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Published on Leave a comment on Health Benefits of Dog Ownership

Another study that found benefits to dog ownership. The study authors concluded that: "Our study provides evidence that dog owners are at a lower risk for ischemic stroke, hemorrhagic stroke and heart failure." This could be to daily exercise, or that dog ownership results in less stress or better psychosocial health, or even some other reason (perhaps dog owners are healthier to start with).   Note: myocardial infarction (MI) is commonly known as a heart attack. From Medscape:

Canine Companions Appear to Help Heart Health: Swedish Study

Middle-aged and older dog owners were less likely to die from cardiovascular heart disease (CVD) or all causes, and those who lived alone were less likely to have an MI (myocardial infarction) or stroke, during a decade of follow-up in a large study based on Swedish national registry data[1]. The findings suggest that "especially for those who live alone, dog ownership makes a significant difference . . . in health status," Dr Mwenya Mubanga (Uppsala University, Sweden) told Heartwire from Medscape.....

Dog owners get daily exercise from walking their dogs, and canine companions can reduce stress, which might explain these findings, the researchers speculate....Similarly, Dr Gang Hu (Pennington Biomedical Research, Baton Rouge, LA).....pointed out that the dog owners do more exercise (by walking their dogs), which may contribute to having a lower body weight, lower blood pressure, and possibly good lipid levels and a lower risk of diabetes—which may all act to lower mortality. Having a dog may also reduce the chances of having depression, which might partly explain the more striking findings in the people who lived alone, he added.

Since 2001, dog owners in Sweden have been required by law to register their dogs, and an estimated 83% of dogs were registered that year with the Swedish Board of Agriculture and/or the Swedish Kennel Club dog registries, Mubanga and colleagues explain. They examined the Swedish national registry data to see how dog ownership was related to new CVD events or mortality.....This included 162,091 dog owners (4.8% of the population) and 3,195,153 people who were not dog owners.

Dog owners who lived alone or with at least one child or adult were less likely to die of CVD or all causes during follow-up compared with those who did not own a dog, but the relationships were stronger for solitary dwellers. Among dog owners, solitary dwellers (but not others) were also significantly less likely to have an MI or stroke than people who did not have a dog.

Published on Leave a comment on Many Health Benefits of Nuts and Seeds

Nice summary article about the known benefits of nuts and seeds, and the nutrients they contain. Bottom line: all nuts and seeds are beneficial to health. It's best to eat a variety of nuts, and eat some nuts daily or at least a few times a week. A typical serving is 1/4 cup or small handful of nuts. Go to the article for the complete nut and seed list and a nut and seed nutrient chart. From Today's Dietician:

The Wonders of Nuts and Seeds

Nuts and seeds have been part of the human diet since Paleolithic times. A few nuts, such as almonds and walnuts, and seeds, namely flax and chia, get most of the glory, but the fact is each nut and seed brings something beneficial to the table. While exact nutrient compositions vary, nuts and seeds are rich sources of heart-healthy fats, fiber, plant protein, essential vitamins and minerals, and other bioactive compounds, including an array of phytochemicals that appear to have antioxidant and anti-inflammatory properties.

A wealth of data from prospective observational studies and clinical trials suggest that tree nut consumption reduces the risk of several chronic diseases, including cardiovascular disease (CVD), type 2 diabetes, and some forms of cancer. Moreover, there may be benefits for cognitive health. Adding support to these findings is research suggesting that incorporating tree nuts in the diet lowers the risk of conditions that contribute to disease, such as hypertension, high cholesterol, insulin resistance, abdominal obesity, endothelial dysfunction, oxidative stress, and inflammation. Various components of nuts, such as heart-healthy monounsaturated and polyunsaturated fats, plant-based protein, fiber, vitamins, minerals, and phytochemicals may work together to offer protection against oxidation, inflammation, cancer, and CVD.

Recent findings from the PREDIMED trial suggest that a Mediterranean diet that includes one serving of nuts per day protects against heart attack, stroke, or death from other cardiovascular causes in people at high risk due to type 2 diabetes or metabolic syndrome. PREDIMED data also suggest that eating more than three servings of nuts per week reduces risk of death from all causes, especially if also following a Mediterranean diet. Subjects who frequently consumed both total nuts and walnuts had a lower rate of death from cancer....While the number of nuts per serving varies by type, a typical serving is 1 oz or about 1/4 cup or a small handful (palm of the hand only)....

• Almonds are high in monounsaturated fats, which may explain their association with lower LDL cholesterol levels and reduced heart disease risk. The antioxidant function of the vitamin E (37% DV in 1 oz) in almonds along with their magnesium and potassium also may play a role in cardiovascular health. One study found that almonds may reduce LDL as much as statins.

• Brazil and cashew nuts: Technically a seed, 1 oz of Brazil nuts contains a whopping 767% DV for selenium. That's over the Tolerable Upper Intake Level of 400 mcg. But eating two Brazil nuts per day has been shown to be an effective way to increase blood levels of this antioxidant mineral healthfully. Cashews are lower in fat than most nuts and contain anacardic acid, which may improve insulin sensitivity and help prevent chronic inflammation.

• Pecans contain multiple forms of vitamin E and are especially rich in gamma-tocopherol, which has been shown to inhibit oxidation of LDL cholesterol. Oxidized LDL contributes to inflammation in the arteries and is a risk factor for CVD. Pecans also have the highest polyphenol and flavonoid content of the tree nuts.

• Pistachios: Two studies have shown that eating in-shell pistachios enhances feelings of fullness and satisfaction while reducing caloric intake. When eating in-shell pistachios, study subjects consumed about 40% fewer calories compared with pistachio kernels. Pistachios have the second highest polyphenol and flavonoid content of the tree nuts. 

• Walnuts are another excellent source of plant-based omega-3 fatty acids. Walnuts also boast the highest antioxidant content of the tree nuts, followed by pecans and cashew nuts. This makes walnuts one of the best nuts for anti-inflammatory benefits. Like pecans, walnuts are unusually rich in the gamma-tocopherol form of vitamin E. ... Walnut consumption among NHANES subjects is positively associated with cognitive function in both younger and older adults. They're a natural source of melatonin, which is critical in the regulation of sleep, circadian (daily) rhythms, and may play a role in walnuts' anticancer benefits.

Published on Leave a comment on Toxoplasmosis Infection Linked to Aggression

 Numerous studies link toxoplasmosis to a number of psychiatric conditions, including bipolar disorder, schizophrenia, and obsessive-compulsive disorder. This infection is also linked to aspects of behavior and personality, from impulsivity to prolonged feelings of guilt and excessive worry, and may even slow a person's reflexes. Now new research has linked latent toxoplasmosis infection to aggression and impulsivity. Those with a psychiatric condition called intermittent explosive disorder (IED) have a greater likelihood of toxoplasmosis infection (when compared to people without IED). People who have IED typically experience recurrent outbursts of extreme, impulsive anger, such as seen in road rage.

Three groups (normal healthy control group, intermittent explosive disorder (IED) group, and non-IED psychiatric disorders group) were studied, and in all 3 groups those who tested positive for the infection had higher levels of aggression within their group. 22% of the IED group had the infection, 17% in the non-IED psychiatric group, and only 9% in the healthy normal control group.This research suggested that toxoplasmosis infection is linked to aggression and impulsivity (with aggression being stronger).

Toxoplasmosis is caused by an infection with Toxoplasma gondii, a protozoan parasite carried by cats. It can also infect humans, through contact with cat feces, poorly cooked meat or contaminated water, and as many as one-third of the world’s population may be infected. The person may not feel sick, but the parasite may form cysts in the brain where it can remain for the rest of a person’s life. In this study they determined that someone had a latent T. gondii infection by the circulating immunoglobulin G (IgG) antibodies to T. gondii in the blood (IgG > 12 IU). And yes, the infection can be successfully treated with medications. From Science Daily:

People with rage disorder twice as likely to have latent toxoplasmosis parasite infection

Individuals with a psychiatric disorder involving recurrent bouts of extreme, impulsive anger--road rage, for example--are more than twice as likely to have been exposed to a common parasite than healthy individuals with no psychiatric diagnosis. In a study involving 358 adult subjects, a team led by researchers from the University of Chicago found that toxoplasmosis, a relatively harmless parasitic infection carried by an estimated 30 percent of all humans, is associated with intermittent explosive disorder and increased aggression.

"Our work suggests that latent infection with the toxoplasma gondii parasite may change brain chemistry in a fashion that increases the risk of aggressive behavior," said senior study author Emil Coccaro, MD, Ellen. C. Manning Professor and Chair of Psychiatry and Behavioral Neuroscience at the University of Chicago. "However, we do not know if this relationship is causal, and not everyone that tests positive for toxoplasmosis will have aggression issues," Coccaro said, adding that additional studies are needed.

Intermittent explosive disorder (IED) is defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, as recurrent, impulsive, problematic outbursts of verbal or physical aggression that are disproportionate to the situations that trigger them. IED is thought to affect as many as 16 million Americans, more than bipolar disorder and schizophrenia combined.....examined possible connections to toxoplasmosis, an extremely common parasitic infection. Transmitted through the feces of infected cats, undercooked meat or contaminated water, toxoplasmosis is typically latent and harmless for healthy adults. However, it is known to reside in brain tissue, and has been linked to several psychiatric diseases, including schizophrenia, bipolar disorder and suicidal behavior.

The research team recruited 358 adult subjects from the U.S., who were evaluated for IED, personality disorder, depression and other psychiatric disorders. Study participants were also scored on traits including anger, aggression and impulsivity. Participants fell into one of three groups. Roughly one third had IED. One third were healthy controls with no psychiatric history. The remaining third were individuals diagnosed with some psychiatric disorder, but not IED. This last group served as a control to distinguish IED from possible confounding psychiatric factors.

The research team found that IED-diagnosed group was more than twice as likely to test positive for toxoplasmosis exposure (22 percent) as measured by a blood test, compared to the healthy control group (9 percent). Around 16 percent of the psychiatric control group tested positive for toxoplasmosis, but had similar aggression and impulsivity scores to the healthy control group. IED-diagnosed subjects scored much higher on both measures than either control group.

Across all study subjects, toxoplasmosis-positive individuals scored significantly higher on scores of anger and aggression. The team noted a link between toxoplasmosis and increased impulsivity, but when adjusted for aggression scores, this link became non-significant. This finding suggests toxoplasmosis and aggression are most strongly correlated. However, the authors caution that the study results do not address whether toxoplasmosis infection may cause increased aggression or IED. "Correlation is not causation, and this is definitely not a sign that people should get rid of their cats," said study co-author Royce Lee, MD.... "We don't yet understand the mechanisms involved..."

 Toxoplasma gondii  tissue cyst in a mouse brain Credit: Jitinder P. Dubey, Wikipedia

Published on Leave a comment on More Sunlight Exposure, Live Longer?

A recent study in the Journal of Internal Medicine had interesting results regarding sun exposure - more was beneficial for health.

In the study, women were followed for 20 years, and any  deaths were put into one of 3 groups: as being from: heart disease, cancer, or other (non-heart disease and non-cancer). Swedish women followed for 20 years found that the more sunlight exposure they had, the longer the life expectancy, the less death from heart disease (cardiovascular disease) and causes other than heart disease or cancer (non-heart disease and non-cancer group), but the more skin cancer (basal cell carcinoma, squamous cell carcinoma and melanoma) they developed. 

Thus the main finding is of a dose-dependent relationship between sun exposure and life expectancy.

One surprising result was that nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group. Those who avoided sun exposure had an increased risk of death mainly due to heart disease and "other causes" (non-cancer/non-heart disease).

I wondered about other cancers in this study, and this is all they had to say in the journal article:  "Thus, women with NMSC (nonmalignant skin cancer) had a 37% higher prevalence of other internal cancers than those without NMSC and a fourfold increased prevalence of MM (malignant melanoma). The incidence of other internal cancer was not increased subsequently on NMSC diagnosis."  I now have another question:  How do the women with cancer in the high and low sun exposure group do after another 10 or 20 years?  I would have liked for this study to continue longer.

The researchers felt that sunshine and vitamin D had a role in these results, and suggested that we need to rethink the "avoid sunshine" advice now given to people. In other words, some sunshine is good for health. From Science Daily:

Why do sunbathers live longer than those who avoid the sun?

New research looks into the paradox that women who sunbathe are likely to live longer than those who avoid the sun, even though sunbathers are at an increased risk of developing skin cancer. An analysis of information on 29,518 Swedish women who were followed for 20 years revealed that longer life expectancy among women with active sun exposure habits was related to a decrease in heart disease and noncancer/non-heart disease deaths, causing the relative contribution of death due to cancer to increase.

Whether the positive effect of sun exposure demonstrated in this observational study is mediated by vitamin D, another mechanism related to UV radiation, or by unmeasured bias cannot be determined. Therefore, additional research is warranted. 

"We found smokers in the highest sun exposure group were at a similar risk as non-smokers avoiding sun exposure, indicating avoidance of sun exposure to be a risk factor of the same magnitude as smoking," said Dr. Pelle Lindqvist, lead author of the Journal of Internal Medicine study. "Guidelines being too restrictive regarding sun exposure may do more harm than good for health."

Published on Leave a comment on Cataracts and Vitamin C Rich Foods

A cataract is a clouding of the lens in the eye leading to a decrease in vision. It can affect one or both eyes, it is more common with age, and can even lead to blindness. About 20 million people globally are blind due to cataracts. Vitamin supplements have failed to find an effect in numerous studies.

But in this study, eating foods rich in vitamin C and to a smaller degree manganese had the beneficial effect of slowing cataract progression over the course of 9 1/2 years. Manganese is a micronutrient that is necessary in small amounts, but it is rare to be deficient in manganese. However manganese has numerous negative effects if too much is ingested or if there is too much exposure. Bottom line: increased intake of fruit and vegetables (for vitamin C) could help prevent the development or progression of cataracts.  From Medical Xpress:

Increased vitamin C in the diet could help protect against cataracts

Higher dietary intake of vitamin C has been found to have a potentially preventative effect on cataract progression in the first twin study of cataracts to examine to what degree genetic and environmental factors influence their progression with age. Cataract is a common condition in which the lens of the eye becomes cloudy as a result of oxidation over time. Whilst this is a natural part of ageing for many, for others it is more severe and causes blurred vision, glare and dazzle that cannot be corrected by glasses or contact lenses.

The study, led by King's College London and published in the journal Ophthalmology, looked at the progression of cataracts in the eyes of 324 pairs of female twins .... They found that those participants who had a higher intake of vitamin C were associated with a 33 per cent risk reduction of cataract progression and had 'clearer' lenses after the 10 years than those who had consumed less vitamin C as part of their diet.

The study, funded by the Wellcome Trust and Guide Dogs for the Blind, also found that environmental factors (including diet) influenced cataract more than genetic factors, which only explained a third of the change in lens opacity. The fluid in the eye that bathes the lens is high in vitamin C, which helps to stop the lens from oxidising and protects it from becoming cloudy. It is thought that increased intake of vitamin C has a protective effect on cataract progression by increasing the vitamin C available in the eye fluid.

Kate Yonova-Doing, the study's first author said: 'The human body cannot manufacture vitamin C, so we depend on vitamins in the food we eat. We did not find a significantly reduced risk in people who took vitamin tablets, so it seems that a healthy diet is better than supplements.'

Published on Leave a comment on Wearing Contact Lenses Alters Normal Eye Bacteria

The eye has a normal community of microbes or eye microbiome, just like other body sites (i.e., the gut, the sinuses, the mouth). This community of bacteria is thought to offer resistance from invaders (such as pathogenic bacteria).

The researchers of a recent study found differences in the eye microbiome of contact lens wearers as compared to non-lens wearers. The results indicate that wearing contact lenses "alters the microbial structure of the ocular conjunctiva, making it more similar to that of the skin microbiota" (the community of microbes living on the skin).

Further research is needed to determine whether these differences in the eye microbiome in contact lens wearers is the reason why contact lens wearers develop more eye conditions and infections (such as giant papillary conjunctivitis and keratitis). Over 30 million Americans wear contact lenses so these are important issues.

From Science Daily: Contact lenses alter eye bacteria, making it more skin-like

Contact lenses may alter the natural microbial community of the eyes, according to a study published this week in mBio®, an online open-access journal of the American Society for Microbiology. In a study of 58 adults seeking outpatient eye care, researchers at New York University School of Medicine found that contact lenses make the eye microbiome more skin-like, with higher proportions of the skin bacteria Pseudomonas, Acinetobacter, Methylobacterium, and Lactobacillus and lower proportions of Haemophilus, Streptococcus, Staphylococcus, and Corynebacterium.

It's unclear how these changes occur, said senior study author Maria Dominguez-Bello, PhD, an associate professor of medicine at the university, "if these bacteria are transferred from the fingers to the lens and to the eye surface, or if the lenses exert selective pressures on the eye bacterial community in favor of skin bacteria." Wearing contact lenses has been identified as a risk factor for the development of eye infections such as giant papillary conjunctivitis and keratitis, "so these questions are important," she said.

Researchers used a laboratory technique called 16s rRNA sequencing to compare the bacterial communities of the conjunctiva (the eye surface) and the skin under the eye from 58 adults. They also analyzed samples from 20 of the study participants (9 lens wearers and 11 non-lens wearers) at three time points over the course of six weeks....researchers found a higher diversity of bacteria on the ocular surface than on the skin under the eye or on the contact lenses, which was a surprising result, Dominguez-Bello said.

The ocular surface microbiota of those who wore contact lenses was more skin-like compared to those who did not wear lenses. It was enriched in the bacteria Pseudomonas, Acinetobacter, Methylobacterium, and Lactobacillus. In non-lens wearers, these bacteria were detected at a higher relative abundance in skin samples compared to the eye (except for Lactobacillus), suggesting that these bacteria could be classified as skin bacteria. The bacteria Haemophilus, Streptococcus, Staphylococcus, and Corynebacterium were depleted in the ocular microbiota of lens wearers compared to non-lens wearers.

Published on Leave a comment on Research Using Bacteria to Treat Cancer

The possibility of giving microbes in the future (whether bacteria, viruses, or fungi) to treat cancer is amazing. Of course big pharma is pursuing this line of research, which is called immunotherapy (stimulating the body's ability to fight tumors). The Bloomberg Business article discusses a number of big pharma companies entering the field and their main focus. The study in the journal Science finding that giving common beneficial bacteria (Bifidobacterium breve and Bifidobacterium longum) to mice to slow down melanoma tumor growth is a first step. The researchers themselves said that the 2 common beneficial bacteria species exhibited anti-tumor activity in the mice and was as effective as an immunotherapy in controlling the growth of skin cancer. But note that the bacteria needed to be live. Stay tuned....

From Bloomberg News: How Gut Bacteria Are Shaking Up Cancer Research

Top scientists at Roche Holding AG and AstraZeneca Plc are sizing up potential allies in the fight against cancer: the trillions of bacteria that live in the human body. "Five years ago, if you had asked me about bacteria in your gut playing an important role in your systemic immune response, I probably would have laughed it off," Daniel Chen, head of cancer immunotherapy research at Roche’s Genentech division, said in a phone interview. "Most of us immunologists now believe that there really is an important interaction there."

Two recent studies published in the journal Science have intrigued Chen and others who are developing medicines called immunotherapies that stimulate the body’s ability to fight tumors.In November, University of Chicago researchers wrote that giving mice Bifidobacterium, which normally resides in the gastrointestinal tract, was as effective as an immunotherapy in controlling the growth of skin cancer. Combining the two practically eliminated tumor growth. In the second study, scientists in France found that some bacterial species activated a response to immunotherapy, which didn’t occur without the microbes.  ...continue reading "Research Using Bacteria to Treat Cancer"

Published on Leave a comment on A Benefit of Taking Mass Transit, Walking, or Bicycling to Work

Makes sense that not driving to work in a car, but using mass transit (public transport), cycling, or walking to work results in lower body mass index (BMI) and body fat. They're moving more! From Science Daily:

Public transport, walking and cycling to work are all associated with reductions in body fat for adults in mid-life

Adults who commute to work via cycling or walking have lower body fat percentage and body mass index (BMI) measures in mid-life compared to adults who commute via car, according to a new study incThe Lancet Diabetes & Endocrinology journal. Even people who commute via public transport also showed reductions in BMI and percentage body fat compared with those who commuted only by car. This suggests that even the incidental physical activity involved in public transport journeys may be important.

The study looked at data from over 150000 individuals from the UK Biobank data set, a large, observational study of 500000 individuals aged between 40 and 69 in the UK. The study is the largest to date to analyse the health benefits of active transport.

The strongest associations were seen for adults who commuted via bicycle, compared to those who commute via car. For the average man in the sample (age 53 years; height 176.7cm; weight 85.9kg), cycling to work rather than driving was associated with a weight difference of 5kg or 11lbs (BMI difference 1.71 kg/m2). For the average woman in the sample (age 52 years; height 163.6cm; weight 70.6kg), the weight difference was 4.4kg or 9.7lbs (BMI difference 1.65 kg/m2). After cycling, walking to work was associated with the greatest reduction in BMI and percentage body fat, compared to car-users (BMI difference 0.98 kg/m2 for men; 0.80 kg/m2 for women). For both cycling and walking, greater travelling distances were associated with greater reductions in BMI and percentage body fat.

Commuters who only used public transport also had lower BMI compared to car-users (BMI difference of 0.70kg/m2 for men), as did commuters who combined public transport with other active methods (BMI difference 1.00 kg/m2 for men; 0.67 kg/m2 for women). The effect of public transport on BMI was slightly greater than for commuters who combined car use with other active methods (BMI difference 0.56 kg/m2 for men). The link between active commuting and BMI was independent of other factors such as income, area deprivation, urban or rural residence, education, alcohol intake, smoking, general physical activity and overall health and disability.

Published on Leave a comment on Our Gut Microbes Need Dietary Diversity

A thought-provoking article by Heiman and Greenway was just published in the journal Molecular Metabolism making the case that changes in farming practices over the last 50 years have resulted in decreased agricultural diversity which, in turn, has resulted in decreased dietary diversity, and that the reduction in dietary diversity has changed and decreased the richness of the human gut microbiota (microbes living in the gut). And meanwhile, during the past 50 years, the rates of obesity, type 2 diabetes, and inflammatory bowel diseases sharply increased - and in each of these conditions there is a reduction of the gut microbial diversity. Similar views have also been stated by others in the field of microbiology.

The thinking is that the more diverse the diet, the more diverse the gut microbiome (and healthier), and the more it can adapt to disturbances. Heiman and Greenway state: "Unfortunately, dietary diversity has been lost during the past 50 years because of economic pressures for greater food production to support a growing world population.... Of the 250,000 to 300,000 known edible plant species, humans use only 150 to 200...Today, 75 percent of the world's food is generated from only 12 plants and five animal species."

Also, agricultural practices of using antibiotics as growth promoters for poultry, swine, and cattle further harm the human gut microbiome when the meat is ingested by humans, and pesticide residues on crops ingested by humans may have gut microbiome effects. Even emulsifiers, used in processed foods, reduce microbial richness. Every time a person goes on a certain diet (vegan, Paleo, etc) or makes dietary choices in which some foods are eliminated, it makes it easier for some microbial species, and gives them a competitive advantage over other gut microbes. From Science Daily:

Reduction in dietary diversity impacts richness of human gut microbiota

Changes in farming practices over the last 50 years have resulted in decreased agro-diversity which, in turn, has resulted in decreased dietary diversity. The significant impact of this change in dietary richness on human health is an emerging topic for discussion

Heiman and Greenway describe how the reduction in dietary diversity has changed the richness of human gut microbiota, the community of microorganisms living in the gut. The researchers point out that healthy individuals have diverse gut microbiota and many of the common pathologies of the 21st century, including type 2 diabetes, obesity and inflammatory bowel disease, are associated with reduced microbiotic richness.

Gut microbiota function as an endocrine organ, metabolizing specific nutrients from the diet and producing specific substances that act as metabolic signals in the host. It follows then that highly specialized diets will change the landscape of the gut microbiome over time. In fact, it takes only a few days of changing diet to alter the microbiotic makeup of the human gut. And if the dietary change involves elimination of one or more macronutrients (think Atkins or Paleo or vegan), humans are essentially selecting for some microbiotic species over others.

The importance of microbiota diversity cannot be overstated. They produce an abundance of important molecules for the host and with increased variation comes increased adaptability and an increased range of physiological responses. "The greater the repertoire of signals, the more likely is the ability to maintain homeostasis when dietary intake is perturbed," explain Heiman and Greenway. "Furthermore, because each particular macronutrient has the potential to be metabolized by microbiota into unique metabolic signals, the greater the variety in signals, the greater the variety of responses possible."

Published on Leave a comment on Higher Activity Levels and the Aging Brain

Another study showing that higher physical activity (from a variety of activities) is "related to larger gray matter volume in the elderly, regardless of cognitive status", specifically in gray matter areas of the brain responsible for memory, learning, and cognition. In other words, higher levels of physical activity reduce brain atrophy that occurs with aging and improves cognitive function in elderly individuals.  There is also discussion of higher activity levels improving cerebral (brain) blood flow. Bottom line: get off your butt and move more for better brain health. From Medical Xpress:

Burning more calories linked with greater gray matter volume, reduced Alzheimer's risk

Whether they jog, swim, garden or dance, physically active older persons have larger gray matter volume in key brain areas responsible for memory and cognition, according to a new study by researchers at the University of Pittsburgh School of Medicine and UCLA.The findings, published today in the Journal of Alzheimer's Disease, showed also that people who had Alzheimer's disease or mild cognitive impairment experienced less gray matter volume reduction over time if their exercise-associated calorie burn was high.

A growing number of studies indicate physical activity can help protect the brain from cognitive decline, said investigator James T. Becker, Ph.D., professor of psychiatry, Pitt School of Medicine..... "Our study is one of the largest to examine the relationship between physical activity and cognitive decline, and the results strongly support the notion that staying active maintains brain health."

Led by Cyrus Raji, M.D., Ph.D., formerly a student at Pitt School of Medicine and now a senior radiology resident at UCLA, the team examined data obtained over five years from nearly 876 people 65 or older participating in the multicenter Cardiovascular Health Study. All participants had brain scans and periodic cognitive assessments. They also were surveyed about how frequently they engaged in physical activities, such as walking, tennis, dancing and golfing, to assess their calorie expenditure or energy output per week.

Using mathematical modeling, the researchers found that the individuals who burned the most calories had larger gray matter volumes in the frontal, temporal and parietal lobes of the brain, areas that are associated with memory, learning and performing complex cognitive tasks. In a subset of more than 300 participants at the Pitt site, those with the highest energy expenditure had larger gray matter volumes in key areas on initial brain scans and were half as likely to have developed Alzheimer's disease five years later.

"Gray matter houses all of the neurons in your brain, so its volume can reflect neuronal health," Dr. Raji explained. "We also noted that these volumes increased if people became more active over five years leading up to their brain MRI."