The front of a can or jar can scream “Low Sodium!” or “33% Less Sugar,” but the truth comes out when you read the ingredients list.

Diet expert Terri Johnson advises her patients to buy most of their food fresh in the vegetable or meat areas of the store, but she teaches them to read labels and make smart decisions when shopping grocery store shelves.

“I recognize that for the majority of our population, they are still going to grab things in the aisles,” says Johnson, a dietitian at Baton Rouge General Medical Center. “If you’re going to make this decision, then we need to arm you with information to make the best decision that you can in that circumstance.”

Ingredients, not numbers

It’s tempting to judge a product’s healthfulness based on the Nutrition Facts on the label, which provides the number of calories, fat grams, carbohydrates and a laundry list of vitamins and minerals.

But all those figures can be difficult to understand, Johnson says.

“These numbers can be skewed to where they are favorable for the company that makes the product,” she says. “Oftentimes, it’s deceiving to consumers.”

The serving sizes listed are sometimes smaller than what most people actually eat, causing many consumers to eat more calories, sodium or carbohydrates without knowing.

Instead of focusing on the calories or fat listed in a product, Johnson recommends you search the ingredient list for unhealthy additives.

For example, a popular peanut butter advertises itself as a healthy alternative because it contains less sodium and sugar. The label also claims it contains zero trans fats, which are considered by many doctors to be a huge threat to health because they raise your bad cholesterol and lower good cholesterol.

Yet the ingredient list contains two types of trans fats — fully hydrogenated vegetable oils and mono- and diglycerides. If each serving contains .49 grams of trans fat, the producer can round down and claim zero grams on the label. Eating multiple servings would definitely add trans fats to your diet.

Can’t pronounce it? Don’t eat it.

Even foods that appear to be healthy or advertise themselves as “all natural” often contain multi-syllablic chemicals.

Johnson advises her patients to avoid foods if they don’t understand the ingredients.

“If you don’t know what it is — or you don’t know how to say it — it shouldn’t go in your mouth,” Johnson says. “Typically, those words that are hard to pronounce are additives or preservatives.”

A popular weight-loss shake Johnson uses as an example has dozens of ingredients containing things like carrageenan, which is a natural ingredient from red seaweed used to thicken drinks. It can upset your stomach.

The healthiest diet relies on the most natural foods, she says.

Search for hidden additives

Canned and packaged products sometimes have unexpected extra preservatives and sweeteners. It takes a bit of detective work to suss them out, Johnson teaches.

“People should focus on looking for the hidden sugars in foods,” she says.

Johnson uses canned beans as an example. Most cans of black beans contain beans, water and salt. But red kidney beans are often sweetened with corn syrup and canned with a food coloring.

Any types of syrup — high fructose corn syrup is the most popular sweetener — or any ingredient ending with the suffix “ose” — such as dextrose, sucrose or maltose — add sugar to the product.

Additional sugars can cause inflammation in the body.

Short is best

During her classes, Johnson compares two types of sliced cheese. On its label, one says it is a “process cheese food,” while the other is just “cheddar cheese.”

The processed cheese food has a long ingredient list containing soybean oil, different types of acids and gums. But real cheese has few ingredients — milk, cheese enzymes, salt.

“The shorter the better,” Johnson says. “Know what is in your food — if you don’t know what it is, you shouldn’t eat it.”