Eating and Drinking Before Surgery: Why It’s a No-No

If you or a loved one have a surgery coming up, you probably went over a handful of instructions to prepare.

Your doctor may want you to take certain medications. To not take others. To wash with a special soap. And — no one’s favorite — to avoid eating or drinking several hours before your procedure. It’s a rule that healthcare professionals refer to as NPO. That’s an acronym for a Latin phrase that translates to “nothing by mouth.”

Why? Why can’t you have a nice breakfast and a latte on the way to the hospital? Is your surgeon trying to make life more difficult as you prepare for a potentially stressful event?

No. They’re not. They’re doing their job, which means keeping you safe.

So, why can’t you eat before surgery? Or have some OJ to jump-start the morning? General surgeon Diya Alaedeen, MD, explains.

What happens if you eat before surgery?

If you eat in the hours before elective surgery, your provider will likely advise rescheduling. It’s that important. If you need emergency surgery, a healthcare provider will weigh the risks of having food in your stomach against the risk of pushing back surgery.

What are the risks?

Dr. Alaedeen shares the reasons why it’s advised to go into surgery on an empty stomach.

Risk of aspirating

The biggest risk of eating before undergoing general anesthesia is the chance that you could aspirate. That means that the undigested food that’s in your stomach can travel up into your esophagus and into your airway.

“We’re not made to breathe food. We’re made to breathe air. When you’re under anesthesia and lying down on the operating table, if your stomach is full, that food can potentially come up the esophagus into the airway. That can create a serious problem, like choking, pneumonia or major complications in your airway," Dr. Alaedeen explains.

Why would that happen?

While some people will talk about general anesthesia as being “put to sleep,” it’s not like a regular night’s rest. When you sleep normally, certain automatic processes in your body, like breathing and digestion, are still active. When you’re under anesthesia, it’s all shut down.

“When you’re under general anesthesia, you will lose all the protective mechanisms of the body,” Dr. Alaedeen continues. “That includes paralyzing the smooth muscles — the ones that we don’t control. We have muscles that protect us from inhaling our saliva, food and water, and those mechanisms are paralyzed as well. So, they’re not providing any protection to your airway.”

While those muscles are “asleep,” they can’t keep your undigested breakfast bagel or your morning smoothie down in the stomach where they belong.

Food takes up space in your abdomen

Your stomach and your bowels swell after eating.

If you’re having abdominal surgery, a full belly means less space for your surgical team to do their work.

Food in your system can also create trouble if you’re having an endoscopic procedure.

During an endoscopy, your provider uses a thin tube with a camera on it to see inside your body. They use endoscopy to see organs like your colon, small intestines, trachea (windpipe) and more.

If there’s food in the way, it’s tough for the camera to see the actual structure of the organs. There’s simply too much stuff in the way.

Eating and drinking before an endoscopy can also increase your risk of aspiration, even if you’re not under general anesthesia.

“An endoscopy blows air into your stomach. So, the food can come out when we remove the scope and you can aspirate on it,” Dr. Alaedeen warns.

Digestion puts extra strain on your body

When you eat, it triggers reactions in your body to break down your food to get energy. And the process of digestion takes some work.

So, if you go into surgery with a full belly, it can put extra strain on your system and distract it from the task at hand.

“If your stomach is full, your body focuses on getting the food where it needs to go,” Dr. Alaedeen points out. "It’s busy with digesting and not on fighting the physiologic insult of surgery.”

Risk of anesthesia side effects

Not all surgeries require general anesthesia or endoscopy but still come with strict instructions against eating and drinking before surgery.

Good reason for that, too.

If you’ll be having local anesthesia — where just a part of your body is numbed but you’re awake — there are still concerns that come with eating or drinking before your procedure.

“For people having local anesthesia, we’re not as worried about aspiration from sedation, but we do worry about people having a negative reaction to the needles or the injection,” Dr. Alaedeen explains.

Namely, nausea and vomiting.

Both are common reactions to the medication used in anesthesia. And no one wants to add a bout of vomiting to their post-surgical recovery.

Fasting guidelines before surgery

The exact recommendations for how long to fast before surgery will depend on a few factors. So, ask your surgical team if you have questions.

But in general, most guidelines about eating or drinking before surgery are something like:

• Don’t eat after midnight the night before surgery.
• Water is OK to drink the morning of your surgery.
• One cup of black coffee (without any sugar, milk or whiteners) is OK the morning of your surgery.

“Food takes about four hours to clear through your stomach. Fluid takes about two hours. So, if you stop eating at midnight and only have water or black coffee in the morning, that should be plenty of time for your body to digest it before most procedures,” Dr. Alaedeen reports.

Neither black coffee nor water contains any nutrients that your body has to work to break down. So, they pass through without too much effort. On the other hand, things like juice take more work because it contains vitamins and sugars that stick around longer. Same with cream in your coffee.

Can you brush your teeth before surgery?

Sure, you might swallow a teeny bit of toothpaste or water when you brush your teeth and rinse your mouth.

But it’s not enough to make a difference in your risk for aspiration or other negative effects.

When it comes to brushing before your procedure, Dr. Alaedeen’s advice is clear, “Please do. Your surgical team will appreciate it.”

What to eat leading up to surgery

If you’re thinking about planning an 11 p.m. feast the night before surgery, Dr. Alaedeen suggests a different approach. “Your body responds to surgery similar to how it handles strenuous exercise. You want to fuel your body well in the days and weeks before surgery, if you can, to help it prepare for the work ahead.”

His best advice for a pre-surgery diet?

• Drink plenty of water.
• Limit your intake of beverages that include alcohol, caffeine and sugar.
• Limit saturated fats (like red meat and fried foods).
• Limit simple carbohydrates (like white bread and pasta).
• Eat plenty of fruits and vegetables (a good rule of thumb is that fruits and vegetables should fill half your plate).

Follow your surgical team’s instructions about any medication to take and avoid before surgery and when to fast. They’re looking out for you. Not trying to starve you. We promise.