Do Blood Glucose Levels Affect Hunger and Satiety?

You've heard the story before: when you eat carbohydrate-rich foods that digest quickly, it sends your blood sugar and insulin levels soaring, then your blood sugar level comes crashing back down and you feel hungry and cranky.  You reach for more carbohydrate, perpetuating the cycle of crashes, overeating, and fat gain.

It sounds pretty reasonable-- in fact, so reasonable that it's commonly stated as fact in popular media and in casual conversation.  This idea is so deeply ingrained in the popular psyche that people often say "I have low blood sugar" instead of "I'm hungry" or "I'm tired".  But this hypothesis has a big problem: despite extensive research, it hasn't been clearly supported.  I've written about this issue before (1).

A new study offers a straightforward test of the hypothesis, and once again finds it lacking.

The study

Bernd Schultes and colleagues used a clever design to isolate the effect of blood glucose on appetite (2).  They recruited 15 healthy young men, and on two occasions fed them an identical light breakfast.

On one occasion, they waited one hour after the meal and infused saline containing 50 grams of glucose into the volunteers' bloodstream over a one-hour period.  On the other occasion, they did the same thing except using saline without glucose.  Throughout the infusion, and one hour afterward, the researchers monitored levels of blood glucose, blood insulin, and markers of appetite.

The results

As expected, the glucose infusion markedly increased blood glucose and insulin levels in the hour following the meal.  After the researchers stopped the glucose infusion, the volunteers' blood glucose levels declined, eventually reaching a level significantly lower than the control condition (54 mg/dL vs 70 mg/dL).  This is the post-meal "crash" that is supposed to trigger appetite.

Yet levels of hunger, appetite, satiety, and fullness didn't differ between groups at any time-- either during the infusion or afterward.

Discussion

We have extensive evidence that the brain pays attention to blood glucose levels, and triggers appetite when it goes too low as part of a suite of protective responses to maintain blood glucose level (this is called the "counterregulatory response").  However, the evidence overall suggests that you have to have pretty serious hypoglycemia for this to happen-- something that rarely occurs in people who aren't using insulin to treat diabetes.  When researchers actually measure the blood glucose level of non-diabetic people who report feeling "hypoglycemic", a small percentage of them really are hypoglycemic, but the vast majority have perfectly normal blood glucose levels (3, 4, 5, 6).  Hypoglycemia is not something that occurs frequently in the general non-diabetic population, and it doesn't offer a compelling explanation for why we feel hungry or tired between meals.

The brain listens to a variety of signals that indicate the body's energy status, and it integrates these signals to determine your sensation of hunger or satiety (7).  Glucose is one of the signals the brain listens to, but there are many others, and the brain doesn't appear to pay very much attention to the glucose signal when it's within the range that occurs in the daily life of most people.  In contrast, the brain pays attention to levels of leptin, CCK, GLP-1, glucagon, amylin, ghrelin, and signals ascending from the gut via the vagus nerve (7).

I like this study because it manipulated blood glucose levels in a way that's not likely to be confounded by variables that bedevil other study designs.  They pulled this off by directly manipulating blood glucose, mimicking the glucose profile of a high-glycemic meal to see if post-meal fluctuations at the extreme end of the normal range affect appetite.

And, consistent with most previous research, it looks like they don't.  How do we reconcile this with the fact that some single-meal studies have found that lower-glycemic meals are more sating than higher-glycemic meals (8)?  Here's what I think.  The sating effect of low-glycemic meals probably doesn't have much to do with blood glucose at all, but rather: 1) the fact that these studies are usually not properly controlled for other variables known to affect satiety, such as calorie density, fiber, protein, and palatability; and 2) the fact that lower-glycemic foods digest more slowly and therefore tend to leave carbohydrate hanging around in the gut interacting with intestinal satiety receptors for longer.

The authors conclude:
These findings clearly speak against the notion that fluctuations in glycemia and also insulinemia represent major signals in the short-term regulation of hunger and satiety.
Bariatric MD Arya Sharma also had some good thoughts on this study (9):
The lesson here, I guess is that, just because there is a seemingly compelling narrative to support an idea, it does not mean that that’s how biology in real life actually works.
I agree!

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How do I download or save a YouTube video to my computer?

YouTube has been designed to only allow users to watch and view videos on their website. Many users want to download or save their favorite YouTube videos to their computer so they can watch them without being connected to the Internet or on other devices. Below are the steps required for downloading and watching YouTube videos on your computer for free.

Note: This page only provides instructions for downloading or saving a YouTube video to your computer. Instructions for uploading or saving a YouTube video to the YouTube website or saving only the audio of a YouTube video to an MP3 file are not covered.

Saving YouTube video as a video file on your computer

Today, there are many websites that allow you to enter the URL of the video you want to save to your computer and get a link to download the video file. Below is a simple three-step process to download any YouTube video.

Note: If you are at a school or job that is blocking YouTube, these steps may not work.

1. First, go to the YouTube page containing the video you want to download. When you've found the page, press Ctrl + L on your keyboard to highlight the text in the address bar, and then Ctrl + C to copy the Internet address.

2. Once this address has been copied, paste that URL into the text field below url by clicking inside the box and pressing Ctrl + V on your keyboard. Then, click the Download Video button.

http://en.savefrom.net/

3. If done properly, a new window will appear displaying a preview of the video (as shown below), along with a green Download button and the video format. The default format for downloading the video is the MP4 360p format.

If you click on the "MP4 360p" format option, a drop-down list will appear. Click on theMore option in that drop-down list to see additional video formats, such as FLV, 3GP, and WebM. Select the video format you want and click the green Download button.

After the file has been downloaded, it will be available in your downloads folder.

What about a private video?

You cannot download private videos because the YouTube download service will not have the necessary rights to access the video.

I still can't download a video

If after following the above steps, you do not get a preview like our example, make sure that the link you are using works by opening the page in a new window. Once verified as working, try the above steps again. If the steps continue to not work, try refreshing this page by pressing the F5 key on your keyboard and following the above steps again. If that still does not work, try one of the other YouTube download sites below.

It is only saving as audio and not video

Make sure you are choosing the "MP4 360p" or "MP4 480p" option from the download link. If you choose "Audio MP4 128", it only downloads the audio and not the video. If you did choose the right download link to download the file, it is very likely that the player you are using does not have the necessary codec for video files. Download the free VLC player for your computer and try to play the video file from within VLC and not the player you are currently using.

YouTube bookmarklet

If you plan on downloading several videos, use the Computer Hope YouTube bookmarklet. See our bookmarklet page for more information about bookmarklets.

Other YouTube download sites

There are also other websites and services that allow you to download YouTube videos. Below are a couple of our favorites.

Caution: Some of these services can be used to save adult-related videos, which means when viewing these pages, you may be subjected to adult-related content.

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Trouble With RSS Feed?

I’ve received several comments that my blog posts are no longer showing up in peoples’ RSS feeds. I’ve gone into my settings, and the blog is still set to full feed mode, so I don’t know why that would be. I’m trying to understand if the problem is widespread or only affects a few people. Please let me know in the comments section if new posts (since the potatoes and human health series) are not showing up in your reader. Also, please let me know if new posts are showing up. Thanks!

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Interview with Chris Voigt of 20 Potatoes a Day

Introduction

Chris Voigt is the executive director of the Washington State Potato Commission, which supports and promotes the Washington state potato industry (1). On October 1st, Mr. Voigt began a two month, potato-only diet to raise awareness about the health properties of potatoes. It was partially in response to the recent decision by the federal WIC (Women, Infants and Children) low-income assistance program to remove potatoes from the list of vegetables it will pay for. Mr. Voigt’s potato diet has been a media sensation, leading to widespread coverage in several countries. He maintains a website and blog called 20 Potatoes a Day.


Diet Facts

For 60 days, Mr Voigt’s diet consisted of nothing but potatoes and a small amount of cooking oil (canola and olive), with no added nutritional supplements. Based on what he has told me, I estimate that 10-15% of his calories came from fat, 10% from protein and 75-80% from high-glycemic carbohydrate. His calorie intake ranged from 1,600 kcal (first 3 weeks) to 2,200 kcal (remaining 5.5 weeks) per day. Prior to the diet, he estimated that his calorie requirement was 2,200 kcal, so he attempted to stay as close to that as possible.

Health Markers

Mr. Voigt has posted the results of physical examinations, including bloodwork, from the beginning, middle and end of the diet. The change he experienced during that time is nothing short of remarkable. He shed 21 pounds, his fasting glucose decreased by 10 mg/dL (104 to 94 mg/dL), his serum triglycerides dropped by nearly 50%, his HDL cholesterol increased slightly, and his calculated LDL cholesterol dropped by a stunning 41% (142 to 84 mg/dL). The changes in his HDL, triglycerides and fasting glucose are consistent with improved insulin sensitivity (2, 3), and are not consistent with a shift of LDL particle size to the dangerous “small, dense” variety (4).

Interview

What was your diet like prior to the potato diet?

My best estimate is that it was probably a little better than the average US citizen only because of a high rate of produce consumption. I generally would eat about 10 servings of fruits and vegetables a day. But I ate everything else too. I would eat a wide range of food, a little bit of everything, including foods that aren’t considered “healthy”.

You essentially ate nothing but potatoes, fat and flavorings for two months. Can you give us an idea of how much fat you were eating? What kind of fat was it?

I averaged about 2 tablespoons of cooking oil a day over the span of the 60 days. Canola oil was used for frying and olive oil was used for roasting.

How was your digestion?

Potatoes are pretty easy on the digestive system. I actually got a lot of emails from people who suffer from severe digestive disorders and literally, potatoes are the only thing they can eat. My 60 days of potatoes was nothing compared to some folks with these digestive disorders. I was getting a lot of fiber so things were pretty regular, but not too regular :)

You lost 21 pounds during your two months of eating only potatoes. Do you have a sense of whether it came out of fat, muscle or both? For example, did your pants become looser?

Pants definitely became looser. I also noticed it in my neck size for shirts. I’m assuming most all of it was due to fat loss.

Do you think you were able to meet your calorie goal of 2,200 calories per day? Were you hungry during the diet?

I was not meeting the goal of 2,200 calories a day during the first 3 weeks of the diet. During the first three weeks of the diet I only ate until I was full. I didn’t realize that potatoes would give me such a high sense of fullness after each meal. So for those first 3 weeks, I was only consuming about 1,600 calories a day. After the third week I had lost 12 pounds and realized that I needed to change strategy. I then began to eat more potatoes despite the sense of fullness I was experiencing. So for the remaining 5 ½ weeks I was very diligent about eating the 2,200 calories. I continued to lose weight but at a slower place. I lost an additional 9 pounds over the course of those remaining 5 ½ weeks. At the start of my diet I estimated, via a couple different on line calorie calculators, that I burn about 2,200 calories a day. Since I continued to lose weight, I’m assuming I actually burn closer to 2,800 calories a day. Something that may have also played a role in continued weight loss was the amount of resistant starch I was getting from potatoes. I ate a lot of cooked potatoes that had been refrigerated. These are generally higher in resistant starch. If I were to do the diet again, I would like to set up an experiment to gauge the effect of resistant starch.

What foods did you crave the most?

I craved mostly foods that had a “juicy crunch”, like an apple, or cucumbers, or carrots, or celery. I never acquired a taste for raw potatoes so virtually all the potatoes I consumed were cooked. No matter how you cook your potatoes, you always get that same soft cooked texture. I craved foods with a crisper texture.

How was your energy level?

My energy level was very good the entire time of the diet. I really didn’t notice a change in energy at the start of the diet so I assumed that the potato diet didn’t have a positive or negative effect on my energy level. It wasn’t until I finished the diet and started to consume other foods that I noticed my energy level has seemed to drop a bit.

How did you feel overall? Were there any unexpected effects of the diet?

I felt really good on the diet. I had lots of energy, slept good at night, and seemed to avoid the cold viruses that circulated at home and work.

The only unusual thing that occurred is what my wife told me. I’m a habitual snorer. The day I started eating only potatoes, my snoring stopped. It restarted the day I started to include other foods in my diet. I’m assuming it was just some weird coincidence but that’s what she tells me.

My doctor and I expected my cholesterol to drop but not at the level we saw. I’ve had borderline high cholesterol for the past decade. I started the diet at 214 and saw it drop to 147 at the end of 60 days. We anticipated a drop of maybe 10-25 points. It was a huge surprise to see a 67 point drop.

Your fasting glucose went from 104 mg/dL, which I consider high, to 94 mg/dL, which is on the high side for someone eating a high-carbohydrate diet, but within the clinically normal range. Do you have a family history of diabetes?

No history of diabetes. My parents are in their early eighties and their parents lived to their 70’s and 80’s with no history of type one or two diabetes.

Reading your blog posts, it seemed like you were having a hard time with the diet at first, but after a while you complained less and even seemed to enjoy it at times. Did you get used to it?

I would say that week 2 and 3 were probably the hardest. The first week was easy probably because of the novelty of the diet. Then reality set in for week 2 and 3. After that, I found my groove and it got easier. During the work week was easy but weekends, particularly Sunday’s, were the hardest. During the work week I did most of my eating at my desk so I wasn’t around a lot of other people eating or surrounded by other foods. Weekends were more difficult because I was around other people every meal and always had other foods in front of me at home.

What kinds of potatoes did you eat?

I literally ate every kind of potato I could get my hands on. I ate yellow skin/yellow flesh potatoes, red skin/white flesh, red skin/red flesh, purple skin/white flesh, purple skin/purple flesh, russet potatoes with white flesh, russet potatoes with yellow flesh, white potatoes, yellow potatoes with white flesh, purple fingerlings, yellow fingerlings, red fingerlings and numerous experimental varieties.

Did you peel them or eat the skin?

I ate the skin at least 90% of the time if not more. There is a myth that all the nutrition in a potato is in the skin or right under the skin. That’s not true, there are nutrients spread throughout the potato but most of the fiber is located in the skin.

What variety of potato is your favorite?

It really depended on the cooking method. For frying, I preferred russet potatoes. For baking, I preferred red potatoes. For mashed, I preferred yellow potatoes. For roasting, a toss-up between russets and reds.

How long did it take you after the diet ended to eat another potato?

As strange as it sounds, potatoes were my first two meals after my diet ended. I was saving my first non-potato meal for a special event that was planned at the local Head Start facility. The beef, dairy, apple, and potato producers put together a nice dinner event and nutrition workshop for all the kids and their parents at the Head Start center in Moses Lake. I still eat potatoes pretty regularly, but most of the time now I’m eating them with more than just seasonings.

Are there any other facts about potatoes you think Whole Health Source readers might find interesting?

Just a reminder that I’m not encouraging anyone to follow in my footsteps and eat just potatoes. This diet is not intended to be the next “fad” diet but was simply a bold statement to remind people that there is a tremendous amount of nutrition in a potato. There is no one food product that can meet all of your nutritional needs. I fully support a well balanced healthy diet, which potatoes can be a part of.

In 2008, the United Nations declared it to be the “Year of the Potato”. This was done to bring attention to the fact that the potato is one of the most efficient crops for developing nations to grow, as a way of delivery a high level of nutrition to growing populations, with fewer needed resources than other traditional crops. In the summer of 2010, China approved new government policies that positioned the potato as the key crop to feed its growing population. The Chinese government formed a partnership with the International Potato Center in Peru to help them facilitate this new emphasis on the potato.

Thanks Chris, for doing your experiment and taking the time to share these details with us!

In the next post, I’ll give my interpretation of all this.

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Dr. Mellanby's Tooth Decay Reversal Diet

I have a lot of admiration for Drs. Edward and May Mellanby. A husband-and-wife team, they discovered vitamin D, and determined that rickets is caused by poor calcium (or phosphorus) status, typically due to vitamin D deficiency. They believed that an ideal diet is omnivorous, based on whole foods, and offers an adequate supply of fat-soluble vitamins and easily absorbed minerals. They also felt that grain intake should be modest, as their research showed that unsoaked whole grains antagonize the effect of vitamins D and A.

Not only did the Mellanbys discover vitamin D and end the rickets epidemic that was devastating Western cities at the time, they also discovered a cure for early-stage tooth decay that has been gathering dust in medical libraries throughout the world since 1924.

It was in that year that Dr. May Mellanby published a summary of the results of the Mellanby tooth decay reversal studies in the British Medical Journal, titled “Remarks on the Influence of a Cereal-free Diet Rich in Vitamin D and Calcium on Dental Caries in Children”. Last year, I had to specially request this article from the basement of the University of Washington medical library (1). Thanks to the magic of the internet, the full version of the paper is now freely available online (2).

You don’t need my help to read the study, but in this post I offer a little background, a summary and my interpretation.

In previous studies, the Mellanbys used dogs to define the dietary factors that influence tooth development and repair. They identified three, which together made the difference between excellent and poor dental health (from Nutrition and Disease):

1. The diet’s mineral content, particularly calcium and phosphorus
2. The diet’s fat-soluble vitamin content, chiefly vitamin D
3. The diet’s content of inhibitors of mineral absorption, primarily phytic acid

Once they had defined these factors, they set about testing their hypotheses in humans. They performed eight trials, each one in children in an institutionalized setting where diet could be completely controlled. The number of cavities in each child’s mouth was noted at the beginning and end of the period. I’ll only discuss the three most informative, and only the most successful in detail. First, the results:

I’ll start with diet 1. Children on this diet ate the typical fare, plus extra oatmeal. Oatmeal is typically eaten as an unsoaked whole grain (and soaking it isn’t very effective in any case), and so it is high in phytic acid, which effectively inhibits the absorption of a number of minerals including calcium. These children formed 5.8 cavities each and healed virtually none– not good!

Diet number 2 was similar to diet 1, except there was no extra oatmeal and the children received a large supplemental dose of vitamin D. Over 28 weeks, only 1 cavity per child developed or worsened, while 3.9 healed. Thus, simply adding vitamin D to a reasonable diet allowed most of their cavities to heal.

Diet number 3 was the most effective. This was a grain-free diet plus supplemental vitamin D. Over 26 weeks, children in this group saw an average of only 0.4 cavities form or worsen, while 4.7 healed. The Mellanbys considered that they had essentially found a cure for this disorder in its early stages.

What exactly was this diet? Here’s how it was described in the paper (note: cereals = grains):

…instead of cereals- for example, bread, oatmeal, rice, and tapioca- an increased allowance of potatoes and other vegetables, milk, fat, meat, and eggs was given. The total sugar, jam, and syrup intake was the same as before. Vitamin D was present in abundance in either cod-liver oil or irradiated ergosterol, and in egg yolk, butter, milk, etc. The diet of these children was thus rich in those factors, especially vitamin D and calcium, which experimental evidence has shown to assist calcification, and was devoid of those factors- namely, cereals- which interfere with the process.

Carbohydrate intake was reduced by almost half. Bread and oatmeal were replaced by potatoes, milk, meat, fish, eggs, butter and vegetables. The diet is reminiscent of what Dr. Weston Price used to reverse tooth decay in his dental clinic in Cleveland, although Price’s diet did include rolls made from freshly ground whole wheat. Price also identified the fat-soluble vitamin K2 MK-4 as another important factor in tooth decay reversal, which would have been abundant in Mellanby’s studies due to the dairy. The Mellanbys and Price were contemporaries and had parallel and complementary findings. The Mellanbys did not understand the role of vitamin K2 in mineral metabolism, and Price did not seem to appreciate the role of phytic acid from unsoaked whole grains in preventing mineral absorption.

Here are two sample meals provided in Dr. Mellanby’s paper. I believe the word “dinner” refers to the noon meal, and “supper” refers to the evening meal:

Breakfast- Omelette, cocoa, with milk.
Lunch- Milk.
Dinner- Potatoes, steamed minced meat, carrots, stewed fruit, milk.
Tea- Fresh fruit salad, cocoa made with milk.
Supper- Fish and potatoes fried in dripping, milk.

Breakfast- Scrambled egg, milk, fresh salad.
Dinner- Irish stew, potatoes, cabbage, stewed fruit, milk.
Tea- Minced meat warmed with bovril, green salad, milk.
Supper- Thick potato soup made with milk.

In addition, children received vitamin D daily. Here’s Dr. Mellanby’s summary of their findings:

The tests do not indicate that in order to prevent dental caries children must live on a cereal-free diet, but in association with the results of the other investigations on animals and children they do indicate that the amount of cereal eaten should be reduced, particularly during infancy and in the earlier years of life, and should be replaced by an increased consumption of milk, eggs, butter, potatoes, and other vegetables. They also indicate that a sufficiency of vitamin D and calcium should be given from birth, and before birth, by supplying a suitable diet to the pregnant mother. The teeth of the children would be well formed and more resistant to dental caries instead of being hypoplastic and badly calcified, as were those in this investigation.

If I could add something to this program, I would recommend daily tooth brushing and flossing, avoiding sugar, and rinsing the mouth with water after each meal.

This diet is capable of reversing early stage tooth decay. It will not reverse advanced decay, which requires professional dental treatment as soon as possible. It is not a substitute for dental care in general, and if you try using diet to reverse your own tooth decay, please do it under the supervision of a dentist. And while you’re there, tell her about Edward and May Mellanby!

Preventing Tooth Decay
Reversing Tooth Decay
Images of Tooth Decay Healing due to an Improved Diet
Dental Anecdotes

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Interview with a Kitavan

Kitava is a Melanesian island that has maintained an almost entirely traditional, non-industrial diet until very recently. It was the subject of a study by Dr. Staffan Lindeberg and colleagues, which I have written about many times, in which they demonstrated that Kitavans have a very low (undetectable) rate of heart attack, stroke, diabetes and overweight. Dr. Lindeberg described their diet as consisting mostly of yam, sweet potato, taro, cassava, coconut, fruit, fish and vegetables. Over the seven days that Dr. Lindeberg measured food intake, they ate 69% of their calories as carbohydrate, 21% as fat (mostly from coconut) and 10% as protein.

I recently received an e-mail from a Kitavan by the name of Job Daniel. He’s working at the Papua New Guinea Institute of Medical Research in Madang, studying the social and economic impacts of malaria and related health issues in Papua New Guinea. He recalls many details of Dr. Lindeberg’s visit to Kitava, which Dr. Lindeberg has confirmed are correct. Job generously offered to answer some of my questions about the traditional Kitavan diet. My questions are in bold, and his responses are below.

How many meals a day do Kitavans eat?
People on the island eat mostly two meals a day. But nowadays, breakfast is mainly comprised of tubers (yam and sweet potato and greens all cooked in coconut cream and salt) and dinner is the same with the inclusion of fish as protein most often. In between these two meals, lunch is seen as a light refreshment with fruits or young coconut only to mention these two popular ones. In between the morning and the evening, we mostly eat fruits as snack or lunch. Generally speaking, there are only two main meals per day, i.e breakfast and dinner.

Do Kitavans eat any fermented food?
There are fermented fruits and nuts like you’ve said for breadfruit, nuts, yams and not forgetting fish. We ferment them by using the traditional method of drying them over the fire for months. And this fermented foods last for almost one to two years without getting stale or spoiled. Food preservation is a skill inherited from our great grand fathers taking into consideration the island’s location and availability of food. Foods such as bread fruit and fish are fermented and preserved to serve as substitutes to fresh food in times of trouble or shortage. Otherwise, they’re eaten along the way.

Is this really fermentation or simply drying?
To your query about the fermentation methods we use, apart from drying food over the fire, we also use this method like the Hawaiians do with taro [poi- SJG]. For our case we bury a special kind of fruit collected from the tree and buried in the ground to ripen, which takes about 2 - 3 days. I don’t really know the English name, but we call it ‘Natu’ in vernecular. There’s also a certain nut when it falls from the tree, women collect them and peel off the rotten skin, then mumu [earth oven- SJG] them in the ground covered with leaves to protect them from burning from the extreme heat of the fire, both from the open fire on top and hot stones underneath. After a day, the nuts are removed from the mumu and loaded into very big baskets which are then shifted to the sea for fermentation. This takes a week (minimum) to ferment or be ready for consumption at last. After the fermentation period is over, i.e one week some days or two
weeks to be exact, then the nuts are finally ready for eating. The length of time it takes before the nuts are no longer edible is roughly one week.

What parts of the fish are eaten?
As islanders, we eat almost every creature and body part of a sea creature. Especially fish eggs, it is one of the favorites of children. They always prefer it burnt on the fire and consumed greedily. Every part of the fish is eaten except for the feces, gall bladder, bones and the scales.

Is food shortage really rare on Kitava?
Generally speaking it is rare. BUT sometimes we run out of food only if there is a drought and the sea is useless. Otherwise, we tend to use the preserved or fermented foods on the dryer in the kitchen. As you would understand, we have seasons and they affect the type and availability of food on the island. In the beginning of the year, we eat sweet potato, cassava and mostly tuna for protein. During mid year, before yam comes in to replace sweet potato and cassava, taro is then ready for harvest. And then yams are ready for harvesting so the food supply is continued on. OK when yams are harvested, some are eaten, some are stored away for reserve and seedlings. In this way, we don’t run out food towards the end of the year before sweet potato would be ready for harvest. So as you can see, the food supply on the island is somewhat planned by our ancestral economists where it continues throughout the year without stopping.

Do Kitavans traditionally eat pork, and if so, how often?
We do eat pork but not that often because pork meat is chiefly regarded important on the island. We only eat pork on special occasions so I’d rather say that pork is only eaten occasionally. In most cases in the middle of the year when the yams are harvested (yam harvest celebrations and towards the end of the year for certain rites and activities). Otherwise the everyday meal is always topped with fish.

How long are infants breast fed on Kitava?
Women breast feed for a minimum of 2 years. But breast feeding is again determined by the size and health situation of the baby. If the baby is looking healthy and big, it is most likely that this baby would be adopted temporarily by someone else so as to be removed from breast milk after two years of age minimum. Child care nowadays is paramount as people start to realize the importance of health and hygiene in general. But Kitavans are well known in that part of the country for their hygiene practices. They also got the provincial and district awards for a 'clean community’ in early 90s and right now, they still maintain their hygiene level and awareness.

Are there any other foods that are commonly eaten on Kitava that I might not be aware of?
Bananas, pineapple, corn and watermelons. For watermelon and corn, they are plentiful especially at this time of the year.

Thanks for your help, Job! I know many people will appreciate reading these responses.

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Diet-Heart Controlled Trials: a New Literature Review

Many controlled studies have measured the cardiovascular effects of replacing animal (“saturated”) fats with seed oils (predominantly the omega-6 polyunsaturated fat linoleic acid) in humans. A number of these studies recorded heart attacks and total mortality during the following 1-8 years. Several investigators have done meta-analyses (literature reviews) to try to tease out overall conclusions from these studies.

I’m pleased to point out a new meta-analysis of these controlled trials by Dr. Christopher Ramsden and colleagues (1). This paper finally cleans up the mess that previous meta-analyses have made of the diet-heart literature. One recent paper in particular by Dr. Dariush Mozaffarian and colleagues concluded that overall, the controlled trials show that replacing animal fat with linoleic acid (LA)-rich seed oils reduces heart attack risk (2). I disagreed strongly with their conclusion because I felt their methods were faulty (3).

Dr. Ramsden and colleagues pointed out several fundamental flaws in the review paper by Dr. Mozaffarian and colleagues, as well as in the prevailing interpretation of these studies in the scientific literature in general. These overlap with the concerns that I voiced in my post (4):

1. Omission of unfavorable studies, including the Rose corn oil trial and the Sydney diet-heart trial.
2. Inclusion of weak trials with major confounding variables, such as the Finnish mental hospital trial.
3. Failure to distinguish between omega-6 and omega-3 fatty acids.
4. Failure to acknowledge that seed oils often replaced large quantities of industrial trans fats in addition to animal fat in these trials.
   

Dr. Ramsden and colleagues accounted for all of these factors in their analysis, which has never been done before. They chose inclusion criteria* that made sense, and stuck with them. In addition, they did an impressive amount of historical work, digging up old unpublished data from these trials to determine the exact composition of the control and experimental diets. The paper is published in the British Journal of Nutrition, an excellent journal, and overall is written in a scientific and professional manner.

What did they find?

• Interventions that replaced animal and trans fat with seed oils that were rich in LA but low in omega-3 caused a non-significant trend toward increased heart attacks (13% increase) and overall mortality.
  
• Interventions that replaced animal and trans fat with a combination of LA and omega-3 fats significantly reduced heart attacks (by 22%). The numbers for total mortality followed a similar trend.

In other words, LA-rich seed oils do not prevent heart attacks (and may actually promote them), but correcting an omega-3 deficiency and reducing industrial trans fat intake may be protective. This is similar to what I’ve been saying for a while now, based on my own interpretation of the same studies and others. However, Dr. Ramsden and colleagues have taken the idea to a new level by their thorough and sophisticated detective work and analysis. For example, I didn’t realize that in virtually all of these controlled trials, the intervention group reduced its trans fat intake substantially in addition to reducing animal fat. From the paper:

…experimental diets replaced common ‘hard’ margarines, industrial shortenings and other sources of [trans fat] in all seven of the [controlled trials] included in the meta-analysis by Mozaffarian et al. The mean estimated [trans fat] content of the seven control diets was 3·0 [% of calories] (range 1·5–9·6 [%]).
…the displacement of [trans fat], rather than the substitution of mixed n-3/n-6 [polyunsaturated fat] for [saturated fat], may account for some or all of the 22% reduction in non-fatal [heart attacks and heart attack] death in our meta-analysis. By contrast, the increased [heart attack] risks from n-6 specific [polyunsaturated fat] diets in our meta-analysis may be underestimated as n-6 [polyunsaturated fat] also replaced substantial quantities of [trans fat] (Table 3). The consistent trends towards increased [heart attack] risk of n-6 specific [polyunsaturated fat] diets may have become significant if the n-6 [polyunsaturated fat] replaced only [saturated fat], instead of a combination of [saturated fat] and [trans fat].

In other words, it looks like trans fat is probably the issue, not animal fat, but these trials replaced both simultaneously so we can’t know for sure. I will note here that trans fat does not generally promote atherosclerosis (thickening and hardening of arteries) in animal models, so if it does truly increase heart attack risk as many studies suggest, it’s probably through a mechanism that is independent of atherosclerosis.

The article also contains an excellent discussion of the Finnish mental hospital trial (5, 6) and why it was excluded from the meta-analysis, in which Dr. Ramsden and colleagues point out major design flaws, some of which I was not aware of. For example, trans fat intake was on average 13 times higher in the control groups than in the experimental groups. In addition, one of the control groups received more than twice as much of the antipsychotic drug thioridazine, which is known to be highly toxic to the heart, as any other group. Ouch. I’m glad to see this study finally discussed in an open and honest manner. I discussed my own problems with the Finnish trial in an earlier post (7).

I was also glad to see an open discussion of the Oslo Diet-heart study (8), in which diet changes led to a reduction in heart attack risk over five years. Dr. Mozaffarian and colleagues included it in their analysis as if it were a controlled trial in which animal fat was replaced by seed oils only. In reality, the investigators changed many variables at once, which I had also pointed out in my critique of Dr. Mozaffarian’s meta-analysis (9). Here’s what Dr. Ramsden and colleagues had to say about it:

First, experimental dieters were instructed to substitute fish, shellfish and ‘whale beef’ for meats and eggs, and were actually supplied with ‘considerable quantities of Norwegian sardines canned in cod liver oil, which proved to be popular as a bread spread’(32)… Second, the experimental group consumed massive amounts of soybean oil, which provided large quantities of both LA (15·6 en %) and ALA (2·7 en %). ALA consumption was about 4·5 times average US intake(42), or about twelve typical flax oil pills (1 g pill ¼ 560 mg ALA) per d. In addition, the fish and cod liver oil consumption provided Oslo (598N latitude) dieters with 610 IU (15·25 mg) of daily vitamin D3, recently linked to lower blood pressure, plaque stabilisation, and reduced [heart attack risk] (64). Furthermore, experimental dieters were encouraged to eat more nuts, fruits, and vegetables; to limit animal fats; and to restrict their intake of refined grains and sugar.

trans fat intake was also reduced substantially by excluding margarine in the experimental group. Other review papers have used this trial as a justification to replace animal fat with seed oils. Hmm… The only reason they get away with this is because the trial was published in 1966 and almost no one today has actually read it.

One criticism I have of Dr. Ramsden’s paper is that they used the Oslo trial in their analysis, despite the major limitation described above. However, they were extremely open about it and discussed the problem in detail. Furthermore, the overall result would have been essentially the same even if they had excluded the Oslo trial from the analysis.

Overall, the paper is an excellent addition to the literature, and I hope it will bring a new level of sophistication to the dialogue on dietary prevention of cardiovascular disease. In the meantime, brace yourselves for an avalanche of criticism from the seed oil brigade.


* Guidelines that determine which studies to include in the analysis. For example, you want to exclude any study that wasn’t randomized, because it will not be interpretable from a statistical standpoint. You also want to exclude trials where major variables differ between groups besides the specific variable you’re trying to test. The Finnish mental hospital trial fails by both criteria.

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