Tuesday, October 31, 2006

Now Alzheimer's Disease

There is a laboratory mouse strain which has been genetically engineered to develop Alzheimer's Disease. Not nice for the mouse, but very useful for research purposes. If you have a look at this abstract, it suggests that limiting calorie intake completely protects against Alzheimer's in this strain of mouse. So why does Alzheimer's still progress in humans, even when weight maintenance becomes very difficult due to the effects of the disease?

Well, the abstract is somewhat disingenuous. It is spectacularly silent about the type of calorie restriction used. Luckily the full paper is available as a pdf at the click of a link. Be warned though, this paper is about as readable as a telephone directory, in the dark, but not as well written. You have to read the abstract, the introduction, the materials and methods until finally you get to the results section. Then you find the best kept secret so far. It's on line three of the results.

Carbohydrate restriction.

OK, yes these animals were calorie restricted, but the ONLY calories removed were carbohydrate.

The discussion actually uses the C word quite a lot. That is, it mentions carbohydrate restriction rather than calorie restriction. But the final paragraph, the sum it all up paragraph, the "this is what we found" paragraph, drops right back to calorie restriction.

Can you imagine the outcry if this group had come up with the headline "Atkins type diet provides 100% protection against Alzheimer's disease in highly susceptible mouse model"? You would actually have heard the "pop" as their funding evaporated. Anyway, it was only mice.

What about humans? No one has done the study yet, though one is planned by the group that did the Parkinson's work I mentioned yesterday. What has already been done is the flip side. That is, increasing the carbohydrate intake of nursing home patients with Alzheimer's disease. This was done to try to limit their weight loss. Adding extra carbohydrate resulted in "increased carbohydrate preference, poorer memory and increased aberrant motor behavior".

And it made them fatter too.


Monday, October 30, 2006

Parkinson's Disease

There is a good summary of what to expect from Parkinson's Disease available at the USA based National Parkinson's Foundation website. Briefly, the problem is incurable, progressive and not particularly pleasant. This is the story of a Parkinson's sufferer who was given the possibility of modifying the usual outcome and the pressures which influenced her choice.

Last year, 2005, there was a report in the medical journal Neurology. It described a pilot study of a special diet for the management of Parkinson's Disease. The whole trial only lasted 28 days and only involved seven people, of whom only five completed the full month. In these five there was an improvement in their Parkinson's disease. Keep in mind Parkinson's is supposed to be irreversible... By the way, a small trial like this is VERY significant. If you have a therapy which makes a big difference it will show in a small trial. If your trial needs 100,000 people to show a minor benefit, the benefit for an isolated individual will clearly be pretty well undetectable.

That's interesting in its own right. But much more interesting was the interview with one of the participants published in USA Today. The article tells us what she ate and mentions that she lost 26lb. The study lasted 28 days. That is an impressive weight loss. So what sort of a diet combines modest reversal of an irreversible disease with dramatic weight loss? The diet is what is known as a ketogenic diet. Just a little meat or eggs each day, plus lots and lots of fat. No carbohydrate. Under these conditions the liver manufactures large quantities of ketone bodies, which are an excellent fuel for the brain and easily able to replace at least half of the daily glucose which is usually considered "essential".

It appears that if you feed dopaminergic brain cells on ketone bodies they stop dying, and maybe the sick-but-not-yet-dead ones recover. The brain likes ketone bodies. Why did the weight loss happen? It is self evident that eating fat makes you fat. Just ask any dietician. It's obvious. Very obvious. But not true. Ketogenic diets are excellent for weight loss. The physiology is logical and unimportant here, but minimal carbohydrate intake is essential for it to work.

The USA Today interview finished with the plan for the next phase of the investigation, using a less extreme ketogenic diet. Ketogenic diets are not easy to adhere to. The interviewee had been invited to take part in this next phase but she had refused. That would be fair enough for a minor problem. Having flicked through the description of advanced Parkinson's disease, I personally would want a serious reason to discontinue a diet which might protect me from the ravages described.

What is so wrong with a ketogenic diet that this lady couldn't stand it?

No carrots were allowed.

There is at least one person out there who would rather allow progression of their Parkinson's Disease than give up nice crispy raw carrots.

Carrots. Raw. And pass me the l-dopa please.