These days, when we talk about nutritional bad guys, it's often a tossup between saturated fat and added sugar. But that hasn't always been the case.

About 50 years ago, according to recently released historical documents, the sugar industry secretly paid scientists to downplay the link between sugar and heart disease and shift the blame to saturated fat.

The revelation is raising eyebrows as people realize the power wielded by industry trade groups. Saturated fat certainly was the bad guy for decades while sugar wasn't scrutinized until relatively recently.

So, looking back, who was right? Is added sugar or saturated fat worse for you?

Saturated fat

Saturated fats are found naturally in many foods, especially in meat and dairy products, as well as some baked goods and fried foods. The main concern with saturated fats has been the link with cholesterol and heart disease. However, in recent years, there's been conflicting information about the role saturated fats may or may not play in heart disease and cholesterol. In 2014, a meta-analysis of 72 published studies on fatty acids and heart risk found no evidence to support guidelines that lowering saturated fats would lower heart disease.

Some researchers have found those conclusions misleading, and some studies since have reinforced earlier links between saturated fats and heart issues.

For years, saturated fats have been linked to raising LDL (bad) cholesterol, which increases your chances of developing heart disease. Although reviews of studies have called that link into question, the American Heart Association still recommends limiting saturated fats, saying they raise your risk of heart disease. The organization recommends replacing saturating and trans fat with healthier monounsaturated and polyunsaturated fats instead.

The USDA's ChooseMyPlate healthy food groups site also suggests cutting back on saturated fats, saying, "Eating more unsaturated fat than saturated and trans fats can reduce your risk of heart disease and improve 'good' (HDL) cholesterol levels."

Added sugar

The sugar in foods and drinks can be naturally occurring — like in fruits and vegetables — or added during processing or preparation. Too much added sugar has a number of potential health concerns.

Weight gain and poor nutrition. All foods can contribute to weight gain and obesity, if you eat too much in general. But often, health experts like to blame the "empty" calories in sugar, because they are devoid of fiber, vitamins, minerals and other nutrients. The American Heart Association recommends that women have less than 100 calories of added sugar per day (about 6 teaspoons) and men consume less than 150 per day (about 9 teaspoons). And filling up on no-nutrient sugary foods and drinks can mean poor nutrition. If you drink a lot of soda, for example, you may skip milk. If you're too full of cookies and sweet snacks, you're more likely to ignore that healthy apple.

Cholesterol. Researchers believe there may be a link between sugar and unhealthy cholesterol. A 2010 study found that people who ate large amounts of added sugar had high blood triglyceride levels and low HDL (good) cholesterol levels. The study, published in the Journal of the American Medical Association, also found that eating a lot of sugar increased the chances of having low HDL cholesterol by more than three times. The people who consumed the least sugar had the highest HDL levels and the lowest triglyceride levels.

Heart disease. Eating a lot of sugar can raise your risk of dying of heart disease, according to a 2014 study. Researchers found that over a 15-year period, people who got 25 percent or more of their daily calories as sugar were more than two times as likely to die from heart disease as those who had less than 10 percent added sugar in their diets. The results of the study, published in the Journal of the American Medical Association, found that the odds of dying from heart disease rose with the percentage of sugar in a diet, regardless of someone's age, sex, activity level or body mass index (BMI).

Tooth decay. You've heard that sugar rots your teeth. Well, we don't know about rotting but it definitely causes tooth decay. A 2014 report published in the journal BMC Public Health suggests that sugar is the sole cause of tooth decay. "Only 2% of people at all ages living in Nigeria had tooth decay when their diet contained almost no sugar, around 2g per day. This is in stark contrast to the USA, where 92% of adults have experienced tooth decay," study author Aubrey Sheiham, emeritus professor of Dental Public Health at University College London, said in a statement.

So what's the answer to the bigger question? Unfortunately, it's not a black-and-white answer, but moderation in all things is a good rule of thumb.

Mary Jo DiLonardo covers a wide range of topics focused on nature, health, science and anything that helps make the world a better place.

Added sugar or saturated fat: Which is worse?
For years, the sugar industry paid scientists to shift the blame for heart disease from sugar to saturated fat, but there's more to the story.