By Dr. Mercola

In a global survey of more than 27,000 people, 26 percent reported that confusion about which foods are healthy was a major barrier to eating right.¹ That confusion is only compounded upon because many of the "official" dietary recommendations are contrary to optimal health.

There is no one-size-fits-all diet that benefits everyone, but there are certain principles that will help most people thrive. You want to be centering your diet on whole foods, for starters – those that come from nature, are minimally processed and, ideally, are grown locally and without synthetic chemicals.

At the same time, you want to minimize your intake of processed foods, particularly snack foods and convenience foods that have little to offer in the way of nutritional value. Such foods will add to your toxic load by way of high-fructose corn syrup, artificial colors and flavors, preservatives, and genetically modified (GM) ingredients while offering your body next to nothing in return.

Some foods do not fall neatly into these two categories, however, and may masquerade as "healthy" foods when in fact they should be avoided. Below you'll find examples of some of these "healthy" foods that could be sabotaging your healthy-eating intentions.

7 Top 'Healthy' Foods to Avoid

1. Yogurt

Yogurt can be incredibly healthy, rich in high-quality protein, beneficial probiotics, calcium, B vitamins, and even cancer-fighting conjugated linoleic acid (CLA). But the key words are "can be."

Most yogurts sold in US grocery stores resemble more of a dessert than a health food. One six-ounce container of Yoplait yogurt may contain 26 grams of sugar (for the red raspberry flavor, for example).²

The negative effects of the sugar far outweigh any marginal benefits of the minimal beneficial bacteria they have. Remember, the most important step in building healthy gut flora is avoiding sugar, as that will cause disease-causing microbes to crowd out your beneficial flora.

Many other yogurts contain artificial colors, artificial sweeteners, artificial flavors, and additives, yet masquerade as health food. Mark A. Kastel, co-director of The Cornucopia Institute, which released the Yogurt Report last year, said:³

"What is most egregious about our findings is the marketing employed by many of the largest agribusinesses selling junk food masquerading as health food, mostly aimed at moms, who are hoping to provide their children an alternative, a more nutritious snack.

In some cases, they might as well be serving their children soda pop or a candy bar with a glass of milk on the side."

If you want to know which commercial yogurts are healthy and which are not, refer to The Cornucopia Institute's Yogurt Report. Their investigation found many products being sold as yogurt do not even meet the standards for real yogurt. The report also includes a comparative cost analysis of commercial yogurt brands.

The top-rated yogurts are generally VAT pasteurized at relatively low temperatures and are made from raw milk rather than previously pasteurized milk.

The good news is many organic yogurts are actually less expensive, on a price-per-ounce basis, than conventional, heavily processed yogurts (although some of the organic brands of yogurt actually contained some of the highest amounts of sugar).

Your absolute best bet when it comes to yogurt, however, is to make your own using a starter culture and raw grass-fed milk.

2. Fish

Fish has always been the best source for the animal-based omega-3 fats EPA and DHA, but as levels of pollution have increased, you have to be very choosey about which types of seafood you decide to eat.

If you're not careful, the toxic effects from the pollutants in the fish will outweigh the benefits of the omega-3 fats. About half of the world's seafood comes from fish farms, including in the US, and this is expected to increase. At first glance, farmed fish may seem like a good idea to help protect wild seafood populations from overfishing.

In reality, however, the industry is plagued with many of the same problems surrounding land-based concentrated animal feeding operations (CAFOs), including pollution, disease, and inferior nutritional quality.

It's getting so bad that fish farms can easily be described as "CAFOs of the sea." Many farmed fish are fed genetically modified (GM) corn and soy, which is a completely unnatural diet for marine life. Others are fed fishmeal, which is known to accumulate industrial chemicals like PCBs and dioxins.

In a global assessment of farmed salmon published in the journal Science, for instance, 13 persistent organic pollutants were found.⁴ Some of the most dangerous are PCBs, strongly associated with cancer, reproductive, and other health problems. PCB concentrations in farmed salmon were found to be eight times higher than in wild salmon.

Certain types of farmed fish, including farmed catfish imported from china and farmed shrimp from China, India, Malaysia, Mexico, Vietnam, Bangladesh, and Indonesia are even on the US Food and Drug Administration's (FDA) watch list for illegal drug residues, including antibiotics and anti-fungal compounds.⁵

Levels of critical omega-3 fats may also be reduced by about 50 percent in farmed salmon, compared to wild salmon, due to increasing amounts of grain feed.

One study published in the Journal of the American Dietetic Association found farmed tilapia and farmed catfish also have much lower concentrations of omega-3s and very high ratios of omega-6 fats to omega-3 fats.⁶

So is any fish still considered a "health food"?

Among the safest in terms of contamination, and the highest in healthy omega-3 fat, is wild-caught Alaskan and sockeye salmon. Neither is allowed to be farmed, and are therefore always wild-caught. The two designations you want to look for on the label are: "Alaskan salmon" (or wild Alaskan salmon) and "Sockeye salmon."

Canned salmon labeled "Alaskan salmon" is also a good choice and offers a less expensive alternative to salmon fillets. A general guideline is that the closer to the bottom of the food chain the fish is, the less contamination it will have accumulated, so other safer choices include smaller fish like sardines, anchovies, and herring.

Sardines, in particular, are one of the most concentrated sources of omega-3 fats, with one serving containing more than 50 percent of your recommended daily value.⁷

They also contain a wealth of other nutrients, from vitamin B12 and selenium to protein, calcium, and choline, making them one of the best dietary sources of animal-based omega-3s.

Finally, no matter what type of fish you're considering, look for varieties that have received the Marine Stewardship Council (MSC) certification. This certification assures that every component of the manufacturing process – from how the raw materials are harvested to how the product is manufactured – has been scrutinized by MSC and has been independently audited to ensure it meets sustainable standards.

3. Soy

Soy is touted as a healthy vegetarian source of protein, but its phytoestrogens (or isoflavones) can mimic the effects of the female hormone estrogen. These phytoestrogens have been found to have adverse effects on various human tissues, as they produce a variety of mild hormonal actions within the human body.

An increased risk of breast cancer is another potential hazard, especially if you're exposed to high amounts of estrogen-mimicking compounds from birth.

Unfermented soy also contains natural toxins known as "anti-nutrients," along with additional anti-nutritional factors such as saponins, soyatoxin, protease inhibitors, and oxalates. Some of these factors interfere with the enzymes you need to digest protein.

While a small amount of anti-nutrients would not likely cause a problem, the amount of soy that many Americans in products like tofu, soy milk, soy oil, soy protein powder, and soybeans, can be extremely high. Further, one of the worst problems with soy comes from the fact that 94 percent of soybeans grown in the US are genetically modified.⁸ One of the best studies ever done to document the dangers of GM foods found that overall, inflammation levels were 2.6 times higher in GM-fed pigs than those fed a non-GM diet, and male pigs fared worse than the females.

If you eat Roundup Ready soy, one common GM variety that's engineered to withstand the herbicide Roundup, you'll be exposed to its active ingredient, glyphosate. The International Agency for Research on Cancer (IARC), which is the research arm of the World Health Organization (WHO), determined glyphosate to be a "probable carcinogen" (Class 2A). This was based on "limited evidence" showing that the popular weed killer can cause non-Hodgkin's lymphoma and lung cancer in humans, along with "convincing evidence" it can also cause cancer in animals.

Glyphosate and glyphosate formulations have also been shown to induce DNA and chromosomal damage in mammals, as well as human and animal cells in vitro. Even if you opt for organically grown soy, I still don't recommend consuming it, however, unless it's in fermented form. For centuries, Asian people have been consuming fermented soy products such as natto, tempeh, and traditionally made soy sauce -- and enjoying the health benefits. Fermented soy does not wreak havoc on your body like unfermented soy products do, but unfortunately, most soy sold in the US market is the unfermented, processed variety.

4. Agave

Most agave nectar or syrup is nothing more than a laboratory-generated super-condensed fructose syrup, devoid of virtually all nutrient value. This so-called "healthy" sweetener is mostly fructose and is so highly processed and refined that it bears no resemblance to the plant for which it's named. Depending on how it's processed, it may contain anywhere from 55 percent to 90 percent fructose. High-fructose corn syrup is also about 55 percent fructose so, even in the best case, agave syrup offers no advantage.

The evidence is overwhelming that, when consumed in large quantities, fructose is among the most damaging sugars you can eat. Fructose drives up uric acid, which is a direct pathway toward hypertension, insulin resistance, diabetes, kidney, and liver disease. Fructose is, in many ways, very similar to alcohol in the damage that it can do to your body… and your liver. Unlike glucose, which can be used by virtually every cell in your body, fructose can only be metabolized by your liver, because your liver is the only organ that has the transporter for it.⁹

Since nearly all fructose gets shuttled to your liver, and, if you eat a typical Western-style diet, you consume high amounts of it, fructose ends up taxing and damaging your liver in the same way alcohol and other toxins do. In fact, fructose is virtually identical to alcohol with regard to the metabolic havoc it wreaks. According to Dr. Lustig, Professor of Pediatrics in the Division of Endocrinology at the University of California, fructose is a "chronic, dose-dependent liver toxin." And just like alcohol, fructose is metabolized directly into fat – not cellular energy, like glucose. A better sweetener options is stevia, a natural herb.

5. Veggie Chips

Veggie chips sound like a healthy way to satisfy your snack cravings, but they're nothing more than glorified potato chips. Most are made from corn flour or potato as a base and have only veggie powder or puree added in. Not only are most of the vitamins in veggies therefore NOT in veggie chips, but these snacks are then either fried or baked at high temperatures. When carbohydrate-rich foods like chips are cooked at high temperatures, acrylamide -- a tasteless, invisible chemical byproduct -- is formed.

Animal studies have shown that exposure to acrylamide increases the risk of several types of cancer, and the International Agency for Research on Cancer considers acrylamide a "probable human carcinogen." It has also been linked to nerve damage and other neurotoxic effects, including neurological problems in workers handling the substance. While this chemical can be formed in many foods when they're heated to a temperature above 120 degrees Celsius (248 degrees Fahrenheit), French fries and potato chips are the biggest offenders.

So whether they're laced with veggie powder or not, veggie chips are not a smart food choice. A far healthier alternative would be to chop up some fresh kale and toss it with some olive oil and natural salt, then bake it in your oven until crispy (homemade kale chips are also a favorite of "soul surfer" Bethany Hamilton).¹⁰ You can, of course, also snack on fresh veggies like carrot sticks, celery sticks, radishes, bell pepper, and even asparagus, to increase your nutrient and fiber intake while satisfying your craving for a crunchy snack.

6. Fruit Juice

The primary problem with fruit juice is that it simply contains far too much fructose to be healthy, not to mention the rarely mentioned methanol toxicity in any preserved juice. While whole fruits do contain fructose, they're also rich in fiber, antioxidants, and a vast array of health-promoting phytochemicals. Fruit juices, particularly pasteurized, commercially available fruit juices, have virtually none of these phytonutrients. The fiber in the whole fruits also plays a large role in protecting you from a rapid and exaggerated rise in blood sugar.

The fiber slows the rate at which sugar is absorbed into your bloodstream, and fruit juice will not provide such protection. According to a study published in the British Medical Journal, those who drank one or more servings of fruit juiceeach day had a 21 percent higher risk for type 2 diabetes compared to those who ate whole fruits.¹¹ So if you're in the mood for something fruity, eat a piece of fruit instead of drinking a glass of juice.

An alternative that can be healthy is a homemade fruit smoothie, provided it's balanced with moderate amounts of fruit, protein, and healthy fats, like this avocado super smoothie (which also contains blueberries and pineapple). Most store-bought fruit smoothies are far too high in sugar and/or fructose to be considered healthy.

7. Gluten-Free Foods

Gluten, a protein found in grains such as wheat, rye, and barley, causes the immune system to attack the intestines in people with celiac disease. But non-celiac gluten sensitivity may actually affect as many as 30 percent to 40 percent of the population, and according to Dr. Alessio Fasano at Massachusetts General Hospital, virtually all of us are affected to some degree.¹² This is because we all create a substance called zonulin in the intestine in response to gluten.

Glutinous proteins, known as prolamines, can make your gut more permeable, which allows partially digested proteins to get into your bloodstream that would otherwise have been excluded, any of which can sensitize your immune system and promote inflammation, contribute to chronic disease. Once gluten sensitizes your gut, it then becomes more permeable and all manner of gut bacterial components and previously excluded dietary proteins—including casein and other dairy proteins—have direct access to your bloodstream, thereby further challenging your immune system.

Gluten may even negatively impact mood and brain health.¹³ Gluten also makes your gut more permeable, which allows proteins to get into your bloodstream, where they don't belong. That then sensitizes your immune system and promotes inflammation and autoimmunity. Gluten-free foods are becoming more widely available in supermarkets and restaurants, due to growing consumer demand, but while this seems like it would be a healthy transition, most gluten-free products are nothing more than refined, processed junk foods.

Some may contain gluten-free grains in their place, which if you are insulin and leptin resistant will only raise your insulin and leptin levels, which is a major driver of most chronic diseases. And many gluten-free products contain high amounts of sugar, corn syrup, and alternative forms of starch, none of which is healthy. So while I believe many people can benefit from removing gluten from their diets, stick with gluten-free whole foods as a replacement – not the processed gluten-free junk foods lining many store shelves.

As an aside, many food products bearing the gluten-free label have been found to be contaminated with sometimes high amounts of gluten. In one study, even naturally gluten-free products tested positive for gluten, courtesy of cross-contamination during processing. So if you're eating gluten-free due to celiac disease, avoiding processed gluten-free products may be even more important.

Additional Unhealthy Foods to Avoid

For a comprehensive guide on what to eat to be healthy, see my free optimized nutrition plan. Generally speaking, as mentioned, you'll want to focus your diet on whole, ideally organic, unprocessed or minimally processed foods. For the best nutrition and health benefits, you'll also want to eat a good portion of your food raw. To help sort through more of the confusion surrounding "health" foods that aren't, check out the infographic below. It has even more details on commonly consumed foods that you're better off avoiding.