Should you try these fad diets?

Healthy drink, vegetable juice, studio shot (Copyright: Maxim Khytra)

They purport to be the secret to better health, increased energy, and a smaller pant size. But which of the latest crazes deserves a place at your table?

Here’s some food for thought.

1. Green Smoothies
The trend explained: These super-concentrated blends of green vegetables and fruit can deliver your five daily servings in one glass. They’re usually packed with the kinds of leafy greens, such as kale and spinach, that we don’t consume enough of. Sometimes made with almond or coconut milk, they taste sweet, not bitter. Whether made from fresh produce or from a powdered mix of dried greens, these smoothies are loaded with vitamins, minerals, and other nutrients. Proponents claim they boost energy and overall health.

Expert opinion: “The phytonutrients in green smoothies may help lower inflammation in your body, which could help reduce your risk of many diseases, from heart disease to cancer,” said Liz Applegate, the director of sports nutrition at the University of California, Davis.

There’s no hard evidence that they increase energy. But adding a bit of protein and fat to your green smoothie—a tablespoon of walnuts or ground flaxseed, say—can help stabilize blood sugar, keeping you off the energy-spike-then-crash roller coaster.

The bottom line: If green smoothies help you up your daily intake of fruits and vegetables, go for it. Just keep in mind that they’re not meant to be a meal replacement, Applegate said, since they lack substantial calories.

2. Gluten-Free
The trend explained: The label is popping up on everything from pancake mix to bottled water (really!). According to research from the University of Maryland, about 18 million people in the United States have a sensitivity to gluten, a protein found in wheat, rye, barley, and oats, which can cause symptoms such as gas, bloating, fatigue, and weight gain. (This is not the same thing as celiac disease. People with celiac cannot process gluten at all and suffer a severe autoimmune response when they ingest it.)

Expert opinion: The only way to know if you have a sensitivity is to “eliminate foods that contain gluten for a few weeks and see how you feel,” said Kris Clark, a registered dietitian and the director of sports nutrition at Penn State University, in University Park, Pa. “If you notice a reduction in bloating or constipation, you may, in fact, have a gluten sensitivity.”

Forgoing gluten may help you lose weight, but that’s probably because you’ll have to give up calorie-dense grains, which are easy to overeat.

The bottom line: No one, except those diagnosed with celiac disease, needs to totally eliminate gluten. But if you have a confirmed sensitivity or suspect that you might feel better on a gluten-free regimen, it’s perfectly healthy to do without it. You can still maintain a balanced diet full of fruits, vegetables, lean proteins, and starchy foods that don’t contain gluten, such as all types of rice, quinoa, corn, and potatoes.

3. Probiotics
The trend explained: Probiotics are “healthy bacteria” found in cultured foods, like yogurt and kefir; fermented products, like sauerkraut, tempeh, and kimchi; and special supplements. Fermented vegetables, including pickled beets, carrots, and green beans, often contain probiotics. (Since probiotics are living organisms, some supplements need to be refrigerated to stay active.) They take up residence in the intestinal tract and help strengthen the immune system.

Related: How to Feel Better Every Day

Expert opinion: Many doctors suggest probiotics when you’re on antibiotics, to help preserve the good bacteria in your gastrointestinal tract.

“We know that women who tend to get yeast infections after taking antibiotics can ward them off this way,” said Dr. David Heber, the director of the Center for Human Nutrition at the David Geffen School of Medicine, at the University of California at Los Angeles.

The bottom line: Probiotics may be a smart addition to your diet, especially as cold-and-flu season approaches. Those with digestive issues, such as irritable bowel syndrome, and women prone to yeast infections may find them particularly helpful.

4. Chia Seeds
The trend explained: These fun-sounding seeds (yep, the same stuff you sprinkle on a Chia Pet) come from the salvia plant and are chock-full of two health powerhouses: omega-3 fatty acids and fiber. Some say adding the seeds to yogurt or a smoothie helps keep you full.

Expert opinion: “Ounce for ounce, chia seeds provide more omega-3s than salmon,” said Koren Barwis, a certified health and wellness coach in Ashburn, Va. (Of course, it would take a lot longer to eat four ounces of chia seeds than four ounces of salmon.)

Plus, “they can absorb 10 times their weight in water, so once inside your stomach, they really do help fill you up,” Barwis said.

And they may even have blood-sugar benefits: A 2011 study in The Journal of Nutritional Biochemistry showed that when rats consumed chia seeds, their bodies were better able to process glucose and insulin (key for diabetics). The study also found that chia seeds helped reduce fat around the internal organs of obese rats.

The bottom line: Chia seeds are an easy way to take in more fiber and omega-3s, especially if your diet is lacking in fruits and vegetables or if you’re not a fan of salmon (or of choking down fish-oil pills).

5. Bee Pollen
The trend explained: Not to be confused with honey, bee pollen is what bees take from flowers and bring back to the hive to feed their young. It’s rich in carbohydrates, protein, antioxidants, and vitamins. Proponents claim that it can do everything from boosting stamina to easing allergy symptoms. It has a mild, bittersweet taste and a crunchy texture, so it can be mixed into yogurt or oatmeal or sprinkled on salads.

Expert opinion: Some research has shown that bee pollen could be beneficial. A 2010 study published in the journal Pharmaceutical Biology found that a mix of honey and bee pollen had significant anti-inflammatory properties, and a 2012 study from Turkey showed that, in rats, bee pollen decreased bone loss due to osteoporosis.

The bottom line: There’s not yet enough supporting evidence to give bee pollen a ringing endorsement. If you like a little crunch in your yogurt and want to load up on antioxidants, give it a try.

6. Coconut Water
The trend explained: This slightly sweet, milky beverage is getting to be as ubiquitous as flavored waters. Brands like Zico, Vita Coco, and O.N.E. contain loads of potassium and electrolytes, and devotees swear that the liquid helps them rehydrate better than straight water does.

Expert opinion: “Coconut water is water, carbohydrates, and electrolytes being marketed as the all-natural sports drink,” said Mike Roussell, a nutritionist in State College, Pennsylvania, and the author of, "The Six Pillars of Nutrition."

There is some evidence to support the hydration hype: Research published in the Journal of Physiological Anthropology and Applied Human Science showed that coconut water was effective at rehydrating subjects after exercise. The same study also showed that coconut water was just as thirst-quenching as a commercial sports drink but inflicted less nausea and stomach upset, and that subjects could drink more of it than they could a sports drink or even plain water.

The bottom line: “Coconut water is good for replenishing electrolytes when you’re exercising on a really hot day or if you’re experiencing fluid loss due to diarrhea or other digestive issues,” said celebrity nutritionist JJ Virgin.

And if you find it tastier than plain water, drink up—but remember that, unlike the plain stuff, coconut water can have about 5 calories per ounce.

7. Genetic Diet Testing
The trend explained: Born out of a field called nutrigenomics—the study of how the foods we eat can alter disease-causing genes—this new technology can tell you whether you have genes that may play a role in weight gain.

Companies such as Newtopia screen your saliva for the genes, then recommend a diet (and sometimes supplements) tailored to your genetic “type.” For example, if your genes indicate that you don’t metabolize carbohydrates efficiently, you would get a low-carbohydrate plan.

The process is simple: You spit into a tube, send in your sample, and receive results in about two weeks. However, it’s not cheap ($399 for Newtopia). You can also sign up for ongoing telephone and Web coaching based on your results; prices start at $149 a month.

Expert opinion: “The connection between your diet and your genes is very complicated,” Roussell said. And while the test can give some general information, it’s not sophisticated enough to tell you that your genetic type will cause you to lose more weight if you eat, say, more cauliflower than carrots.

The bottom line: If you want to spend the money, it’s interesting, even fun, to see your customized results. But don’t forget the (less fun) truth about weight loss: No matter what your genes, to lose weight, you need to eat less and move more.

8. The Paleo Diet
The trend explained: Some experts believe that conditions like type 2 diabetes and obesity are so prevalent because our bodies weren’t designed to handle our typical modern-day diets, which are full of sugar, refined carbs, and processed foods. They argue that by eating what our ancient ancestors did—only things that we can hunt, gather, and grow—we can prevent or even reverse these diseases.

The paleo diet emphasizes fish, meats, vegetables, fruits, and nuts. It does not include dairy, as paleo enthusiasts say we’re designed to drink only mother’s milk as infants, and most grains, which they say weren’t part of the human diet until the rise of modern-day agriculture.

Expert opinion: People who eat paleo do tend to lose weight rapidly.

“When you lower your refined-carb intake, it changes how your body metabolizes fat,” Roussell said. And with the emphasis on fruits and vegetables, you’re getting more phytonutrients, vitamins, and minerals on a paleo plan than you would eating a typical American diet (and probably enough calcium, if you consume plenty of leafy greens and add a supplement).

The bottom line: While the paleo diet could feel restrictive if you were used to enjoying bread and ice cream regularly, it’s nevertheless a sound plan.

9. Coconut Oil
The trend explained: Fans say that this rich oil (which solidifies at temperatures below 76 degrees Fahrenheit) may have metabolism-boosting benefits. It’s a dietary fat composed of medium-chain triglycerides, which, unlike the long-chain triglycerides found in some other oils, are used by the body for energy rather than being stored as fat. It has a nutty taste that works well for baking and sautéing. Some fitness and nutrition pros use it in place of butter on toast.

Expert opinion: The research on coconut oil is promising: One 2002 study published in The Journal of Nutrition showed your body may expend more calories digesting medium-chain triglycerides than it does digesting longer-chain fatty acids. This means coconut oil could aid weight loss.

The bottom line: Give it a try if you’re looking for a healthier alternative to butter and vegetable oil. As with any fat, keep an eye on portion size, says Los Angeles–based registered dietitian Ashley Koff. One tablespoon of coconut oil has about 115 calories, which is slightly more than butter. And choose the cold-processed, extra-virgin variety.

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