Tuesday, June 05, 2007

Living on the isolated island of Kitava

On the island of Kitava there are coconuts, sweet potatoes, yams, a few other starches and fish to eat. This leads to an interesting diet. The estimated percentages of energy from protein, fat and carbohydrates are 10%, 21% and 69% in Kitava. Most of the fat is saturated. Three quarters of the population smoke.

Obviously high carb eating should mean catastrophic blood lipids. You would expect low HDL cholesterol and high triglycerides. And this is exactly what you find. HDL-C down at 1.1mmol/l (some as low as 0.5mmol/l) and triglycerides up at 1.7mmol/l (some up at 3.0mmol/l). Not a good ratio. They smoke too. Must be a hotbed of cardiovascular disease. Especially as some of the total cholesterol readings were up around the (gasp) 7.0mmol/l mark. Pravastatin in the local well water is the obvious answer.

Except they have no heart disease. On a diet of 70% carbohydrate. Life expectancy, ignoring neonatal mortality which appears to be high, is around seventy years. That's without any medical facilities. How do they do it?

BTW there were two amusing comments in the discussion of this paper. The best was:

"Evaluation of TGs and HDL-C as cardiovascular risk factors must thus be restricted to the study population"

I'll rephrase that. In Sweden "bad" lipds (and smoking!) are BAD. Not so in Kitava, here "bad" lipids are not bad. They're a product of diet composition. As there is no heart disease they must be good!

So what's happening? Do horrible triglycerides block to your arteries like hot beef fat blocks a cold sewer in Sweden, but then by magic they become non sticky in Kitava? Go figure. Hint, maybe it's not the lipids that trigger the blocked arteries.

Second comment was

"our findings lend no support to the concept that a very high intake of carbohydrates (>60% of energy) increases the risk of cardiovascular disease"

ie living on low fat doughnuts is safe for everyone. Everyone. No suggestion that you have to live in Kitava for this to be the case. So if you eat a junk diet in Sweden and get Kitava lipids in Sweden plus smoke Kitava cigarettes, will you be OK? Somehow I doubt it!

So why are the Kitavans free of heart disease?

Their average fasting glucose is 3.7mmol/l and their fasting insulin 4.0 microU/ml. They do not have any features of metabolic syndrome! Except the lipids of course. Despite eating appalling quantities of carbohydrate. If we define metabolic syndrome as carbohydrate intolerance how do the Kitavans manage this?

I think that this goes back to the main limit on population growth, which is food. Daniel Quinn is the best source of information on this subject. As the Kitavans live with minimal Western food it seems they must be living within the food production capacity of their island. The basic principle is that populations grow to the limit set by their food supply. On Kitava you cannot make babies out of thin air. No extra yams means no extra people. The fluctuations in food and population must mean there are fluctuations in hunger and plenty, but if populations really do expand to the limits of food supply, the island location must ultimately apply calorie restriction. On average.

Ad lib food on a global basis has resulted in a population explosion. On an individual basis it results in a waistline explosion. As carbohydrate is cheap, addictive and hunger generating it is what usually fuels the metabolic syndrome, hence "bad" lipids are associated with metabolic syndrome as carbohydrates are the usual tool of excess calorie intake.

Calorie restriction, intermittent fasting and once daily eating all limit the development of insulin resistance and hyperglycaemia, pretty well independent of macro nutrient ratio. On Kitava there must be accidental calorie restriction as the population is in equilibrium with with a fixed food supply, hence no metabolic syndrome. Despite the "bad" lipids, which merely reflect the composition of their restricted diet.

Can we all do the same? Probably yes, but having read about life on the calorie restricted optimal nutrition (CRON) diet this is definitely not for me. Licking the plate clean because the sauce is delicious is one thing. Doing it because you are starving is quite another! No, there does appear to be a better way.

Eating a ketogenic diet appears to mimic calorie restriction. Ketosis limits appetite so allows modest calorie restriction without any hunger. Forget any drug which may be developed to mimic eating a high fat diet. Better pile on the lard, dump the "healthy" carbohydrate and generate a few ketone bodies. Enough to keep your energy intake reasonable without that desperate dreaming of food which is reputed to go with CRON.

Or you can starve on a balanced diet.

Peter

12 comments:

migraineur said...

Oh, my goodness - that article on CRON. "Orange hands, aren't they pretty?" No, they're not.

Kayaman said...

I'm aware this is an older post, and you've since written much about other causes, but do you still consider "calorie restriction" as a possible explanation for their cardiovascular health? Here's another document on the Kitava study indicating their average daily calorie intake is 9200kJ (2,198 kCal).

Peter said...

Hi Kayaman,

Yes, I still think it's an aspect, but alongside D3, fish derived lipids, saturation of what bulk fat was eaten and consumption of real food. This game is a learning process...

It's interesting that Lindeberg cites differing caloric intakes in different papers. Food availability must vary and it's lean times which limit population...

Peter

mtflight said...

How about this ad-hoc hypothesis (added to the vitamin D3):

Kitavans have low PUFA intake, and their decent blood sugar (from fasting/CR or whatever) does not cause damage to the endothelial glycoccalyx. Furthermore their insulin level is too low to damage/harden the arteries.

Peter said...

I'd love this to be the case but we only have fasting bloods and no HbA1s/fructosamine. But I'd bet they're good, ditto post prandial insulins.

Peter

Jeremiah said...
This comment has been removed by the author.
Jeremiah said...

On the topic of calorie restriction...

Fruit flies, while animals, are nonetheless quite different from humans. Still, I think you might find this study interesting, Peter:

Fruit Fly DR Study

In particular, the abstract:

"Dietary restriction (DR) extends life span in diverse organisms, including mammals, and common mechanisms may be at work. DR is often known as calorie restriction, because it has been suggested that reduction of calories, rather than of particular nutrients in the diet, mediates extension of life span in rodents. We here demonstrate that extension of life span by DR in Drosophila is not attributable to the reduction in calorie intake. Reduction of either dietary yeast or sugar can reduce mortality and extend life span, but by an amount that is unrelated to the calorie content of the food, and with yeast having a much greater effect per calorie than does sugar. Calorie intake is therefore not the key factor in the reduction of mortality rate by DR in this species."

and

Figure 3

Now, the researchers stated that the only source of protein and lipid for the flies is from yeast powder, yielding confounding variables (is it the restriction of protein or fat or both that really helps...I think I know what the Hyperlipid response would be).

Also, the researchers extrapolated their findings to rodents, and I doubt it would be unfounded to suppose they have assumptions about humans as well. Restrict sugar and protein if you are a fruit fly, and you'll live quite long. Restrict sugar and protein if you are a human and you___________ (who wants to fill in the blank?)

Heather Twist said...

They also live on a very low iron diet. It would be interesting to see what their ferritin levels are. There are a number of populations that eat a lot of fat and a lot of carbs, but they don't eat either wheat or beef, and they don't get iron-fortified foods. Wheat messes up gut permeability, and beef is high-heme iron (and helps other iron absorb). High ferritin levels are very much associated with heart disease: iron oxidizes blood vessels and makes the other oxidants worse. Saturated fat helps iron absorb, but I think it gets the bad rap because it's usually from beef, so you get a large shot of iron when you eat a fatty steak (though drinking tea with the steak would help prevent that, or red wine).

Peter said...

Hi Heather,

There are a lot of factors which interact here an I gathered a few of them together in the posts on diabetes, cirrhosis, iron, gluten and PUFA. But you should be correct. The only fly in the ointment is the anecdote from Lutz that blood Hb drops on LC when the level is very high at the start, without iron restriction. How many of his patients had haemochromatosis he never checked. I've never chased why this should be or if there is any logic even. One thing which came to mind about this is that, in rats fed alcohol and fish oil to get cirrhosis, the iron content of their liver was a lot higher than controls. Can't remember which post or paper it was in, but iron may be secondary as well as primary. Hope that's not too gibberish. Sounds a bit that way to me!

I was going to develop this in to a post on haemochromatosis and diabetes but it fell by the wayside, as so many posts do!

Peter

Peter said...

Hi Jeremiah from back in 2008,

I've no idea how I missed this comment but I did! Apologies. The study IS interesting and I think I have the full text, which is on file for another post, some day!

Peter

Heather Twist said...

I've done CRON and also intermittent fasting, and I think both affect iron levels too. So MANY things affect iron levels: which is why I think it basically gets overlooked. It's not just a matter of "how much iron is in food". It depends on the entire makeup of the meal.

In India, the iron content of the food is pretty high, but because they also have tea and turmeric, and maybe because so little of the iron comes from beef, they tend to have low ferritin levels. The lactoferrin in whey chelates iron, so milk-drinkers are somewhat protected, and whole grain fiber blocks it from being absorbed.

Some seafood is pretty high in iron, but ingesting seafood isn't associated with high blood iron. And people who have either parasites or celiac don't get high iron levels regardless. People with hemochromatosis have a certain gene: but people without that gene still get high ferritin levels. Even though in theory, they should not, because iron levels are supposed to be tightly regulated. Interestingly T2 diabetes is now even showing up in horses, when they are fed iron-enriched feed.

Anyway, I'd like to see studies where they lower ferritin levels and see what happens to insulin sensitivity. It's already been done some:

http://diabetes.diabetesjournals.org/content/51/4/1000.full

AubergineInTexas said...

I'm curious as to what their magnesium intake looks like. I've read that around seventy percent of Americans are magnesium deficient. Magnesium is part of 300 processes in the body including Sugar Uptake, Heart Function, and Brain Function...

Could there be a link between Magnesium Deficiency and Metabolic Syndrome, Heart Disease and who knows how many brain disfunctions big pharma tells us it has the answer for? Y'think?