Senin, 18 Agustus 2008
Sociology of education
The sociology of education is the learning of how social institutions and services have an effect on educational processes and outcomes, and vice versa. By many, education is understood to be a means of overcome the handicaps, achieve greater equality and acquire wealth and status for all (Sargent 1994). Learners may be provoked by aspirations for progress and betterment. Education is perceived
Minggu, 17 Agustus 2008
Cardiovascular Risk Factors on Kitava, Part III: Insulin
The Kitava study continues to get more and more interesting in later publications. Dr. Lindeberg and his colleagues continued exploring disease markers in the Kitavans, perhaps because their blood lipid findings were not consistent with what one would expect to find in a modern Western population with a low prevalence of CVD.
In their next study, the researchers examined Kitavans' insulin levels compared to Swedish controls. This paper is short but very sweet. Young Kitavan men and women have a fasting serum insulin level considerably lower than their Swedish counterparts (KM 3.9 IU/mL; SM 5.7; KW 3.5; SW 6.2). Kitavan insulin is relatively stable with age, whereas Swedish insulin increases. In the 60-74 year old group, Kitavans have approximately half the fasting serum insulin of Swedes. One thing to keep in mind is that these are average numbers. There is some overlap between the Kitavan and Swedish numbers, with a few Kitavans above the Swedish mean.
In figure 2, they address the possibility that exercise is the reason for Kitavans' low insulin levels. Kitavans have an activity level comparable to a moderately active Swedish person. They divided the Swedes into three categories: low, medium, and high amounts of physical activity at work. The people in the "low" category had the highest insulin, followed by the "high" group and then the "medium" group. The differences were small, however, and Kitavans had far lower serum insulin, on average, than any of the three Swedish groups. These data show that exercise can not explain Kitavans' low insulin levels.
The researchers also found that they could accurately predict average Swedish and Kitavan insulin levels using an equation that factored in age, BMI and waist circumference. This shows that there is a strong correlation between body composition and insulin levels, which applies across cultures.
Now it's time to take a step back and do some interpreting. First of all, this paper is consistent with the idea (but does not prove) that elevated insulin is a central element of overweight, vascular disease and possibly the other diseases of civilization. While we saw previously that mainstream blood lipid markers do not correlate well with CVD or stroke on Kitava, insulin has withstood the cross-cultural test.
In my opinion, the most important finding in this paper is that a high-carbohydrate diet does not necessarily lead to elevated fasting insulin. This is why I think the statement "carbohydrate drives insulin drives fat" is an oversimplification. With a properly-functioning pancreas and insulin-sensitive tissues (which many people in industrial societies do not have), a healthy person can eat a high-carbohydrate meal and keep blood glucose under control. Insulin definitely spikes, but it's temporary. The rest of the day, insulin is at basal levels. The Kitavans show that insulin spikes per se do not cause hyperinsulinemia.
So this leads to the Big Question: what causes hyperinsulinemia?? The best I can give you is informed speculation. Who has hyperinsulinemia? Industrial populations, especially the U.S. and native populations that have adopted Western foods. Who doesn't? Non-industrial populations that have not been affected by Western food habits, including the traditional Inuit, the Kuna, the traditional Masai and the Kitavans.
We can guess that total fat, saturated fat and carbohydrate do not cause hyperinsulinemia, based on data from the Inuit, the Masai and the Kitavans, respectively. We can also guess that there's not some specific food that protects these populations, since they eat completely different things. Exercise also can not completely account for these findings. What does that leave us with? Western food habits. In my opinion, the trail of metabolic destruction that has followed Westerners throughout the world is probably due in large part to industrial foods, including refined wheat flour, sugar and seed oils.
I'm not the first person to come up with this idea, far from it. The idea that specific types of carbohydrate foods, rather than carbohydrate in general, are responsible for the diseases of civilization, has been around for at least a century. It was an inescapable conclusion in the time of Weston Price, when anthropologists and field physicians could observe the transitions of native people to Western diets all over the world. This information has gradually faded from our collective consciousness as native cultures have become increasingly rare. The Kitava study is a helpful modern-day reminder.
In their next study, the researchers examined Kitavans' insulin levels compared to Swedish controls. This paper is short but very sweet. Young Kitavan men and women have a fasting serum insulin level considerably lower than their Swedish counterparts (KM 3.9 IU/mL; SM 5.7; KW 3.5; SW 6.2). Kitavan insulin is relatively stable with age, whereas Swedish insulin increases. In the 60-74 year old group, Kitavans have approximately half the fasting serum insulin of Swedes. One thing to keep in mind is that these are average numbers. There is some overlap between the Kitavan and Swedish numbers, with a few Kitavans above the Swedish mean.
In figure 2, they address the possibility that exercise is the reason for Kitavans' low insulin levels. Kitavans have an activity level comparable to a moderately active Swedish person. They divided the Swedes into three categories: low, medium, and high amounts of physical activity at work. The people in the "low" category had the highest insulin, followed by the "high" group and then the "medium" group. The differences were small, however, and Kitavans had far lower serum insulin, on average, than any of the three Swedish groups. These data show that exercise can not explain Kitavans' low insulin levels.
The researchers also found that they could accurately predict average Swedish and Kitavan insulin levels using an equation that factored in age, BMI and waist circumference. This shows that there is a strong correlation between body composition and insulin levels, which applies across cultures.
Now it's time to take a step back and do some interpreting. First of all, this paper is consistent with the idea (but does not prove) that elevated insulin is a central element of overweight, vascular disease and possibly the other diseases of civilization. While we saw previously that mainstream blood lipid markers do not correlate well with CVD or stroke on Kitava, insulin has withstood the cross-cultural test.
In my opinion, the most important finding in this paper is that a high-carbohydrate diet does not necessarily lead to elevated fasting insulin. This is why I think the statement "carbohydrate drives insulin drives fat" is an oversimplification. With a properly-functioning pancreas and insulin-sensitive tissues (which many people in industrial societies do not have), a healthy person can eat a high-carbohydrate meal and keep blood glucose under control. Insulin definitely spikes, but it's temporary. The rest of the day, insulin is at basal levels. The Kitavans show that insulin spikes per se do not cause hyperinsulinemia.
So this leads to the Big Question: what causes hyperinsulinemia?? The best I can give you is informed speculation. Who has hyperinsulinemia? Industrial populations, especially the U.S. and native populations that have adopted Western foods. Who doesn't? Non-industrial populations that have not been affected by Western food habits, including the traditional Inuit, the Kuna, the traditional Masai and the Kitavans.
We can guess that total fat, saturated fat and carbohydrate do not cause hyperinsulinemia, based on data from the Inuit, the Masai and the Kitavans, respectively. We can also guess that there's not some specific food that protects these populations, since they eat completely different things. Exercise also can not completely account for these findings. What does that leave us with? Western food habits. In my opinion, the trail of metabolic destruction that has followed Westerners throughout the world is probably due in large part to industrial foods, including refined wheat flour, sugar and seed oils.
I'm not the first person to come up with this idea, far from it. The idea that specific types of carbohydrate foods, rather than carbohydrate in general, are responsible for the diseases of civilization, has been around for at least a century. It was an inescapable conclusion in the time of Weston Price, when anthropologists and field physicians could observe the transitions of native people to Western diets all over the world. This information has gradually faded from our collective consciousness as native cultures have become increasingly rare. The Kitava study is a helpful modern-day reminder.
Jumat, 15 Agustus 2008
Cardiovascular Risk Factors on Kitava, Part II: Blood Lipids
The findings in the previous post are all pretty much expected in a population that doesn't get heart disease. However, things started to get interesting when Lindeberg's group measured the Kitavans' serum lipids ("cholesterol"). Kitavan and Swedish total cholesterol is about the same in young men, around 174 mg/dL (4.5 mmol/L). It rises with age in older Swedish men but not Kitavans.
Doctors commonly refer to total cholesterol over 200 mg/dL (5.2 mmol/L) as "high", so Kitavan men are in the clear. On the other hand, Kitavan women should be dying of heart disease left and right with their high middle-age cholesterol of 247 mg/dL (6.4 mmol/L)! That's actually higher than the value for Swedish women of the same age, who are far more prone to heart disease than Kitavans.
The fun doesn't stop there. Total cholesterol isn't a good predictor of heart attack risk, but there are better measures. LDL on Kitava is lower in males than in Sweden, but for females it's about the same until old age. HDL is slightly lower than Swedes' at middle and old age, and triglycerides are higher on average. Judging by these numbers, Kitavans should have cardiovascular disease (CVD) comparable to Swedes, who suffer from a high rate of cardiovascular mortality.
Kitavan smokers had a lower HDL than nonsmokers, yet still did not develop CVD. Smoking is considered one of the most powerful risk factors for cardiovascular disease in Western populations. I think it's worth noting, however, that Kitavans tend to be light smokers.
These data are difficult to reconcile with the hypothesis that certain patterns of blood lipids cause CVD. Kitavans, particularly the women, have a blood lipid profile that should have them clutching their chests, yet they remain healthy.
There is a theory of the relationship between blood lipids and CVD that can explain these data. Perhaps blood lipids, rather than causing CVD, simply reflect diet composition and other lifestyle factors. Both on Kitava and in the West, low HDL and elevated triglycerides imply a high carbohydrate intake. Low-carbohydrate diets consistently raise HDL and lower triglycerides. On Kitava, carbohydrate comes mostly from root crops. In the West, it comes mostly from processed grains (typically wheat) and sugar. So the blood lipid pattern that associates best with CVD and the metabolic syndrome in the West is simply a marker of industrial food intake.
Doctors commonly refer to total cholesterol over 200 mg/dL (5.2 mmol/L) as "high", so Kitavan men are in the clear. On the other hand, Kitavan women should be dying of heart disease left and right with their high middle-age cholesterol of 247 mg/dL (6.4 mmol/L)! That's actually higher than the value for Swedish women of the same age, who are far more prone to heart disease than Kitavans.
The fun doesn't stop there. Total cholesterol isn't a good predictor of heart attack risk, but there are better measures. LDL on Kitava is lower in males than in Sweden, but for females it's about the same until old age. HDL is slightly lower than Swedes' at middle and old age, and triglycerides are higher on average. Judging by these numbers, Kitavans should have cardiovascular disease (CVD) comparable to Swedes, who suffer from a high rate of cardiovascular mortality.
Kitavan smokers had a lower HDL than nonsmokers, yet still did not develop CVD. Smoking is considered one of the most powerful risk factors for cardiovascular disease in Western populations. I think it's worth noting, however, that Kitavans tend to be light smokers.
These data are difficult to reconcile with the hypothesis that certain patterns of blood lipids cause CVD. Kitavans, particularly the women, have a blood lipid profile that should have them clutching their chests, yet they remain healthy.
There is a theory of the relationship between blood lipids and CVD that can explain these data. Perhaps blood lipids, rather than causing CVD, simply reflect diet composition and other lifestyle factors. Both on Kitava and in the West, low HDL and elevated triglycerides imply a high carbohydrate intake. Low-carbohydrate diets consistently raise HDL and lower triglycerides. On Kitava, carbohydrate comes mostly from root crops. In the West, it comes mostly from processed grains (typically wheat) and sugar. So the blood lipid pattern that associates best with CVD and the metabolic syndrome in the West is simply a marker of industrial food intake.
Kamis, 14 Agustus 2008
Cardiovascular Risk Factors on Kitava, Part I: Weight and Blood Pressure
The Kitavans are an isolated population free of cardiovascular disease and stroke, despite the fact that more than three quarters of them smoke cigarettes (although not very frequently). They eat a carbohydrate-heavy, whole-foods diet that is uninfluenced by modern food habits and consists mostly of starchy root crops, fruit, vegetables, coconut and fish. Their intake of grains and processed foods is negligible.
Naturally, when Dr. Lindeberg's group discovered that Kitavans don't suffer from heart disease or stroke, they investigated further. In the second paper of the series, they analyzed the Kitavans' "cardiovascular risk factors" that sometimes associate with heart disease in Western populations, such as overweight, hypertension, elevated total cholesterol and other blood lipid markers.
Kitavans are lean. Adult male body mass index (BMI) starts out at 22, and diminishes with age. For comparison, Swedes begin at a BMI of 25 and stay that way. Both populations lose muscle mass with age, so Kitavans are staying lean while Swedes are gaining fat. The average American has a BMI of about 28, which is considered overweight and 2 points away from being obese.
Kitavans also have a low blood pressure that rises modestly with age. This is actually a bit surprising to me, since other non-industrial groups like the Kuna do not experience a rise in blood pressure with age. Compared with Swedes, Kitavans' blood pressure is considerably lower at all ages.
In the next post, I'll discuss the Kitavans' blood lipid numbers ("cholesterol"), which challenge current thinking about heart disease risk factors.
Naturally, when Dr. Lindeberg's group discovered that Kitavans don't suffer from heart disease or stroke, they investigated further. In the second paper of the series, they analyzed the Kitavans' "cardiovascular risk factors" that sometimes associate with heart disease in Western populations, such as overweight, hypertension, elevated total cholesterol and other blood lipid markers.
Kitavans are lean. Adult male body mass index (BMI) starts out at 22, and diminishes with age. For comparison, Swedes begin at a BMI of 25 and stay that way. Both populations lose muscle mass with age, so Kitavans are staying lean while Swedes are gaining fat. The average American has a BMI of about 28, which is considered overweight and 2 points away from being obese.
Kitavans also have a low blood pressure that rises modestly with age. This is actually a bit surprising to me, since other non-industrial groups like the Kuna do not experience a rise in blood pressure with age. Compared with Swedes, Kitavans' blood pressure is considerably lower at all ages.
In the next post, I'll discuss the Kitavans' blood lipid numbers ("cholesterol"), which challenge current thinking about heart disease risk factors.
Rabu, 13 Agustus 2008
The Kitavans: Wisdom from the Pacific Islands
There are very few cultures left on this planet that have not been affected by modern food habits. There are even fewer that have been studied thoroughly. The island of Kitava in Papua New Guinea is host to one such culture, and its inhabitants have many profound things to teach us about diet and health.
The Kitava study, a series of papers produced primarily by Dr. Staffan Lindeberg and his collaborators, offers a glimpse into the nutrition and health of an ancient society, using modern scientific methods. This study is one of the most complete and useful characterizations of the diet and health of a non-industrial society I have come across. It's also the study that created, and ultimately resolved, my cognitive dissonance over the health effects of carbohydrate.
From the photos I've seen, the Kitavans are beautiful people. They have the broad, attractive faces, smooth skin and excellent teeth typical of healthy non-industrial peoples.
Like the Kuna, Kitavans straddle the line between agricultural and hunter-gatherer lifestyles. They eat a diet primarily composed of tubers (yam, sweet potato, taro and cassava), fruit, vegetables, coconut and fish, in order of calories. This is typical of traditional Pacific island cultures, although the relative amounts differ.
Grains, refined sugar, vegetable oils and other processed foods are virtually nonexistent on Kitava. They get an estimated 69% of their calories from carbohydrate, 21% from fat, 17% from saturated fat and 10% from protein. Most of their fat intake is saturated because it comes from coconuts. They have an omega-6 : omega-3 ratio of approximately 1:2. Average caloric intake is 2,200 calories per day (9,200 kJ). By Western standards, their diet is high in carbohydrate, high in saturated fat, low in total fat, a bit low in protein and high in calories.
Now for a few relevant facts before we really start diving in:
Overall, Kitavans possess a resistance to degenerative diseases that is baffling to industrialized societies. Not only is this typical of non-industrial cultures, I believe it represents the natural state of existence for Homo sapiens. Like all other animals, humans are healthy and robust when occupying their preferred ecological niche. Our niche happens to be a particularly broad one, ranging from near-complete carnivory to plant-rich omnivory. But it does not include large amounts of industrial foods.
In the next few posts, I'll discuss more specific data about the health of the Kitavans.
The Kitava study, a series of papers produced primarily by Dr. Staffan Lindeberg and his collaborators, offers a glimpse into the nutrition and health of an ancient society, using modern scientific methods. This study is one of the most complete and useful characterizations of the diet and health of a non-industrial society I have come across. It's also the study that created, and ultimately resolved, my cognitive dissonance over the health effects of carbohydrate.
From the photos I've seen, the Kitavans are beautiful people. They have the broad, attractive faces, smooth skin and excellent teeth typical of healthy non-industrial peoples.
Like the Kuna, Kitavans straddle the line between agricultural and hunter-gatherer lifestyles. They eat a diet primarily composed of tubers (yam, sweet potato, taro and cassava), fruit, vegetables, coconut and fish, in order of calories. This is typical of traditional Pacific island cultures, although the relative amounts differ.
Grains, refined sugar, vegetable oils and other processed foods are virtually nonexistent on Kitava. They get an estimated 69% of their calories from carbohydrate, 21% from fat, 17% from saturated fat and 10% from protein. Most of their fat intake is saturated because it comes from coconuts. They have an omega-6 : omega-3 ratio of approximately 1:2. Average caloric intake is 2,200 calories per day (9,200 kJ). By Western standards, their diet is high in carbohydrate, high in saturated fat, low in total fat, a bit low in protein and high in calories.
Now for a few relevant facts before we really start diving in:
- Kitavans are moderately active. They have an activity level comparable to a moderately active Swede, the population to which Dr. Lindeberg draws frequent comparisons.
- They have abundant food, and shortage is uncommon.
- Their good health is probably not related to genetics, since genetically similar groups in the same region are exquisitely sensitive to the ravages of industrial food. Furthermore, the only Kitavan who moved away from the island to live a modern life is also the only fat Kitavan.
- Their life expectancy at birth is estimated at 45 years (includes infant mortality), and life expectancy at age 50 is an additional 25 years. This is remarkable for a culture with limited access to modern medicine.
- Over 75% of Kitavans smoke cigarettes, although in small amounts. Even the most isolated societies have their modern vices.
For the whole of PNG, no case of IHD or atherothrombotic stroke has been reported in clinical investigations and autopsy studies among traditionally living Melanesians for more than seven decades, though an increasing number of myocardial infarctions [heart attacks] and angina pectoris in urbanized populations have been reported since the 1960s.Dementia was not found except in in two young Kitavans, who were born handicapped. The elderly remained sharp until death, including one man who reached 100 years of age. Kitavans are also unfamiliar with external cancers, with the exception of one possible case of breast cancer in an elderly woman.
Overall, Kitavans possess a resistance to degenerative diseases that is baffling to industrialized societies. Not only is this typical of non-industrial cultures, I believe it represents the natural state of existence for Homo sapiens. Like all other animals, humans are healthy and robust when occupying their preferred ecological niche. Our niche happens to be a particularly broad one, ranging from near-complete carnivory to plant-rich omnivory. But it does not include large amounts of industrial foods.
In the next few posts, I'll discuss more specific data about the health of the Kitavans.
Senin, 11 Agustus 2008
Alkali soils
As the word akali correspond to sodic, the notion alkali soil is, similar to the notion sodic soil, is not explicit.Alkali, or alkaline, soils are clay soils with a comparatively high exchangeable sodium percentage, a relative high pH (> 9), a poor soil arrangement and a little infiltration capacity. Frequently they have a hard calcareous layer at 0.5 to 1 m. depth in India this coating is called
Letter to the Editor
I wrote a letter to the New York Times about their recent article "The Overflowing American Dinnerplate", which I reviewed here. The letter didn't get accepted, so I will publish it here:
In the article "The Overflowing American Dinner Plate", Bill Marsh cites USDA data showing a 59% increase in fat consumption from 1970 to 2006, coinciding with the doubling of the obesity rate in America. However, according to Centers for Disease Control NHANES nutrition survey data, total fat intake in the US has remained relatively constant since 1971, and has actually decreased as a percentage of calories. The apparent discrepancy disappears when we understand that the USDA data Marsh cites are not comprehensive. They do not include the fat contained in milk and meat, which have been steadily decreasing since 1970.
The change Marsh reported refers primarily to the increasing use of industrially processed vegetable oils such as soybean oil. These have gradually replaced animal fats in our diet over the last 30 years. Since overall fat intake has changed little since the 1970s, it cannot be blamed for rising obesity.
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