Our nutritionist shares tips to finding healthy Subway menu options at any store.

This past December, CNBC asked passersby on the streets of New York a question: "What fast food chain has the most locations across the globe?" If you immediately thought of McDonald's, you're not alone: three of those on camera jumped to the same conclusion. But Subway actually operates more than 43,912 stores globally, making it the most widely available fast food option. McDonald's, on the other hand, has 37,241 stores, closely followed by Starbucks, which slings coffee across the world in 27,399 locations.

Despite being the largest fast food chain in the United States, according to data from Business Insider, consumers aren't visiting the sandwich chain as much as other fast food restaurants. Yearly sales have fallen at Subway every year since 2014. A recent report by Restaurant Business Online even says the chain closed over 1,100 stores in the past year, and more closings are likely throughout 2019. The company only predicted 500 closings for 2018 and is having to make drastic strategical changes. 

In light of having the fewest amount of Subway locations since 2011, spokespeople for the company noted they are planning to expand more globally, particularly in India, Mexico, China, and the U.K. They also noted that while we may be seeing more closings in 2019, the company is focusing on relocating or remodeling other locations in hopes of more profitability. 

Why are sales slumping at Subway? The team at CNBC cites a few possible reasons—like the fact that the menu has remained mostly the same since the late '60s, when Subway was founded in Connecticut. The RBO report said smaller chains, like Jimmy John's, Firehouse Subs, and Jersey Mike's have risen in popularity over the past few years, and their current average annual sales are 80 percent higher than Subway's. 

Regardless of sales, you may ask: Is Subway healthy? Subway's menu is one of the most redeeming for your health, especially when you compare the chain's offerings to that of a fast food drive-thru. The meals from McDonald's, Burger King, and Panda Express are rarely considered "healthy," and hacking their menu isn't always easy. We’re not saying that every sandwich option at Subway is a safe bet, but if you know what to order, you can find a healthy and filling meal for less than $5.

Looking for the healthiest option while dining out? Read more:

Brierley Horton, Cooking Light's nutrition director, has a few general tips to avoid excess calories, salt, and fat while dining at Subway.

Healthy Subway Sandwiches

"Overall, choose a sandwich made on their whole-wheat subs. While wraps may sound like a better alternative to bread, the sodium found within some tortilla-based options is excessive compared to Subway's wheat bread," Horton says.

Credit: Getty: Joe Raedle

Don't choose to double up on extra meat or cheese, because that can easily push total sodium levels over 1,500mg, Horton advises. But you can feel good about asking for extra vegetables, and don't feel bad about asking for every veggie on the bar—especially if it's in season. "Diversify the veggies you choose if something isn't in season, like if tomatoes look lackluster in the middle of the winter."

You might be surprised to hear that adding mayonnaise to any sandwich might be a better bet than light mayonnaise—but Horton says there's exponentially more sodium in "light" mayonnaise than in the traditional condiment.

"Go for oil and vinegar when you can, as this dressing only adds around 45 calories and is light on everything else," Horton says. "But if you have to have mayo, the regular variety could be best—you'll save on sodium, even though Subway's serving of regular mayo is double the calories than that of light mayo. Choose the lesser of two evils."

One thing to avoid at Subway? The chain's pre-mixed sauces and dressings.

"Subway's buffalo sauce contains 400mg of sodium for one serving, which isn't the best option," she says. "Stick to your basic condiments, and know that light mayo and mustard are higher in sodium than oil and vinegar. If you feel the need to shake it up, ask for fresh avocado or Subway's guacamole, which is still more redeeming than add-ons like ranch."

Remember that Subway has a nutritional calculator you can use for free before ordering from their restaurants. Take a second to check your favorite order to see if there's anything you can swap in or out for a more wholesome sub.

With Horton's tips in mind, we dove into Subway's menu and found five healthy Subway sandwiches you can order at any store. Each are under 350 calories, 7g of fat, and 950 mg of sodium.

1) Rotisserie-Style Chicken Sub

One of Subway's newest items has pulled chicken, cucumbers, green peppers, lettuce, red onions, spinach, and tomatoes on a six-inch wheat sub. There are only 350 calories, 670mg of sodium, 7g of sugar, and 6g of fat in this sub. If you must have a condiment with your order, try the light mayonnaise, which will add an extra 50 calories and 100mg of sodium.

2) Veggie Delight

A great option for vegetarians, the Veggie Delight sandwich contains only 230 calories, 280mg of sodium, 2.5g of fat, and 7g of sugar—which is impressive, considering it’s loaded with cucumbers, green peppers, lettuce, onions, spinach, and tomatoes on wheat bread. Adding cheese will up the fat and sodium content, but a dash of Subway's oil and vinegar dressing to this veggie medley only costs 45 calories with no additional sodium.

Horton says this is also the best option if you want one of Subway's sides, like baked potato chips or a cookie.

3) Turkey and Provolone

If you add provolone cheese to a six-inch turkey wheat sub, you'll still have a wholesome sandwich at just 340 calories, 8g of fat, and a manageable 790mg of sodium. Adding sauce or a condiment could push sodium levels into the 1,000mg area, so stick with yellow mustard, which will only add 10 calories and 100mg of sodium.

4) Roast Beef

Subway's roast beef sub is hearty, and is loaded with cucumbers, lettuce, green peppers, onions, spinach, and tomatoes. A six-inch serving has just 320 calories, 5g of fat, and 670mg of sodium, which means you can definitely customize the sandwich with cheese or a condiment. Swiss is your best choice for cheese (only 50 more calories and a mere 30mg of sodium), but you can add honey mustard, light mayonnaise, sweet onion sauce, yellow mustard, or barbecue sauce without exceeding the 350-calorie mark.

5) Black Forest Ham and Monterey Cheddar

This is one of Subway's more sodium-rich subs, and it’s best enjoyed with either Swiss or Monterey cheddar cheese, as both of these options keep the total sodium count under 900mg. On a six-inch wheat sub, add cucumbers, green peppers, lettuce, onions, spinach, and tomatoes for a sandwich that has just 340 calories with 9g of fat and 8g of sugar.