Scarfing a sandwich at your desk might seem like a great way to eke a little more productivity out of your day, but according to a host of experts, spending a little more time thinking about what you shove in your mouth at lunchtime will be more than made up for in greater energy and more ideas later in the afternoon.

As Buffer's Leo Widrich notes, our brains run best when we have about 25 grams of glucose circulating in our blood. You can get that glucose from basically any food, but that doesn't mean a donut will do you as well as a salad.

"There is virtually no difference in the very short term for your brain activity," he writes, but "over the stretch of a normal eight-hour day however, the differences are spectacular. After eating the donut, we will release glucose into our blood very quickly. We will have about 20 minutes of alertness. Then our glucose level will drop rapidly, leaving you unfocused and easy to distract."

Opt for something slower to release it's glucose, however, and your blood sugar level will remain steady for far longer, keeping your brain focused and productive. So what are the ideal foods to munch at lunch for the slow-but-steady glucose release we're after? A variety of nutritionists have offered tons of yummy suggestions.

1. The souped-up home sandwich

Eating well at lunch doesn't have to mean ordering something fancy. You can make a sandwich that's perfectly tuned to fuel your brain with the usual suspects from your pantry, insists WaPo food reporter Ellie Krieger.

First, she instructs, avoid a carb overload by opting for the right sort of whole grain bread. Instead of that bagel, go with "two slices of sandwich bread, a six-inch pita or a nine-inch wrap. Scooping the center out of a crusty baguette or roll is also a great way to keep starch portions in check and still have the satisfying sandwich you crave," she writes.

Then, be crafty when it comes to fillings: "get yourself out of a mayo rut by exploring condiments that are bursting with flavor and nutrients. Try slathering a basil or sun-dried tomato pesto on bread for a punch of flavor, indulging in a spread of buttery ripe avocado, or smearing on some rich, creamy hummus. And instead of overstuffing your sandwich with cold cuts and cheese, leave lots of room for vegetables."

2. Or just good, old PB&J.

If even that sounds to complicated for you, you could just stick with a standard PB&J. "Believe it or not, a peanut butter and jelly on whole grain bread is a great choice," dietician Lisa De Fazio tells Business Insider. "Pack some baby carrots and an apple, and you have a healthy vegetarian lunch that reminds you of your childhood," she adds.

3. Everybody loves chickpeas.

OK, not everybody loves chickpeas, but just about every nutrition expert I found raves about them as a lunch food. (See Krieger's suggestion for sandwich spreads above for one example.)

"Chickpeas are the ultimate food for brain function because they combine protein to keep you alert along with complex carbohydrates to fuel your brain. Because the carbs are digested slowly they give you a sustained energy release that keeps you energized and focused," according to Karen Ansel, a spokesperson for the Academy of Nutrition and Dietetics and the co-author of The Calendar Diet.

"Hummus is a good source of calcium, iron, protein, fiber, and heart-healthy fats, which prevents blood sugar levels from rising too rapidly," agrees the same BI article above.

4. A substantial salad

It's probably no shock to you that salads are a healthful choice, but if you want to turn that bowl of greens into a real brain booster, consider adding some substantial extras.

"Think about adding an egg to the mix," suggests a Lifehack article on brain food. "Egg yolk is a leading source for choline, a nutrient that, recently, has been proven to boost brainpower by speeding up the sending of signals to nerve cells in the brain." De Fazio concurs that a cobb or seafood salad is always a solid choice.

5. Pair with yogurt and nuts

Everyone likes a little nibble on the side with their sandwich or salad. Instead of a bag of chips, Lifehack has other ideas: "Ending lunch with a yogurt helps produce neurotransmitters, improving signals amongst neurons. Complementing this with nuts [particularly walnuts] balance omega-3 acids with omega-6's while neutralizing blood sugar levels."

6. Fancier fare (aka leftovers, supercharged)

If you're something of a master chef, the options are pretty much endless, but if you're looking for nutritionist-approved inspiration, a separate WaPo article on the science of the ideal lunch offers a helpful slideshow of healthful recipes including lunch-friendly fare like Flatbread Pizzas With Broccoli Pesto, Sun-Dried Tomato and Egg; Sesame Rice Balls; and Creole-Spiced Fresh Corn and Crab Soup.

Feel free to make something the night before and pack the leftovers in a Tupperware. "The easiest trick is to make lunch with food from dinner the night before," notes De Fazio.

7. And if you're ordering out?

Of course, people are busy (or hate cooking) so sometimes lunch is going to be ordered out. But that doesn't mean you're doomed to late-day bloat and a truly rough afternoon slump. Even takeaway joints offer healthful choices. De Fazio suggests a Chipotle burrito bowl, for instance.

"The rice will give you just enough carbs to feed your brain without overdoing it. The chicken or beef give you protein to keep blood sugars steady, and guacamole is a healthy fat that keeps you fuller longer. If you want to order double protein, go for it," she says. Just go easy on the cheese.

Even if you're colleague is a fast food junky and there's no escaping the occasional trip to McDonald's of Taco Bell, there are options. This helpful BuzzFeed article lists the healthiest menu items for 26 takeout joints, including nutritional details.

Once lunch is sorted out, has you covered if you're in the market for easy, brain-boosting afternoon snacks as well.