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Category Archives: Health

Infection defense: Call for support by the killer cells

 A few days after a viral infection, countless killer cells swarm out to track down and kill infected body cells. In this way, they are highly effective at preventing pathogens from being able to spread further. An international research team has now explained an important mechanism behind building this army. The work under the aegis of the University of Bonn is published in the journalImmunity.

Killer cells — called cytotoxic T cells in the technical jargon — are somewhat like a well-trained police dog: as long as they don’t know that an infection is currently spreading somewhere in the body, they behave peacefully. They only become active and multiply when forensics rubs a “piece of property” of the pathogen under their nose. Only then do they head out to destroy the intruder.

The role of forensics is assumed by the dendritic cells. They patrol around the clock and keep a lookout for molecules that should not actually be inside the body. When they make a find, they present the foreign molecule on their surface. Then they wait for a killer cell, to which they can show their find.

However, there are a great many different killer cells in the body. Each of them specializes in a certain foreign substance and can only be activated by a specific one. It thus usually takes a little time until the right bloodhound comes across the dendritic cell. But then things happen quickly: the killer cell begins to divide rapidly. Within a couple of days, an army of special forces is thus created, which can advance towards the pathogen.

Cooperation at a cellular level

“We have investigated what has to happen so that the killer cells multiply as effectively as possible,” explains Prof. Wolfgang Kastenmüller. The scientists at the Institute of Experimental Immunology at the University of Bonn led a study involving researchers from Japan, the USA, Italy and Germany. “Until now, it was thought that contact with the dendritic cell was sufficient here. However, we were able to show that the killer cell first forms a kind of team by ordering up other cell types in a targeted way.

Immediately after instruction by a dendritic cell, the killer cell thus triggers a kind of chemical help signal. Images from a special microscope show for the first time how specialized cells of the body’s defenses then head towards it. Upon arrival, these helpers set various immune processes in motion. Only in this way is the killer cell fully activated.

This now begins to divide significantly. What’s more, the arising army differentiates itself: some cells become particularly strong, but short-lived, killers. Others, meanwhile, become a kind of memory cell, which can be activated quickly in the event of another infection.

“The killer cell thus first creates a very specific microenvironment,” emphasizes Kastenmüller. “This is essential for a coordinated and strong immune defense mechanism.” The scientists hope that their fundamental work will open up new possibilities over the long term for further improving vaccinations against viruses or tumors

Could You Have a Fractured Bone?

Any crack or break in a bone is considered to be a fractured bone. Although auto accidents are a common cause of fractured bones, most fractures actually occur inside the home.

The most common fractured bone in children is an arm bone, because kids hold out their arms when they fall. For people over age 65 who fall, the most common fractures are hip, spine, arm, and leg fractures.

Fractured bone symptoms depend on what bone is fractured and the type of break you experience, from a stress fracture in the shin or a compression fracture in the spine. The shin bone is the most commonly broken long bone in the body, but fractured leg symptoms from the shin bone can range from mild swelling to a bone actually sticking out through the skin.

Avoid These Hip-Fracture Risk Factors

Symptoms that may occur with most fractured bones include:

  • A misshapen or deformed bone or joint
  • Bruising and swelling around the fracture
  • Severe pain that is worse with movement
  • Broken skin with visible bone showing
  • Loss of sensation or a tingling
  • Limited or complete loss of movement

Types of Bone Fractures

A bone fracture can range from a tiny crack in one spot to multiple complete breaks. Doctors use different terms to describe these types of fractured bones:

  • Greenstick. A greenstick fracture is a crack on one side of a bone that does not go all the way through.
  • Complete. A complete fracture is one that goes all the way through the bone.
  • Stress. A stress fracture is a hairline crack that occurs from overuse. Minor leg fracture symptoms often occur from stress fractures.
  • Compression. A compression fracture is when a bone collapses. This type of fracture usually occurs in the bones of the spine.
  • Open. An open fracture is a fracture that has broken the skin. These are also called compound fractures.
  • Comminuted. A comminuted fracture means that the bone is broken in more than one place.

Who Is at Risk for Fractures?

You are at greatest risk for a fractured bone when you are under age 20 or over age 65. After middle age, women are at greater risk for fractured bones than men because of osteoporosis. Loss of estrogen after menopause can cause low levels of calcium, which can make a woman’s bones weaker and easier to fracture.

Other risk factors include:

  • Participating in sports, especially contact sports
  • Weak muscles and bones from not getting enough exercise
  • Having a bone tumor
  • Having a disease that weakens bones

What to Do for a Fractured Bone

If you or a loved one might have a fractured bone, the first thing to do is stay calm and get help. Movement of a fractured bone can make things worse. Lower leg fracture symptoms or suspected fracture of a hand or arm may require a call to the doctor. More severe fractures may require first aid and emergency treatment. Here are some basic first-aid rules for fractures:

  • Never move a broken bone if it is unstable or if it involves the head, neck, spine, or hip. If a person needs to be moved to safety, he should be grabbed by his clothing (the top of the shirt, belt, or pant legs) and dragged gently.
  • Apply ice packs to reduce swelling.
  • Avoid shock by keeping the person flat and warm with a blanket. The feet can be elevated 12 inches above the head. Do not move a person to get him flat or raise his legs if a head, neck, or back injury is suspected.
  • For an open fracture, rinse the wound to remove dirt and cover it with a clean dressing. Control bleeding with gentle pressure.

Not all fractured bones are medical emergencies, but all fractured bone symptoms need to be checked by a doctor. Call 911 for fractured bone emergencies such as open fractures; severe bleeding; cold, clammy, or blue skin; and possible fractures of the head, neck, back, hip, or upper leg.

Onions Make Us Cry|Why ?

 For some people, slicing a raw onion is no big deal, but for others, it causes a stinging reaction that results in tears and mild discomfort.

What’s to blame for this teary reaction? Enzymes in the onion that release a pungent gas when you slice into it, and when the gas comes into contact with your eyes, it forms sulfuric acid, which is responsible for that telltale stinging sensation. “The more pungent the onion is, the more likely it will make you tear up,” says Irwin Goldman, PhD, department chair and professor of horticulture at the University of Wisconsin-Madison.

That means that yellow onions popular in cooking are the biggest culprits, and sweet, mild Vidalia onions are the least likely to trigger tears. Luckily, onions are the only type of vegetable that cause this crying reaction, because of their unique sulfur compounds.

So why do onions make you well up, but don’t seem to make your partner weepy at all? Dr. Goldman says it’s probably due to the individual chemistry of your eyes: Some people have little or no reaction to sulfuric acid, while others have a stronger sensitivity. And while some people find that wearing contact lenses reduces their onion-related tears, others may find it makes no difference.

Dry Up Those Onion Tears

To minimize onion-triggered weepiness, Goldman recommends freezing or chilling onions before cutting them up. The cold temperature causes a slower release of the enzymes, which helps reduce your reaction. “You can also start chopping an onion from the top end — where the skin comes together — instead of from the bottom end, where the stem is,” he adds. Enzymes are more conentrated in the bottom of the onion.

If onions cause you to tear up excessively, consider wearing eye protection when you slice them. “Swimming goggles really do work,” says Goldman. Or just delegate the chore to another cook in the kitchen.

Basic Health Advice of Little Help

Primary care doctors should be selective in offering lifestyle-change behavioral programs aimed at preventing cardiovascular disease (CVD) to healthy patients who have unhealthy habits, the U.S. Preventive Services Task Force recommended.

“Although the correlation among healthful diet, physical activity, and the incidence of CVD is strong, existing evidence indicates that the health benefit of initiating behavioral counseling in the primary care setting to promote a healthful diet and physical activity is small,” according to Virginia Moyer, MD, MPH, and other USPSTF members writing online in Annals of Internal Medicine.

“Clinicians may choose to selectively counsel patients rather than incorporate counseling into the care of all adults in the general population,” they concluded.

The recommendations applied to what the task force called “medium- or high-intensity behavioral counseling interventions in the primary care setting,” not to simple, brief advice to exercise more and cut back on ice cream.

Medium-intensity programs were those that involved from 31 minutes to 6 hours of direct patient contact. Interventions with more than 6 hours of contact were considered high-intensity.

Although such intensive counseling is unlikely to cause direct harm to patients, spending such time with patients who end up with no benefit represents a “lost opportunity to provide other services that have a greater health effect,” the task force argued.

In deciding which patients would be the best candidates for medium- to high-intensity counseling interventions, clinicians should consider “other risk factors for CVD, a patient’s readiness for change, social support and community resources that support behavioral change, and other healthcare and preventive service priorities,” Moyer and colleagues wrote.

With most adults in the U.S. overweight or obese, and with large numbers getting little to no regular exercise, the benefits of a healthy diet and physical activity in reducing cardiovascular disease risk are not in dispute.

But in patients without a formal diagnosis of hypertension, diabetes, hyperlipidemia, or overt cardiovascular disease, “there is adequate evidence that the benefits of medium- to high-intensity behavioral counseling interventions to improve diet and increase physical activity are small to moderate,” the task force found after reviewing the literature.

Only a few programs, such as those directed at cutting salt intake, appeared to have a clinically significant effect on risk factors and outcomes. These did succeed in reducing blood pressure and subsequent cardiovascular events in patients with baseline diastolic pressure of 80 to 89 mm Hg, according to a 2010 review.

Moyer and colleagues also pointed to the Women’s Health Initiative Dietary Modification Trial, in which women were randomized to low-fat or conventional diets and followed for 8 years. Blood pressure and plasma glucose levels were reduced in the first year with the low-fat diet, but the improvement faded over time.

“More important, no differences occurred in major CVD events or mortality after 8 years,” the task force observed.

But few medium-intensity and no high-intensity programs had been studied in the primary care setting, the group observed, suggesting that such interventions probably are not practical in routine primary care.

In arguing against such interventions as routine care for relatively healthy patients, the USPSTF noted that it has issued other recommendations addressing lifestyle counseling for patients with clearer cardiovascular risks.

For example, it has recommended intensive behavioral counseling for patients “with hyperlipidemia and other known risk factors,” as well as screening for hypertension in all adults and for lipid disorders in those with certain factors.

The group has also urged screening for obesity and intensive behavioral counseling for obese patients.

Whether medium- to high-intensity lifestyle interventions would be valuable for otherwise healthy people remains a valid research topic, Moyer and colleagues emphasized, especially for younger adults.

The task force also called for more studies of the combined effects of clinical and community-based programs, as well as on whether small physiologic changes can produce significant improvements in long-term clinical outcomes.

Coffee Linked to Lower Death Risk

Analysis of a large prospective study of more than 400,000 people found that men who drank four to five cups of coffee daily reduced their risk of death over a 13-year period by 12 percent, while women’s risk dropped by 16 percent, according to Neal Freedman, PhD, of the National Cancer Institute, and colleagues.

The inverse associations were seen for deaths due to heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections, but not for deaths due to cancer, the researchers found.

On the other hand, a suite of other behaviors that often go hand-in-hand with coffee drinking – smoking, lack of exercise, and poor diet – usually combine to mask the benefit, the researchers noted in the May 17 issue of The New England Journal of Medicine.

Freedman and colleagues cautioned that the study could not prove that coffee is good for you.

“It may be that there’s something that goes along with coffee-drinking that’s affecting our results that we couldn’t take into account in our analysis,” Freedman toldMedPage Today.

But, together with previous research, he said, the findings provide “some reassurance that coffee drinkers don’t have a higher risk of death (and suggest) that there might be some benefit from drinking coffee.”

Indeed, the findings are not surprising, according to Frank Hu, MD, PhD, of the Harvard School of Public Health, who was senior author on a 2008 study that also found an apparent benefit for coffee drinking.

“All the evidence is coming together to indicate a potential health benefit of regular coffee consumption,” Hu told MedPage Today.

The only way to prove the benefit exists, Hu said, would be to conduct a large randomized trial, but such a study “may not be feasible” because it would need too many participants.

In the meantime, a large prospective cohort, such as the National Institutes of Health–AARP Diet and Health Study analyzed by Freedman and colleagues, provides the “best available evidence.”

The NIH-AARP cohort has been running since 1995 and includes 229,119 men and 173,141 women who were 50 to 71 when the study started. Over the period from 1995 through 2008, Freedman and colleagues reported, 33,731 men and 18,784 women died.

In an analysis that only took age into account, coffee consumption was associated with an increased risk of death, they reported.

But coffee drinkers were also more likely to smoke, to eat more red meat and fewer fruits and vegetables, to drink alcohol, and to have less vigorous physical activity.

When those factors were taken into account, Freedman and colleagues found, coffee emerged as being inversely associated with all-cause mortality, as well as a range of major causes of death.

Compared with non-drinkers, there was little effect for those who drank some coffee, but less than a cup a day. But for more coffee, the odds of death dropped significantly.

While most of the outcomes showed a benefit for coffee, “the effect was modest,” Freedman said.

Indeed, other experts said other behavioral changes are likely to be more useful than drinking more coffee.

“Based on this study alone, I would not tell people to start drinking more coffee to lower their risk of death,” said Lona Sandon, RD, of UT Southwestern Medical Center in Dallas.

“There are other things with bigger impact on mortality that they probably should be doing,” Sandon said in an email to MedPage Today and ABC News.

Freedman told MedPage Today that people should consult their physicians before making a change – or not – in their diet.

Sandon also questioned one of the acknowledged limitations of the study — that the coffee consumption was measured only at the beginning. “It is possible that their coffee-drinking habits changed over the 12 years of the study,” she said.

Again Freedman agreed, but noted that other studies have shown that coffee drinking as a part of diet is relatively stable over time.

The bottom line, Sandon said, is to “stop smoking, be more physically active, eat your fruits, veggies, whole grains, and healthy fats, and a little coffee doesn’t appear to hurt.”

The study is well done and the conclusions are supported by the data, argued Peter McCullough, MD, of the St. John Providence Health System in Detroit.

In an email to MedPage Today and ABC News, McCullough noted that even decaffeinated coffee appeared to be beneficial – “good news” for people who like coffee but fear caffeine.

But he and others called for a deeper understanding of the complex mix of compounds found in coffee.

“If you are not a coffee drinker, this study is not a good enough reason to start,” commented Cheryl Williams, RD, of Emory Heart & Vascular Center in Atlanta.

Williams said in an email to MedPage Today and ABC News that she’s not confident coffee is truly beneficial, given that other factors might also play a role in the outcomes reported by Freedman and colleagues.

“Overall,” she said, “more research needs to be done to truly understand the compounds in coffee (including those unknown) and their biological activity and effect on health.”

Bug Bites may Infect a Skin

 Zebras evolved from all black to striped in order to repel insects that distract them from feeding, a new study contends.

Researchers from Hungary and Sweden said that zebras’ black and white stripes are the least-attractive hide pattern to disease-carrying bloodsuckers known as tabanids or more commonly, horseflies.

The researchers found that horseflies are drawn to horizontally polarized light resembling reflections from water. They explained that this is how insects find areas of water where they can lay their eggs. Female horseflies also use the light reflected from animals’ hides, particularly black hides, to detect their victims, the study noted.

The study, published online in the March issue of the Journal of Experimental Biology, pointed out that as embryos, zebras start out with dark skin. They go on to develop their white stripes before birth. The researchers suggested this was an evolutionary adaptation to help them avoid bug bites.

The researchers tested their theory at a horse farm near Budapest that was infested with horse flies. They altered the width, angle and density of the stripes and changed the direction of polarization of the light they reflected. Using oil and glue, they trapped the insects to reveal which pattern attracted the most horse flies.

The study showed the narrower the stripes, the fewer flies they attracted. The researchers also tested the attractiveness of a white, dark and striped horse. The study found the striped horse drew the least flies.

“We conclude that zebras have evolved a coat pattern in which the stripes are narrow enough to ensure minimum attractiveness to tabanid flies,” the researchers wrote in a journal news release.

Federal Judge Strikes

A federal judge ruled Monday that the new U.S. health-care reform law is unconstitutional, saying the federal government has no authority to require citizens to buy health insurance.

That provision is a cornerstone of the new legislation, signed into law in March by President Barack Obama.

The judge’s decision was not unexpected, and both supports and opponents of the legislation anticipate the validity of the new health law ultimately will be decided by the U.S. Supreme Court.

The ruling was handed down by U.S. District Judge Henry E. Hudson, a Republican appointed by President George W. Bush who had seemed sympathetic to the state of Virginia’s case when oral arguments were heard in October, the Associated Press reported.

Last week, White House officials said a negative ruling would not affect the implementation of the law because its major provisions don’t take effect until 2014, the AP reported.

Virginia Attorney General Kenneth Cuccinelli, a Republican, had filed a lawsuit in defense of a new Virginia law barring the federal government from requiring state residents to buy health insurance. He argued that it is unconstitutional for the federal law to force citizens to buy health insurance and to assess a penalty if they don’t.

The U.S. Justice Department said the insurance mandate falls within the scope of the federal government’s authority under the Commerce Clause. But Cuccinelli said deciding not to buy insurance is an economic matter outside the government’s domain.

By 2019, the law will expand health insurance access to 94 percent of non-elderly Americans. Advocates say that between now and then, it will also provide Americans with many new rights and protections.

Key provisions include:

  • Health plans may no longer deny coverage to people based on pre-existing health conditions.
  • Health plans that cover dependents must permit children to stay on a parent’s family policy until age 26.
  • Insurers may no longer place lifetime dollar limits on essential benefits.
  • New health plans must offer preventive services such as mammogramsand colon cancer screenings without charging a deductible, co-payment or coinsurance. (This provision does not apply to existing plans that are “grandfathered.”)

Copyright © 2010 HealthDay. All rights reserved.

Pill Bottle Warnings Often Go Unnoticed

Those colorful warning labels on vials of medication don’t always capture a patient’s attention, especially if the patient is older, researchers found.

When groups of older and younger participants were tested on their ability to notice information on medication vials, just 54 percent of the older group fixed their gaze on the prescription warning labels, compared with 91.8 percent of the younger participants, according to Laura Bix, PhD, of Michigan State University in East Lansing, Mich., and colleagues.

And that means that many older patients simply fail to remember their contents and act on them, Bix and colleagues argued online in PLoS ONE. The finding may help to explain why older patients — who often take several medications — are at greater risk for adverse drug events.

The researchers tested two age groups — 15 volunteers ages 20 to 29, and 17 volunteers ages 51 to 77 — for their ability to notice the information on the vials, using eye-tracking technology to see what parts they examined.

In addition, they were tested on how well they remembered what they had looked at, Bix and colleagues reported.

The vials had different-colored warning labels, a white pharmacy label, and a cap with opening instructions.

The color of the label had no effect on the probability that participants would notice it.

As was the case with noticing the warning labels, a similar difference between older and younger patients was seen for the vial cap — 2.4 percent of the older population and 24.4 percent of the younger group looked at it.

On the other hand, 100 percent of both groups looked at the white pharmacy label.

To test recall, participants were presented with a sheet of 10 warning labels and asked which had been on the five vials they had examined, Bix and colleagues reported.

Recognition differed significantly between age groups, with a probability of correctly identifying the warning labels of 68.5 percent for the younger group and 53.6 percent for the older participants.

But when the researchers analyzed the results using a model that included whether participants had actually fixed their gaze on the colored warning labels, the effect of age disappeared.

The volunteers were significantly more likely to recognize the labels if they had fixated on them first. Specifically:

  • When participants fixated on the warning labels, recognition rates were 61.7 percent for young adults and 54.0 percent for the older group.
  • When they failed to fixate on the labels, rates were low — 23.9 percent for the younger group and 9.5 percent for the older volunteers.

In other words, Bix and colleagues argued, the differences in recall appear to be a result of differences in paying attention to the labels in the first place.

Interestingly, that lack of attention was common — when handed five vials in succession, only half of the volunteers fixated on all five warning labels and 22 percent did not fixate on any, the researchers reported.

They concluded that the first step in getting warning messages across is to design labels that will attract attention, and only after that should wording and content be tweaked.

6 foods that can damage your metabolism

Soda

One of the main reasons soda gets a bad rap is because it’s sweetened with a little something known as high fructose corn syrup (HFCS). HFCS, a sweetener found in many of America’s highly processed foods and soft drinks, is as damaging as it is cheap. It has been argued that Fructose consumed in the same quantities as other sugar has more damaging effects on the metabolism (making it an even more sinister commodity).  A study published in the American Journal of Clinical Nutritionfurther explained the link between HFCS and obesity. HFCS may lead to obesity because of its negative effects on the metabolism. In fact, consuming high fructose corn syrup can cause something called “metabolic syndrome,” which is basically a group of risk factors for diabetes, heart disease and stroke. Therefore, drinking a glass of soda can directly hurt your metabolism.

Margarine

Fortunately most sources of trans fat are off the market, but they can still be found in stick margarine and baked goods. The trans fats in the margarine can wreak havoc on your metabolism because they can lead to insulin resistance (which is when the body can’t use insulin effectively). Insulin is a hormone used in fat and carbohydrate metabolism, and insulin resistance results in slower metabolism and weight gain, especially around the abdomen, as it causes our bodies to store fat more easily.

White Bread

White bread and other simple carbohydrates are easily broken down by the body because the fiber (which slows digestion) has been removed during processing. The body does not have to burn any extra calories to try to break down these easy-to-digest-foods, leaving your metabolism operating at a slower level. Foods that are high in fiber like whole wheat bread ramp up your metabolism due to the extra work required to try and break down the indigestible fiber.

Farmed Beef (vs. Grass-Fed)

Conventionally farmed beef can hurt our metabolisms. Conventionally farmed beef has more antibiotics than grass-fed beef. For years, we were unaware what deleterious effects the antibiotics would have on our health. One study published inFront Public Health explained the harm antibiotics have on the good bacteria in the gut of consumers. This change in bacteria in the gut is correlated with an increase in weight gain, as it changes and negatively affects the way we process food. Simply stated, consuming antibiotics from meat can make us gain weight. Our recommendation is to choose grass-fed meat as much as possible.

Conventional (non-organic) apples

Organic fruits are more expensive for more reasons than one. One study published in the Journal of Medical Toxicology showed the toxic effects of pesticides from fruits and vegetables actually caused metabolic changes (by increasing the rate at which fat cells were made) in mice, causing them to gain weight. This means the mice were eating “healthy” fruits and vegetables in the same quantities as the organic control group and were STILL gaining weight. This illustrates the metabolic changes in the mice directly from the pesticides. To limit exposure to pesticides, when it comes to the “Dirty Dozen,” (the fruits and vegetables which are most likely to soak up pesticides and bad bacteria) buy organic. To further limit pesticide exposure be sure to wash all fruits and vegetables well after purchase.

Canola/Vegetable oil

Although previously touted as a health food, canola oil is actually quite the opposite. That’s because it’s a major source of omega-6 fatty acids, which may lead to a slower metabolism.  Whereby the American diet used to be balanced in both omega-6 and omega-3 fatty acids, a push towards higher processing has left our country filled with vegetable oils and hydrogenated fats (high sources of Omega-6), which are pro-inflammatory, and the consumption of these are correlated with obesity. A review published in the journal Nutrients explained that “A high omega-6 fatty acid intake and a high omega-6/omega-3 ratio are associated with weight gain in both animal and human studies, whereas a high omega-3 fatty acid intake decreases the risk for weight gain.” The review further explains that omega-6 fatty acids promote insulin resistance (where our body turns too much of our carbohydrates into fat) and leptin resistance (leptin is the hormone which tells us when we are full; if we are resistant, we never feel full). To limit omega-6s in your diet, switch canola oil out for olive oil.

Omega-3 Fatty Acids

Researchers found that people with the highest blood levels of these essential fatty acids — found in fish such as salmon and tuna — were more likely to perform well on tests of mental functioning and to experience less age-related brain shrinkage.

“We feel fatty acid consumption exerts a beneficial effect on brain aging by promoting vascular health,” said study lead author Dr. Zaldy Tan, an associate professor in the Easton Center for Alzheimer’s Disease Research and the division of geriatrics at the University of California, Los Angeles. This might include reducing blood pressure and inflammation, he added.

Previous research linked dementia risk with the amount of omega-3 fatty acids in blood plasma, which reflects how much people had eaten in the past few days. But in the current work, researchers could estimate the amount of omega-3s that participants had consumed in the past several months by looking at how much had built up in their red blood cells.

“This represents their average intake of fatty acids, not just a snapshot,” Tan said.

The study, published in the Feb. 28 issue of the journal Neurology, did not prove that omega-3 fatty acids prevent mental decline, merely that there may be an association between consumption of fatty acids and brain health.

For the study, researchers measured the red blood cell level of fatty acids in 1,575 dementia-free people whose average age was 67. About three months later, participants underwent mental-functioning tests and MRI scans that examined brain size and blood supply in the brain.

The participants were in the Framingham Offspring Study, which is predominately white. Whether the association would apply to other ethnic and racial groups needs to be explored, the authors said.

The researchers found that those with the lowest levels of omega-3s had worse scores on tests of visual memory, attention and abstract thinking than people who ranked in the top 75 percent for fatty acid levels.

Adults in the bottom 25 percent also tended to have smaller brains overall. The decrease in brain volume was enough to make their brains appear two years older than those of people in the top three quarters for fatty acid levels.

Brain scans also showed signs of less blood supply in the brains of people with the lowest omega-3s levels. This suggests they may play a role in promoting general vascular, or blood vessel, health in the brain, similar to how they are thought to help heart health, rather than acting on just one brain area, Tan said.

The researchers took into account various health and lifestyle factors, including age, education and weight, to explore whether other differences among the people with low levels of omega-3s could help explain their more rapid brain aging.

But after controlling for those risk factors, “the difference [in brain aging] is still there so we conclude that omega-3 fatty acids likely explain them,” Tan said.

However, Tan added that it remains possible that factors they did not control for, such as fruit and vegetable consumption, are really responsible for the brain benefits. Another possibility is that the slight mental decline that the people in the older brain group were experiencing caused them to eat less healthy omega-3 rich foods, instead of vice versa.

“This is a strengthening of the argument that people with less [omega-3 fatty acids] have higher risk of dementia,” said Dr. Nikolaos Scarmeas, associate professor of neurology at Columbia University in New York City.

But questions remain over whether fatty acid levels really influence changes in brain size, Scarmeas added. A clinical trial comparing high and low intake of omega-3s in relation to brain imaging would help answer those questions, he said.

In the meantime, fish is “a good prescription for other things and we have a hint it might be helpful for the brain,” Scarmeas said.

That the current study reported a difference in brain health between people with omega-3 fatty acid levels in the bottom 25 percent and top 75 percent suggests that there is a threshold level of consumption to attain brain gains.

A previous study in which participants filled out food surveys found decreased risk of vascular brain problems among those who ate at least three servings of fish a week.