Alzheimer's disease, a severe form of dementia, affects an estimated 5.2 million Americans, according to 2013 statistics. 
One in nine seniors over the age of 65 has Alzheimer's, and the disease is now thought to be the third leading cause of death in the US, right behind heart disease and cancer.
A growing body of research suggests there's a powerful connection between your diet and your risk of developing Alzheimer's disease, via similar pathways that cause type 2 diabetes.
Contrary to popular belief, your brain does not require glucose, and actually functions better burning alternative fuels, especially ketones, which your body makes in response to digesting healthy fats.
Alzheimer's disease was tentatively dubbed "type 3 diabetes" in early 2005 when researchers discovered that in addition to your pancreas, your brain also produces insulin, and this brain insulin is necessary for the survival of brain cells.
Sugar Damages Brain Structure and Function
In your brain, insulin helps with neuron glucose-uptake and the regulation of neurotransmitters, such as acetylcholine, which are crucial for memory and learning. This is why reducing the level of insulin in your brain impairs your cognition.
Research  has also shown that type 2 diabetics lose more brain volume with age than expected—particularly gray matter. This kind of brain atrophy is yet another contributing factor for dementia.
Studies have found that people with lower levels of insulin and insulin receptors in their brain often have Alzheimer's disease. But according to recent research published in the journal Neurology,  sugar and other carbohydrates can disrupt your brain function even if you're not diabetic or have any signs of dementia.
To test their theory, they evaluated short- and long-term glucose markers in 141 healthy, non-diabetic, non-demented seniors. Memory tests and brain imaging were administered to assess their brain function and the actual structure of their hippocampus. As reported by Scientific American: 
"Higher levels on both glucose measures were associated with worse memory, as well as a smaller hippocampus and compromised hippocampal structure.The findings suggest that even if you're not diabetic or insulin resistant (and about 80 percent of Americans fall into the latter category), sugar consumption can still disrupt your memory.
The researchers also found that the structural changes partially accounted for the statistical link between glucose and memory. According to study co-author Agnes Flöel, a neurologist at Charité, the results 'provide further evidence that glucose might directly contribute to hippocampal atrophy.'"
Long-term, it can contribute to the shrinking of your hippocampus, which is a hallmark symptom of Alzheimer's disease. (Your hippocampus is involved with the formation, organization, and storage of memories.)
The authors of the study suggest that "strategies aimed at lowering glucose levels even in the normal range may beneficially influence cognition in the older population."
'Normal' Blood Sugar Levels May Still Be High Enough to Cause Problems
Normally, a fasting blood sugar level between 100-125 mg/dl is diagnosed as a pre-diabetic state. A fasting blood sugar level of 90-100 is considered "normal." But in addition to the featured research, other studies have also found that brain atrophy occurs even in this "normal" blood sugar range.
Neurologist Dr. David Perlmutter, MD insists that being very strict in limiting your consumption of sugar and non-vegetable carbs is one of THE most important steps you can take to prevent Alzheimer's disease for this very reason.
He cites research from the Mayo Clinic, which found that diets rich in carbohydrates are associated with an 89 percent increased risk for dementia. Meanwhile, high-fat diets are associated with a 44 percent reduced risk.
Sugar Lobby Threatens Organizations and Buries Science on Health Effects
Compelling research shows that your brain has great plasticity, which you control through your diet and lifestyle choices. Unfortunately, the American public has been grossly brainwashed by the sugar and processed food industries into believing that sugar is a perfectly reasonable "nutrient" that belongs in a healthy diet.
Without accurate information, it's certainly more difficult to make health-affirming choices. Newsweek  recently ran an article revealing just how far the sugar industry will go to defend its market share:
"According to a new report  from the Center for Science and Democracy... industry groups representing companies that sell sweeteners, like the Sugar Association and the Corn Refiners Association... have poured millions of dollars into countering science that indicates negative health consequences of eating their products.According to the Center for Science report, the Sugar Association even threatened the director general of the World Health Organization (WHO). WHO had published a paper on sugar, recommending a 10 percent limit on added sugars, stating that added sugars "threaten the nutritional quality of diets."
For example, when a University of Southern California study from 2013 found that the actual high fructose corn syrup content in sodas 'varied significantly' from the sugar content disclosed on soda labels, the Corn Refiners Association considered paying for its own counter research.
A consultant suggested that the counter research should only be published if the results aligned with their goal of disputing the USC study: 'If for any reason the results confirm [the University of Southern California study], we can just bury the data,' the consultant wrote, according to the report."
The Sugar Association shot off a letter to the director general, warning him that, unless WHO withdrew the study, the Sugar Association would persuade the US Congress to withdraw the WHO's federal funding. The following year, when WHO published its global health strategy on diet and health, there was no mention of the offending sugar study.
The Sugar Lobby Deserves Blame for Fueling Chronic Disease Epidemics
Indeed, despite overwhelming evidence showing that sugar, and processed fructose in particular, is at the heart of our burgeoning obesity and chronic disease epidemics, the sugar lobby has been so successful in its efforts to thwart the impact of such evidence that there's still no consensus among our regulatory agencies as to the "factual" dangers of sugar...
According to Centers for Disease Control and Prevention (CDC) data,  13 percent of the average American's diet is sugar. In the UK, a recently published report  by the Scientific Advisory Committee on Nutrition (SACN) recommends limiting your added sugar intake to five percent, in order to avoid obesity and type 2 diabetes. They calculate this to be the equivalent of 25 grams of sugar (5-6 teaspoons) per day for women, and 35 grams (7-8 teaspoons) for men.
This matches my own recommendations for healthy, non-insulin resistant individuals—with one key difference. I recommend restricting sugar/fructose consumption to 25 grams from ALL sources, not just added sugar. This includes limiting your non-vegetable carbohydrates as well. Crazy enough, the Scientific Advisory Committee on Nutrition still recommends you get 50 percent of your daily energy intake in the form of starchy carbohydrates, which will undoubtedly and significantly raise your risk of insulin resistance. If you're insulin/leptin resistant, diabetic, overweight, or have high blood pressure, heart disease, or cancer, I recommend restricting your sugar/fructose consumption to a maximum of 15 grams per day from all sources, until your insulin/leptin resistance has been resolved.
Dietary Guidelines for Maintaining Healthy Brain Function and Avoiding Alzheimer's Disease
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 over-indulge on sugar and grains, your brain becomes overwhelmed by the consistently high levels of glucose and insulin that blunts its insulin signaling, leading to impairments in your thinking and memory abilities, eventually causing permanent brain damage.
Additionally, when your liver is busy processing fructose (which your liver turns into fat), it severely hampers its ability to make cholesterol, an essential building block of your brain that is crucial for optimal brain function. Indeed, mounting evidence supports the notion that significantly reducing fructose consumption is a very important step for preventing Alzheimer's disease.
Because of the very limited treatments, and no available cure as of yet, you're really left with just one solid solution, and that is to prevent Alzheimer's from happening to you in the first place. As explained by neurologist Dr. David Perlmutter, Alzheimer's is a disease predicated primarily on lifestyle choices; the two main culprits being excessive sugar and gluten consumption.
Another major factor is the development and increased consumption of genetically engineered (GE) grains, which are now pervasive in most processed foods sold in the US. The beauty of following my optimized nutrition plan is that it helps prevent and treat virtually ALL chronic degenerative diseases, including Alzheimer's. Dr. Perlmutter's book, Grain Brain, also provides powerful arguments for eliminating grains from your diet, particularly if you want to protect the health of your brain. In terms of your diet, the following suggestions may be among the most important for Alzheimer's prevention:
Avoid sugar and refined fructose. Ideally, you'll want to keep your total sugar and fructose below 25 grams per day, or as low as 15 grams per day if you have insulin resistance or any related disorders. In one recent animal study, a junk food diet high in sugar resulted in impaired memory after just one week!  Place recognition, specifically, was adversely affected.
As a general rule, you'll want to keep your fasting insulin levels below 3, and this is indirectly related to fructose, as it will clearly lead to insulin resistance. However, other sugars (sucrose is 50 percent fructose by weight), grains, and lack of exercise are also important factors. Lowering insulin will also help lower leptin levels which is another factor for Alzheimer's.
Avoid gluten and casein (primarily wheat and pasteurized dairy, but not dairy fat, such as butter). Research shows that your blood-brain barrier, the barrier that keeps things out of your brain where they don't belong, is negatively affected by gluten. Gluten also makes your gut more permeable, which allows proteins to get into your bloodstream, where they don't belong. That then sensitizes your immune system and promotes inflammation and autoimmunity, both of which play a role in the development of Alzheimer's.
Eat a nutritious diet, rich in folate, such as the one described in my nutrition plan. Vegetables, without question, are your best form of folate, and we should all eat plenty of fresh raw veggies every day. Avoid supplements like folic acid, which is the inferior synthetic version of folate.
Increase consumption of all healthful fats, including animal-based omega-3. Beneficial health-promoting fats that your brain needs for optimal function include organic butter from raw milk, clarified butter called ghee, organic grass fed raw butter, olives, organic virgin olive oil and coconut oil, nuts like pecans and macadamia, free-range eggs, wild Alaskan salmon, and avocado.
Contrary to popular belief, the ideal fuel for your brain is not glucose but ketones. Ketones are what your body produces when it converts fat (as opposed to glucose) into energy. The medium-chain triglycerides (MCTs) found in coconut oil are a great source of ketone bodies, because coconut oil is about 66 percent MCTs. In 2010, I published Dr. Mary Newport's theory that coconut oil might offer profound benefits in the fight against Alzheimer's disease. She has since launched one of the first clinical trials of its kind to test this theory.
Also make sure you're getting enough animal-based omega-3 fats, such as krill oil. (I recommend avoiding most fish because, although fish is naturally high in omega-3, most fish are now severely contaminated with mercury.) High intake of the omega-3 fats EPA and DHA help by preventing cell damage caused by Alzheimer's disease, thereby slowing down its progression, and lowering your risk of developing the disorder.
Optimize your gut flora by regularly eating fermented foods or taking a high-potency and high-quality probiotic supplement.
Eat blueberries. Wild blueberries, which have high anthocyanin and antioxidant content, are known to guard against Alzheimer's and other neurological diseases.
Other Helpful Dietary Tips and Valuable Supplements
Another helpful tip is to reduce your overall calorie consumption, and/or intermittently fast. As mentioned above, ketones are mobilized when you replace carbs with coconut oil and other sources of healthy fats. A one-day fast can help your body to "reset" itself, and start to burn fat instead of sugar. As part of a healthy lifestyle, I prefer an intermittent fasting schedule that simply calls for limiting your eating to a narrower window of time each day. By restricting your eating to a 6-8 hour window, you effectively fast 16-18 hours each day. To learn more about intermittent fasting, please see this previous article.
Also be aware that when it comes to cholesterol levels and Alzheimer's, lower is NOT better. Quite the contrary. According to Dr. Perlmutter, research shows that elderly individuals with the lowest cholesterol levels have the highest risk for Alzheimer's. They also have the highest risk for dying. As he says, the war on cholesterol is fundamentally inappropriate and harmful.
Finally, there's a short list of supplement recommendations worth noting for their specific benefits in preventing and treating dementia. So, although your fundamental strategy for preventing dementia should involve a comprehensive lifestyle approach, you may want to take special note of the following natural dietary agents. These four natural foods/supplements have good science behind them, in terms of preventing age-related cognitive changes:
- Gingko biloba: Many scientific studies have found that Ginkgo biloba has positive effects for dementia. A 1997 study from JAMA showed clear evidence that Ginkgo improves cognitive performance and social functioning for those suffering from dementia. Another 2006 study found Ginkgo as effective as the dementia drug Aricept (donepezil) for treating mild to moderate Alzheimer's type dementia. A 2010 meta-analysis also found Ginkgo biloba to be effective for a variety of types of dementia.
- Alpha lipoic acid (ALA): ALA has been shown to help stabilize cognitive functions among Alzheimer's patients and may slow the progression of the disease.
- Vitamin B12: A small Finnish study published in the journal Neurology  found thatpeople who consume foods rich in B12 may reduce their risk of Alzheimer's in their later years. For each unit increase in the marker of vitamin B12 the risk of developing Alzheimer's was reduced by two percent. Remember sublingual methylcobalamin may be your best bet here.
Lifestyle choices such as getting regular sun exposure and exercise, along with avoiding toxins, are also important factors when it comes to maintaining optimal brain health. Here are several of my lifestyle suggestions:
Optimize your vitamin D levels with safe sun exposure. Strong links between low levels of vitamin D in Alzheimer's patients and poor outcomes on cognitive tests have been revealed. Researchers believe that optimal vitamin D levels may enhance the amount of important chemicals in your brain and protect brain cells by increasing the effectiveness of the glial cells in nursing damaged neurons back to health.
Vitamin D may also exert some of its beneficial effects on Alzheimer's through its anti-inflammatory and immune-boosting properties. Sufficient vitamin D is imperative for proper functioning of your immune system to combat inflammation that is also associated with Alzheimer's.
Exercise regularly. It's been suggested that exercise can trigger a change in the way the amyloid precursor protein is metabolized,  thus, slowing down the onset and progression of Alzheimer's. Exercise also increases levels of the protein PGC-1alpha. Research has also shown that people with Alzheimer's have less PGC-1alpha in their brains  and cells that contain more of the protein produce less of the toxic amyloid protein associated with Alzheimer's. I would strongly recommend reviewing the Peak Fitness Technique for my specific recommendations.
Avoid and eliminate mercury from your body. Dental amalgam fillings, which are 50 percent mercury by weight, are one of the major sources of heavy metal toxicity. However, you should be healthy prior to having them removed. Once you have adjusted to following the diet described in my optimized nutrition plan, you can follow the mercury detox protocol and then find a biological dentist to have your amalgams removed.
Avoid aluminum, such as antiperspirants, non-stick cookware, vaccine adjuvants, etc.
Avoid flu vaccinations as most contain both mercury and aluminum, well-known neurotoxic and immunotoxic agents.
Avoid anticholinergics and statin drugs. Drugs that block acetylcholine, a nervous system neurotransmitter, have been shown to increase your risk of dementia. These drugs include certain nighttime pain relievers, antihistamines, sleep aids, certain antidepressants, medications to control incontinence, and certain narcotic pain relievers.
Statin drugs are particularly problematic because they suppress the synthesis of cholesterol, deplete your brain of coenzyme Q10 and neurotransmitter precursors, and prevent adequate delivery of essential fatty acids and fat-soluble antioxidants to your brain by inhibiting the production of the indispensable carrier biomolecule known as low-density lipoprotein.
Challenge your mind daily. Mental stimulation, especially learning something new, such as learning to play an instrument or a new language, is associated with a decreased risk of Alzheimer's. Researchers suspect that mental challenge helps to build up your brain, making it less susceptible to the lesions associated with Alzheimer's disease.