By Dr. Mercola
It's become a well-known fact that excess sugar harms your health by setting up the conditions for obesity and diabetes. Research1 has also shown a steady diet high in high-fructose corn syrup (HFCS) can significantly impair your cognitive abilities by producing a decline in synaptic activity.
In one animal study, rats fed fructose syrup for six weeks showed signs of cognitive impairment, as they struggled to find their way out of a maze. Their brain cells had trouble signaling each other, disrupting the rats' ability to think clearly and recall the route they'd learned six weeks earlier.
The fructose-fed rats also showed signs of resistance to insulin, a hormone that — in addition to controlling your blood sugar — also controls synaptic function in your brain.
Because insulin is able to pass through your blood-brain barrier, it can trigger neurological processes that are important for learning and memory. Consuming large amounts of fructose may block insulin's ability to regulate how your brain cells store and use sugar for the energy needed to fuel thoughts and emotions.
Considering the fact that HFCS, which is so prevalent in processed foods, is a major risk factor for obesity, it's not such a stretch to imagine that obesity may be linked to declining brain health as well. In fact, this is precisely what studies show.
Obesity Speeds Up Brain Aging
Most recently, a study published in the journal Neurobiology of Aging found structural changes in the brains of overweight people — changes typically seen in far older individuals. As reported in the Borneo Post:2
"After scanning brains of 473 people aged between 20 and 87 and dividing them into lean and overweight categories, scientists discovered that extra weight would accelerate the loss of the brain's white matter …
Scientists then calculated how much that white matter volume related to age across the two groups. They found that an overweight 50-year-old had a comparable white matter volume to a slim 60-year-old person.
'The overall message is that brains basically appear to be 10 years older if you are overweight or obese,' said Lisa Ronan, lead author of the study from Cambridge University."
Your white brain matter allows for communication between the different parts of your brain, and previous investigations have shown that this tissue tends to decrease with age. Loss of white brain matter has also been linked to cognitive decline, and it's a recognized risk factor for dementia.
Fat Cells May Promote Inflammation That Speeds Brain Aging
Interestingly, while overweight individuals showed more rapid loss of white brain matter, and other studies have linked obesity to an increased risk of Alzheimer's disease, no discernible differences in thinking skills were observed in this study.
This surprising finding has yet to be explained.
The exact reason why excess body weight promotes loss of white brain matter is also undetermined. WebMD quotes Mike Henne, Ph.D., a spokesman for the American Federation for Aging Research, who says:3
"One possibility, and the researchers talk about that [in the report], is that when you are obese your fat cells are producing more inflammatory agents and your white matter is more sensitive to it. That is a leading theory in the field."
Mediterranean Diet Boosts Cognition
In related news, a review of 135 studies recently concluded that a Mediterranean-style diet benefits cognition and reduces your chances of developing Alzheimer's. As reported by Medical News Today:4
"In relation to memory, participants who closely followed the Mediterranean diet experienced improvements in long-term and working memory, as well as improvements in delayed recognition, executive memory and visual constructs.
Greater adherence to the Mediterranean diet was also associated with improvements in attention and language …"
While there are many variations, this type of diet is typically high in plant-based foods and healthy fats such as raw nuts and olive oil, while fish and poultry are emphasized over red meat.
Perhaps most importantly, the Mediterranean diet focuses on real food, downplaying processed foods that are invariably loaded with health-harming sugars and processed, damaged fats like vegetable oils.
The present study did not try to determine exactly WHY the Mediterranean diet boosts brain health, but this type of diet has already been shown to produce a number of beneficial health effects that can help answer this question. For example, the Mediterranean diet has been shown to:
✓ Reduce inflammation
✓ Improve weight management and reduce risk of obesity
✓ Increase micronutrient intake
✓ Improve antioxidant intake
✓ Improve vitamin and mineral balances
✓ Improve cellular energy metabolism
✓ Improve lipid profiles
✓ Beneficially alter gut microbiome
Your Brain Requires Healthy Fats for Optimal Functioning
Answers were also gleaned from a 2015 study,5 which found that seniors with risk factors for cardiovascular disease who followed a low-fat diet experienced a significant decrease in memory and cognition compared to those who ate a Mediterranean diet high in either olive oil or nuts.
Those who fared the best, in terms of memory, were those who ate a Mediterranean diet supplemented with 30 grams of nuts each day. They had the most significant improvements in memory.
Meanwhile, those who ate a Mediterranean diet supplemented with 1 liter of extra virgin olive oil each week had the most significant improvements in cognitive function. Both nuts and olive oil are healthy natural, unprocessed fats your body needs, so it's not surprising to find higher amounts of healthy fats improved brain function.
Previous research from the Mayo Clinic has also shown that high-fat diets are associated with a 42 percent reduced risk of mild cognitive impairment (a precursor to Alzheimer's), while diets rich in carbohydrates raise your risk by 89 percent! As reported by USA Today in 2012:6
"Several popular diets, including the Mediterranean (fish, poultry-based protein and plenty of plant-based foods and healthy fats) … make pitches for the multiple health benefits derived from lowering carbohydrate intake, including reduced risk for heart disease, diabetes and improved brain health."
Keep in mind that while limiting net carbs (total carbohydrates minus fiber) is one important aspect, increasing healthy fats is part and parcel of the whole equation.
Not only do you need healthy fats for optimal brain function, you also need it for energy, hormone production and an array of other biological functions, including optimal mitochondrial function and, believe it or not, weight management.
DHA — An Important Brain Health Component
Perhaps the most important fat for your brain is the animal-based omega-3 fat docosahexaenoic acid (DHA), found in certain seafood. Good choices include fatty cold-water fish such as wild-caught Alaskan sockeye salmon, sardines, anchovies and herring. Fish roe and krill oil are other good sources.
The importance of animal-based omega-3 fats (especially DHA) for brain health has been demonstrated in many studies.
For example, studies have shown it can help prevent Alzheimer's,7 improve attention-deficit/hyperactivity disorder (ADHD) symptoms and depression and delay progression to psychosis among patients at high risk for schizophrenia.
Going back to the rat study mentioned earlier, rats given DHA in conjunction with their high fructose diet were able to navigate the maze better and faster than the rats in the non-DHA group, suggesting the DHA is protective against the harmful effects of fructose.
DHA is essential for synaptic function — it helps your brain cells transmit signals to one another, which is the mechanism that makes learning and memory possible. And since your body cannot produce DHA, you must get it from your diet.
Importantly, DHA is a structural element of every cell in your body and plays a role in the communication within the cell and between cells. As such, DHA is not just another food (fuel). The fact that it is a structural element of your cells help explain why omega-3 deficiency is so detrimental to your health.
And since more than 90 percent of the omega-3 fat found in brain tissue is DHA, it's particularly important for brain health. DHA and eicosapentaenoic acid (EPA) also have a profoundly important influence on your mitochondrial function.
DHA in your cell membranes actually helps convert the photons from sunlight into DC electric current, which in turns fuels your mitochondria and energy production. I am convinced that having enough DHA in your cell membranes is one of the most important health strategies available. And remember, your body simply cannot convert plant-based omega-3 to DHA in any quantity that is therapeutically useful.
Other Studies Linking Obesity With Declines in Cognition
The idea that your weight may be a risk factor for Alzheimer's has been brought forth by a number of studies. Obese adults often have additional risk factors for Alzheimer's, including high blood pressure and diabetes. Obesity is also linked to chronic inflammation, which might make Alzheimer's worse, along with insulin resistance, another known risk factor for Alzheimer's.
- In 2008, research revealed that central obesity (excess weight around your midsection) is linked with an increased risk of dementia.8
- Research published in 2011 found a strong correlation between body mass index (BMI) and high levels of beta-amyloid, the protein that tends to accumulate in the brains of Alzheimer's patients, causing plaque buildup. It is believed that beta-amyloid destroys nerve cells, contributing to the cognitive and behavioral problems typical of the disease.9
- A 14-year-long study published in July 2016, found that among people who developed Alzheimer's disease, those who were overweight or obese at the age of 50 developed symptoms nearly seven months' sooner than those of a healthy mid-life weight. Further, the onset of symptoms moved up by 6.7 months for each unit increase in midlife BMI. Those with a high BMI were also more likely to have greater amounts of amyloid proteins in their brain.10
Three Keys for Weight Loss and Brain Health
On the bright side, a number of simple lifestyle strategies can help optimize your brain health and ward off age-related decline. This includes the following, which just so happen to be identical to those for weight loss:
- Exercise, especially high-intensity interval training.
- Calorie restriction (intermittent fasting appears to have many of the same benefits while being easier to comply with).
- Reducing net carbs (especially grains and sugars) and increasing high-quality healthy fats (such as olive oil, coconut oil, MC oil, butter from raw grass-fed organic milk, raw nuts, organic pastured egg yolks and avocados). According to neurologist Dr. David Perlmutter, author of the book, "Grain Brain," a low-carb diet high in healthy fats is a key component of Alzheimer's prevention.
Other Strategies That Help Protect Your Brain
You also need plenty of high-quality omega-3 fats, especially DHA. I prefer krill oil to fish oil, as krill oil also contains astaxanthin, which is particularly beneficial for your brain. Astaxanthin is a carotenoid that's very good for reducing free radical-mediated damage to fat, and as mentioned, the majority of your brain — 60 or 70 percent — is fat; mostly DHA. Two other nutrients that play important roles in your brain health are:
- Vitamin D: Researchers have located metabolic pathways for vitamin D in the brain's hippocampus and cerebellum; areas that are involved in planning, information processing and memory formation. In older adults, research has shown that low vitamin D levels are associated with poorer brain function.
- Choline: Choline reduces inflammation and plays a role in nerve communication. Eggs and meat are two of the best dietary sources of choline. If you do not consume animal foods, you may be at risk of a deficiency and want to consider supplementation.
The state of your gastrointestinal (GI) tract is another important consideration that can have a significant influence on your brain function. Your gut is quite literally your "second brain." Just as you have neurons in your brain, you also have neurons in your gut, and gut bacteria transmit information from your GI tract to your brain via your vagus nerve.
Abnormal gut flora has been associated with abnormal brain development, and may be an overlooked culprit in many cases of depression. In addition to avoiding sugar, one of the best ways to support gut health is to consume fermented vegetables, which are loaded with beneficial bacteria.
Last but not least, it is crucial to fully appreciate the importance of sleep. The latest sleep guidelines, based on 300 studies looking at the health effects of sleep, confirm that most adults need right around eight hours of sleep for optimal health.
It's particularly important for brain health, because the ONLY time your brain can detoxify is during deep sleep, which is why poor sleepers are more prone to developing neurological disorders such as Alzheimer's. So truly, if you want your brain to function optimally, be sure to address any sleep problems you may have.