Physical activity needed to reap benefits of dietary restriction

ScienceDaily (July 2, 2012) — Fruit flies on dietary restriction (DR) need to be physically active in order to get the lifespan extending benefits that come from their Spartan diet. If the same axiom holds true in humans, those practicing caloric restriction in hopes of living longer need to make sure they eat enough to avoid fatigue.

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According to research at the Buck Institute, flies on DR shift their metabolism toward increasing fatty acid synthesis and breakdown, specifically in muscle tissue. "Dietary restriction is known to enhance spontaneous movement in a variety of species including primates, however this is the first examination of whether enhanced physical activity is necessary for its beneficial effects," said Buck faculty Pankaj Kapahi, PhD, who runs the lab where the research took place. "This study establishes a link between DR-mediated metabolic activity in muscle, increased movement and the benefits derived from restricting nutrients," he said, adding that flies on DR who could not move or had inhibited fat metabolism in their muscle did not exhibit an extended lifespan. "Our work argues that simply restricting nutrients without physical activity may not be beneficial in humans," said Kapahi.

The research is published in the July 3, 2012 edition of Cell Metabolism.

The research also points to a potential target that could yield a drug that mimics the beneficial effects of DR. Lead author, Subhash D. Katewa, PhD, Buck Institute staff scientist, said flies genetically engineered to overexpress the circulating peptide AKH (the fly equivalent of glucagon in mammals) showed increased fat metabolism, spontaneous activity and extended lifespan even though their diet was unrestricted. AKH plays a critical role in glucose and lipid metabolism. "Our data suggests that DR may induce changes in muscle similar to those observed under endurance exercise and that molecules like AKH could serve as potential mimetics for DR that enhance activity and healthspan," said Katewa.

"A better understanding of the dynamics of fat metabolism is needed in order to clarify its role in aging and disease," Katewa said. "These current results suggest that enhanced fat metabolism could help slow aging and the onset of age-related disease."

Contributors to the work: Other Buck Institute researchers involved in the study include Marysia Kolipinski, and Simon Melov. Other collaborators include Fabio Demontis and Norbert Perrimon, Department of Genetics, Harvard Medical School, Boston; Allan Hubbard, School of Public Health, Division of Biostatistics, University of California, Berkeley; and Matthew S. Gill, Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL. The work was funded by grants from the American Federation of Aging Research, and the National Institutes of Health.

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Dietary fiber alters gut bacteria, supports gastrointestinal health

ScienceDaily (June 28, 2012) — A University of Illinois study shows that dietary fiber promotes a shift in the gut toward different types of beneficial bacteria. And the microbes that live in the gut, scientists now believe, can support a healthy gastrointestinal tract as well as affect our susceptibility to conditions as varied as type 2 diabetes, obesity, inflammatory bowel disease, colon cancer, and autoimmune disorders such as rheumatoid arthritis.

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As these microbes ferment fiber in the intestine, short-chain fatty acids and other metabolites are produced, resulting in many health benefits for the host, said Kelly Swanson, a U of I professor of animal sciences.

"When we understand what kinds of fiber best nurture these health-promoting bacteria, we should be able to modify imbalances to support and improve gastrointestinal health," he said.

This research suggests that fiber is good for more than laxation, which means helping food move through the intestines, he added.

"Unfortunately, people eat only about half of the 30 to 35 grams of daily fiber that is recommended. To achieve these health benefits, consumers should read nutrition labels and choose foods that have high fiber content," said Swanson.

In the placebo-controlled, double-blind intervention study, 20 healthy men with an average fiber intake of 14 grams a day were given snack bars to supplement their diet. The control group received bars that contained no fiber; a second group ate bars that contained 21 grams of polydextrose, which is a common fiber food additive; and a third group received bars with 21 grams of soluble corn fiber.

On days 16-21, fecal samples were collected from the participants, and researchers used the microbial DNA they obtained to identify which bacteria were present. DNA was then subjected to 454 pyrosequencing, a "fingerprinting" technique that provides a snapshot of all the bacterial types present.

Both types of fiber affected the abundance of bacteria at the phyla, genus, and species level. When soluble corn fiber was consumed, Lactobacillus, often used as a probiotic for its beneficial effects on the gut, increased. Faecalibacterium populations rose in the groups consuming both types of fiber.

According to Swanson, the shifts in bacteria seen in this study--which occurred when more and differing types of fiber were consumed--were the opposite of what you would find in a person who has poor gastrointestinal health. That leads him to believe that there are new possibilities for using pre- and probiotics to promote intestinal health.

"For example, one type of bacteria that thrived as a result of the types of fiber fed in this study is inherently anti-inflammatory, and their growth could be stimulated by using prebiotics, foods that promote the bacteria's growth, or probiotics, foods that contain the live microorganism," he said.

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Dietary changes help some children with ADHD

ScienceDaily (Apr. 24, 2012) — Together with child and adolescent psychiatrists, researchers from the University of Copenhagen have just completed an extensive report which reviews the studies which have been done so far on the significance of diet for children and young people with ADHD. The report shows that there are potential benefits in changing the diets of children with ADHD, but that key knowledge in the area is still lacking.

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The comprehensive report covers the scientific literature on the significance of diet for children with ADHD: "Our conclusion is that more research is required in the area. There is a lot to suggest that by changing their diet, it is possible to improve the condition for some ADHD children," says professor in paediatric nutrition Kim Fleischer Michaelsen from the Department of Human Nutrition at the Faculty of Life Sciences, University of Copenhagen, who is heading the study.

Professor Kim Fleischer stresses that more research is needed: "Several of the studies show, for example, that fatty acids from fatty fish moderate the symptoms. Other studies detect no effect. Elimination diets are also promising. These look at whether there is anything in the diet which the children cannot consume without adverse side effects. However, we still lack knowledge about which children with ADHD benefit from dietary changes, how positive the effect is in the long term and what the changes mean for children's health."

Dietary changes not beneficial for everyone

The report shows that not all ADHD children benefit from changes to their diet, and that there are still many unknown factors. Tine Houmann, a consultant at the Centre for Child & Adolescent Psychiatry, says:

"There are different types of ADHD, and the disturbance is probably due to both genetic and environmental factors. We know that children with ADHD react very differently to both medication and dietary changes. We therefore need to study which children benefit from dietary changes, and whether we can identify genetic or environmental factors that can predict this."

Bigger studies needed

The experts hope that, by acquiring more knowledge on the subject, it is possible to reduce the use of medication and instead develop special dietary advice for the children: "It is promising that many research results indicate that dietary changes can help some ADHD children. However, it is crucial that bigger studies on dietary changes are conducted on children with ADHD to see how effective this is and how long the benefits last," says Kim Fleischer Michaelsen, while stressing that parents should always seek professional advice before changing their children's diet.

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