In a world of constant admonitions to eat this and not that, it’s hard to know what we're supposed to be putting into our mouths. Science flip-flops, experts disagree and food companies get creative with spin — leaving even the best intentioned among us scratching our heads. What to eat?

One way to tackle the problem is by narrowing down the no-no list to the foods that rank as the worst in specific areas. With that in mind, here are our contenders for foods that you might want to kick to the curb if you share the related health concern.

1. If you value healthy cholesterol levels, never eat stick margarine.

At one point we were supposed to give up butter for the healthier option of margarine, but there was just one little problem. Early margarine was chockablock with trans fats, which deliver a double-whammy to cholesterol by raising LDL ("bad") cholesterol and lowering HDL ("good") cholesterol. Many margarines have been reformulated over the years, but not all margarines are created equal. In general, notes the Mayo Clinic, the more solid the margarine, the more trans fat it contains, so margarine that comes in stick form has more trans fat than tub margarines. Also, if you’re watching your processed food intake, remember that margarine is highly processed – so you’re better sticking with butter or olive oil.

2. If you think artificial sweeteners are helping you lose weight, you're wrong.

One would assume that swapping caloric sugar for a non-caloric sweetener would lead to weight loss, but apparently the body has an ironic sense of humor. Evidence is mounting that artificial sweeteners may lead to weight gain, and even worse, may lead to higher glucose levels. Time reports on a study that found sugar substitutes contribute to changes in the way the body breaks down glucose. As part of the study, researchers gave people who didn’t normally use fake sweeteners the sugar substitutes for seven days, and half of them showed higher blood glucose levels after just four days. Study author Dr. Eran says, “We found that the artificial sweeteners we think of as beneficial and that we use as treatment or preventive measures against obesity and its complications are contributing to the same epidemics they are aimed to prevent.” And not only are they bad for you, scientists have found artificial sweeteners in treated wastewater, posing potential risks to fish and other marine life.

3. If you like a calm hormone system, never eat canned coconut milk, soup and vegetables

Not all cans used for food are lined with the industrial chemical, Bisphenol A (BPA), but those that are should be avoided. BPA is a synthetic estrogen that can disrupt the hormone system, even in small amounts. It has been associated with an array of ills, from infertility and breast cancer to obesity, diabetes, early puberty and behavioral changes in children. In 2011, FDA tests of 78 popular canned foods found the chemical in 71 of them; and a Harvard study found that those eating a single serving of canned soup daily for five days had 10 times the amount of BPA in their systems compared to those who ate fresh soup instead. BPA concentrations in different cans of the same food differ a lot, so specific items to steer clear of are hard to discern. But a study by the Breast Cancer Fund found the highest concentrations in canned coconut milk, soup and vegetables. Look for products from companies that have moved away from using BPA.

Avoid cereal

Sugar shock. (Photo: Jiri Hera/Shutterstock)

4. Never eat kids' cereal if you’re watching your sugar intake.

This may come as no surprise, but cereals aimed at kids are packed with sugar. What you may not realize, however, is just how much sugar they contain. The leading sugar-crammed cereals, Kellogg’s Honey Smacks and Malt-O-Meal Golden Puffs, both contain 56 percent sugar by weight. Yes, more than half of their weight is sugar. Ouch! And one serving, which is only three-fourths of a cup, delivers 50 percent of the recommended daily sugar intake per serving as recommended by the World Health Organization.

5. Never eat soybeans and soybean products if you’re concerned about genetically modified food.

Regardless of what side of the genetically modified (GM) fence you sit on, avoiding GM ingredients is not easy. Some say that more than 75 percent of the food in grocery stores is genetically engineered or contains GM ingredients. Corn and soybeans top that list. And while corn may be the more prevalent crop, much of the GE corn goes to livestock feed. Soybeans and their products, however are in a surprising array of products we consume. Around 93 percent of soybeans grown in this United States have been genetically modified, reports Environmental Working Group. Meaning that if you want to avoid GM foods, watch out for labels that list soy proteins, soybean oil, soy milk, soy flour, soy sauce, tofu or soy lecithin unless they are certified organic or GMO-free.

6. Never eat tilefish, shark, swordfish and king mackerel if you're worried about mercury.

Methylmercury is a neurotoxin that can be harmful to the brain and nervous system when a person is exposed to too much of it. Thanks to human activity, it is found in most types of fish and in some fish in much higher concentrations that others. The FDA and the EPA have this to say to pregnant women, those who may become pregnant, breastfeeding mothers, and young children: Avoid tilefish from the Gulf of Mexico, shark, swordfish and king mackerel. Sounds like a good plan for everyone.

7. Never eat "industrial" hamburgers if you like clean food.

Grass-fed beef from cows that live on a farm is one thing, but industrial meat from factory farm cattle is a whole different beast. Filthy conditions, copious growth hormones and a diet comprised of genetically modified corn all add up to abysmal beef — but that’s not all. As Michael Pollan tells Rodale News, a steak or roast usually comes from a single animal, but processed ground beef is a mix of meat from hundreds of animals. "This vastly increases the risk of contamination," he says — and indeed, the USDA has found dangerous levels of disease-causing bacteria in more than 50 percent of the ground beef samples it has tested. "I love hamburgers, but only eat them when they're grass-fed and ground by a butcher," Pollan says.

Avoid soda

Diabetes in a bottle! (Photo: Brent Hofacker/Shutterstock)

8. Never drink soda if you don’t want diabetes.

A European study found that people who drank a 12-ounce sugar-sweetened soda daily were 18 percent more likely to develop Type 2 diabetes over a 16-year period compared with those who did not consume soda. Previous studies in the United States found that daily soda consumption increased the risk of Type 2 diabetes by 25 percent.

9. Never eat certain apples if you’re worried about pesticides.

Organic apples are okay, but if you’re concerned about pesticides steer clear of conventional ones. For four years running apples have topped EWG’s Dirty Dozen list with U.S. Department of Agriculture scientists detecting an average of five or more pesticides on raw apple samples, including some at high concentrations. One chemical in particular has caused a stir; diphenylamine (DPA) was found on 80 percent of samples tested. In 2012, the European Commission banned DPA due to its potentially potent carcinogens.

10. Never eat processed meat if you want to avoid … premature death!

We know you don’t want to hear this, but studies show that people who indulge in a lot of processed meat (like ham, bacon and sausage) have a greater risk of premature death and developing conditions such as cancer and heart disease. One comprehensive study included data from 448,568 people in 10 European countries and concluded that those who ate the most processed meat were 44 percent more likely to die prematurely from any cause than those who ate little of it. High levels of consumption bumped up the risk of death from heart disease by 72 percent and cancer by 11 percent. Many studies concur. One study from Harvard found that those who ate processed meat on a regular basis were more likely to die over a 20- to 30-year period, compared with those who didn't consume red meat regularly; the same study also found that substituting other healthy protein sources, such as fish, poultry, nuts or legumes was associated with a lower risk of death over the study period. We know beans aren't exactly the same as salty, smoky meat ...  but if you want to work towards living a longer life, you may want to abandon the bacon.

Related on MNN: