You may have heard it a few times already by now: obese people are more likely to develop dementia earlier than thin people.
You could also hear Dr Lustig asking whether sugar causes dementia and seeing him presenting this slide in his lecture at 52:27:
He spent some time referring to the statements you can see on the left side of the slide. Let me just summarize these points:
We have proven association between obesity and dementia in humans and animals but only for animals there was some data for causative relationship between the consumption of sugar and declined cognitive skills, which were not affected by the obesity of the animals.
Since you have learned in the previous article, that sugar is not the main cause of obesity (it was fried potato products) and the sugar consumption has been declining over the past 14 years while the dementia cases continue to rise, can we still say that it can be predicted that sugar causes cognitive decline independently of the consumption of other fast food items and possibly other environmental factors? Remember that the consumption of fast-food continued to rise when the sugar consumption started to decline in 2000. You could also hear Dr Lustig saying that the western diet as whole has been associated with dementia in humans and that we do not know which aspect of it can be attributed to the dementia cases.
It is also a fact that rodents, which the rats are, have much higher de-novo lipogenesis (DNL) capacity in their bodies than humans have. Could we hypothesize that this factor could have contributed to the decline of the cognitive function of rats while it would be less straightforward in humans if we managed to assess it a similar way? The scientists already made this mistake in the past when predicting the same DNL in humans after finding the extend of DNL in rodents. Now we know that in humans it is different.
What is more, while it was obesity that was correlated with dementia in both animals and humans, regardless of whether it was sugar or fat as a proximate cause, can we hypothesize that obesity is an absolute cause of dementia? That point that it was sugar, not fat, which leads to the declined cognitive function in animals does not dismiss the link between obesity and dementia as such. Dr Lustig also said that the omega-3 fats produced increased cognitive function in rats. How about omega-6 which is prevalent in our diet? How about the fats, if consumed at high amounts, leading to obesity even without the sugar? It is enough to consume fats with processed carbohydrates such as white bread or the chips as such.
For now, as Dr Lustig said it openly, we do not have the causative data for dementia in humans in relation to sugar or any other dietary component. We only know that omega-3 fatty acids help reduce the risk. And I would like to keep it at this point, instead of drawing suggestive conclusions, until we have the data.
What I remember though is that even brain can be insulin resistant. But can this be due to fructose content in our diet? Fructose concentrations in the blood appears at 10 - 1000 lower amounts than of glucose. People can become obese even at relatively low amount of refined sugar or HFCS, by simply overeating on processed foods, when muscles do not take much energy in and the increased glucose and insulin concentrations in blood can lead to inflammation of the cells sensitive to insulin and finally down-regulation of insulin receptors. I have heard about patients who improved their cognitive function by consuming coconut oil. A portion of this energy source is converted into ketone bodies by the liver and these serve as an alternative fuel for the insulin resistant brain. Interesting, is it not?
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