hi Adrian,
Most of the well-planned low carbohydrate programs provide enough carbohydrates - in the form of vegetables, low-sugar fruits, dairy products and/or small amouts of whole grains - in the daily plan to yield sufficient glucose for brain functioning. As well, the body can use dietary protein to manufacture glucose.
Perhaps you're thinking of
ketogenic diets, where the carbohydrate intake is severely restricted for a longterm, ongoing basis. Even the Atkins program only restricts carb intake to below 20 grams per day for the initial 2 week Induction period.
Yes, the brain uses glucose as fuel when it's available. However, the brain functions very well on ketones, in the ABSENCE of glucose.
Here is a quote from the Ketogenic Diet Summary -- you may wish to read the rest of this article, as well as more information at
http://www.keto.org/
Quote:
A Ketogenic Diet is a muscle-sparing fat-loss diet that works by forcing the body into ketosis through carbohydrate deprivation. Ketosis is a state where the body converts fat into ketones that the brain can use for fuel when glucose (carbohydrates) are in short supply. .........
It's a common misconception, even among doctors, that the brain can only use glucose for fuel. In actuality, it can burn either glucose or ketones, but under normal circumstances ketones aren't produced by the body. Most of the time, everyone in the world has their brain burning glucose. The only time the body would create and burn ketones in large quantities is when insufficient glucose is available as a fuel source. The way to make glucose (a basic sugar) unavailable, is to simply restrict carbohydrate consumption to 30g/day or less. For example, if you stop eating all carbs at, say, 6:00 PM on Sunday, and then do a heavy weightlifting workout Monday and Tuesday, this will deplete your liver and bloodstream of and glucose, and your muscles of glycogen. At that point, your liver will start producing ketones, so the brain has a fuel to work with, and if you consume no carbohydrates at all, the body will start converting protein into glucose as it will still need at least 30g glucose per day.
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Ketogenic diets are used by training athletes and body-builders for the efficient fat-burning. Ketogenic diets are also used in young children for controlling intractable epilepsy seizures that are unresponsive to the usual drug therapies. Infants as young as one year old manage quite well, with no brain deficit -- often kids are on such a diet for years at a time.
You may wish to check out the Epilepsy Foundation of America (EFA)
http://www.efa.org/answerplace/epusa/ketogenic.html and
http://www.efa.org/answerplace/epUSA/newketogenic.html
where you'll find several up to date articles and more information on this subject.
For an excellent explanation of the difference between diet-induced ketosis, and the ketoacidosis of extreme starvation and diabetes mellitus, check out this article
http://www.lowcarb.org/ketosis.html
And, finally, a handful of article abstracts on the effects of ketosis on rat's brains
http://www.lowcarb.org/josh_yelon/topic5.html
and
http://www.lowcarb.org/josh_yelon/topic11.html
Hope this answers your questions. And congratulations on your own weight loss thus far ..
Doreen