a variety of other ingredients. They are both highly processed foods.
  • Iron is another important nutrient you expect to get from a beef burger. The Impossible Burger contains 4.5 mg of iron and the Beyond Burger contains 5.4 mg of iron.
    • However, that is only part of the story. When iron is attached to a heme molecule, it is more efficiently absorbed by our bodies. Beef burgers and the Impossible Burger contain heme iron. The Beyond Burger does not.
  • In addition, the Impossible Burger adds in the vitamins, including B12, that we would expect to get from a beef burger. The Beyond Burger does not.

What Are The Pluses Of The Impossible Burger?

thumbs upThere are some definite pluses for the Impossible Burger and Beyond Burger:

  • Both the Impossible Burger and Beyond Burger are made from plant-based ingredients rather than from meat.
  • Both are cholesterol free.
  • Both contain modest amounts of fiber (3 grams for the Impossible Burger and 2 grams for the Beyond Burger), while a meat burger contains none.
  • Both are good sources of iron, and the iron in the Impossible Burger is heme-iron, which is efficiently absorbed by our bodies.

What Are The Minuses of the Impossible Burger?

thumbs downThere are, however, some definite minuses as well.

  • Both the Impossible Burger and Beyond Burger are high in saturated fat. The Impossible Burger is higher in saturated fat and the Beyond Burger contains the same amount of saturated fat as a real burger. That’s important because the latest advisory of the American Heart Association warns that saturated fat increases our risk of heart disease (I have discussed this finding in detail in a previous issue of “Health Tips From the Professor”).
    • The saturated fat in both burgers comes from coconut oil. However, as I discussed above, we don’t know whether coconut oil is better or worse for us than other saturated fats. The relevant studies have not been done.
  • Both the Impossible and Beyond burgers are high in sodium. They have almost 5-times more sodium than a beef burger.
  • The heme in red meat catalyzes the formation of N-nitroso compounds in our gut which increase the risk of colon cancer. We do not know whether the form of heme added to Impossible Burgers catalyzes the same reaction, but it is likely.
  • Both plant-based burgers are low in protein compared to a beef burger (~20 grams versus 27 grams). On the other hand, 20 grams of protein is reasonable for a single meal.
  • The plant proteins used for these burgers (soy for the Impossible Burger and pea for the Beyond Burger) are highly processed. They lack the phytonutrients found in the unprocessed proteins.
    • The isoflavones found in soy are thought to decrease the risk of cancer and osteoporosis.
    • The phytonutrients found in peas have antioxidant and anti-inflammatory benefits. They are also thought to decrease the risk of certain cancers.
  • The Impossible Burger is GMO. The leghemoglobin is produced by genetically engineered yeast, and the soy is also GMO.
  • Neither the Impossible Burger nor Beyond Burger are certified organic. Organic certification refers to how the plant was grown. Both burgers are highly processed. Many of the ingredients in both burgers came from factories, not farms.

Is The Impossible Burger Healthy For You?

Eating Impossible BurgerNow, it is time to return to the original question: “Is the Impossible Burger healthy for you?” Since it is plant-based, it would be easy to assume that it is healthier than a burger made from beef. However, when you look more closely, it is not clear that it is healthier.

The manufacturers of the Impossible Burger and similar burgers have gone to the laboratory and have been successful at creating meatless burgers with the taste, mouth feel, and texture of real burgers. However, these improvements have come with a price.

  • The Impossible Burger and similar burgers are higher in saturated fat than a beef burger. This means they may be just as likely to increase the risk of heart disease as a beef burger.
  • The Impossible Burger contains as much heme as a beef burger, which means it may be just as likely to increase the risk of cancer as a beef burger.
  • The Impossible Burger and similar burgers are highly processed. That means:
    • The plant proteins no longer contain the phytonutrients thought to be responsible for some of their health benefits.
    • They also don’t contain the vitamins you would expect to find associated with the plant proteins.
  • The Impossible Burger and similar burgers are not organic. Even worse, the Impossible Burger is GMO.

On balance, we can’t really assume the Impossible Burger is any healthier than the beef burgers it replaces. Plus, if you include the usual condiments and add fries and a soft drink, any slight health benefits of the Impossible Burger will be lost.

It would be much healthier to choose a bean burger. They don’t taste like beef, but many of them are quite tasty. Plus, if you do some label reading, you can find ones that use only whole, unprocessed ingredients.

For example, I looked up the Organic Sunshine brand South West Black Bean burgers. It only provides half as much protein as an Impossible Burger, but all the ingredients are organic, non-GMO, and minimally processed. Note: I am not recommending a particular brand. However, with a little research I am confident you can find a healthy meatless burger with a taste you will enjoy.

Is The Impossible Burger Healthy For the Planet?

impossible burger good for planetNow, let’s look at the second question: “Is the Impossible Burger healthy for the planet?” The answer to this question seems obvious. As the Impossible Burger company states in their mission statement: “Animal agriculture occupies almost half the land on earth, consumes a quarter of our freshwater, and destroys our ecosystems”. It seems logical that any meatless burger would be an improvement.

If we are talking about a minimally processed black bean burger, like the one I described above, the answer is a clear yes. It is healthier for the planet. However, when you look more closely at the Impossible Burger, the answer isn’t as clear.

  • As coconut oil has increased in popularity massive areas of untouched, forested land have been cleared for coconut plantations.
    • These forested areas provide an essential ecosystem for animals and provide natural storm protection by absorbing rainwater. Therefore, coconut oil, like beef, also destroys our ecosystems.
    • In addition, many of the coconut plantations use large amounts of chemical fertilizers which contribute to phosphate pollution and algae overgrowth in lakes, rivers, and coastal ocean areas. This also degrades our environment.
  • The Impossible Burgers and similar meatless burgers contain many highly processed ingredients. Each of these ingredients imposes its own environmental burden. For example:
    • Coconut oil is often processed with hexane, which is categorized as a hazardous air pollutant by the Environmental Protection Agency.
    • In addition, coconut oil is primarily grown in the Philippines, Indonesia, and India. Transporting it to this country generates significant greenhouse gas emissions.
    • And, of course, coconut oil represents only one of the many highly processed ingredients in the Impossible Burger and similar meatless burgers.

In short, the Impossible Burger may be slightly healthier for the planet than a beef burger, but it is much less environmentally friendly than your typical, minimally processed, bean burger.

The Bottom Line

Two weeks ago, I wrote about recent headlines claiming that the best advice for the American public was to eat as much red meat as they like. I looked at the study behind the headlines and pointed out the many flaws in that study.

Last week I wrote about headlines claiming that red meat was just as heart healthy as white meat. I looked at the study behind the headlines and showed it was an excellent example of how the beef industry influences the design of clinical trials to minimize the health risks of red meat. It is also an example of how the media misleads and confuses the public about the effect of nutrition on their health.

What the studies I reviewed the last two weeks really showed was that very small amounts (2-3 ounces) of very lean red meat is probably OK as part of a healthy diet like the Mediterranean diet. Larger servings of fattier cuts of red meat as part of the typical American diet is problematic.

However, if you love your burgers, what are you to do? Are the meatless burgers like the Impossible Burger and Beyond Burger that are showing up in your favorite fast food restaurants the answer? Specifically, you are probably asking:

  • Is the Impossible Burger, and similar burgers, healthy for you?
  • Is the Impossible Burger, and similar burgers, healthy for the planet?

I looked at the composition, pluses, and minuses of this new generation of meatless burgers in this article. The bottom line is:

  • On balance, the Impossible Burger is only slightly healthier than the beef burgers it replaces. And, if you include the usual condiments and add fries and a soft drink, any slight health benefits of the Impossible Burger will be lost.

It would be much healthier to choose a bean burger. They don’t taste like beef, but many of them are quite tasty. Plus, if you do some label reading, you can find ones that are organic, non-GMO, and use only whole, unprocessed ingredients.

  • Similarly, the Impossible Burger may be slightly healthier for the planet than a beef burger, but it is much less environmentally friendly than your typical, minimally processed, bean burger.

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.

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

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