The Health Benefits of Walnuts – A True "Super Food"

The Greeks called the walnut “the nut of Jupiter,” fit for the gods. Native to Persia, walnuts now come from California, which has over 122,000 acres of walnut trees. The tree itself is very hardy and is 15 years old before reaching full production. The average tree produces for 45 years.

Walnuts are high in unsaturated, fatty acids, iron, and B vitamins. The oil in walnuts has a tendency to absorb strong odors, so they should be kept in cold storage. Manufacturers of syrup toppings, ice cream, candy, casseroles and baking products all rely on walnuts.

Although many nuts have proven to be really beneficial to your health, studies are showing that walnuts contain almost twice as many antioxidants as other nuts. And that’s not just an interesting statistic — all of those antioxidants really do your body a lot of good. Below, we’ll take a look at two big stand-out benefits of walnuts.

Walnuts Boost Brain Power

Since there’s a high concentration of omega-3 fatty acids in walnuts, they’re excellent for brain health. Your brain consists mostly of structural fats that are critical for normal brain cell function. For this reason, walnuts really are “brain food.”

The American diet is almost devoid of all omega-3s, with researchers finding that about two-thirds of Americans are deficient in omega-3 fatty acids. This lack of omega-3 fat can make it tough for the brain to function at a high level.

A study done at Purdue University showed that children with a lower concentration of omega-3 fatty acids have a higher risk of hyperactivity, learning disorders, and behavioral problems.¹ There have actually been hundreds of scientific studies signifying a variety of problems linked to omega-3 deficiencies.

Walnuts Will Keep Your Ticker Ticking

The most in-depth side of walnut research has been around the benefits they offer for the heart and circulatory system. They have had a very favorable impact on vascular reactivity, which is the ability of our blood vessels to respond to stimuli in a healthy way.²

Walnuts contain high amounts of alpha-linolenic acid, or ALA, which is a major contributor to heart health. A study in theAmerican Journal of Clinical Nutrition reviewed the heart health benefits of walnuts on 365 participants who were monitored during control diets and diets supplemented with walnuts. Results showed the walnut eating group to have a significantly greater decrease in total cholesterol and low-density lipoprotein (LDL).³

Even the Food and Drug Administration (FDA) has recently cleared the health claim that eating 1.5 ounces per day of walnuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.⁴ This is the first time a whole food, not its isolated components, has shown this beneficial effect on vascular health. 

Other Healthy Nuts - It Runs in the Family

While walnuts may be the healthiest nuts on the planet, many other nuts can be extremely beneficial to maintaining a healthy lifestyle. The following table comes from the August 2011 issue of Life Extension^® Magazine.

Almonds	Most beneficial to keeping your heart healthy and lowering cholesterol.5
Pecans	Lower blood pressure and may prevent prostate and breast cancers.6
Hazelnuts	One of the best sources of vitamin E.
Brazil Nuts	One of the best sources of magnesium.
Pistachios	Contain two unique antioxidants not found in other nuts, and promote heart and eye health.7

Table: Healthy Nuts and their Benefits

A Word of Caution — Don’t Go Too Nuts

Remember — walnuts are very high in calories. This means you should incorporate walnuts into your normal meals and avoid using them as regular snacks. Eating many of them throughout the day could easily sabotage your diet. The best way to benefit from walnuts is to substitute them for other calories so that your total daily calorie intake is not increased.

Also, be careful how you store walnuts; if they’re not properly stored, they can become rancid. For long-term storage, it is best to buy unshelled nuts and store them in the refrigerator for 2 to 3 months or freeze them for up to 1 year. 

Shelled walnuts should be kept refrigerated in an airtight container, and they can be frozen for up to 1 year. For reference, 1 pound of walnuts will yield about 2 cups of nutmeat. 

WHY SUMMER MAKES US LAZY

In his meticulous diaries, written from 1846 to 1882, the Harvard librarian John Langdon Sibley complains often about the withering summer heat: “The heat wilts & enervates me & makes me sick,” he wrote in 1852. Sibley lived before the age of air-conditioning, but recent research suggests that his observation is still accurate: summer really does tend to be a time of reduced productivity. Our brains do, figuratively, wilt.

One of the key issues is motivation: when the weather is unpleasant, no one wants to go outside, but when the sun is shining, the air is warm, and the sky is blue, leisure calls. A 2008 study using data from the American Time Use Survey found that, on rainy days, men spent, on average, thirty more minutes at work than they did on comparatively sunny days. In 2012, a group of researchers from Harvard University and the University of North Carolina at Chapel Hill conducted a field study of Japanese bank workers and found a similar pattern: bad weather made workers more productive, as measured by the time it took them to complete assigned tasks in a loan-application process.

When the weather improved, in contrast, productivity fell. To determine why this was the case, the researchers assigned Harvard students data entry on either sunny or rainy days. The students were randomly assigned to one of two conditions: before starting to work, they were either shown six photographs of outdoor activities in nice weather, such as sailing or eating outdoors, or were asked to describe their daily routines. The researchers found that participants were less productive when they’d viewed pleasant outdoor photographs. Instead of focussing on their work, they focussed on what they’d rather be doing—whether or not it was actually sunny or rainy outside (though the effect was stronger on sunny days). The mere thought of pleasant alternatives made people concentrate less.

But each season has its share of attractive days—and a skier’s mind would likely have many opportunities to wander in the dead of winter. There’s evidence, however, that in summer, our thinking itself may simply become lazier. In 1994, Gerald Clore, a pioneer in researching how ambient mood-altering phenomena affect cognition and judgment, found that pleasant weather can often lead to a disconcerting lapse in thoughtfulness. Clore’s team approached a hundred and twenty-two undergraduates on days with either good or bad weather and asked them to participate in a survey on higher education. The better the weather, the easier it was to get the students to buy into a less-than-solid argument: on days that were sunny, clear, and warm, people were equally persuaded by both strong and weak arguments in favor of end-of-year comprehensive exams. When the weather was rainy, cloudy, and cold, their critical faculties improved: in that condition, only the strong argument was persuasive. Clore and his colleagues concluded that pleasant weather led people to embrace more heuristic-based thinking—that is, they relied heavily on mental shortcuts at the expense of actual analysis.

Summer weather—especially the muggy kind—may also reduce both our attention and our energy levels. In one study, high humidity lowered concentration and increased sleepiness among participants. The weather also hurt their ability to think critically: the hotter it got, the less likely they were to question what they were told.

The shift toward mindlessness may be rooted in our emotions. One common finding is a link between relative sunshine and happiness: although people who live in sunnier places, like Southern California, are no happier than those who live in the harsher conditions of the Midwest, day-to-day variations in sunshine make a difference. People get happier as days get longer and warmer in the approach to the summer solstice, and less happy as days get colder and shorter. They also report higher life satisfaction on relatively pleasant days. The happiest season, then, is summer.

A good mood, generally speaking, has in turn been linked to the same type of heuristic, relatively mindless thinking that Clore observed in his pleasant-weather participants. On the flip side, a bad mood tends to stimulate more rigorous analytical thought. Weather-related mood effects can thus play out in our real-life decisions—even weighty ones. In one recent project, the psychologist Uri Simonsohn found that students were more likely to enroll in a university that was famous for its academic rigor if they visited on days that were cloudy. When the weather turned sour, he concluded, the value they placed on academics increased.

There’s a limit, however, to heat’s ability to boost our mood: when temperatures reach the kind of summer highs that mark heat waves all over the world, the effect rapidly deteriorates. In a 2013 study of perceived well-being, the economist Marie Connolly found that on days when the temperature rose above ninety degrees, the negative impact on happiness levels was greater than the consequences of being widowed or divorced.

Conversely, the effects of heat on our brains aren’t entirely negative. Many of the behaviors that psychologists study follow a so-called inverted-U pattern: as one factor steadily increases, a related behavior improves, plateaus, and then starts to deteriorate. A famous example of this is the Yerkes-Dodson curve, which charts the effect of stress on how well someone performs a given task. If we experience too little stress, or too much, our performance suffers. Like Goldilocks, we want to get it just right. Similarly, our cognitive abilities seem to improve up to a certain temperature, and then, as the temperature continues to rise, quickly diminish. An early study suggested that the optimal temperature hovered around seventy-two degrees Fahrenheit. Amore recent review of the literature shows a target of twenty-seven degrees Celsius, or roughly eighty-one degrees Fahrenheit. (An important caveat, however, is that neither of these studies take humidity or sunshine into account, two major factors when it comes to assessing the influence of summer weather on behavior.)

Maybe best of all, blistering heat does give us a perfectly good reason to eat ice cream: studies have shown again and again that blood glucose levels are tied to cognitive performance and willpower. A bite of something frozen and sweet, boosting depleted glucose stores, might be just what a brain needs as the temperature spikes

Simple math equals easy weight loss

The pleasure of eating a candy bar lasts but a few minutes. Burning off the calories it delivers can take nearly three-quarters of an hour.

To lose one pound by exercising, you need to burn approximately 3,500 calories. It can take days of moderate exercise to do this. A better strategy for weight loss involves a two-pronged approach: exercising and cutting calories.

Although exercise by itself isn’t the fast track to weight loss, it does offer important benefits beyond cancelling out calories. It slightly increases the rate at which you burn calories even when you’re not working out. And pounds lost through boosting your activity level consist almost entirely of fat, not muscle.

Do the math

Start with this number: 3,500. That’s how many calories are stored in a pound of body fat. With that number you can tally up how much weight you can lose through activity, cutting calories, or both.

1. Walking or jogging uses roughly 100 calories per mile. (Precisely how many calories you’ll burn depends on a number of things, including your weight and how fast you walk.) So you’d lose a pound for every 35 miles you walk — provided you keep food intake and other activities constant.
2. If you walk briskly (at a pace of 4 miles per hour) for 30 minutes on five out of seven days, you’ll log 10 miles a week. That means it would take three-and-a-half weeks to lose one pound if the number of calories you consume stays the same.
3. If you alter your diet and cut back by 250 calories a day (½ cup of ice cream or two sugar-sweetened sodas), you’d lose a pound in two weeks.
4. By eating 250 fewer calories and walking for 30 minutes a day, it would take just over a week to lose one pound. Reducing calorie intake even more and exercising more would further speed the process.

How Circadian Rhythms Give Vegetables A Healthy Boost

Just as we have internal clocks that help regulate the systems in our bodies, fruit and vegetable plants have circadian rhythms, too.

And a new study published in Current Biology finds there may be a way to boost some of the beneficial compounds in plants by simulating the light-dark cycle after crops are harvested.

So, how does it work?

Well, take cruciferous vegetables such as cabbage, which contains cancer-fighting compoundscalled glucosinolates. Studies have shown that glucosinolates secrete enzymes that can remove carcinogens.

"The protective effect of these vegetables is that they rev up the capacity of cells to dispose of toxic compounds," says Paul Talalay, a pharmacologist at Johns Hopkins University.

In other words, they help our bodies get rid of harmful substances.

Now, as vegetables go from the field to the store to our plate, the levels of these compounds start to fizzle out.

If you listen to my story on All Things Considered, you'll hear how researcher Janet Braam of Rice University and her colleagues conducted lab studies to test the possibilities of coaxing more life — and more of these beneficial compounds — out of the fruits and vegetables we buy.

They put cabbages under light for 12 hours a day, followed by 12 hours of darkness, to try to re-create the light-dark cycle in the field.

Prior research has already shown that plants use circadian rhythms to help them judge when to turn on their chemical defenses. Some plants release these beneficial chemicals to fend off bugs in the field or cope with the stresses of heat or drought.

"And sure enough we found that when we put the plants under light-dark cycles, we found periods of accumulation of those [beneficial] chemicals," explains Braam.

The peak of the compounds came in the afternoon, in the hours before dusk.

They were "significantly higher in the day," Braam says — about twice as high. It was as if the plants were still alive, even though they're no longer attached to their roots or the earth. "This very much surprised us," Braam says.

Her team found similar responses with a range of crops including lettuce, spinach, sweet potatoes and blueberries.

More research is needed to see whether the findings carry over into real-life situations, like our kitchens or in grocery stores. "It just opens the door to many possibilities," says Braam.

For instance, it might make sense for supermarkets — or consumers at home — to think abut storing our produce under light-dark cycles.

Or maybe it's time for a vegetable happy hour: eating our produce in the hours before dusk when some of the most beneficial compounds are at their peak

Breathing And Your Brain: Five Reasons To Grab The Controls

The advice to “just breathe” when you’re stressed may be a cliché of Godzilla-sized proportions, but that doesn't make it untrue. The substance behind the saying is research-tested—and not only to manage stress.

Breathing is an unusual bodily function in that it is both involuntary and voluntary. Other major functions—take digestion and blood flow, for example—occur without conscious influence, and for the most part we couldn’t influence them if we tried. They are involuntarily managed in the vast processing system of the unconscious mind.

Breathing is also managed in the unconscious, but at any moment we can grab the controls and consciously change how we breathe. We can make our breathing shallow or deep, fast or slow, or we can choose to stop breathing altogether (until we pass out and the unconscious takes over again)

Since we are breathing all the time, the oddness of this dual-control system doesn’t usually dawn on us—but it’s this control flexibility that makes breathing especially worthy of attention. We can change how we breathe, and to an extent change how breathing affects our bodies.

Controlled breathing, also known as “paced respiration,” “diaphragmatic breathing” and “deep breathing,” has long been a feature of Eastern health practices. It became more visible in the West after Dr. Herbert Benson’s book, “The Relaxation Response”, hit shelves in the mid 1970s. Whatever you choose to call controlled breathing, the dynamic at work is full oxygen exchange: more oxygen enters the body and more carbon dioxide exits.

The basic mechanics of controlled breathing differ a bit depending on who is describing them, but they usually include three parts: (1) inhaling deeply through the nose for a count of five or so, making sure that the abdomen expands, (2) holding the breath for a moment, and (3) exhaling completely through the mouth for a count longer than the inhalation.

Benson argued that controlling breathing in this way triggers the parasympathetic nervous system to come online and counter our sympathetic nervous system’s fight or flight response to daily stresses. In effect, the relaxation response is the anti-fight or flight response. Subsequent research has backed up and expanded Benson’s argument.

What follows are five science-based reasons for paying more attention to an ability most of us aren't maximizing.

1. Managing Stress.

This is the most direct application of controlled breathing and the one we hear about most. Our brains are routinely on high alert for threats in our environment—we’re wired to react defensively to anything that hints of imperiling us physically or psychologically.

Controlled breathing may be the most potent tool we have to prevent our brains from keeping us in a state of stress, and preventing subsequent damage caused by high stress levels.  The relaxation response is a built-in way to keep stress in check

2. Managing Anxiety.

The means by which controlled breathing triggers the parasympathetic nervous system is linked to stimulation of the vagus nerve—a nerve running from the base of the brain to the abdomen, responsible for mediating nervous system responses and lowering heart rate, among other things.

The vagus nerve releases a neurotransmitter called acetylcholine that catalyzes increased focus and calmness. A direct benefit of more acetylcholine is a decrease in feelings of anxiety. Stimulating the vagus nerve may also play a role in treating depression, even in people who are resistant to anti-depressant medications.

3. Lowering Blood Pressure and Heart Rate.

Research suggests that when practiced consistently, controlled breathing will result in lower blood pressure and heart rate, which in turn results in less wear and tear on blood vessels.  As described above, the vagus nerve plays a key role in this response.

Over time, using controlled breathing to lower blood pressure and heart rate can help prevent stroke and lower risk of cerebral aneurysm.

4. Sparking Brain Growth.

One of the more intriguing research developments involving controlled breathing is that when it’s used to facilitate meditation, the result can be an actual increase in brain size. Specifically, the brain experiences growth in areas associated with attention and processing of sensory input.

The effect seems to be more noticeable in older people, which is especially good news because it’s the reverse of what typically happens as we age—gray matter usually becomes thinner.  The result is consistent with other research showing an increase in thickness of music areas of the brain in musicians and visual-motor areas in the brains of jugglers. As in those cases, the key is consistent practice over time.

5. Changing Gene Expression.

Another unexpected research finding is that controlled breathing can alter the expression of genes involved in immune function, energy metabolism and insulin secretion. The study uncovering this finding was co-authored by none other than Herbert Benson himself, some 40 years after he brought controlled breathing into the spotlight with his book.

And this isn’t the first study linking controlled breathing to changes in genetic expression. Benson was also involved in a 2008 study indicating that long-term practice of the relaxation response results in changes to the expression of genes associated with how the body reacts to stress.

Too Little Sleep Can Really Mess Our Bodies Up

Sacrifice sleep for several nights in a row to meet a deadline or study for exams, and you risk disrupting hundreds of genes that promote health, fight disease and combat stress. According to a new study, more than 700 genes rely upon a solid night’s sleep in order to function properly. The Guardian reports that the study results raise questions about what sleep might have to do with a host of diseases, including diabetes, obesity, heart disease and depression.

To arrive at these findings, researchers at Surrey University asked 26 healthy men and women to stay at their laboratory for twelve nights. The visits were broken into two parts. During the first session, the participants were allowed to sleep for up to ten hours. In the second, the researchers cut their sleep off at a measly six hours each night. At the very end of each of those two weeks, the participants were kept awake for a full day and night.

The researchers used EEGs to measure brain activity in their participants. When the subjects were allowed to lie in bed for ten hours, they actually slept for an average of 8.5 hours, while on the six hour nights, participants only got 5 hours and 42 minutes of sleep. In the latter scenario, 444 genes were repressed, and 267 genes were more active than they normally would be under more favorable sleeping conditions.

Some of those genes affect metabolism, others the immune system or stress regulation. People who slept normally had more than 1,800 functioning genes over a 24 hour period, whereas nearly 400 of those were knocked out of service completely when participants were not allowed to sleep.

Read more: http://blogs.smithsonianmag.com/smartnews/2013/02/too-little-sleep-can-really-mess-our-bodies-up/#ixzz2ZX5pKBlx 
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Being a Lifelong Bookworm May Keep You Sharp in Old Age

To keep their bodies running at peak performance, people often hit the gym, pounding away at the treadmill to strengthen muscles and build endurance. This dedication has enormous benefits—being in shape now means warding off a host of diseases when you get older. But does the brain work in the same way? That is, can doing mental exercises help your mind stay just as sharp in old age?

Experts say it’s possible. As a corollary to working out, people have begun joining brain gyms to flex their mental muscles. For a monthly fee of around $15, websites like Lumosity.com and MyBrainTrainer.com promise to enhance memory, attention and other mental processes through a series of games and brain teasers. Such ready-made mind exercises are an alluring route for people who worry about their ticking clock. But there’s no need to slap down the money right away—new research suggests the secret to preserving mental agility may lie in simply cracking open a book.

The findings, published online today in Neurology, suggest that reading books, writing and engaging in other similar brain-stimulating activities slows down cognitive decline in old age, independent of common age-related neurodegenerative diseases. In particular, people who participated in mentally stimulating activities over their lifetimes, both in young, middle and old age, had a slower rate of decline in memory and other mental capacities than those who did not.

Researchers used an array of tests to measure 294 people’s memory and thinking every year for six years years. Participants also answered a questionnaire about their reading and writing habits, from childhood to adulthood to advanced age. Following the participants’ deaths at an average age of 89, researchers examined their brains for evidence of the physical signs of dementia, such as lesions, plaques and tangles. Such brain abnormalities are most common in older people, causing them to experience memory lapses. They proliferate in the brains of people with Alzheimer’s disease, leading to memory and thinking impairments that can severely affect victims’ daily lives.

Using information from the questionnaire and autopsy results, the researchers found that any reading and writing is better than none at all. Remaining a bookworm into old age reduced the rate of memory decline by 32 percent compared to engaging in average mental activity. Those who didn’t read or write often later in life did even worse: their memory decline was 48 percent faster than people who spent an average amount of time on these activities.

The researchers found that mental activity accounted for nearly 15 percent of the difference in memory decline, beyond what could be explained by the presence of plaque buildup. “Based on this, we shouldn’t underestimate the effects of everyday activities, such as reading and writing, on our children, ourselves and our parents or grandparents,” says study author Robert S. Wilson, a neuropsychologist at the Rush University Medical Center in Chicago, in a statement.

Reading gives our brains a workout because comprehending text requires more mental energy than, for example, processing an image on a television screen. Reading exercises our working memory, which actively processes and stores new information as it comes. Eventually, that information gets transferred into long-term memory, where our understanding of any given material deepens. Writing can be likened to practice: the more we rehearse the perfect squat, the better our form becomes, tightening all the right muscles. Writing helps us consolidate new information for the times we may need to recall it, which boosts our memory skills.

So the key to keeping our brains sharp for the long haul does have something in common with physical exercise: we have to stick with it. And it’s best to start early. In 2009, a seven-year study of 2,000 healthy individuals aged 18 to 60 found that mental agility peaks at 22. By 27, mental processes like reasoning, spatial visualization and speed of thought began to decline.

Read more: http://blogs.smithsonianmag.com/science/2013/07/being-a-lifelong-bookworm-may-keep-you-sharp-in-old-age/#ixzz2ZX2O9qji 
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Your Alarm Clock May Be Hazardous to Your Health

Switching up your sleep schedule is wreaking havoc on your body’s natural rhythm  

 »A 15th-century French calendar depicts the natural cycle of day and night.  

One overlooked culprit in the world’s obesity epidemic may be the alarm clock, according to Till Roenneberg, a professor at the University of Munich’s Institute of Medical Psychology.

He studies “social jet lag,” a term he coined, perhaps not surprisingly, on an airplane. But unlike the jet lag you get from shifting time zones, social jet lag is the chronic clash between what our bodies need (more sleep) and what our lives demand (being on time). And his research suggests that it’s playing havoc with our biological clocks.

In a study, published in May, Roenneberg and colleagues analyzed the sleep habits of more than 65,000 adults. Two-thirds of them suffered from social jet lag, experiencing at least a one-hour disparity between how long they slept on workdays and weekends.

The researchers also found that, over the past decade, people have been going to bed later but still getting up at the same time, losing about 40 minutes of sleep on workdays. They are also spending less time outside, which could account for why their circadian rhythms have become so late.

Previous studies have linked sleep deprivation with excessive weight, but Roenneberg’s team concludes that it isn’t just how much sleep people get that matters—it’s how much they mess with their internal clocks. For every hour of social jet lag accrued, the risk of being overweight or obese rises by about 33 percent. Obesity results from a host of influences, but Roenneberg says “one contributing factor is not living according to your biological temporal needs.” No one knows the precise mechanism, but other studies suggest that lack of sleep causes higher secretions of ghrelin, the appetite hormone, and a reduction of leptin, the satiety hormone.

Our daily lives are controlled by two naturally occurring phenomena: our internal circadian clock and the rotation of the earth. The hub of the body clock resides in a bundle of nerves called the suprachiasmatic nucleus, in the brain’s hypothalamus. This central clock acts as a pacemaker, synchronizing other cellular clocks that scientists believe exist throughout the body. This circadian clock system controls a variety of functions, including body temperature, hormone secretion and blood pressure. It also regulates the daily activities of organs.

The circadian clock must be rewound every day to keep it operating on a cycle of roughly 24 hours. It is reset by sunlight and darkness, the signals traveling to the brain through the optic nerve. Into that elaborate finely tuned natural system bursts the alarm clock.

Sleep is often viewed as an indulgence. But Roenneberg warns that people who sleep for fewer hours are not as efficient at their jobs, which creates a vicious cycle of working more and sleeping less. “Sleep has not been put out there by evolution as a time when we’re lazy,” he says. “ It’s a time when we’re preparing to be extremely active.”

Roenneberg doesn’t set an alarm clock unless he has to catch a plane, and he feels great. “I go through 16 hours without feeling a yawn,” he says.

Read more: http://www.smithsonianmag.com/science-nature/Your-Alarm-Clock-May-Be-Hazardous-to-Your-Health-183826751.html#ixzz2ZX1RrL89 
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Eating fruits and vegetables tied to longer life

Eating fewer than five servings of fruit and vegetables each day is linked with a higher chance of dying early, according to a large study from Sweden.

People who said they never ate fruit and vegetables died an average of three years sooner than those who ate plenty of apples, carrots and tomatoes, researchers found.

Many public health organizations worldwide recommend eating five servings of fruit and vegetables a day, but previous studies have been inconclusive on whether meeting that guideline helps improve health and by how much, researchers said.

The new study, published in the American Journal of Clinical Nutrition, shows the five-a-day recommendations are optimal, said Alicja Wolk, who worked on the research at the Karolinska Institute in Stockholm.

Her team did not find any improvement in survival for people who ate more than five servings of fruit and vegetables each day, compared to those who just met the guideline.

The results are based on data collected from more than 71,000 Swedes, aged 45 to 83, who were followed for 13 years.

Participants were surveyed about their diets in 1997 and 1998 and reported how often they ate fruit - including oranges, apples, bananas and berries - and vegetables, such as carrots, beets, lettuce, cabbage, tomatoes and pea soup.

Nearly 11,500 of those enrolled had died by December 2010.

Wolk's team found that people who had reported eating no fruit or vegetables at the start of the study were 53 percent more likely to die during the follow-up period than those who got their five daily servings.

Participants who ate at least one serving of fruit daily lived 19 months longer than those who never ate fruit, on average. And those who ate at least three servings of vegetables per day lived 32 months longer than people who reported not eating vegetables.

Fruits and vegetables contain different types of vitamins, and fruit is generally higher in calories, Wolk noted.

Most diet discussions consider them as a combined group, she told Reuters Health. "But when I speak to lay people I actually say, ‘Eat vegetables more than fruit, but eat both.'"

Women in the study tended to eat more fruit and vegetables than men.

People who said they ate fewer fruits and vegetables were more likely to smoke and tended to be less educated and eat more red meat, high-fat dairy products, sweets and snacks. On the other hand, those who ate a lot of fruit and vegetables tended to take in more calories per day overall than those who did not, Wolk noted.

The study cannot prove that eating fruits and vegetables lengthened lifespans, and there could have been other differences between those who ate produce and those who didn't.

But when the researchers accounted for gender, smoking, exercise, alcohol consumption and body weight, the overall results did not change.

Few very large studies have looked at the effect of eating fruit and vegetables on a person's chance of dying early, according to the study authors.

Those that have showed contradictory results, said Kelly L. Pritchett, a registered dietician from Central Washington University in Ellensburg and a spokesperson for the Academy of Nutrition and Dietetics. Larger studies have suggested there is no clear benefit, but "smaller studies found a stronger decrease in mortality risk," she said.

This study "falls right in line with the recommendations," Pritchett, who wasn't involved in the new research, told Reuters Health.

Still, one weakness of the study, the Karolinska researchers noted, is that diet information was reported by the participants - rather than measured independently - and people may not always report what they eat accurately.

Do Diet Drinks Mess Up Metabolisms?

It may seem counterintuitive, but there's a body of evidence to suggest that the millions of Americans with a diet soda habit may not be doing their waistlines — or their blood sugar — any favors.

As the consumption of diet drinks made with artificial sweeteners continues to rise, researchers are beginning to make some uncomfortable associations with weight gain and other diseases.

For instance, as researcher Susan Swithers writes in a new opinion piece published in the journal Trends in Endocrinology and Metabolism, "accumulating evidence suggests that frequent consumers of these sugar substitutes (such as aspartame, sucralose, and saccharin) may also be at increased risk of ... metabolic syndrome, type 2 diabetes and cardiovascular disease."

If you listen to my conversation on Here & Now, you'll hear that there are two schools of thought here. Not everyone is convinced that diet soda is so bad.

For instance, a study I reported on last year by researchers at Boston Children's Hospital found that overweight teens did well when they switched from sugar-laden drinks to zero-calorie options such as diet soda.

But it's also hard to ignore the gathering body of evidence that points to potentially bad outcomes associated with a diet soda habit.

One example: the findings of the San Antonio Heart Study, which pointed to a strong link between diet soda consumption and weight gain over time.

"On average, for each diet soft drink our participants drank per day, they were 65 percent more likely to become overweight during the next seven to eight years" said Sharon Fowler, in a release announcing the findings several years back.

Another bit of evidence: A multi-ethnic study, which included some 5,000 men and women, found that diet soda consumption was linked to a significantly increased risk of both type-2 diabetes and metabolic syndrome.

So, what gives? How could consuming less sugar set the stage for more weight gain and an increased risk of disease?

Well, since being overweight is a major contributor to the development of type 2 diabetes, it's possible that some diet-soda drinkers suffer from a mindset problem: They justify eating lots of high-calorie foods because their drinks are calorie-free.

It's the "hey, I'll go ahead and have those fries and a cheeseburger, since I'm having a Diet Coke" mentality.

It's also possible that something much more complicated and nuanced is happening in the bodies and brains of diet soda drinkers.

As Swithers points out, "Frequent consumption of high-intensity [artificial] sweeteners may have the counterintuitive effect of inducing metabolic derangements."

Say what? Metabolic derangements?

One theory is that diet soda may throw off the metabolism by blunting the body's responses to sugar.

You see, from the moment sugar touches our lips, our bodies start to release hormones to begin processing the sugar. It's part of a feedback loop that helps the body predict what's coming.

But if we develop a habit of consuming artificial sugar, our bodies may get confused. And it might not respond the same when we consume real sugar. "We may no longer release the hormones" needed to process sugar — or at least, not as much of them as before, Swithers told me during an interview.

And researchers think this change in hormone levels could contribute to increases in how much we eat, says Swithers, "as well as to bigger spikes in our blood sugar, which may be related to things like diabetes."

Now, Swithers says much more research is needed to nail down what's happening when people consume artificial sweeteners.

What is clear is that diet soda consumption continues to rise. Women tend to lead the way, and increasingly, children are popping open the calorie-free sodas that mom and dad are drinking.

Update: After we published our post, we received this statement from the American Beverage Association:

"Low-calorie sweeteners are some of the most studied and reviewed ingredients in the food supply today. They are safe and an effective tool in weight loss and weight management, according to decades of scientific research and regulatory agencies around the globe."