Thinking Red

We’ve been completely surrounded by the color red on this Valentine’s Day weekend. 

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So of course it had me thinking red too…about red meat that is.

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One of the questions that we get asked frequently is how much our diets can really affect our health. The answer, simply, is “a lot”.

A recent study highlighted the impact of red meat on our health, more specifically our brain health. This study looked at two large groups of people and analyzed the effects of red meat on the risk of dementia in 50 year olds, and separately looked at the risk of cognitive decline in 70 year olds. Both of these analyses looked at large groups: the dementia analysis included >133,000 participants, and the cognitive function analyses included a group of >17,000 women with a mean age of ~74 years and a group of ~44,000 people with an average age of  78 years. 

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The researchers compared people who ate more than ¼ of a serving of red meat per day to people who ate <0.10 serving per day. How much is a quarter serving? Well, typically a serving of meat is considered to be about the size of the palm of your hand. So divide the palm of your hand into four parts and you have the right idea of how little a quarter serving is. 

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In this study, those who ate more red meat (again, just as little as ¼ of a serving per day!) had a 13% higher risk of dementia and a 14% higher risk of cognitive decline in their older years. Higher processed red meat intake was associated with accelerated aging in global cognition and in verbal memory. There was a 16% higher risk of cognitive decline for eating ≥1 serving per day of unprocessed red meat compared with <1/2 serving.

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These researchers also showed that replacing 1 serving per day of processed red meat with a healthier serving of nuts and legumes (beans, lentils, etc) was associated with a 19% lower risk of dementia, 1.37 fewer years of cognitive aging, and a 21% lower risk of cognitive decline.

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Older studies have also shown that higher consumption of processed meat is consistently associated with an increased risk of dementia, including Alzheimer's disease and vascular dementia. These prior studies have shown that each additional portion of processed meat per week is linked to a significant increase in dementia risk.

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Processed red meat consumption was associated with a 20% higher risk of dementia mortality, and of course replacing animal protein with plant protein was associated with a lower risk of dementia mortality. 

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OK: We get the picture. Red meat is bad. But if we reduce our dietary cholesterol, wouldn’t that HURT our brains? Because our brains need cholesterol, right? 

These are questions that we get asked all the time. And the answer is: Yes. Absolutely. Brains need cholesterol. Cholesterol is essential for lots of brain functions, including myelin sheath formation, healthy synapses, and neuronal function. But cholesterol metabolism in the brain is unique compared to the rest of the body due to the presence of the blood-brain barrier (BBB), which restricts the exchange of cholesterol between the brain and systemic circulation. 

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Because cholesterol does not readily cross the BBB, the brain has to make its own cholesterol. In fact, the brain is actually almost completely self-sufficient in making cholesterol. Studies using a variety of different experimental animals have consistently indicated that >95% of the cholesterol content in the brain is made “on-site”, and there is minimal exchange of brain cholesterol with the rest of the body. Additionally, the actual pathway and building blocks that the brain uses to make cholesterol are different from those used by the rest of the body.

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And because cholesterol is so important to the brain, it lasts a long time there. The half-life of cholesterol in the brain is over 5 YEARS, rather than hours/days in the bloodstream and the rest of the body. The amount of cholesterol in the human brain is actually determined in early development and remains relatively constant throughout adulthood.

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So what does all this mean? What happens in the body, stays in the body. The brain is separate.

Because of the many differences between cholesterol in the brain versus the rest of the body, dietary cholesterol also has little direct impact on brain cholesterol levels.

Statins medications, which lower cholesterol in the body, also have limited effects in the brain due to the Blood Brain Barrier. So lipid-lowering medications can effectively lower peripheral cholesterol without significantly affecting brain cholesterol levels. 

A 2015 meta-analysis of 25 RCTs found no link between statin therapy and cognitive impairment. More recent meta-analyses have generally shown either a neutral or even positive impact of statins on cognitive function. 

So while the research discussed above shows that red meat intake increases the risk of dementia, it’s not likely to be due to the cholesterol content. It’s more likely to be one of the other harmful actors, like TMA, Heme-Iron, AGEs, carnitine, or the many other compounds that are found in red meat, but not in plant-based foods.

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So what does this all mean? 

Firstly, our diets really can affect our brain health, for better or worse.

Secondly, our brains evolved to be able to function even if we couldn’t depend on finding food easily.

Thirdly, for those of us who need the additional help that medication can provide, we should be able to feel comfortable and secure that lipid-lowering medications are safe for our brains, and do not lead to dementia.

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As we put Valentine’s in the past, let’s say goodbye to all that red, and move into spring with green on the mind!

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At Wisconsin Cardiology Associates, we always counsel our patients to aim for a healthy, plant-based diet, rich with unprocessed whole foods like fruits, vegetables, beans, lentils, whole grains and nuts. Have questions about the best way you can prevent heart disease? Call us and make an appointment for a consultation.

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References:

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Yanping Li, Y et al. Neurology 104 (3)

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