We all know the feeling - it's only Tuesday and you've rolled out of bed bleary-eyed, not-quite-human until you've had your caffeine fix.

But before you reach for that first magical cup of coffee, hold on a second. Metro spoke to Samantha Heller, a nutritionist at NYU's Center for Musculoskeletal Care & Sports Performance Center about how to manage your energy levels throughout your work day.

She thinks drinking coffee is not harmful in itself - it's just about controlling the amount (the recommended amount is 3-5 8 oz. cups a day) and what else goes into it (cream, sugar, syrup).

"If we look at the overall reality of caffeine consumption, particularly in the form of coffee, it doesn't seem to be doing anybody a whole lot of harm when it's consumed in reasonable amounts," said Heller.

You might also want to take a closer look at what you're consuming if you're a decaf drinker. 

"Decaf coffees can contain a range of caffeine from 2 milligrams to 15 mg. If you really do not want to consume caffeine opt for "caffeine free" products," said Heller.

Good alternatives to coffee could be black, green or white tea - which also have other health benefits and lower levels of caffeine.

And to avoid that afternoon crash? What you eat earlier in the day can have a huge impact on how you feel as you get closer to the end of the day.

"We all tend to crash around 3 or 4 o'clock ... That crash can be mitigated by (A) getting more sleep and (B) what we eat during the day," she said.

Foods to avoid, she said, include fast food and sugary refined carbohydrates - instead, vegetables, whole grains and beans can help to sustain energy.

But she said ultimately there's no way around the fact that getting more sleep is the best solution if your energy levels are flagging during the day.

" Somewhere between 50 and 70 million Americans complain about not sleeping well, not getting enough sleep, not feeling refreshed, so our default is to go to caffeine whether its in an energy drink or coffee to get us through our day, when really what we need is more sleep," she said.

If you're having trouble sleeping, it might be helpful to keep a food record and write down how much coffee or caffeine you're drinking and at what time of day, she added.

An article in the Washington Post on Monday suggested that drinking coffee first thing in the morning might not be the best time, because that tends to be when your body's production of the stress hormone cortisol is at its highest. Cortisol works, in part, to wake you up. 

They reported that a study found cortisol levels tend to be at their highest in the morning, between 6 a.m. and 10 a.m., and peak again around 12 p.m. and 5 p.m. 

Which, Heller says, makes sense - but having your coffee first thing in the morning is probably still a better idea than drinking it in the late afternoon, when it's likely to interfere with your sleep that night.

"Caffeine has a long half-life, like up to six hours, and if you're caffeine sensitive it might be more," she said. "So if you drink a heavy dose of caffeine at 4 or 5 in the afternoon, you forget about it but when you can't get to sleep by 10 or 11 it could still be related to that caffeine."