By Dr. Mercola

Your brain is intricately linked to your diet. You know this is true if you've ever found yourself foggy-headed and unable to concentrate because you've gone too long without eating.

Yet, changes in your cognitive abilities as you get older are generally not attributed directly to your food choices, the way some other diseases, like heart disease and type 2 diabetes, often are.

This may soon change, and rightly so, as a growing body of research is highlighting the drastic effect your diet plays in your future brain health, such as significantly raising your risk of cognitive impairment.

Too Many Carbs and Too Much Sugar Increases Your Risk of Cognitive Impairment

Among people aged 70 to 89, diet proved very influential in contributing to the risk of mild cognitive impairment, including problems with memory, language, thinking and judgment, down the line. The new study revealed carbs and sugar to be the biggest culprits, while protein and fats were protective:¹

• Those with the highest carbohydrate intake were nearly twice as likely to develop mild cognitive impairment than those with the lowest intake of carbohydrates.
• Those with the highest sugar intake were 1.5 times more likely to experience mild cognitive impairment than those with the lowest levels.
• Those with the highest fat intake were 42 percent less likely to develop cognitive impairment
• Those with the highest protein intake reduced their risk by 21 percent
• When compared with total fat and protein intake, those with the highest carb intake were 3.6 times more likely to develop mild cognitive impairment

Why might this be? Because a diet that's focused on unhealthy carbs and sugar seriously interferes with the ability of insulin to do its job  Researchers noted:

"A dietary pattern with relatively high caloric intake from carbohydrates and low caloric intake from fat and proteins may increase the risk of MCI [mild cognitive impairment] or dementia in elderly persons."

Interfering with Insulin Signaling is Damaging to Your Brain

In a recent animal study, researchers from Brown University in Providence, Rhode Island were able to induce many of the characteristic brain changes seen with Alzheimer's disease (disorientation, confusion, inability to learn and remember) by interfering with insulin signaling in their brains.²

Faulty insulin (and leptin, another hormone) signaling is an underlying cause of insulin resistance, which, of course, typically leads to type 2 diabetes. However, while insulin is usually associated with its role in keeping your blood sugar levels in a healthy range, it also plays a role in brain health. When researchers disrupted the proper signaling of insulin in the brain, it resulted in dementia.

The over-consumption of sugars and grains is what ultimately causes your body to be incapable of "hearing" the proper signals from insulin and leptin, leaving you insulin resistant in both body and brain. A drop in insulin production in your brain may contribute to the degeneration of your brain cells, mainly by depriving them of glucose. It's even been said that "reducing the level of insulin in the brain can immediately impair cognition."³

Alzheimer's disease was tentatively dubbed "type 3 diabetes" in early 2005 when researchers learned that the pancreas is not the only organ that produces insulin. Your brain also produces insulin, and this brain insulin is necessary for the survival of your brain cells.

So it's not surprising that the featured study found a link between mild cognitive impairment and diets high in sugar and carbs. It's becoming increasingly clear that the same pathological process that leads to insulin resistance and type 2 diabetes may also hold true for your brain. As you overindulge on sugar and grains, your brain becomes overwhelmed by the consistently higher levels of insulin and eventually shuts down its insulin signaling and sensitivity, leading to impairments in your thinking and memory abilities, and eventually causing permanent brain damage.

As the study's lead author said:⁴

"A high carbohydrate intake could be bad for you because carbohydrates impact your glucose and insulin metabolism … Sugar fuels the brain — so moderate intake is good. However, high levels of sugar may actually prevent the brain from using the sugar — similar to what we see with type 2 diabetes."

Cut THIS From Your Diet if You Want to Protect Your Brain …

When researchers fed rats a fructose solution as drinking water for six weeks, then tested their ability to remember their way out of a maze, the results certainly grabbed the researchers' attention – and they should grab yours, too.

The rats fed fructose syrup showed significant impairment in their cognitive abilities—they struggled to remember their way out of the maze. They were slower, and their brains showed a decline in synaptic activity. 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.⁵

Additionally, the fructose-fed rats showed signs of resistance to insulin, again showing that consuming large amounts of sugar, and in this case fructose, may block insulin's ability to regulate how your brain cells store and use sugar for the energy needed to form healthy thoughts and emotions.

Researchers concluded that a high-fructose diet harms your brain, as well as the rest of your body. There is NO question in my mind that regularly consuming more than 25 grams of fructose per day will dramatically increase your risk of dementia and Alzheimer's disease, as it will inevitably wreak havoc on your body's ability to regulate proper insulin levels.

Protein Intake Also Crucial 

Earlier this month I interviewed Dr. Ron Rosedale for 14 hours. He is one of the first physicians in the U.S. that started measuring leptin levels clinically and was far ahead of the curve on this one. In our interview, he helped me understand the major importance that excessive protein intake can have on cancer growth.

Eating excessive protein can be an additional synergistically powerful mechanism. When you consume protein in levels higher than one gram of protein per kilogram of LEAN body mass you tend to activate the mTOR pathway, which will radically increase your risk of cancers. It is very easy to consume excess protein and my guess is that most people reading this are. I know I was, and as a result of this new insight I have reduced my protein intake by about half.

To determine your lean body mass find out your percent body fat and subtract from 100. So if you are 20% body fat you would have 80% lean body mass. Just multiply that times your current weight to get lean body mass. For most people this means restricting protein intake from 35 to 75 grams. Pregnant women and those working out extensively need about 25% more protein though.

Of course when you reduce protein you need to replace it with other calories, so the key to replace the lost calories with high-quality fats such as avocados, butter, coconut oil, nuts and eggs. It is also very helpful to avoid eating anything for three hours before going to bed as this allows you to have relatively low blood sugars while you are sleeping. This is another good trick to move your body to fat burning mode.

What Dietary Strategies Help Protect Your Brain?

Obviously the first and most important step is to limit carbs. Ideally your best carbs are fiber-based vegetables. It would be wise to avoid sugar and grains and replace those calories with healthy fats, like butter, avocados, coconut oil and olive oil. Nuts can be used but not overdone as you do not want to increase protein much above one half gram per pound of lean body weight.

On a brighter note, the above-mentioned study also found that rats given omega-3 fats in addition to the high-fructose diet were able to navigate the maze better and faster than the rats in the non-omega-3 group.

The researchers concluded that a type of omega-3 fat called DHA is protective against fructose's harmful effects on the brain. 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. Your body has difficulty producing enough DHA from vegetarian omega-3 precursors, so it must be supplemented through your diet, and this is one reason why getting enough animal-based omega-3 fats is so essential.

In addition, optimizing your gut bacteria by eating fermented vegetables may be one of the most profound ways to improve your brain health. Your gut is your "second brain," and there is a close connection between abnormal gut flora and abnormal brain development and function. Just as you have neurons in your brain, you also have neurons in your gut -- including neurons that produce neurotransmitters like serotonin, which is also found in your brain and is linked to mood.

Quite simply, your gut health can impact your brain function, psyche, and behavior, as they are interconnected and interdependent in a number of different ways.

Interestingly, if eating sugar, fructose and grains is the equivalent of slamming your foot on your brain-aging accelerator, intermittent fasting may be more akin to stepping on the brakes. Fasting increases insulin sensitivity and appears to trigger a variety of health-promoting hormonal and metabolic changes that may help prevent age-related brain shrinkage and other chronic and debilitating diseases. The protective processes triggered in your brain when suddenly decreasing your food intake are similar to the beneficial effects of exercise.

If you want to give it a try, you can find my full intermittent fasting guidelines here.

As for what to eat the rest of the time, following the dietary advice available in my comprehensive nutrition plan is highly recommended. I am confident that if you adhere to the recommendations in this plan, you will be able to optimize your brain health and your overall health simultaneously.