Fructose, Glycation and AGE formation
by Dean Pomerleau
(Pittsburgh, PA)
Dean Pomerleau's Question:
Andrew,
My biggest reservation about adopting a high-carb, low-fat, fruit-based vegan diet by eliminating/reducing the cooked starches I eat now (sweet potatoes, quinoa, barley, black beans) is the issue of fructose, glycation and AGE (advanced glycation end products) formation.
The scientific literature seems to show that fructose results in ~10x the rate of glycation compared with glucose.
Granted, some of the evidence is in-vitro, and some of the animals studies used refined fructose, and human studies have often used high fructose corn syrup, not fructose from whole fruit.
But I would feel much more comfortable ramping up my fruit intake if I knew I wasn't flooding my body with AGEs as a result of eating lots of fruit.
Do you know of any good evidence that a high fruit (and therefore high fructose) diet doesn't results in increased AGE formation relative to a high carb diet with less fruit and more glucose-rich plant foods?
If not, why aren't you concerned about it?
Many extremely health conscious individuals (including me) limit fruit intake (often to to just berries), based on this concern about fructose and AGE formation, So lack of good scientific evidence to the contrary seems to be preventing wider adoption of the high-carb, raw vegan lifestyle.
Thanks so much, and keep up the good work!
Andrew's Answer:
Hi Dean.
I think you too quickly brush off the best reason to disregard the existing studies linking fructose with ill health, and, specifically, with AGE levels - pretty much none of them use humans consuming whole, ripe, unrefined fruits as the basis of their studies, but instead rely on in vitro studies or heavily refined fructose, high fructose corn syrup, etc.
When you divorce an element from its nutrient package and attempt to feed it into a system designed to handle the whole package, it's more surprising when you avoid bad outcomes than when you get them.
Take the devastating results of beta carotene supplementation as your arch example.
But as you point out (in your separate email to me), in studies where we would expect to see the increase AGE formation wreaking havoc on the human body if this was indeed the result of whole fruit consumption, we see nothing of the kind. In fact, we see the opposite - healthier, more disease-resistant people.
Circulating AGEs in the body are correlated with damage to the eyes, and specifically to the onset of diabetic retinopathy (1). But in a study out of Japan, those who ate the most fruit had the least incidence of the disease (2).
The Second Best Reason?
I challenge you to find a well-conducted, peer-reviewed study that doesn't correlate an increased consumption of whole fruits with lower rates of disease, lower body weights, and longer life spans.
The Third Best Reason:
This one is entirely personal. I've started experimenting with low fat raw food diet in 2005, and starting eating entirely raw in 2007. Since then my health has been far better than everyone else I know. I don't get sick, my physical fitness has improved in every capacity, and I simply feel amazing.
If fructose was really damaging me, I think I would have felt the effects by now.
In this light, it's hard for me to believe that I'm overflowing with AGEs.
Deluding Yourself About Berries
Finally, although fruits have wildly varying amounts of fructose, neither wild fruit, nor berries, are particularly low in fructose or otherwise radically distinct from the nutritional composition of other fruit. This is a matter I discuss in Raw Food Weight Loss And Vitality.
I also go into more detail about fructose here.
You can find answers to more than 170 questions readers have asked me about the raw food diet here.
Sources:(1) Milne, R. Et al. "Advanced glycation end products and diabetic retinopathy." Amino Acids. 2011 Sep 11.
(2) Tanaka, S. Et al. "Fruit intake and incident diabetic retinopathy with type 2 diabetes." Epidemiology. 2013 Mar;24(2):204-11.
