Nobody wants to think about the negative effects of those oh-so-deliciously-salty fast-food fries or that extra pastry or two when someone brings doughnuts to the office.

But besides the usual suspects (obesity, heart disease, diabetes) we worry about when it comes to our diets, should cancer be something we should add to our list of food worries?

The frustrating answer is maybe … or maybe not. Despite advances in medical research, scientists and researchers still have had difficulty pinpointing the exact causes of various types of cancer.

Some evidence points to environmental factors, while other research suggests that what we put into our bodies may be to blame. The challenge is to strike a balance between enjoying food and making smart choices when it comes to what we eat.

So, while research is still being done, here are five things you may be eating that have been linked to cancer ...

bottles of soda pop cola

No. 5: Refined sugar

In order to survive, any biological process or system needs a food source in order to generate energy and continue to grow.

Overall, the human body continues to live if people engage in proper nourishment, exercise and ongoing hydration. Unfortunately, the same is true for cancer cells.

A recent UCLA study published in the journal Cancer Research found that tumor cells use fructose to proliferate and other studies have linked fructose intake with pancreatic cancer, one of the deadliest cancer types.

This is bad news for all those people who enjoy ice cream, candy and soft drinks. If people want to ward off some forms of cancer and work to starve tumors, they should avoid sugar, sweeteners and products that contain high-fructose corn syrup.

Giving up sweets may be tough, but it could also be a key to avoiding cancer in the future.

Next, find out what your answer should be to the question "Would you like fries with that?"

Fast food french fries

No. 4: French fries

Most people understand that french fries can lead to coronary heart disease and other problems due to saturated and trans fats.

Another issue with fries may center on something called acrylamide, a chemical researchers have shown causes cancer in rats. The chemical is not found in the fries themselves, but rather occurs as a byproduct of frying potatoes -- be them fries or chips -- in oils at high temperatures, according to the Food and Drug Administration.

A Swedish government report first connected fried foods and acrylamide in 2002. But despite the chemical's known effect on rats, scientists still aren't sure whether acrylamide is carcinogenic to humans.

But if some people had their way, they would label them "cancer fries" instead of french fries. The name-change would most likely cut into sales, but nutritionists would probably be more than happy to see a drop in sales of this unhealthy product.

Now, what are french fries and other foods made with? That's right ... oil ...

trans fat on food label

No. 3: Trans fats

The public has become more and more aware of the dangers of certain oils, and companies have been scrambling to assure their customers that they are using "healthier" oils.

Manufacturers use hydrogenated and partially hydrogenated oils because they extend the shelf life of products. Unfortunately, this can also create trans fats, which can be a factor in cancer but also impact heart disease and a variety of other health problems, according to the Mayo Clinic.

While the American Cancer Society's official position is that a relationship between trans fats and cancer "has not been determined," some studies have linked trans fats to prostate and breast cancer.