Paleo and fructose

I've had a couple of queries which tie together neatly and involved some detailed paper reading, so I thought I'd throw them out for general discussion.

A friend is struggling to keep adequate carb intake on a starch free diet. Anyone who has tried this will soon run in to kilos of cabbage. The easiest answer is fruit and honey but this then means about half of your carbohydrate calories are going to come from fructose. Does this matter?

The other query was from David. He looked through Stephan's discussion of this paper and noted the huge intake of fructose from just about every modern fruit or fruit juice that anyone can imagine a hunter gatherer gathering. You know how it goes, gathering was good that day! This is the same quandary as the first query but worse. For a LC paleo person to eat a little fructose is one thing, to eat nearly quarter of a kilo (dry weight!) of fruit and juice to stay politically correct is pushing it a bit. Yet the results of the study are good. How come? Here's the menu.




The column on the right gives the bit we want. Ignore diets called ramp 1,2 and 3. You can see "Paleo diet" is quite fructose rich. Before we can get on to discuss this, a problem needs to be addressed. I'm either going senile or there is a double typo. It's here



Aside: Look at the HDL. Zilch increase. I'm amazed it didn't drop with all those PUFA!


Fasting glucose pre study is 18mmol/l and on the paleo diet it's 17mmol/l. These are wrong. Certainly for people described as healthy. The HOMA scores allow back calculation, first converting the insulin from the nice pmol/l quoted to grubby microIU/ml needed (HOMA seems to mix IU and SI units...) but even this gives a fasting BG of 7.2mmol/l... Still not exactly normal! And it didn't normalise on the paleo fructose diet either. So either it's a typo, my math is useless (that WOULD be embarrassing!) or these folks had fasting hyperglycaemia. Take your pick!

OK, back to working out what is going on. Here is the key:




If you look at the HOMA-change graph Figure 2 you can see that 4 people (upper left) were normal (HOMA <2), two people were almost normal (HOMA<4) and two were frankly pre diabetic (HOMA 6 and 7.5). In my terms rather than ADA classification. None of the normal or near normal people improved HOMA much on the diet. Why? You can't drop HOMA below normal as it's already normal.

I'd guess the people at the upper left had a moderate American fructose intake pre paleo diet and probably didn't change this much on the honey and carrot juice in the study diet. They started normal, they stayed normal and we can forget about them. The two people with IR on the lower right of the graph are the two who did all of the improving. This certainly applies to HOMA scores but, because we don't have the data broken down by individuals for anything else, we cannot see if that was the case for all improvements in all of the other parameters looked at. I think it might be. Is there anything to support this idea?


The thing to look at is the food intake pre and during diet.





People entered the study on a self selected diet averaging 254g/d carbohydrate. But the standard deviation is 128g/d. The rule of thumb is that three standard deviations include about 99% of the population. In the USA I doubt many people with a BMI of 27 were eating below 200g/d of carbohydrate, so a few individuals will have to have been eating much more than 254g to get that big SD. The easiest way to get your carbohydrate intake up towards three SDs above the mean of 254g [ie 254+(3X128)= 638g/d] is to drink Big Gulps. Big Gulps provide 800kcal per serving of HFCS calories. This has to be a guess as the results do not break carbs down by fructose. Sigh.

On the paleo diet food and drink intake was tightly controlled and everyone will have been consuming near identical fructose. The fall in mean carb intake from SAD to the paleo diet is only 5g/d, but the SD of the drop is 126, essentially the same as the 128 of the pre study carb intake's SD. Taking people from a wide range of macronutrient intakes and putting them all on the same diet will do this. The total carb intake during the paleo diet is 254 minus 5, ie 249g/d but this will have a SD of near zero, because all of the subjects were on university prepared meals of precisely controlled calories and composition for the study.

Anyone who is used obtaining large numbers of calories by drinking Big Gulps will have had a marked reduction in fructose intake on this paleo diet.

From hepatically crippling fructose to liveable with, if not ideal, fructose.

So, in answer to the question, yes, the diet is high in fructose by my standards. But my guess is that it is markedly reduced in fructose intake for those two people who did all of the improving in terms of insulin sensitivity. Most of the other changes will follow on from this specific change. We are very lucky to have Figure 3 to allow us to tease this out! Few papers include individual data nowadays, though it was quite common in early research (1950s etc).

That's how I see this paleo diet. Good, but could do better.

Two asides:

The second aspect is fatty acids. The PUFA increased, which should have worsened liver damage, but omega 3s were added in modest amounts, which should have ameliorated liver damage. Fatty liver from omega threes is unheard of in remotely recognisable human diets. End result of fatty acid manipulation; probably neutral. They didn't hurt anyone. Good.

Finally; endotoxin. Endotoxin is needed to convert the relatively benign condition of NAFLD to the much more serious and cirrhosing NASH. Endotoxin uptake is markedly facilitated by gut damage. Gluten is the primary opener of intestinal tight junctions. There were no grains in this diet. That should reduce liver insult. Liver insulin resistance is primary to metabolic syndrome.




Back to the first query: For those wanting to avoid ketosis when unable to tolerate starch. Some fruit seems relatively benign. You can get away with moderate amounts of fructose for years before it gets you, probably half a lifetime. Unless you make Big Gulps your only significant source of calories.

It really does seem possible to break your liver in childhood if you really work at the Big Gulps.

Peter