High fructose diet hampers memory! Well, sort of. It was a combination study looking at the effects of deficiencies in n-3 fatty acids (omega-3?) and added fructose. This changed insulin levels and other chemicals I’m not familiar with, which isn’t a big surprise and not the point of the headlines. The authors posit that excess insulin monkeys with brain membrane fluidity (at minimum—have a look for yourself).
I skipped the chemical level details to go to the good stuff. They divided the rats into 4 samples, with 6 rats in each sample. (Alarm bells) Some got normal diets and some got low omega-3 diets. Each of these groups was further divided into sets that got extra fructose and not. The difference in weight gain was minor. Before the diet, the groups were tested on a maze. Before you ask:
All surfaces were routinely cleaned before and after each trial to eliminate possible olfactory cues from preceding animals.
That’s good, but I wonder how sensitive rat noses are. (Maybe high sugar levels decreases sensitivity?)
They measured "latency" time, which I suppose this is how long it took the rats to run the maze. They trained the rats on the maze for 5 days, gave them 6 weeks of the special diet, and then tested them again one day. Their result was that the high omega-3 diet without extra fructose rats ran at pretty much the same rate as the last time, those with low omega-3 or high fructose didn’t run the maze quite as fast, and those with both low omega-3 and high fructose even less rapidly. The lights over the maze were bright, to encourage the rats to find a way out quickly. (Maybe high-fructose diets leave rats feeling more laid-back and not so irritated by light?)
Figure 1 is very odd. A shows that all rats tended to run the maze in about the same time by day 5: about 40 seconds if I read the graph correctly. B shows that the good diet rats ran it in 20 seconds on the average 6 weeks later. Something doesn’t add up.
Also notice how huge the errors are in A until they converge by day 4. One sample averaged twice as fast on day 4 as on day 5. Those large errors are consistent with the authors’ interpretation of forgetfulness, since one sees large errors on the 6-week later test samples also.
Figure 2 shows the correlation between serum triglyceride levels (and insulin resistance) and the "latency". Except for one flier (is it the same animal both times?) the high and low omega-3 diet (both low fructose) rats seem to have the same speed running the maze. It is interesting that the insulin resistance level seems to have a cleaner correlation with "latency" than the serum levels do. I suppose that’s consistent with the authors’ interpretation that excess insulin changes the brain, so the overall resistance, a proxy for the history of insulin exposure, would be more important than the triglyceride levels of the moment.
This is flawed, and does not justify the headlines. It needs more work, and to address some of the alternative interpretations I mentioned.
I hope it doesn’t pan out. The folks who know what’s good for you (FWKWGFY) already say we shouldn’t eat meat (canine teeth must have no reason for existence), and now fruit is supposed to be bad too. Next year it will be vegetables.
2 comments:
From what I can tell on the nutritional research front, those who say we shouldn't eat meat and those who say we shouldn't eat fruit are actually fighting each other. I think you're supposed to pick a side.
Some day someone's going to come up with the brilliant idea that maybe we all have genetic variations that make slightly different proportions of different types of food good for different people, and that person will be set for life.
They'll be set if they can map the genetic variants to the diet.
In the meantime, on the say-so of the no-fruit folks I'll have pizza; and the no-meat guys orange juice; and banana splits on my own say-so.
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