Sunday, 4 January 2009

Everybody knows.........Part 2

.........that ketogenic diets like the Atkins diet destroy your kidneys and rot your bones, right? Wrong!
.........that the Atkins diet causes ketoacidosis which is a very dangerous condition requiring urgent hospital treatment, right? Wrong!

There's a lot of nonsense spoken about ketogenic diets by people who really should know better. I suspect that they have been taught wrongly at uni or med school as per the quote in Everybody knows.........Part 1.

Benign Dietary Ketosis is NOT Ketoacidosis.

Consider the following four cases:- Note: Figures are from "Introduction to Nutrition and Metabolism" By David A Bender (Senior Lecturer in Biochemistry, UCL)

1) Healthy human, fed state: Glycogen stores are replete. Serum glucose = ~5.5mmol/L. Serum fatty acids = ~0.3mmol/L. Serum ketones = 0mmol/L. No gluconeogenesis is taking place. Amino acid pool is replete. Cortisol level is normal so there is no loss of muscle mass.

2) Healthy human, fasting for 7 days: Glycogen stores are depleted. Serum glucose falls to ~3.5mmol/L. Serum fatty acids rise to ~1.2mmol/L. Serum ketones (mainly D-3-hydroxybutyrate) rise to ~4.5mmol/L (not high enough to cause acidosis). Gluconeogenesis is occurring. Amino acid pool is depleted. Cortisol level is high, causing slow loss of muscle mass. This is bad ketosis.

3) Healthy human, low-carbohydrate diet: Glycogen stores are depleted. Serum glucose falls to ~5mmol/L.
Serum fatty acids rise to ~1.2mmol/L. Serum ketones (mainly D-3-hydroxybutyrate) rise to ~4.5mmol/L (not high enough to cause acidosis). Gluconeogenesis is occurring. Amino acid pool is replete (due to protein intake). Cortisol level is normal so there is no loss of muscle mass. This is good ketosis.

4) Human with untreated type 1 diabetes: Glycogen stores are depleted. Due to lack of insulin, the Glu-T4 transporters in cells cannot move to the surface so glucose cannot enter cells. Serum glucose = >20mmol/L. This causes major damage to kidneys, arteries, eyes, nerves etc by cross-linking with proteins (glycation) resulting in major disability and eventual death. As the body is forced to run on fatty acids & ketones, metabolic processes are out of control and ketones rise to much higher levels than in 2) or 3) (I don't know how high exactly) resulting in acidosis and eventual death. This is ketoacidosis.

Conclusion: Low-carbohydrate, very-low-carbohydrate & ketogenic dieting is similar to fasting in that serum glucose levels are lower than normal and glycogen stores are depleted. The body is encouraged to burn less glucose and more fatty acids & ketones, but the metabolic processes are all under control. The big difference between low-carbohydrate dieting and fasting is in the amino acid pool and cortisol levels.

4 comments:

Dr. Art Ayers said...

You make it sound so straightforward and simple, after you clear away the typical misinformation.
One little detail: the distinction between glycosylation and glycation. Both are involved, but I think that you mean glycation, as in advanced glycation end products (AGE). Glycosylation is an information-rich, enzyme-catalyzed process, whereas glucose glycation is just determined by concentration (perhaps catalyzed by fructose.)
The generalizations you discuss are the physiology after the nutrients reach the blood. The big unknown is the interactions of food (prebiotics) and gut flora (probiotics) that determine the chemistry at the surface of the intestines. That's where all of the bowel diseases, inflammation and immune system disruption originate. Are allergies, arthritis and Alzheimer's just unhappy gut flora?
Happy New Year.

Nigeepoo said...

You say tomato. I say tomato. Let's call the whole thing off! I think that words have slightly different meanings depending upon which side of the "pond" you live. Over here, we call HbA1c glycosylated haemoglobin.

Happy New Year! Nige.

Dr. Art Ayers said...

Over here in Idaho, if it weighs a pound, has a richly russeted skin, can be covered with chives on top of sour cream and butter, and can produce glycated hemoglobin in a family of six, we call it a baked potato and not a tomato.
....and remember that I determined that the glucan elicitor structure was a 1,3-1,6 beta glucan...and I was the first one to isolate the cellobiose dehydrogenase.
...so you should say glycated hemoglobin, just because I said so!
Besides, the chemical structures and properties of glycated vs. glycosylated glucose are entirely different. Saying glycosylated hemoglobin is like saying that fructose is safe for diabetics, because it doesn't raise blood sugar.
When you are so close to perfection, why not make this one little change?
Cheers for 2009

Nigel Kinbrum B.Sc.(Hons) Eng said...

Oh, all right then!
Nige.