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Category: nutrition

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I have seen a lot of excitement about this research, especially whether several day fasting would be beneficial for other diseases (e.g., Crohn's disease) or even for middle-aged or older people who just want to boost their immune system. From Science Daily:

Fasting triggers stem cell regeneration of damaged, old immune system

In the first evidence of a natural intervention triggering stem cell-based regeneration of an organ or system, a study shows that cycles of prolonged fasting not only protect against immune system damage -- a major side effect of chemotherapy -- but also induce immune system regeneration, shifting stem cells from a dormant state to a state of self-renewal.

In both mice and a Phase 1 human clinical trial, long periods of not eating significantly lowered white blood cell counts. In mice, fasting cycles then "flipped a regenerative switch": changing the signaling pathways for hematopoietic stem cells, which are responsible for the generation of blood and immune systems, the research showed.

The study has major implications for healthier aging, in which immune system decline contributes to increased susceptibility to disease as we age. By outlining how prolonged fasting cycles -- periods of no food for two to four days at a time over the course of six months -- kill older and damaged immune cells and generate new ones, the research also has implications for chemotherapy tolerance and for those with a wide range of immune system deficiencies, including autoimmunity disorders.

"When you starve, the system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged," Longo said. "What we started noticing in both our human work and animal work is that the white blood cell count goes down with prolonged fasting. Then when you re-feed, the blood cells come back. So we started thinking, well, where does it come from?"

Prolonged fasting forces the body to use stores of glucose, fat and ketones, but also breaks down a significant portion of white blood cells. Longo likens the effect to lightening a plane of excess cargo.

During each cycle of fasting, this depletion of white blood cells induces changes that trigger stem cell-based regeneration of new immune system cells. In particular, prolonged fasting reduced the enzyme PKA, an effect previously discovered by the Longo team to extend longevity in simple organisms and which has been linked in other research to the regulation of stem cell self-renewal and pluripotency -- that is, the potential for one cell to develop into many different cell types. Prolonged fasting also lowered levels of IGF-1, a growth-factor hormone that Longo and others have linked to aging, tumor progression and cancer risk.

"PKA is the key gene that needs to shut down in order for these stem cells to switch into regenerative mode. It gives the 'okay' for stem cells to go ahead and begin proliferating and rebuild the entire system," explained Longo, noting the potential of clinical applications that mimic the effects of prolonged fasting to rejuvenate the immune system. "And the good news is that the body got rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting. Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system."

Prolonged fasting also protected against toxicity in a pilot clinical trial in which a small group of patients fasted for a 72-hour period prior to chemotherapy, extending Longo's influential past research: "While chemotherapy saves lives, it causes significant collateral damage to the immune system. The results of this study suggest that fasting may mitigate some of the harmful effects of chemotherapy," said co-author Tanya Dorff, assistant professor of clinical medicine at the USC Norris Comprehensive Cancer Center and Hospital. 

"We are investigating the possibility that these effects are applicable to many different systems and organs, not just the immune system," said Longo, whose lab is in the process of conducting further research on controlled dietary interventions and stem cell regeneration in both animal and clinical studies.

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Yes, going out in the sunshine for a while is a good way to get vitamin D. From Science Daily:

Link between vitamin D, dementia risk confirmed

Vitamin D deficiency is associated with a substantially increased risk of dementia and Alzheimer's disease in older people, according to the most robust study of its kind ever conducted. An international team found that study participants who were severely vitamin D deficient were more than twice as likely to develop dementia and Alzheimer's disease.

The team studied elderly Americans who took part in the Cardiovascular Health Study. They discovered that adults in the study who were moderately deficient in vitamin D had a 53 per cent increased risk of developing dementia of any kind, and the risk increased to 125 per cent in those who were severely deficient.

Similar results were recorded for Alzheimer's disease, with the moderately deficient group 69 per cent more likely to develop this type of dementia, jumping to a 122 per cent increased risk for those severely deficient.

The study was part-funded by the Alzheimer's Association, and is published in Neurology, the medical journal of the American Academy of Neurology. It looked at 1,658 adults aged 65 and over, who were able to walk unaided and were free from dementia, cardiovascular disease and stroke at the start of the study. The participants were then followed for six years to investigate who went on to develop Alzheimer's disease and other forms of dementia.... Previous research established that people with low vitamin D levels are more likely to go on to experience cognitive problems, but this study confirms that this translates into a substantial increase in the risk of Alzheimer's disease and dementia.

Vitamin D comes from three main sources -- exposure of skin to sunlight, foods such as oily fish, and supplements. Older people's skin can be less efficient at converting sunlight into virVitamin D, making them more likely to be deficient and reliant on other sources. In many countries the amount of UVB radiation in winter is too low to allow vitamin D production.

The study also found evidence that there is a threshold level of Vitamin D circulating in the bloodstream below which the risk of developing dementia and Alzheimer's disease increases. The team had previously hypothesized that this might lie in the region of 25-50 nmol/L, and their new findings confirm that vitamin D levels above 50 nmol/L are most strongly associated with good brain health....During this hottest of summers, hitting the beach for just 15 minutes of sunshine is enough to boost your vitamin D levels. 

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Very interesting. Gives people a way to eat red meat, but not increase their colorectal cancer risk (by also eating resistant starch, e.g., potato salad or beans). From Science Daily:

Eating resistant starch may help reduce red meat-related colorectal cancer risk

Consumption of a type of starch that acts like fiber may help reduce colorectal cancer risk associated with a high red meat diet, according to a study. "Red meat and resistant starch have opposite effects on the colorectal cancer-promoting miRNAs, the miR-17-92 cluster," said one researcher. "This finding supports consumption of resistant starch as a means of reducing the risk associated with a high red meat diet.

Unlike most starches, resistant starch escapes digestion in the stomach and small intestine, and passes through to the colon (large bowel) where it has similar properties to fiber, Humphreys explained. Resistant starch is readily fermented by gut microbes to produce beneficial molecules called short-chain fatty acids, such as butyrate, she added.

"Good examples of natural sources of resistant starch include bananas that are still slightly green, cooked and cooled potatoes [such as potato salad], whole grains, beans, chickpeas, and lentils. Scientists have also been working to modify grains such as maize so they contain higher levels of resistant starch," said Humphreys.

After eating 300 g of lean red meat per day for four weeks, study participants had a 30 percent increase in the levels of certain genetic molecules called miR-17-92 in their rectal tissue, and an associated increase in cell proliferation. Consuming 40 g of butyrated resistant starch per day along with red meat for four weeks brought miR-17-92 levels down to baseline levels.

The study involved 23 healthy volunteers, 17 male and six female, ages 50 to 75. Participants either ate the red meat diet or the red meat plus butyrated resistant starch diet for four weeks, and after a four-week washout period switched to the other diet for another four weeks.

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Fish consumption was beneficial for the brain, but brain differences among the groups not correlating with blood omega-3 levels was a surprise. From  Science Daily:

Eating baked, broiled fish weekly boosts brain health, study says

Eating baked or broiled fish once a week is good for the brain, regardless of how much omega-3 fatty acid it contains, according to researchers. The findings add to growing evidence that lifestyle factors contribute to brain health later in life. Scientists estimate that more than 80 million people will have dementia by 2040, which could become a substantial burden to families and drive up health care costs.

"Our study shows that people who ate a diet that included baked or broiled, but not fried, fish have larger brain volumes in regions associated with memory and cognition," Dr. Becker said. "We did not find a relationship between omega-3 levels and these brain changes, which surprised us a little. It led us to conclude that we were tapping into a more general set of lifestyle factors that were affecting brain health of which diet is just one part."

Lead investigator Cyrus Raji, M.D., Ph.D., who now is in radiology residency training at UCLA, and the research team analyzed data from 260 people who provided information on their dietary intake, had high-resolution brain MRI scans, and were cognitively normal at two time points during their participation in the Cardiovascular Health Study (CHS), a 10-year multicenter effort that began in 1989 to identify risk factors for heart disease in people over 65.

"The subset of CHS participants answered questionnaires about their eating habits, such as how much fish did they eat and how was it prepared," Dr. Raji said. "Baked or broiled fish contains higher levels of omega-3s than fried fish because the fatty acids are destroyed in the high heat of frying, so we took that into consideration when we examined their brain scans."

People who ate baked or broiled fish at least once a week had greater grey matter brain volumes in areas of the brain responsible for memory (4.3 percent) and cognition (14 percent) and were more likely to have a college education than those who didn't eat fish regularly, the researchers found. But no association was found between the brain differences and blood levels of omega-3s.

"This suggests that lifestyle factors, in this case eating fish, rather than biological factors contribute to structural changes in the brain," Dr. Becker noted. "A confluence of lifestyle factors likely are responsible for better brain health, and this reserve might prevent or delay cognitive problems that can develop later in life."

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Great reason to enjoy spicy food. From Science Daily:

Chili peppers for a healthy gut: Spicy chemical may inhibit gut tumors

Researchers report that dietary capsaicin – the active ingredient in chili peppers – produces chronic activation of a receptor on cells lining the intestines of mice, triggering a reaction that ultimately reduces the risk of colorectal tumors.

...the current study suggests one potential remedy might be spicy capsaicin, which acts as an irritant in mammals, generating a burning sensation in contact with tissue. Capsaicin is already broadly used as an analgesic in topical ointments, where its properties as an irritant overwhelm nerves, rendering them unable to report pain for extended periods of time. It's also the active ingredient in pepper spray.

The researchers fed capsaicin to mice genetically prone to developing multiple tumors in the gastrointestinal tract. The treatment resulted in a reduced tumor burden and extended the lifespans of the mice by more than 30 percent. The treatment was even more effective when combined with celecoxib, a COX-2 non-steroidal anti-inflammatory drug already approved for treating some forms of arthritis and pain.

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This research review suggests that 5 servings a day of fruits and vegetables has the best health benefits. They surprisingly did not find that fruit/vegetable consumption was protective against cancer. But the authors point out that other studies of cancer and fruit/vegetable consumption have also been inconsistent, and this might be partly explained if certain fruits and vegetables only have effects on certain cancers. From Medical Daily:

An Apple A Day Keeps The Doctor Away? Actually It's 5 Apples, And They Keep Death Away

A review of the eating habits of more than 800,000 people seems to discredit the old maxim about "an apple a day." In fact, five servings of fruit and vegetables offers the best health benefits, particularly against heart disease, and reduces your chances of dying for any reason.

After calculating the odds, researchers write in the Journal of Epidemiology and Community Health that "the risk of all-cause mortality was decreased by 5 percent for each additional serving a day of fruit and vegetables." But, contrary to other reports, they found the benefits drop off after five servings, at which point, they wrote, "we observed a threshold." Previous studies have said seven fruit and vegetable servings is the optimum number.

Other studies have also made the case for fruits and vegetables as a ward against cancer. This one, led by Professor Frank B. Hu in the Harvard School of Public Health, saw no evidence for that. They did, however, find a "significant inverse association" between a fruit and veggie diet and death by heart disease. "The results support current recommendations to increase consumption to promote health and overall longevity," Hu and his colleagues wrote.

Of course, the authors admit, the studies they looked at may have been corrupted by participants lying or guessing on their diet questionnaires. But one thing this study has going for it is the massive sample size. They looked at 16 papers involving 833,234 people and 56,423 deaths. Most of those deaths — as is the case in the general population — were caused by cardiovascular disease and cancer. The people who lived longest adhered to what's called the Mediterranean diet, which favors carrots and tomatoes to steak and bacon.

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Two related articles, the first from a month ago, but both discuss eating fresh foods of summer and the effect on the microbiota. From Gut Microbiota Worldwatch:

Seasonal diet changes affect the composition of our gut microbiota

The mix of bacteria that live in our gut changes throughout the year, to match the food we eat in every specific season. For example, bacteria that process fresh fruit and vegetables are more abundant in the summer, and those that process fats are mode abundant in winter times. A group of scientists at the University of Chicago has found evidence of this seasonal shift in the gut flora, by studying the remote Hutterite population, in North America. The traditional diet and common meals of this community have allowed researchers to study the effect of one common diet in a large population over a long period of time.

Hutterites live in communal farms (colonies) and eat meals in common dining rooms, using traditional recipes that have been relatively stable over time and between colonies. They have little contact with the world outside their colonies, which translates into a very homogeneous genetic pool. Sixty Hutterites from six colonies answered questionnaires about what they ate over the course of a year. During the same period, scientists sampled their stool periodically, to find the genetic sequences of bacteria contained in their gut.

The Hutterites’ diet is relatively stable, except that in summer they eat more fresh fruit and vegetables, and in winter they eat less, and turn to frozen or canned food. Remarkably, their gut flora responded to these changes with massive modification in the abundance of certain bacteria. For example, during summer Bacteroidetes were more abundant: this group of bacteria contain complex carbohydrate digesters, which may be at work in processing fresh fruit and vegetables.

On the other hand Actinobacteria increased in winter: these microbes are associated with processing fat, and with a decreased content of fibre in food. Researchers also found seasonal shifts in other types of bacteria, whose associations with food are still unknown. Notably, the trends were almost identical in all six colonies, possibly a result of a very homogenous lifestyle carried on in a very similar environment.

Although Hutterites live in a relatively isolated way, they use technology and medicine, which makes their lifestyle closer to the general population than that of other more traditional communities. That is why the authors believe that these results may be extended to the general population.

This healthy living article promotes eating fresh fruits and vegetables (tomatoes, blueberries, asparagus, and leeks) as good for the gut microbiome. From Huffington Post:

4 Summer Foods That Can Help Trim Your Waist

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Future microbiome research and therapy will have to take into account that diet affects the gut microbes of men and women differently. From Science Daily:

Diet affects males' and females' gut microbes differently

The microbes living in the guts of males and females react differently to diet, even when the diets are identical, according to a new study. These results suggest that therapies designed to improve human health and treat diseases through nutrition might need to be tailored for each sex.

The researchers studied the gut microbes in two species of fish and in mice, and also conducted an in-depth analysis of data that other researchers collected on humans. They found that in fish and humans diet affected the microbiota of males and females differently. In some cases, different species of microbes would dominate, while in others, the diversity of bacteria would be higher in one sex than the other.

These results suggest that any therapies designed to improve human health through diet should take into account whether the patient is male or female.

Genetics and diet can affect the variety and number of these microbes in the human gut, which can in turn have a profound influence on human health. Obesity, diabetes, and inflammatory bowel disease have all been linked to low diversity of bacteria in the human gut.

Why men and women would react differently to changes in diet is unclear, but there are a couple of possibilities. The hormones associated with each sex could potentially influence gut microbes, favoring one strain over another. Also, the sexes often differ in how their immune systems function, which could affect which microbes live and die in the microbiome.

One notable exception in Bolnick's results was in the mice. Although there was a tiny difference between male and female mice, for the most part the microbiota of each sex reacted to diet in the same manner. Because most dietary studies are conducted on mice, this result could have a huge effect on such research, and it raises questions about how well studies of gut microbes in lab mice can be generalized to other species, particularly humans.

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This research illustrates how little we currently know about gut bacteria.But it did show the importance of diet. From Science Daily:

Monitoring rise and fall of the microbiome

Trillions of bacteria live in each person's digestive tract. Scientists believe that some of these bacteria help digest food and stave off harmful infections, but their role in human health is not well understood.

To help shed light on the role of these bacteria, a team of researchers led by MIT associate professor Eric Alm recently tracked fluctuations in the bacterial populations of two research subjects over a full year. The findings, described in the July 25 issue of the journal Genome Biology, suggest that while these populations are fairly stable, they undergo daily fluctuations in response to changes in diet and other factors...."To a large extent, the main factor we found that explained a lot of that variance was the diet."

There are a few thousand strains of bacteria that can inhabit the human gut, but only a few hundred of those are found in any given individual, Alm says. For one year, the two subjects in the study collected daily stool samples so bacterial populations could be measured. They also used an iPhone app to track lifestyle factors such as diet, sleep, mood, and exercise, generating a huge amount of data.

Analysis of this data revealed that dietary changes could produce daily variations in the populations of different strains of bacteria. For example, an increase in fiber correlated with a boost in the populations of Bifidobacteria, Roseburia, and Eubacterium rectale. Four strains -- including Faecalibacterium prausnitzii, which has been implicated in protecting against inflammatory bowel disease -- were correlated with eating citrus.

During the study, each of the two subjects experienced an event that dramatically altered the gut microbiome. Subject B experienced food poisoning caused by Salmonella, and Subject A traveled to a developing nation, where he experienced diarrheal illness for two weeks.

During Subject B's infection, Salmonella leapt from 10 percent of the gut microbiome to nearly 30 percent. At the same time, populations of bacteria from the phylum Firmicutes, believed to be beneficial to human health, nearly disappeared. After the subject recovered, Firmicutes rebounded to about 40 percent of the total microbiome, but most of the strains were different from those originally present.

Subject A also exhibited severe disruptions to his microbiome during his trip, but once he returned to the United States, it returned to normal. Unlike Subject B's recovery from food poisoning, Subject A's populations returned to their original composition.

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Great reason to add more rosemary and oregano to your diet. From Science Daily:

Rosemary, oregano contain diabetes-fighting compounds

The popular culinary herbs oregano and rosemary are packed with healthful compounds, and now lab tests show they could work in much the same way as prescription anti-diabetic medication, scientists report. In their new study, researchers found that how the herbs are grown makes a difference, and they also identified which compounds contribute the most to this promising trait.

Elvira Gonzalez de Mejia and colleagues point out that in 2012, type-2 diabetes affected more than 8 percent of Americans and cost the country $175 billion. ... Recent research has shown that herbs could provide a natural way to help lower glucose in blood. So Gonzalez de Mejia's team decided to take a closer look.They tested four different herbs, either greenhouse-grown or dried commercial versions, for their ability to interfere with a diabetes-related enzyme, which is also a target of a prescription drug for the disease.

They found that greenhouse herbs contained more polyphenols and flavonoids compared to the equivalent commercial herbs. But this didn't affect the concentration required to inhibit the enzyme. Commercial extracts of Greek oregano, Mexican oregano and rosemary were better inhibitors of the enzyme, required to reduce risk of type-2 diabetes, than greenhouse-grown herbs.