A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.
Thursday, 14 January 2010
New Saturated Fat Review Article by Dr. Ronald Krauss
Dr. Ronald Krauss's group has published a review article titled "Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease". As anyone who's familiar with the literature could have predicted (including myself), they found no association whatsoever between saturated fat intake and heart disease or stroke:
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Sunday, 10 January 2010
Paleo is Going Mainstream
There was an article on the modern "Paleolithic" lifestyle in the New York Times today. I thought it was a pretty fair treatment of the subject, although it did paint it as more macho and carnivorous than it needs to be. It features three attractive NY cave people. It appeared in the styles section here. Paleo is going mainstream. I expect media health authorities to start getting defensive about it any minute now.
[2013 update. Did I call it or what??]
[2013 update. Did I call it or what??]
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Saturday, 9 January 2010
Okinawa: The island of pork
The original inhabitants of the Ryūkyū Islands, of which the island of Okinawa
One of the staples of their diet is sweet potatoes. The carbohydrate percentage of a sweet potato is about 20; that is, each 100 g of sweet potato mass has about 20 g of carbohydrates. Sweet potatoes have a medium-high glycemic index, and are often avoided by those with impaired insulin sensitivity, and certainly by diabetics.
The other main staple of their diet is pork, as you may have inferred from the title of this post. The quote below is from the first of the three links provided below the quote.
One of the staples of their diet is sweet potatoes. The carbohydrate percentage of a sweet potato is about 20; that is, each 100 g of sweet potato mass has about 20 g of carbohydrates. Sweet potatoes have a medium-high glycemic index, and are often avoided by those with impaired insulin sensitivity, and certainly by diabetics.
The other main staple of their diet is pork, as you may have inferred from the title of this post. The quote below is from the first of the three links provided below the quote.
Pork appears so frequently in the Okinawan diet that to say "meat" is really to say "pork." [...] It is no exaggeration to say that the present-day Okinawan diet begins and ends with pork.
So, what is the secret of the Okinawans’ longevity? Maybe it is the diet. Maybe it is the lifestyle. Maybe it is the fact that their mothers and fathers are Okinawans (the heritability of longevity has been estimated to be about 33%, and to be higher among females than males). Here are some interesting points that are worth noting:
- Their diet is not only of meat, but includes plenty of it.
- Their diet is not particularly low in saturated fat, and maybe it is high in it.
- Their diet is not particularly low in dietary cholesterol, and maybe high in it, since they eat the pig whole, including the parts (e.g., organs) rich in dietary cholesterol.
- Their diet is not a no carb diet, not even a typical low carb diet, but it seems to be very low in refined carbs and sugars.
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Friday, 8 January 2010
Muscle loss during short-term fasting
This is an issue that often comes up in online health discussions, and was the topic of a conversation I had the other day with a friend about some of the benefits of intermittent fasting.
Can the benefits of intermittent fasting be achieved without muscle loss? The answer is “yes”, to the best of my knowledge.
Even if you are not interested in bulking up or becoming a bodybuilder, you probably want to keep the muscle tissue you have. As a norm, muscle takes a long time, and effort, to build. It is generally easier to lose muscle than it is to gain it. Fat, on the other hand, can be gained very easily.
Body fat percentage is positively correlated with measures of inflammation markers and the occurrence of various health problems. Since muscle tissue makes up lean body mass, which excludes fat, it is by definition negatively correlated with inflammation markers and health problems.
As muscle mass increases, so does health; as long as the increase in muscle mass is “natural” – i.e., not caused by things like steroids, for instance.
In short-term fasts (e.g., up to 24 h) one can indeed lose some muscle as the body produces glucose using muscle tissue through a process known as gluconeogenesis. In this sense, muscle is the body’s main reserve of glucose. Adipocytes are the body’s main reserves of fat.
Muscle loss is not pronounced in short-term fasts though. It occurs after the body’s glycogen reserves, particularly those in the liver, are significantly depleted. This often happens 8 to 12 hours into the fast, depending on how depleted the glycogen reserves are when one starts fasting.
When the body is running short on glycogen, it becomes increasingly reliant on fat as a source of energy, sparing muscle tissue. That is, it burns fat, often in the form of ketone bodies, which are byproducts of fat metabolism. This state is known as ketosis. There is evidence that ketosis is a more efficient state from a metabolic perspective (Taubes, 2007, provides a good summary), which may be why many people feel an increase in energy when they fast.
The brain also runs on fat (through ketone byproducts) while in ketosis, although it still needs some glucose to function properly. That is primarily where muscle tissue comes into the picture, to provide the glucose that the brain needs to function. While glucose can also be made from fat, more specifically a lipid component called glycerol, this usually happens only during very prolonged fasting and starvation.
You do not have to consume carbohydrates at all to make up for the glycogen depletion, after you break the fast. Dietary protein will do the job, as it is used in gluconeogenesis as well.
Dietary protein also leads to an insulin response, which is comparable to that elicited by glucose. The difference is that protein also leads to other hormonal responses that have a counterbalancing effect to insulin, by allowing for the body's use of fat as a source of energy. Insulin, by itself, promotes fat deposition and prevents fat release at the same time.
When practicing intermittent fasting, one can increase protein synthesis by doing resistance exercise (weight training, HIT), which tips the scale toward muscle growth, and away from muscle catabolism.
This may actually lead to significant muscle gain in the long term. Fasting itself promotes the secretion of hormones (e.g., growth hormone) that have anabolic effects.
The following sites focus on muscle gain through intermittent fasting; the bloggers are living proof that it works.
Can the benefits of intermittent fasting be achieved without muscle loss? The answer is “yes”, to the best of my knowledge.
Even if you are not interested in bulking up or becoming a bodybuilder, you probably want to keep the muscle tissue you have. As a norm, muscle takes a long time, and effort, to build. It is generally easier to lose muscle than it is to gain it. Fat, on the other hand, can be gained very easily.
Body fat percentage is positively correlated with measures of inflammation markers and the occurrence of various health problems. Since muscle tissue makes up lean body mass, which excludes fat, it is by definition negatively correlated with inflammation markers and health problems.
As muscle mass increases, so does health; as long as the increase in muscle mass is “natural” – i.e., not caused by things like steroids, for instance.
In short-term fasts (e.g., up to 24 h) one can indeed lose some muscle as the body produces glucose using muscle tissue through a process known as gluconeogenesis. In this sense, muscle is the body’s main reserve of glucose. Adipocytes are the body’s main reserves of fat.
Muscle loss is not pronounced in short-term fasts though. It occurs after the body’s glycogen reserves, particularly those in the liver, are significantly depleted. This often happens 8 to 12 hours into the fast, depending on how depleted the glycogen reserves are when one starts fasting.
When the body is running short on glycogen, it becomes increasingly reliant on fat as a source of energy, sparing muscle tissue. That is, it burns fat, often in the form of ketone bodies, which are byproducts of fat metabolism. This state is known as ketosis. There is evidence that ketosis is a more efficient state from a metabolic perspective (Taubes, 2007, provides a good summary), which may be why many people feel an increase in energy when they fast.
The brain also runs on fat (through ketone byproducts) while in ketosis, although it still needs some glucose to function properly. That is primarily where muscle tissue comes into the picture, to provide the glucose that the brain needs to function. While glucose can also be made from fat, more specifically a lipid component called glycerol, this usually happens only during very prolonged fasting and starvation.
You do not have to consume carbohydrates at all to make up for the glycogen depletion, after you break the fast. Dietary protein will do the job, as it is used in gluconeogenesis as well.
Dietary protein also leads to an insulin response, which is comparable to that elicited by glucose. The difference is that protein also leads to other hormonal responses that have a counterbalancing effect to insulin, by allowing for the body's use of fat as a source of energy. Insulin, by itself, promotes fat deposition and prevents fat release at the same time.
When practicing intermittent fasting, one can increase protein synthesis by doing resistance exercise (weight training, HIT), which tips the scale toward muscle growth, and away from muscle catabolism.
This may actually lead to significant muscle gain in the long term. Fasting itself promotes the secretion of hormones (e.g., growth hormone) that have anabolic effects.
The following sites focus on muscle gain through intermittent fasting; the bloggers are living proof that it works.
http://leangains.com/
Muscle catabolism happens all the time, even in the absence of fasting. As with many tissues in the body (e.g., bones), muscle is continuously synthesized and degraded. Muscle tissue grows when that balance is tipped toward synthesis, and is lost otherwise.
Muscle will atrophy (i.e., be degraded) if not used, even if you are not fasting. In fact, you can eat a lot of protein and carbohydrates and still lose muscle. Just note what happens when an arm or a leg is immobilized in a cast for a long period of time.
Short-term fasting is healthy, probably because it happened frequently enough among our hominid ancestors to lead to selective pressures for metabolic and physiological solutions. Consequently, our body is designed to function well while fasting, and triggering those mechanisms correctly may promote overall health.
The relationship between fasting and health likely follows a nonlinear pattern, possibly an inverted U-curve pattern. It brings about benefits up until a point, after which some negative effects ensue.
Long-term fasting may cause severe heart problems, and eventually death, as the heart muscle is used by the body to produce glucose. Here the brain has precedence over the heart, so to speak.
Voluntary, and in some cases forced, short-term fasting was likely very common among our Stone Age ancestors; and consumption of large amounts of high glycemic index carbohydrates very uncommon (Boaz & Almquist, 2001).
References:
Boaz, N.T., & Almquist, A.J. (2001). Biological anthropology: A synthetic approach to human evolution.
Taubes, G. (2007). Good calories, bad calories: Challenging the conventional wisdom on diet, weight control, and disease.
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Saturday, 2 January 2010
Eating fish whole: Smelts
Since different parts of a fish have different types of nutrients that are important for our health, it makes sense to consume the fish whole. This is easier to do with small than big fish.
One of my favorite types of small fish is the smelt; the photo below shows a batch of smelts that I prepared using the recipe below. Another small fish favorite is the sardine. Small fish are usually low in the food chain, and thus have very low concentrations of metals that can be toxic to humans.
Many people dislike the taste of smelts, but will eat them if they are well seasoned and their texture is somewhat hard. Here is a recipe that will get you that.
- Steam cook the smelts for 30 minutes to 1 hour (less time = harder texture).
- Spread the steam cooked smelts on a sheet pan covered with aluminum foil; use light olive oil to prevent the fish from sticking to the foil.
- Preheat oven to 350 degrees Fahrenheit.
- Season the steam cooked smelts to taste; I suggest using salt, chili powder, garlic powder, and herbs.
- Bake the smelts for 30 minutes, turn the oven off, and leave them there for 1 hour.
There is no need to clean, or gut, the smelts for the recipe above. Since they feed primarily on plant matter, and have a very small digestive tract, there is not much to be “cleaned” off of them anyway.
They will be ready to store or eat cold. There are several variations of this recipe. For example, you can bake them for 40 minutes, and then serve them hot.
One of my favorite types of small fish is the smelt; the photo below shows a batch of smelts that I prepared using the recipe below. Another small fish favorite is the sardine. Small fish are usually low in the food chain, and thus have very low concentrations of metals that can be toxic to humans.
Many people dislike the taste of smelts, but will eat them if they are well seasoned and their texture is somewhat hard. Here is a recipe that will get you that.
- Steam cook the smelts for 30 minutes to 1 hour (less time = harder texture).
- Spread the steam cooked smelts on a sheet pan covered with aluminum foil; use light olive oil to prevent the fish from sticking to the foil.
- Preheat oven to 350 degrees Fahrenheit.
- Season the steam cooked smelts to taste; I suggest using salt, chili powder, garlic powder, and herbs.
- Bake the smelts for 30 minutes, turn the oven off, and leave them there for 1 hour.
There is no need to clean, or gut, the smelts for the recipe above. Since they feed primarily on plant matter, and have a very small digestive tract, there is not much to be “cleaned” off of them anyway.
They will be ready to store or eat cold. There are several variations of this recipe. For example, you can bake them for 40 minutes, and then serve them hot.
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Friday, 1 January 2010
Saturated fat intake not associated with heart disease – Dr. Cordain’s article
I would like to comment on a recent article co-authored by Dr. Loren Cordain, and published in the journal Current Treatment Options in Cardiovascular Medicine, in 2009. Dr. Cordain is probably the leading expert today on the diet of our Stone Age ancestors.
The importance of this article comes from the fact that in the past Dr. Cordain has argued that our Stone Age ancestors have not consumed large amounts of saturated fat, because of the relatively low percentage of fat in the flesh of wild animals. This led, according to Dr. Cordain, to an evolved body design that is not well adapted to the consumption of significant amounts of saturated fat.
Yet, many other researchers have argued that saturated fats are beneficial to our health, with ample empirical evidence to back up their statements. The researchers at the Weston A. Price Foundation have been particularly prominent voices in favor of saturate fats.
Now, this acknowledgement that saturated fats (or saturated fatty acids) are not detrimental to health, particularly heart health, was made with qualifications. And, Dr. Cordain is not the first author of the article. Page 293 of the article states that:
Palmitate refers to palmitic acid, of which meat, butter, eggs, and dark chocolate are all good sources. Even salmon is a good source of palmitic acid, although it is also an excellent source of DHA and EPA omega-3 fat acids. EPA is eicosapentaenoic acid, and DHA is docosahexaenoic acid; both of which are found in fish.
So, the caution in the statement above does not make much sense given the mounting evidence that palmitic acid (especially when consumed with a low carb. diet, in my view), may have cardio-protective effects.
Nevertheless, this is a major shift from Dr. Cordain’s previous position that saturated fats cannot be part of a healthy diet because they do not fit well with what we currently know about the diet of our Stone Age ancestors.
Maybe those ancestors ate a lot of saturated fat after all, and that consumption led to adaptations that make saturated fat consumption healthy; again, in my view, as long as it is not accompanied by high consumption of refined carbs. and sugars.
Saturated fat was probably the most readily available type of fat to those ancestors, a rich source of calories, and virtually impossible to avoid given the main component of those ancestors’ diet – meat.
The importance of this article comes from the fact that in the past Dr. Cordain has argued that our Stone Age ancestors have not consumed large amounts of saturated fat, because of the relatively low percentage of fat in the flesh of wild animals. This led, according to Dr. Cordain, to an evolved body design that is not well adapted to the consumption of significant amounts of saturated fat.
Yet, many other researchers have argued that saturated fats are beneficial to our health, with ample empirical evidence to back up their statements. The researchers at the Weston A. Price Foundation have been particularly prominent voices in favor of saturate fats.
Now, this acknowledgement that saturated fats (or saturated fatty acids) are not detrimental to health, particularly heart health, was made with qualifications. And, Dr. Cordain is not the first author of the article. Page 293 of the article states that:
Replacement of SFAs, especially palmitate, with MUFAs may provide moderate cardiometabolic benefits, and is unlikely to do harm. However, SFA reduction does not appear to be the most important dietary modification for CHD risk reduction.(Notes: SFA=saturated fatty acids=saturated fat, think greasy steak and egg yolk; MUFAs=monounsaturated fatty acids, think olive oil and lard; CHD=coronary heart disease.)
Palmitate refers to palmitic acid, of which meat, butter, eggs, and dark chocolate are all good sources. Even salmon is a good source of palmitic acid, although it is also an excellent source of DHA and EPA omega-3 fat acids. EPA is eicosapentaenoic acid, and DHA is docosahexaenoic acid; both of which are found in fish.
So, the caution in the statement above does not make much sense given the mounting evidence that palmitic acid (especially when consumed with a low carb. diet, in my view), may have cardio-protective effects.
Nevertheless, this is a major shift from Dr. Cordain’s previous position that saturated fats cannot be part of a healthy diet because they do not fit well with what we currently know about the diet of our Stone Age ancestors.
Maybe those ancestors ate a lot of saturated fat after all, and that consumption led to adaptations that make saturated fat consumption healthy; again, in my view, as long as it is not accompanied by high consumption of refined carbs. and sugars.
Saturated fat was probably the most readily available type of fat to those ancestors, a rich source of calories, and virtually impossible to avoid given the main component of those ancestors’ diet – meat.
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Intermittent fasting and reduced inflammation
A recent post on the Primal Wisdom blog led me to do go back to some of the research on an approach to dieting that I tried myself, with some positive results. The approach is known as intermittent fasting (IF). I also found an excellent blog post by Dr. Michael Eades on IF (see here).
Typically IF involves fasting every other day. On the non-fasting days, food and water consumption is not restricted in any way. On fasting days, only water is consumed. Variations of this approach usually involve replacing water with juice, and having an eating window of only a few hours within longer periods – e.g., fasting 19 hours and then eating during a window of 5 hours, for each period of 24 hours.
IF is different from calorie restriction (CR), in that in the latter total daily calorie intake is restricted to a somewhat fixed amount, below one’s basal metabolic rate (the number of calories needed to maintain one’s current weight). In CR the calorie restriction is not normally achieved through fasting, but through careful portion size control and selection of foods based on calorie content. Having said that, some prominent CR practitioners also practice IF.
One interesting aspect of IF studies is that often they do not involve any calorie reduction in the participants' diet; that is, individuals consume the same amount of calories that they would if they were not fasting at all. In other words, they consume 2X outside their fasting window; where X would be their normal caloric consumption without fasting.
Yet, the benefits of IF are still achieved. For example, during Ramadan, the levels of inflammation markers and factors, such as C-reactive protein (CRP) and homocysteine, go down, and remain low for several weeks after IF is interrupted. These inflammation markers and factors are known to be strongly associated with heart disease.
In fact, animal studies suggest that virtually identical benefits can be obtained through IF in terms of increased lifespan and disease resistance, as those normally associated with CR. Again, this is somewhat surprising because often IF does not involve any reduction in calories consumed.
Fasting promotes increased levels of growth hormone in humans. A decline in growth hormone levels is associated with aging. Thus, increased circulating growth hormones may be one of the mechanisms by which IF may affect lifespan.
There have been some reports of IF being associated with negative effects on health, but I suspect that they are associated with gorging on refined carbohydrates and sugars during the eating window. Refined carbohydrates and sugars promote inflammation, and IF reduces inflammation. It is conceivable that a very high consumption of refined carbohydrates and sugars during the eating window may completely negate the benefits of IF, particularly if one is doing a half-hearted version of IF to start with.
A combination of IF and a diet low in refined carbohydrates and sugars probably makes sense in terms of our evolved physiology. Our Stone Age ancestors had to fast on a regular basis, based on the availability of food – there were no refrigerators or grocery stores during the vast majority of our evolutionary history as a species. When food was available, it was consumed to satiety. In other words, our Stone Age ancestors practiced IF, against their will. Because of that, this is the state in which our body evolved to operate optimally.
If you watch enough episodes of the TV show Survivorman, you will probably notice that it is very unlikely that our Stone Age ancestors had access to enough calories to survive on plant foods only, assuming that they faced problems similar to those in the show.
Our digestive tract has evolved over millions of years from a mostly vegetarian diet, practiced by our Australopithecine ancestors, to a primarily carnivorous diet, adopted by human ancestors as far back as Homo erectus, and probably Homo habilis. Given that, only the recent invention of refined carbohydrates and sugars has given us access to enough dense carbohydrate sources of calories.
So, a combination of IF and a diet low in (or devoid of) refined carbohydrates and sugars makes evolutionary sense, and is probably why so many people who adopt Paleolithic diets see so many improvements in health markers such as inflammation markers, blood pressure, and HDL cholesterol.
Typically IF involves fasting every other day. On the non-fasting days, food and water consumption is not restricted in any way. On fasting days, only water is consumed. Variations of this approach usually involve replacing water with juice, and having an eating window of only a few hours within longer periods – e.g., fasting 19 hours and then eating during a window of 5 hours, for each period of 24 hours.
IF is different from calorie restriction (CR), in that in the latter total daily calorie intake is restricted to a somewhat fixed amount, below one’s basal metabolic rate (the number of calories needed to maintain one’s current weight). In CR the calorie restriction is not normally achieved through fasting, but through careful portion size control and selection of foods based on calorie content. Having said that, some prominent CR practitioners also practice IF.
One interesting aspect of IF studies is that often they do not involve any calorie reduction in the participants' diet; that is, individuals consume the same amount of calories that they would if they were not fasting at all. In other words, they consume 2X outside their fasting window; where X would be their normal caloric consumption without fasting.
Yet, the benefits of IF are still achieved. For example, during Ramadan, the levels of inflammation markers and factors, such as C-reactive protein (CRP) and homocysteine, go down, and remain low for several weeks after IF is interrupted. These inflammation markers and factors are known to be strongly associated with heart disease.
In fact, animal studies suggest that virtually identical benefits can be obtained through IF in terms of increased lifespan and disease resistance, as those normally associated with CR. Again, this is somewhat surprising because often IF does not involve any reduction in calories consumed.
Fasting promotes increased levels of growth hormone in humans. A decline in growth hormone levels is associated with aging. Thus, increased circulating growth hormones may be one of the mechanisms by which IF may affect lifespan.
There have been some reports of IF being associated with negative effects on health, but I suspect that they are associated with gorging on refined carbohydrates and sugars during the eating window. Refined carbohydrates and sugars promote inflammation, and IF reduces inflammation. It is conceivable that a very high consumption of refined carbohydrates and sugars during the eating window may completely negate the benefits of IF, particularly if one is doing a half-hearted version of IF to start with.
A combination of IF and a diet low in refined carbohydrates and sugars probably makes sense in terms of our evolved physiology. Our Stone Age ancestors had to fast on a regular basis, based on the availability of food – there were no refrigerators or grocery stores during the vast majority of our evolutionary history as a species. When food was available, it was consumed to satiety. In other words, our Stone Age ancestors practiced IF, against their will. Because of that, this is the state in which our body evolved to operate optimally.
If you watch enough episodes of the TV show Survivorman, you will probably notice that it is very unlikely that our Stone Age ancestors had access to enough calories to survive on plant foods only, assuming that they faced problems similar to those in the show.
Our digestive tract has evolved over millions of years from a mostly vegetarian diet, practiced by our Australopithecine ancestors, to a primarily carnivorous diet, adopted by human ancestors as far back as Homo erectus, and probably Homo habilis. Given that, only the recent invention of refined carbohydrates and sugars has given us access to enough dense carbohydrate sources of calories.
So, a combination of IF and a diet low in (or devoid of) refined carbohydrates and sugars makes evolutionary sense, and is probably why so many people who adopt Paleolithic diets see so many improvements in health markers such as inflammation markers, blood pressure, and HDL cholesterol.
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