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 Nice research that basically says: food is medicine. In other words, eat lots of whole grains and legumes (beans) for gut health - to feed the beneficial microbes in your gut and prevent (hopefully) colon cancer. While the clinical trial studied colorectal cancer survivors and the effects of 4 weeks of adding rice bran or navy beans or placebo (nothing extra) daily to their diet - the positive effects of adding the extra dietary fiber included increased microbiome richness and diversity in the rice bran group (which is good).

And when researchers treated colorectal cancer cells with stool extracts from these groups, they saw reduced cell growth from the groups that had increased rice bran and navy bean consumption. This was an important finding and stresses that adding fiber to the diet is beneficial to gut health, and perhaps may prevent colorectal cancer.

Other studies have also found a diet with lots of legumes (beans), whole grains, vegetables, fruits, nuts, and seeds to be beneficial for gut microbes and gut health. A classic study (from 2015) found dramatic changes in the colon (specifically in the colonic mucosa) from dietary changes in as little as 2 weeks. They compared the typical low-fat, high fiber diet of South Africa with an “American” high-fat, low-fiber diet, and found that after two weeks on the high fiber African diet, there was significantly less inflammation in the colon and reduced biomarkers of cancer risk. On the other hand, measurements indicating cancer risk dramatically increased after two weeks on the western diet. That study found that a major reason for the changes in cancer risk was the way in which the bacteria in the gut (the microbiome) were altered in adapting to the new diet. The researchers suggested trying for at least 50 grams of fiber per day for gut health benefits.

From Medical Xpress: Phase II trial: Rice bran adds microbiome diversity, slows growth of colon cancer cells

Today at the American Association for Cancer Research (AACR) Annual Meeting 2017, University of Colorado Cancer Center researchers at Colorado State University present results of a phase II clinical trial of 29 people exploring the effects of adding rice bran or navy beans to the diets of colorectal cancer survivors. After the 4-week randomized-controlled trial during which people added rice bran, navy bean powder or neither, both the rice bran and navy bean groups showed increased dietary fiber, iron, zinc, thiamin, niacin, vitamin B6, folate, and alpha-tocopherol. The rice bran group also showed increased microbiome richness and diversity. When researchers treated colorectal cancer cells with stool extracts from these groups, they saw reduced cell growth from the groups that had increased rice bran and navy bean consumption.

Previous work shows the ability of these diets to decrease colorectal cancer risk in animal models. The current trial confirms that people can eat enough bean- and rice bran-enhanced foods to promote gut health at levels shown to prevent colorectal cancer in animals. Guidelines from the American Institute for Cancer Research recommend reducing the risk of cancer by eating more vegetables, fruits, whole grains and legumes, such as beans. Ryan has established from these studies that eating a half-cup of beans and 30 grams of rice bran per day is enough to see changes in small molecules that can confer protection against colorectal cancer.

"The simple message is, 'Food is medicine,' and we are looking at how to simplify that and make it apply to our everyday lives," says study co-author Regina Brown, MD, assistant professor at the CU School of Medicine and oncologist for CUHealth...."The evidence is there in animals and we can now study this in people. The question is, what are we doing to achieve adequate levels of intake of these foods?" Ryan said. "It's not enough to say 'I eat them once in a while.' That's not going to work, particularly if you are at higher risk. You have to meet a dose, just like you need a dose of a certain drug, you need to reach intake levels and consume increased amounts of these foods, and that's where people, including me, are challenged. Not everyone wants to open up a can of beans and eat them every day."

The following article excerpts are from the talk "Food and Brain" about the best foods for the brain, at the annual 2015 meeting of the American Psychiatric Association (APA). This is in the new emerging field of food psychiatry, or how certain foods and diet influence the brain. The data is emerging that we can positively influence mental health through dietary interventions. For ex.: recent work reported that adults who followed the Mediterranean dietary pattern the closest over 4.4 years had a significantly reduced risk of developing depression (by 40% to 60%).

One key comment was: "Perhaps diet is the closest we've come to prevention in psychiatry." Some foods that are especially beneficial for the brain: seafood, greens, nuts, legumes (beans) and occasional dark chocolate. Use smaller amounts of meat (more as flavorings rather than just eating huge chunks of it) on top of a plant based diet. Also mentioned were the benefits of turmeric (because of the curcumin in it) and rosemary. And focus on improving the whole dietary pattern rather than just eating or not eating certain foods.

Note that BDNF is Brain-derived neurotrophic factor. This is a protein that acts on the brain, the nervous system, and it is very important for learning, memory, and higher thinking. So increasing BDNF levels is good. And remember, what's good for the brain is also good for the body and microbes - it's all intertwined. From Medscape:

Beans, Greens, and the Best Foods For the Brain

Dr Ramsey, in collaboration with the new International Society for Nutritional Psychiatry, is in the process of developing a standardized "brain food diet." "Food is a very effective and underutilized intervention in mental health," he started off. "We want to help our patients have more resilient brains by using whole foods...by helping get patients off of processed foods, off of white carbohydrates, and off of certain vegetable oils."

Though the field is in its infancy, food psychiatry is increasingly being embraced by clinicians and researchers, as a paper published earlier this year in the Lancet Psychiatry attests. "Although the determinants of mental health are complex," the authors wrote, "the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology." ..."The data are very promising that we can positively influence mental health through dietary interventions," commented Dr Ramsey.

"Hominid diets have changed drastically through millions of years of evolution.,,,But only in the past 100 years has our diet drastically switched from a whole foods diet to one that is more processed and high in refined carbohydrates; that includes more vegetable fats rather than meat fats; and preservatives, emulsifiers, and other additives, which appear to have contributed to a decline in our collective health.

Early humans evolved in the African Rift Valley, which is near a seacoast. It's possible that whatever evolutionary spark occurred that made us human occurred here, in part due to reliable access to seafoodoysters in particular—which glutted our brains with omega-3 fatty acids and cholesterol (our brains are composed of 60% fat). Oysters and other mollusks are also very high in nutrients, including B12, which is commonly deficient in people consuming vegan or vegetarian diets and is necessary for myelin and neurotransmitter function. 

A number of studies have linked the Mediterranean diet (high in fish oils, nuts, and grains and including maybe a little red wine) with advantageous effects on neurologic and mental health. Dr Deans cited recent work reporting that adults who followed the Mediterranean dietary pattern the closest over 4.4 years had a significantly reduced risk of developing depression (40%-60%)....When taken together, most of these dietary pattern studies, which have been conducted all over the world, consistently show that traditional, pre-processed diets are the healthiest, including for the brain. ..."Eat the rainbow," he says, given that bold, bright colors in nature tend to signify valuable vitamins and phytonutrients (the reds, purples, and greens in particular).

Seafood: Seafood is packed with brain-healthy omega-3 fatty acids. These healthy fats are also abundant in plants like chia and flax, but plant-based sources aren't as efficiently converted to docosahexaenoic acid (DHA), an important structural component of neuronal membranes. DHA also influences the expression of brain-derived neurotrophic factor (BDNF), which can benefit people who have mood and anxiety disorders. Bivalves like mussels, oysters, and clams are the top source of vitamin B12 as well as zinc: Six oysters (only about 10 calories each) provide 240% of our recommended daily B12 intake and 500% of our recommended zinc intake! Seafood is also a leading dietary source of vitamin D (we don't get it all from the sun) as well as iodine and chromium. Although many people worry about mercury in fish, Dr Ramsey provided an easy way around the concern: Eat small fish like sardines, anchovies, and herring, which typically don't accumulate toxic levels.

Leafy greens: A great base for a brain-food diet, leafy greens are a good source of fiber, folate (derived from the wordfoliage), magnesium, and vitamin K. Perhaps surprising, kale, mustard greens, and bok choy provide the most absorbable form of calcium on the planet, more so than milk. Greens also provide flavanols and carotenoids that have beneficial epigenetic influences (eg, including upping hepatic toxin processing). 

Nuts:... Nuts are packed with healthy monounsaturated fats. They help keep us full and also aid in absorbing fat-soluble nutrients. Nuts also provide fiber as well as minerals like manganese and selenium. A serving of 22 almonds (just 162 calories) contains 33% of our recommended vitamin E, plenty of protein, and minerals, including iron. One study from 2013 found that the Mediterranean diet augmented with nuts is associated with significantly higher BDNF levels in patients with depression.

Legumes: Dr Ramsey is pro-meat, but he acknowledges that many people are eating far too much and the wrong types of meat, and that nuts and legumes are a great alternative source of protein and nutrients...Some data suggest that vegan and vegetarian diets are associated with improved mood. But as previously mentioned, these dietary patterns can result in B12 deficiency, which has been associated with brain atrophy and developmental delay. Hence, supplementation is important in this population. Vegetarianism has also been linked with depression, anxiety, and eating disorders, as well as increased healthcare utilization and worse quality of life. These negative associations also could be due to the fact that it's harder to absorb nutrients like zinc, iron, and certain omega-3s from plants.

"The notion that the vegan diet is the healthiest diet on the planet is probably incorrect," said Dr Ramsey, before explaining that he just feels that we should approach meat in our diets differently....We want to help patients use beef and seafood more as flavorings on top of a plant-based diet." A modest amount of meat in the diet has its benefits, including nutrient availability: Hemoglobin-derived iron is up to 40% more absorbable than plant-based iron. Unlike most plants, meat provides all of the amino acids necessary for protein synthesis. Dr Ramsey emphasized the importance of seeking out leaner, grass-fed meats if one has the means.

The understanding of how microbiota contribute to our mental and medical well-being is rapidly advancing....One of the most powerful interventions to alter our microbiome is diet. Research shows that stressed mice experienced changes in the gastrointestinal microbiota, reflecting the gut-brain relationship. There are 260 million neurons connecting the gut and the brain; furthermore, many commensal gut bacteria make neurotransmitters and communicate with the brain via the vagus nerve....Although the science of probiotic therapies is relatively young, it's clear that these commensal organisms co-evolved with us and are adapted to our diet.

Finally, to close out the session, Dr Ramsey returned to the stage and asked, "So, can you eat to build a better brain? We think that you can if you focus on dietary patterns and not a single food here or there." He also reminded the audience to help their patients identify and increase their consumption of nutrient-dense foods and to "eat the rainbow,"..."I don't know of anything else that can potentially decrease the risk of depression in a population by 40%," he concluded. "Perhaps diet is the closest we've come to prevention in psychiatry."

...Evidence suggests that curcumin, an ingredient in turmeric, increases BDNF. Other research has found that populations that eat more curry have a decreased risk for dementia, while rosemary extract may help prevent cognitive impairment. "Many spices seem to have healing properties," Dr Ramsey commented.

Although the "Food and the Brain" session at the American Psychiatric Association annual meeting focused on what to eat in the interest of brain health, intermittent fasting might also be beneficial for the brain. In addition to helping maintain a healthy weight, fasting induces ketosis. Ketone metabolism has been shown to be beneficial for the brain and improve cognition in patients with mild cognitive impairment or Alzheimer disease. Keep in mind that fasting can come with risks for some people, particularly diabetics, and should be discussed with a healthcare provider.

To celebrate National Nut Day, two articles about health benefits of nuts. From Medical Daily:

National Nut Day 2014: Peanuts, Tree Nuts, And How Each Helps Your Health

For people who already eat plenty of meat and dairy products…nuts and ‘nutty’ legumes, like Brazil nuts, cashews, peanuts and walnuts, are a good nutritional alternative to meat,” Dr. Donal Murphy-Bokern, independent agri-environmental scientist and author of several studies on food system impacts, said in a statement. Heeding this advice means people can reap the benefits that come with eating nuts — Protein! Fiber! Omega-3 fatty acids! 

Nuts fall into two categories: peanuts (which are really legumes) and tree nuts. The latter includes Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios, walnuts and America’s beloved almonds. ...” And existing research generalizes that eating nuts does everything from reduce risk for a slew of diseases, maintains weight, boosts gastrointestinal and bone health, even adds years to a person’s life.

As previously mentioned, nuts are pretty much equal in terms of calories. There are, however, some nuts that have more heart-healthy nutrients and fats than others. See: pistachios. This particular tree nut is high in healthy fats called monounsaturated fats (MUFA). MUFAs are often associated with belly fat.

One study published in the journal Nutrition found that when middle-aged adults at risk for heart disease and diabetes incorporated more pistachios into their diet, they weighed less and lessened their cholesterol and blood sugar levels after just six months. And a separate study from UCLA found people who regularly ate pistachios lost an average of 10 to 12 pounds. Almonds and cashews are additional nuts high in MUFAs. 

The Harvard School of Public Health reported, “several of the largest cohort studies, including the Adventist Study, the Iowa Women’s Health Study, the Nurses’ Health Study, and the Physicians’ Health Study have shown a consistent 30 percent to 50 percent lower risk of myocardial infarction, sudden cardiac death, or cardiovascular disease associated with eating nuts several times a week.”

Though almonds tend to be associated most with heart health, it’s actually walnuts that take the number one spot. ...Health reported a 2006 Spanish study, which “suggested that walnuts were as effective as olive oil at reducing inflammation and oxidation in the arteries after eating a fatty meal.”

Folate, as defined by Harvard Medical School, is “the naturally occurring form of the vitamin that is in foods or in the blood.” It’s also the vitamin that staves off brain atrophy, or the progressive loss of brain cells over time... A study published in the American Journal of Psychiatry found folate may ward off depression, too. And which nut is super rich in folate? Unsalted peanuts...peanuts are also high in vitamin E and niacin, both of which boost brain health. Hazelnuts and almonds are known to have concentrated amounts of E, too, so either nut is bound to help your noggin.

Study done in mice, but shows benefits of walnuts to brain. From Science Daily:

Fight against Alzheimer's disease: New research on walnuts

A new animal study published in the Journal of Alzheimer's Disease indicates that a diet including walnuts may have a beneficial effect in reducing the risk, delaying the onset, slowing the progression of, or preventing Alzheimer's disease. Research led by Abha Chauhan, PhD, head of the Developmental Neuroscience Laboratory at the New York State Institute for Basic Research in Developmental Disabilities (IBR), found significant improvement in learning skills, memory, reducing anxiety, and motor development in mice fed a walnut-enriched diet.

The researchers suggest that the high antioxidant content of walnuts (3.7 mmol/ounce) may have been a contributing factor in protecting the mouse brain from the degeneration typically seen in Alzheimer's disease. Oxidative stress and inflammation are prominent features in this disease, which affects more than five million Americans.

Walnuts have other nutritional benefits as they contain numerous vitamins and minerals and are the only nut that contains a significant source of alpha-linolenic acid (ALA) (2.5 grams per ounce), an omega-3 fatty acid with heart and brain-health benefits. The researchers also suggest that ALA may have played a role in improving the behavioral symptoms seen in the study.