Denise Minger has just put up another great China Study post that's worth reading if you haven't already. Denise has been busy applying her statistics skills to the mountain of data the study collected. She noted in a previous post that wheat intake was strongly associated with coronary heart disease (CHD), the quintessential modern cardiovascular disease. I, and several other people, requested that she work her mathmagic to see if the association could be due to some other factor. For example, wheat is eaten mostly in the Northern regions of China, and CHD rates are generally higher at higher latitudes (vitamin D insufficiency?). This is true in Europe as well, and may be partly responsible for the purported benefits of the Mediterranean diet. You can mathematically determine if the association between wheat and CHD is simply due to the fact that wheat eaters live further North.
To make a long story short, nothing could explain the association except wheat itself, even latitude. Furthermore, she found a strong association between wheat intake and body mass index, typically a predictor of fat mass although we can't say that for sure. That finding echos a previous study in China where wheat eaters were more likely to be overweight than rice eaters (1, 2). Head over to Denise's post for the full story.
The China Study has major limitations built into its basic design, due to the fact that it was observational and pooled the blood samples of many individuals. Therefore, its findings can never prove anything, they can only suggest or be consistent with hypotheses. However, the study also has some unique advantages, such as a diversity of diets and regions, and the fact that people had presumably been eating a similar diet for a long time. I feel that Denise's efforts are really teasing out some useful information from the study that have been de-emphasized by other investigators.
There has been so little serious investigation into the health effects of wheat in the general population that I have to rely mostly on indirect evidence, such as the observation that the diseases of civilization tend to closely follow the introduction of white flour around the globe. Researchers studying celiac disease and other forms of gluten allergy, and the efforts of the paleolithic diet community in spreading that information (for example, Loren Cordain and Pedro Bastos), have been major contributors to understanding the health effects of wheat. Denise's analysis is one of the strongest pieces of evidence I've come by so far. One of these days, I'll post all of my references incriminating wheat. There are quite a few, although none of them is the smoking gun. I think there's enough indirect evidence that investigators should begin taking the idea seriously that wheat, particularly in the form of industrial flour products, may contribute to chronic disease in more than just a small subset of the population.
Showing posts with label gluten. Show all posts
Showing posts with label gluten. Show all posts
Thursday, September 2, 2010
Tuesday, July 20, 2010
Real Food XI: Sourdough Buckwheat Crepes
Buckwheat was domesticated in Southeast Asia roughly 6,000 years ago. Due to its unusual tolerance of cool growing conditions, poor soils and high altitudes, it spread throughout the Northern latitudes of Eurasia, becoming the staple crop in many regions. It's used to a lesser extent in countries closer to the equator. It was also a staple in the Northeastern US until it was supplanted by wheat and corn.Buckwheat isn't a grain: it's a 'pseudograin' that comes from a broad-leaved plant. As such, it's not related to wheat and contains no allergenic gluten. Like quinoa, it has some unusual properties that make it a particularly nutritious food. It's about 16 percent protein by calories, ranking it among the highest protein grains. However, it has an advantage over grains: it contains complete protein, meaning it has a balance of essential amino acids similar to animal foods. Buckwheat is also an exceptional source of magnesium and copper, two important nutrients that may influence the risk of insulin resistance and cardiovascular disease (1, 2).
However, like all seeds (including grains and nuts), buckwheat is rich in phytic acid. Phyic acid complexes with certain minerals, preventing their absorption by the human digestive tract. This is one of the reasons why traditional cultures prepare their grains carefully (3). During soaking, and particularly fermentation of raw batters, an enzyme called phytase goes to work breaking down the phytic acid. Not all seeds are endowed with enough phytase to break down phytic acid in a short period of time. Buckwheat contains a lot of phytase, and consequently fermented buckwheat batters contain very little phytic acid (4, 5). It's also high in astringent tannins, but thorough soaking in a large volume of water removes them.
Buckwheat is fermented in a number of traditional cultures. In Bhutan, it's fermented to make flatbreads and alcoholic drinks (6). In Brittany (Bretagne; Northwestern France), sourdough buckwheat flour pancakes are traditional. Originally a poverty food, it is now considered a delicacy.
The following simple recipe is based on my own experimentation with buckwheat. It isn't traditional as far as I know, however it is based on traditional methods used to produce sourdough flatbreads in a number of cultures. I used the word 'crepe' to describe it, but I typically make something more akin to a savory pancake or uttapam. You can use it to make crepes if you wish, but this recipe is not for traditional French buckwheat crepes.
It's important that the buckwheat be raw and whole for this recipe. Raw buckwheat is light green to light brown (as in the photo above). Kasha is toasted buckwheat, and will not substitute properly. It's also important that the water be dechlorinated and the salt non-iodized, as both will interfere with fermentation.
For a fermentation starter, you can use leftover batter from a previous batch (although it doesn't keep very long), or rice soaking water from this method (7).
Ingredients and Materials
- 2-3 cups raw buckwheat groats
- Dechlorinated water (filtered, boiled, or rested uncovered overnight)
- Non-iodized salt (sea salt, pickling salt or kosher salt), 2/3 tsp per cup of buckwheat
- Fermentation starter (optional), 2 tablespoons
- Food processor or blender
- Cover buckwheat with a large amount of dechlorinated water and soak for 9-24 hours. Raw buckwheat is astringent due to water-soluble tannins. Soaking in a large volume of water and giving it a stir from time to time will minimize this. The soaking water will also get slimy. This is normal.
- Pour off the soaking water and rinse the buckwheat thoroughly to get rid of the slime and residual tannins.
- Blend the buckwheat, salt, dechlorinated water and fermentation starter in a food processor or blender. Add enough water so that it reaches the consistency of pancake batter. The smoother you get the batter, the better the final product will be.
- Ferment for about 12 hours, a bit longer or shorter depending on the temperature and whether or not you used a starter. The batter may rise a little bit as the microorganisms get to work. The smell will mellow out. Refrigerate it after fermentation.
- In a greased or non-stick skillet, cook the batter at whatever thickness and temperature you prefer. I like to cook a thick 'pancake' with the lid on, at very low heat, so that it steams gently.
Thanks to Christaface for the CC licensed photo (Flickr).
Saturday, June 5, 2010
Fermented Grain Recipes from Around the World
In my last two posts on grains, I described how traditional food processing methods make grains more nutritious and digestible (1, 2). I promised to briefly describe a few recipes from around the world, then got distracted by other things. Here they are.
Africa: Ogi
Grain fermentation is widespread in Africa and is probably nearly as old as agriculture on the continent. The nutritional importance of fermentation is suggested by the amount of time and effort that many African cultures put into it, when they could save themselves a lot of trouble by simply soaking and cooking their grains.
Ogi is a common West African porridge that's eaten as a staple food by people of all ages. It's even used as a weaning food. It's made in essentially the same manner from corn, sorghum or millet.
Whole grain is soaked in water for one to three days. It's then wet milled, mixed with water and sieved to remove a portion of the bran. Extra bran is fed to animals, while the white, starchy sediment is fermented for two to three days. This is then cooked into a thin or thick porridge and eaten.
South America: Pozol
At first glance, some people may think I left the 'e' off the word 'pozole', a traditional Mexican stew. However, pozol is an entirely different beast, an ancient food almost totally unknown in the US, but which fueled the Mayan empire and remains a staple food in Southeastern Mexico.
To make pozol, first the corn must be 'nixtamalized': whole kernels are boiled in a large volume of water with calcium hydroxide (10% w/v). This is a processing step in most traditional South American corn recipes, as it allows a person to avoid pellagra (niacin deficiency)! The loosened bran is removed from the kernels by hand.
The kernels are then ground into dough, formed into balls and placed into banana leaves to ferment for one to 14 days. Following fermentation, pozol is diluted in water and consumed raw.
Europe: Sourdough Bread
Sourdough bread is Europe's quintessential fermented grain food. Before purified yeast strains came into widespread use in the 20th century, all bread would have been some form of sourdough.
Although in my opinion wheat is problematic for many people, sourdough fermentation renders it more nutritious and better tolerated by those with gluten/wheat sensitivity. In an interesting series of studies, Dr. Marco Gobbetti's group, among others, has shown that fermentation partially degrades gluten, explaining the ability of fermentation to decrease the adverse effects of gluten in those who are sensitive to it (3). They even showed that people with celiac disease can safely eat wheat bread that has been long-fermented with selected bacteria and yeasts under laboratory conditions (4). Rye contains about half the gluten of bread wheat, and is generally nutritionally superior to wheat, so sourdough rye is a better choice in my opinion.
To make sourdough bread, first the dry grains are ground into flour. Next, the flour is sifted through a screen to remove a portion of the bran. The earliest bread eaters probably didn't do this, although there is evidence of the wealthy eating sifted flour in societies as old as ancient Egypt and ancient Rome. I don't know what the optimum amount of bran to include in flour is, but it's not zero. I would be inclined to keep at least half of it, recognizing that the bran is disproportionately rich in nutrients.
Next, a portion of flour is mixed with water and a "sourdough starter", until it has a runny consistency. The starter is a diverse culture of bacteria and yeast that is carefully maintained by the bread maker. This culture acidifies the batter and produces carbon dioxide gas. The mixture is allowed to ferment for 8-12 hours. Finally, flour and salt are added to the batter and formed into dough balls. These are allowed to ferment and rise for a few hours, then baked.
My Experience
I've tried making ogi (millet) and pozol, and I have to admit that neither attempt was successful. Pozol in particular may depend on local populations of bacteria and yeast, as the grains' microorganisms are killed during processing. However, I do eat fermented grains regularly in the form of homemade brown rice 'uthappam' and sourdough buckwheat 'crepes'. The buckwheat crepes are tasty and easy to make. I'll post a recipe at some point.
The first two recipes are from the FAO publication Fermented Cereals: a Global Perspective (5).
Africa: Ogi
Grain fermentation is widespread in Africa and is probably nearly as old as agriculture on the continent. The nutritional importance of fermentation is suggested by the amount of time and effort that many African cultures put into it, when they could save themselves a lot of trouble by simply soaking and cooking their grains.
Ogi is a common West African porridge that's eaten as a staple food by people of all ages. It's even used as a weaning food. It's made in essentially the same manner from corn, sorghum or millet.
Whole grain is soaked in water for one to three days. It's then wet milled, mixed with water and sieved to remove a portion of the bran. Extra bran is fed to animals, while the white, starchy sediment is fermented for two to three days. This is then cooked into a thin or thick porridge and eaten.
South America: Pozol
At first glance, some people may think I left the 'e' off the word 'pozole', a traditional Mexican stew. However, pozol is an entirely different beast, an ancient food almost totally unknown in the US, but which fueled the Mayan empire and remains a staple food in Southeastern Mexico.
To make pozol, first the corn must be 'nixtamalized': whole kernels are boiled in a large volume of water with calcium hydroxide (10% w/v). This is a processing step in most traditional South American corn recipes, as it allows a person to avoid pellagra (niacin deficiency)! The loosened bran is removed from the kernels by hand.
The kernels are then ground into dough, formed into balls and placed into banana leaves to ferment for one to 14 days. Following fermentation, pozol is diluted in water and consumed raw.
Europe: Sourdough Bread
Sourdough bread is Europe's quintessential fermented grain food. Before purified yeast strains came into widespread use in the 20th century, all bread would have been some form of sourdough.
Although in my opinion wheat is problematic for many people, sourdough fermentation renders it more nutritious and better tolerated by those with gluten/wheat sensitivity. In an interesting series of studies, Dr. Marco Gobbetti's group, among others, has shown that fermentation partially degrades gluten, explaining the ability of fermentation to decrease the adverse effects of gluten in those who are sensitive to it (3). They even showed that people with celiac disease can safely eat wheat bread that has been long-fermented with selected bacteria and yeasts under laboratory conditions (4). Rye contains about half the gluten of bread wheat, and is generally nutritionally superior to wheat, so sourdough rye is a better choice in my opinion.
To make sourdough bread, first the dry grains are ground into flour. Next, the flour is sifted through a screen to remove a portion of the bran. The earliest bread eaters probably didn't do this, although there is evidence of the wealthy eating sifted flour in societies as old as ancient Egypt and ancient Rome. I don't know what the optimum amount of bran to include in flour is, but it's not zero. I would be inclined to keep at least half of it, recognizing that the bran is disproportionately rich in nutrients.
Next, a portion of flour is mixed with water and a "sourdough starter", until it has a runny consistency. The starter is a diverse culture of bacteria and yeast that is carefully maintained by the bread maker. This culture acidifies the batter and produces carbon dioxide gas. The mixture is allowed to ferment for 8-12 hours. Finally, flour and salt are added to the batter and formed into dough balls. These are allowed to ferment and rise for a few hours, then baked.
My Experience
I've tried making ogi (millet) and pozol, and I have to admit that neither attempt was successful. Pozol in particular may depend on local populations of bacteria and yeast, as the grains' microorganisms are killed during processing. However, I do eat fermented grains regularly in the form of homemade brown rice 'uthappam' and sourdough buckwheat 'crepes'. The buckwheat crepes are tasty and easy to make. I'll post a recipe at some point.
The first two recipes are from the FAO publication Fermented Cereals: a Global Perspective (5).
Sunday, January 31, 2010
The Body Fat Setpoint, Part IV: Changing the Setpoint
Prevention is Easier than Cure
Experiments in animals have confirmed what common sense suggests: it's easier to prevent health problems than to reverse them. Still, many health conditions can be improved, and in some cases reversed, through lifestyle interventions. It's important to have realistic expectations and to be kind to oneself. Cultivating a drill sergeant mentality will not improve quality of life, and isn't likely to be sustainable.
Fat Loss: a New Approach
If there's one thing that's consistent in the medical literature, it's that telling people to eat fewer calories does not help them lose weight in the long term. Gary Taubes has written about this at length in his book Good Calories, Bad Calories, and in his upcoming book on body fat. Many people who use this strategy see transient fat loss, followed by fat regain and a feeling of defeat. There's a simple reason for it: the body doesn't want to lose weight. It's extremely difficult to fight the fat mass setpoint, and the body will use every tool it has to maintain its preferred level of fat: hunger, reduced body temperature, higher muscle efficiency (i.e., less energy is expended for the same movement), lethargy, lowered immune function, et cetera.
Therefore, what we need for sustainable fat loss is not starvation; we need a treatment that lowers the fat mass setpoint. There are several criteria that this treatment will have to meet to qualify:
Strategies: Diet Pattern
The most obvious treatment that fits all of my criteria is low-carbohydrate dieting. Overweight people eating low-carbohydrate diets generally lose fat and spontaneously reduce their calorie intake. In fact, in several diet studies, investigators compared an all-you-can-eat low-carbohydrate diet with a calorie-restricted low-fat diet. The low-carbohydrate dieters generally reduced their calorie intake and body fat to a similar or greater degree than the low-fat dieters, despite the fact that they ate all the calories they wanted (1). This suggest that their fat mass setpoint had changed. At this point, I think moderate carbohydrate restriction may be preferable to strict carbohydrate restriction for some people, due to the increasing number of reports I've read of people doing poorly in the long run on extremely low-carbohydrate diets (2).
Another strategy that appears effective is the "paleolithic" diet. In Dr. Staffan Lindeberg's 2007 diet study, overweight volunteers with heart disease lost fat and reduced their calorie intake to a remarkable degree while eating a diet consistent with our hunter-gatherer heritage (3). This result is consistent with another diet trial of the paleolithic diet in diabetics (4). In post hoc analysis, Dr. Lindeberg's group showed that the reduction in weight was apparently independent of changes in carbohydrate intake*. This suggests that the paleolithic diet has health benefits that are independent of carbohydrate intake.
Strategies: Gastrointestinal Health
Since the gastrointestinal (GI) tract is so intimately involved in body fat metabolism and overall health (see the former post), the next strategy is to improve GI health. There are a number of ways to do this, but they all center around four things:
Oligofructose is similar to inulin, a fiber that occurs naturally in a wide variety of plants. Good sources are jerusalem artichokes, jicama, artichokes, onions, leeks, burdock and chicory root. Certain non-industrial cultures had a high intake of inulin. There are some caveats to inulin, however: inulin and oligofructose can cause gas, and can also exacerbate gastroesophageal reflux disorder (9). So don't eat a big plate of jerusalem artichokes before that important date.
The colon is packed with symbiotic bacteria, and is the site of most intestinal fermentation. The small intestine contains fewer bacteria, but gut barrier function there is critical as well. The small intestine is where the GI doctor will take a biopsy to look for celiac disease. Celiac disease is a degeneration of the small intestinal lining due to an autoimmune reaction caused by gluten (in wheat, barley and rye). This brings us to one of the most important elements of maintaining gut barrier health: avoiding food sensitivities. Gluten and casein (in dairy protein) are the two most common offenders. Gluten sensitivity is widespread and typically undiagnosed (10).
Eating raw fermented foods such as sauerkraut, kimchi, yogurt and half-sour pickles also helps maintain the integrity of the upper GI tract. I doubt these have any effect on the colon, given the huge number of bacteria already present. Other important factors in gut barrier health are keeping the ratio of omega-6 to omega-3 fats in balance, eating nutrient-dense food, and avoiding the questionable chemical additives in processed food. If triglycerides are important for leptin sensitivity, then avoiding sugar and ensuring a regular source of omega-3 should aid weight loss as well.
Strategies: Micronutrients
As I discussed in the last post, micronutrient deficiency probably plays a role in obesity, both in ways that we understand and ways that we (or I) don't. Eating a diet that has a high nutrient density and ensuring a good vitamin D status will help any sustainable fat loss strategy. The easiest way to do this is to eliminate industrially processed foods such as white flour, sugar and seed oils. These constitute more than 50% of calories for the average Westerner.
After that, you can further increase your diet's nutrient density by learning to properly prepare grains and legumes to maximize their nutritional value and digestibility (11, 12; or by avoiding grains and legumes altogether if you wish), selecting organic and/or pasture-raised foods if possible, and eating seafood including seaweed. One of the problems with extremely low-carbohydrate diets is that they may be low in water-soluble micronutrients, although this isn't necessarily the case.
Strategies: Miscellaneous
In general, exercise isn't necessarily helpful for fat loss. However, there is one type of exercise that clearly is: high-intensity intermittent training (HIIT). It's basically a fancy name for sprints. They can be done on a track, on a stationary bicycle, using weight training circuits, or any other way that allows sufficient intensity. The key is to achieve maximal exertion for several brief periods, separated by rest. This type of exercise is not about burning calories through exertion: it's about increasing hormone sensitivity using an intense, brief stressor (hormesis). Even a ridiculously short period of time spent training HIIT each week can result in significant fat loss, despite no change in diet or calorie intake (13).
Anecdotally, many people have had success using intermittent fasting (IF) for fat loss. There's some evidence in the scientific literature that IF and related approaches may be helpful (14). There are different approaches to IF, but a common and effective method is to do two complete 24-hour fasts per week. It's important to note that IF isn't about restricting calories, it's about resetting the fat mass setpoint. After a fast, allow yourself to eat quality food until you're no longer hungry.
Insufficient sleep has been strongly and repeatedly linked to obesity. Whether it's a cause or consequence of obesity I can't say for sure, but in any case it's important for health to sleep until you feel rested. If your sleep quality is poor due to psychological stress, meditating before bedtime may help. I find that meditation has a remarkable effect on my sleep quality. Due to the poor development of oral and nasal structures in industrial nations, many people do not breathe effectively and may suffer from conditions such as sleep apnea that reduce sleep quality. Overweight also contributes to these problems.
I'm sure there are other useful strategies, but that's all I have for now. If you have something to add, please put it in the comments.
* Since reducing carbohydrate intake wasn't part of the intervention, this result is observational.
Experiments in animals have confirmed what common sense suggests: it's easier to prevent health problems than to reverse them. Still, many health conditions can be improved, and in some cases reversed, through lifestyle interventions. It's important to have realistic expectations and to be kind to oneself. Cultivating a drill sergeant mentality will not improve quality of life, and isn't likely to be sustainable.
Fat Loss: a New Approach
If there's one thing that's consistent in the medical literature, it's that telling people to eat fewer calories does not help them lose weight in the long term. Gary Taubes has written about this at length in his book Good Calories, Bad Calories, and in his upcoming book on body fat. Many people who use this strategy see transient fat loss, followed by fat regain and a feeling of defeat. There's a simple reason for it: the body doesn't want to lose weight. It's extremely difficult to fight the fat mass setpoint, and the body will use every tool it has to maintain its preferred level of fat: hunger, reduced body temperature, higher muscle efficiency (i.e., less energy is expended for the same movement), lethargy, lowered immune function, et cetera.
Therefore, what we need for sustainable fat loss is not starvation; we need a treatment that lowers the fat mass setpoint. There are several criteria that this treatment will have to meet to qualify:
- It must cause fat loss
- It must not involve deliberate calorie restriction
- It must maintain fat loss over a long period of time
- It must not be harmful to overall health
Strategies: Diet Pattern
The most obvious treatment that fits all of my criteria is low-carbohydrate dieting. Overweight people eating low-carbohydrate diets generally lose fat and spontaneously reduce their calorie intake. In fact, in several diet studies, investigators compared an all-you-can-eat low-carbohydrate diet with a calorie-restricted low-fat diet. The low-carbohydrate dieters generally reduced their calorie intake and body fat to a similar or greater degree than the low-fat dieters, despite the fact that they ate all the calories they wanted (1). This suggest that their fat mass setpoint had changed. At this point, I think moderate carbohydrate restriction may be preferable to strict carbohydrate restriction for some people, due to the increasing number of reports I've read of people doing poorly in the long run on extremely low-carbohydrate diets (2).
Another strategy that appears effective is the "paleolithic" diet. In Dr. Staffan Lindeberg's 2007 diet study, overweight volunteers with heart disease lost fat and reduced their calorie intake to a remarkable degree while eating a diet consistent with our hunter-gatherer heritage (3). This result is consistent with another diet trial of the paleolithic diet in diabetics (4). In post hoc analysis, Dr. Lindeberg's group showed that the reduction in weight was apparently independent of changes in carbohydrate intake*. This suggests that the paleolithic diet has health benefits that are independent of carbohydrate intake.
Strategies: Gastrointestinal Health
Since the gastrointestinal (GI) tract is so intimately involved in body fat metabolism and overall health (see the former post), the next strategy is to improve GI health. There are a number of ways to do this, but they all center around four things:
- Don't eat food that encourages the growth of harmful bacteria
- Eat food that encourages the growth of good bacteria
- Don't eat food that impairs gut barrier function
- Eat food that promotes gut barrier health
Oligofructose is similar to inulin, a fiber that occurs naturally in a wide variety of plants. Good sources are jerusalem artichokes, jicama, artichokes, onions, leeks, burdock and chicory root. Certain non-industrial cultures had a high intake of inulin. There are some caveats to inulin, however: inulin and oligofructose can cause gas, and can also exacerbate gastroesophageal reflux disorder (9). So don't eat a big plate of jerusalem artichokes before that important date.
The colon is packed with symbiotic bacteria, and is the site of most intestinal fermentation. The small intestine contains fewer bacteria, but gut barrier function there is critical as well. The small intestine is where the GI doctor will take a biopsy to look for celiac disease. Celiac disease is a degeneration of the small intestinal lining due to an autoimmune reaction caused by gluten (in wheat, barley and rye). This brings us to one of the most important elements of maintaining gut barrier health: avoiding food sensitivities. Gluten and casein (in dairy protein) are the two most common offenders. Gluten sensitivity is widespread and typically undiagnosed (10).
Eating raw fermented foods such as sauerkraut, kimchi, yogurt and half-sour pickles also helps maintain the integrity of the upper GI tract. I doubt these have any effect on the colon, given the huge number of bacteria already present. Other important factors in gut barrier health are keeping the ratio of omega-6 to omega-3 fats in balance, eating nutrient-dense food, and avoiding the questionable chemical additives in processed food. If triglycerides are important for leptin sensitivity, then avoiding sugar and ensuring a regular source of omega-3 should aid weight loss as well.
Strategies: Micronutrients
As I discussed in the last post, micronutrient deficiency probably plays a role in obesity, both in ways that we understand and ways that we (or I) don't. Eating a diet that has a high nutrient density and ensuring a good vitamin D status will help any sustainable fat loss strategy. The easiest way to do this is to eliminate industrially processed foods such as white flour, sugar and seed oils. These constitute more than 50% of calories for the average Westerner.
After that, you can further increase your diet's nutrient density by learning to properly prepare grains and legumes to maximize their nutritional value and digestibility (11, 12; or by avoiding grains and legumes altogether if you wish), selecting organic and/or pasture-raised foods if possible, and eating seafood including seaweed. One of the problems with extremely low-carbohydrate diets is that they may be low in water-soluble micronutrients, although this isn't necessarily the case.
Strategies: Miscellaneous
In general, exercise isn't necessarily helpful for fat loss. However, there is one type of exercise that clearly is: high-intensity intermittent training (HIIT). It's basically a fancy name for sprints. They can be done on a track, on a stationary bicycle, using weight training circuits, or any other way that allows sufficient intensity. The key is to achieve maximal exertion for several brief periods, separated by rest. This type of exercise is not about burning calories through exertion: it's about increasing hormone sensitivity using an intense, brief stressor (hormesis). Even a ridiculously short period of time spent training HIIT each week can result in significant fat loss, despite no change in diet or calorie intake (13).
Anecdotally, many people have had success using intermittent fasting (IF) for fat loss. There's some evidence in the scientific literature that IF and related approaches may be helpful (14). There are different approaches to IF, but a common and effective method is to do two complete 24-hour fasts per week. It's important to note that IF isn't about restricting calories, it's about resetting the fat mass setpoint. After a fast, allow yourself to eat quality food until you're no longer hungry.
Insufficient sleep has been strongly and repeatedly linked to obesity. Whether it's a cause or consequence of obesity I can't say for sure, but in any case it's important for health to sleep until you feel rested. If your sleep quality is poor due to psychological stress, meditating before bedtime may help. I find that meditation has a remarkable effect on my sleep quality. Due to the poor development of oral and nasal structures in industrial nations, many people do not breathe effectively and may suffer from conditions such as sleep apnea that reduce sleep quality. Overweight also contributes to these problems.
I'm sure there are other useful strategies, but that's all I have for now. If you have something to add, please put it in the comments.
* Since reducing carbohydrate intake wasn't part of the intervention, this result is observational.
Thursday, March 19, 2009
It's Time to Let Go of The Glycemic Index
The glycemic index (GI) is a measure of how much an individual food elevates blood sugar when it's eaten. To measure it, investigators feed a person a food that contains a fixed amount of carbohydrate, and measure their blood glucose response over time. Then they determine the area under the glucose curve and compare it to a standard quickly digesting food such as white bread or pure glucose.
Each food must contain the same total amount of carbohydrate, so you might have to eat a big plate of carrots to compare with a slice of bread. You end up with a number that reflects the food's ability to elevate glucose when eaten in isolation. It typically depends on how quickly the carbohydrate is absorbed, with higher numbers usually resulting from faster absorption.
The GI is a standby of modern nutritional advice. It's easy to believe in because processed foods tend to have a higher glycemic index than minimally processed foods, high blood sugar is bad, and chronically high insulin is bad. But many people have criticized the concept, and rightly so.
Blood sugar responses to a carbohydrate-containing foods vary greatly from person to person. For example, I can eat a medium potato and a big slice of white bread (roughly 60 g carbohydrate) with nothing else and only see a modest spike in my blood sugar. I barely break 100 mg/dL and I'm back at fasting glucose levels within an hour and a half. You can see a graph of this experiment here. That's what happens when you have a well-functioning pancreas and insulin-sensitive tissues. Your body shunts glucose into the tissues almost as rapidly as it enters the bloodstream. Someone with impaired glucose tolerance might have gone up to 170 mg/dL for two and a half hours on the same meal.
The other factor is that foods aren't eaten in isolation. Fat, protein, acidity and other factors slow carbohydrate absorption in the context of a normal meal, to the point where the GI of the individual foods become much less pronounced.
It's time to put my money where my mouth is. Researchers have conducted a number of controlled trials comparing low-GI diets to high-GI diets. I've done an informal literature review to see what the overall findings are. I'm only interested in long-term studies-- 10 weeks or longer-- and I've excluded studies using subjects with metabolic disorders such as diabetes.
The question I'm asking with this review is, what are the health effects of a low-glycemic index diet on a healthy normal-weight or overweight person? I found a total of seven studies on PubMed in which investigators varied GI while keeping total carbohydrate about the same, for 10 weeks or longer. I'll present them out of chronological order because they flow better that way.
Study #1. Investigators put overweight women on a 12-week diet of either high-GI or low-GI foods with an equal amount of total carbohydrate. Both were unrestricted in calories. Body composition and total food intake were the same on both diets. The reason became apparent when they measured the subjects' glucose and insulin response to the high- and low-GI meals, and found that they were the same!
Study #2. Investigators divided 129 overweight young adults into four different diet groups for 12 weeks. Diet #1: high GI, high carbohydrate (60%). Diet #2: low GI, high carbohydrate. Diet #3: high GI, high-protein (28%). Diet #4: low GI, high protein. The high-protein diets were also a bit higher in fat. Although the differences were small and mostly not statistically significant, participants on diet #3 improved the most overall in my opinion. They lost the most weight, and had the greatest decrease in fasting insulin and calculated insulin resistance. Diet #2 came out modestly ahead of diet #1 on fat loss and fasting insulin.
Study #3. At 18 months, this is by far the longest trial. Investigators assigned 203 healthy Brazilian women to either a low-GI or high-GI energy-restricted diet. The difference in GI between the two diets was very large; the high-GI diet was double the low-GI diet. Weight loss was a meager 1/3 pound greater in the low-GI group, a difference that was not statistically significant at 18 months. Insulin resistance and fasting insulin decreased in the high-GI group but increased in the low-GI group, also not statistically significant.
Study #4. The FUNGENUT study. In this 12-week intervention, investigators divided 47 subjects with the metabolic syndrome into two diet groups. One was a high-glycemic, high-wheat group; the other was a low-glycemic, high-rye group. After 12 weeks, there was an improvement in the insulinogenic index (a marker of early insulin secretion in response to carbohydrate) in the rye group but not the wheat group. Glucose tolerance was essentially the same in both groups.
What makes this study unique is they went on to look at changes in gene expression in subcutaneous fat tissue before and after the diets. They found a decrease in the expression of stress and inflammation-related genes in the rye group, and an increase in stress and inflammation genes in the wheat group. They interpreted this as being the result of the different GIs of the two diets.
I have a different interpretation. I believe wheat is a uniquely unhealthy food, that promotes inflammation and general metabolic havoc over a long period of time. This probably relates at least in part to its gluten content, which is double that of rye. Dr. William Davis has had great success with his cardiac patients by counseling them to eliminate wheat. He agrees based on his clinical experience that wheat has uniquely damaging effects on the metabolism that other sources of starch do not have.
Study #5. This one is really bizarre. Investigators divided 18 subjects with elevated cardiovascular disease risk markers into two diets differing in their GI. In the abstract, they claim that only the low-GI group lost weight. If you look at their data table, it shows that actually the high-GI group lost much more weight than the low-GI group. The high-GI group lost body fat while the low-GI group gained fat. The other variables they measured stayed essentially the same. I don't understand how they got the numbers in their abstract from the numbers in their table. If anyone can figure this out I would be grateful.
Study #6. 45 overweight females were divided between high-GI and low-GI diets for 10 weeks. The low-GI group lost a small amount more fat than the high-GI group, but the difference wasn't significant. The low-GI group also had a 10% drop in LDL cholesterol.
Study #7. This was the second-longest trial, at 4 months. 34 subjects with impaired glucose tolerance were divided into three diet groups. Diet #1: high-carbohydrate (60%), high-GI. Diet #2: high-carbohydrate, low-GI. Diet #3: "low-carbohydrate" (49%), "high-fat" (monounsaturated from olive and canola oil). The diet #1 group lost the most weight, followed by diet #2, while diet #3 gained weight. The differences were small but statistically significant. The insulin and triglyceride response to a test meal improved in diet group #1 but not #2. The insulin response also improved in group #3. The high-GI group came out looking pretty good.
Overall, these studies do not support the idea that lowering the glycemic index of carbohydrate foods is useful for weight loss, insulin or glucose control, or anything else besides complicating your life. If anything, the longest two studies support the alternate hypothesis: that high-GI carbohydrates are superior to low-GI carbohydrates. Why might this be? I'll speculate in my next post.
Further reading:
The Fructose Index is the New Glycemic Index
Each food must contain the same total amount of carbohydrate, so you might have to eat a big plate of carrots to compare with a slice of bread. You end up with a number that reflects the food's ability to elevate glucose when eaten in isolation. It typically depends on how quickly the carbohydrate is absorbed, with higher numbers usually resulting from faster absorption.
The GI is a standby of modern nutritional advice. It's easy to believe in because processed foods tend to have a higher glycemic index than minimally processed foods, high blood sugar is bad, and chronically high insulin is bad. But many people have criticized the concept, and rightly so.
Blood sugar responses to a carbohydrate-containing foods vary greatly from person to person. For example, I can eat a medium potato and a big slice of white bread (roughly 60 g carbohydrate) with nothing else and only see a modest spike in my blood sugar. I barely break 100 mg/dL and I'm back at fasting glucose levels within an hour and a half. You can see a graph of this experiment here. That's what happens when you have a well-functioning pancreas and insulin-sensitive tissues. Your body shunts glucose into the tissues almost as rapidly as it enters the bloodstream. Someone with impaired glucose tolerance might have gone up to 170 mg/dL for two and a half hours on the same meal.
The other factor is that foods aren't eaten in isolation. Fat, protein, acidity and other factors slow carbohydrate absorption in the context of a normal meal, to the point where the GI of the individual foods become much less pronounced.
It's time to put my money where my mouth is. Researchers have conducted a number of controlled trials comparing low-GI diets to high-GI diets. I've done an informal literature review to see what the overall findings are. I'm only interested in long-term studies-- 10 weeks or longer-- and I've excluded studies using subjects with metabolic disorders such as diabetes.
The question I'm asking with this review is, what are the health effects of a low-glycemic index diet on a healthy normal-weight or overweight person? I found a total of seven studies on PubMed in which investigators varied GI while keeping total carbohydrate about the same, for 10 weeks or longer. I'll present them out of chronological order because they flow better that way.
Study #1. Investigators put overweight women on a 12-week diet of either high-GI or low-GI foods with an equal amount of total carbohydrate. Both were unrestricted in calories. Body composition and total food intake were the same on both diets. The reason became apparent when they measured the subjects' glucose and insulin response to the high- and low-GI meals, and found that they were the same!
Study #2. Investigators divided 129 overweight young adults into four different diet groups for 12 weeks. Diet #1: high GI, high carbohydrate (60%). Diet #2: low GI, high carbohydrate. Diet #3: high GI, high-protein (28%). Diet #4: low GI, high protein. The high-protein diets were also a bit higher in fat. Although the differences were small and mostly not statistically significant, participants on diet #3 improved the most overall in my opinion. They lost the most weight, and had the greatest decrease in fasting insulin and calculated insulin resistance. Diet #2 came out modestly ahead of diet #1 on fat loss and fasting insulin.Study #3. At 18 months, this is by far the longest trial. Investigators assigned 203 healthy Brazilian women to either a low-GI or high-GI energy-restricted diet. The difference in GI between the two diets was very large; the high-GI diet was double the low-GI diet. Weight loss was a meager 1/3 pound greater in the low-GI group, a difference that was not statistically significant at 18 months. Insulin resistance and fasting insulin decreased in the high-GI group but increased in the low-GI group, also not statistically significant.
Study #4. The FUNGENUT study. In this 12-week intervention, investigators divided 47 subjects with the metabolic syndrome into two diet groups. One was a high-glycemic, high-wheat group; the other was a low-glycemic, high-rye group. After 12 weeks, there was an improvement in the insulinogenic index (a marker of early insulin secretion in response to carbohydrate) in the rye group but not the wheat group. Glucose tolerance was essentially the same in both groups.
What makes this study unique is they went on to look at changes in gene expression in subcutaneous fat tissue before and after the diets. They found a decrease in the expression of stress and inflammation-related genes in the rye group, and an increase in stress and inflammation genes in the wheat group. They interpreted this as being the result of the different GIs of the two diets.
I have a different interpretation. I believe wheat is a uniquely unhealthy food, that promotes inflammation and general metabolic havoc over a long period of time. This probably relates at least in part to its gluten content, which is double that of rye. Dr. William Davis has had great success with his cardiac patients by counseling them to eliminate wheat. He agrees based on his clinical experience that wheat has uniquely damaging effects on the metabolism that other sources of starch do not have.
Study #5. This one is really bizarre. Investigators divided 18 subjects with elevated cardiovascular disease risk markers into two diets differing in their GI. In the abstract, they claim that only the low-GI group lost weight. If you look at their data table, it shows that actually the high-GI group lost much more weight than the low-GI group. The high-GI group lost body fat while the low-GI group gained fat. The other variables they measured stayed essentially the same. I don't understand how they got the numbers in their abstract from the numbers in their table. If anyone can figure this out I would be grateful.
Study #6. 45 overweight females were divided between high-GI and low-GI diets for 10 weeks. The low-GI group lost a small amount more fat than the high-GI group, but the difference wasn't significant. The low-GI group also had a 10% drop in LDL cholesterol.
Study #7. This was the second-longest trial, at 4 months. 34 subjects with impaired glucose tolerance were divided into three diet groups. Diet #1: high-carbohydrate (60%), high-GI. Diet #2: high-carbohydrate, low-GI. Diet #3: "low-carbohydrate" (49%), "high-fat" (monounsaturated from olive and canola oil). The diet #1 group lost the most weight, followed by diet #2, while diet #3 gained weight. The differences were small but statistically significant. The insulin and triglyceride response to a test meal improved in diet group #1 but not #2. The insulin response also improved in group #3. The high-GI group came out looking pretty good.
Overall, these studies do not support the idea that lowering the glycemic index of carbohydrate foods is useful for weight loss, insulin or glucose control, or anything else besides complicating your life. If anything, the longest two studies support the alternate hypothesis: that high-GI carbohydrates are superior to low-GI carbohydrates. Why might this be? I'll speculate in my next post.
Further reading:
The Fructose Index is the New Glycemic Index
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