When it comes to ideas about healthy eating, there are all sorts of rules, trends and advice about what’s good for you and what isn’t.

Some of the guidance may be legitimate — yet some of it should be taken with a grain of salt.

Multiple experts and researchers from Mass General Brigham in Boston investigated some popular diet concepts that have been circulating — and separated fact from fiction.

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Here are six popular concepts — and a clear explanation of whether they hold water or not, according to experts.

True or false?

1. ‘To live longer, women should follow the Mediterranean diet’

True. In recent studies, the Mediterranean diet has been shown to be beneficial for overall health.

Mass General supports this theory, referencing its own study that found women who followed the nutrition plan for more than 25 years had up to 23% lower risk of mortality, with reductions in cardiovascular and cancer-related deaths.

The study also found that introducing a single component of the diet led to a 5% reduction in the long-term risk of death from certain diseases.

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The Mediterranean diet incorporates healthy foods like fruits, vegetables, legumes, olive oil, nuts and fish, while avoiding sugar and processed or red meats.

Most people don’t realize the impact diet has on health and longevity, according to Samia Mora, M.D., director of the Center for Lipid Metabolomics at Brigham and Women’s Hospital.

“What we eat today has major implications for living a long and healthy life,” she wrote in a statement to Fox News Digital.

“The benefits [of the Mediterranean diet] were seen for both cancer and cardiovascular mortality – the top two causes of death for women and men – and related to multiple biological mechanisms, in particular to lower inflammation and insulin resistance and improved metabolism.” 

2. ‘Removing trigger foods is always the best treatment for digestive issues’

False. While some people do suffer from food allergies or autoimmune conditions, the experts at Mass General found this diet concept to be false overall — as many digestive symptoms are known to have “more complex causes.”

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When patients have bad reactions to certain foods, it’s not the food itself causing the issues, but the digestive tract’s response to eating “in general,” according to Kyle Staller, M.D., director of the Gastrointestinal Motility Laboratory at Massachusetts General Hospital.

“While some people have true allergies to certain foods (for example, an allergy to gluten in celiac disease) or an inability to digest certain foods (such as dairy in lactose intolerance), many symptoms attributed to specific foods are actually driven by your body’s response to eating,” he told Fox News Digital. 

Eating starts a “cascade of nerve activity in the gut” regardless of the kind of food that’s eaten, according to Staller.

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Those with sensitive gut nerves can develop GI discomfort in the form of gas, bloating and a feeling of abnormal fullness.

“These are what we call ‘disorders of gut-brain interaction’ — feeling abnormal sensations even when digestion is seemingly working normally,” Staller said. 

“Irritable bowel syndrome (IBS) is the most classic example.” 

The best way to alleviate these symptoms is to target the abnormal nervous system responses while only eliminating the “most troublesome” foods, according to Staller.

3. ‘Eating blueberries can decrease the risk of some eye diseases’

True. The researchers found this claim to be true: Blueberries indeed can be beneficial for your eyes.

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A Mass General study of nearly 40,000 U.S. middle-aged and older women found that one or more servings of blueberries per week was associated with a 28% lower risk of age-related macular degeneration (AMD), an eye condition that can lead to significant vision loss.

Dr. Howard D. Sesso, director of nutrition and supplements research at Brigham and Women’s Hospital, confirmed that blueberries can optimize eye health.

“Blueberries contain anthocyanins, a bioactive polyphenol that gives them their blue color, and has been linked with possible reductions in eye disease,” he told Fox News Digital.

4. ‘Following a plant-based diet will always improve health outcomes’

False, with caveats. Mass General experts say a plant-based diet is not always the best way to go, though it may seem super healthy.

Plant-based nutrition plans have “diverse and sometimes contrasting health effects,” according to Dr. Qi Sun, associate professor of medicine at Brigham and Women’s Hospital.

“Diet is not a magic bullet by itself.”

A plant-based diet that is dense in refined grains, sugary beverages and candies differs greatly from one containing fresh fruits and vegetables, whole grains, coffee, tea and more, he noted.

The first diet is associated with “many adverse health outcomes,” according to the researchers.

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The second diet is considered a “healthy version of a plant-based diet,” which Sun said has been “robustly associated with better health outcomes, including lower risk of developing diseases such as diabetes, obesity and gout.”

In a statement sent to Fox News Digital, Sun encouraged people to focus on quality ingredients — such as fresh fruits, non-starchy vegetables, whole grains, legumes and nuts, and olive oil and other vegetable oils — and to limit sugary and salty foods.

“Don’t forget regular activity and other healthy lifestyle choices,” he advised. “After all, diet is not a magic bullet by itself.”

5. ‘Food location in the grocery store has no impact on purchases’

False. Mass General deemed this concept as flat-out “false,” as the “choice architecture” of the grocery store “strongly influences what we purchase.”

When healthy items are stocked in visible or convenient locations, that increases the likelihood of making a healthier choice, according to the researchers.

In the Mass General Hospital cafeteria, the foods and beverages are labeled as red, yellow and green – red being the least healthy and green being the most healthy.

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The researchers found that when the healthiest items were in convenient locations or at eye level, employees were more likely to make healthier choices.

Anne Thorndike, M.D., primary care physician at Massachusetts General Hospital, shared with Fox News Digital that the opposite is also true.

“This is well-known by the food industry, which has been placing sugar-sweetened beverages, salty snacks, candy and baked goods in checkout lanes, aisle endcaps and at the front of store,” she said. 

6. ‘Early introduction of foods like peanut butter can prevent allergies’

True. Introducing a small child to foods known to cause allergic reactions can be scary for parents, but Mass General confirmed it can be beneficial in the long run.

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Introducing “developmentally appropriate” forms of peanuts to children between 4 and 6 months old can cause an 80% reduction of peanut allergy in those who are at high risk, according to the LEAP Trial (Learning Early About Peanut Allergy).

Michael Pistiner, M.D., director of Food Allergy Advocacy, Education and Prevention at Mass General Hospital for Children, stressed that these findings show that “timing is important.”

“Once a child reaches a pediatric allergist, it might be too late to prevent some food allergies that could have been avoided with early allergen introduction and family education,” he told Fox News Digital.

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Pistiner added, “With limited access to allergy providers and long wait times that can exceed three months, primary care clinicians play a crucial role in supporting families through infant feeding, early allergen introduction, eczema management, and food allergy diagnosis and referral.”