Have you ever felt a wave of sleepiness come over you after a meal? When it does, you might feel like curling up in a chair and taking a siesta, but that’s not always possible. The larger the meal you ate, the more likely you are to feel sleepy. That’s why so many people take a nap on Thanksgiving Day! You might be able to take a short siesta on Thanksgiving, but if you’re at work, a nap isn’t always feasible. You have things to do! Let’s look at some of the reasons why we feel sleepy after a meal.
The Alkaline Tide
One scientific explanation for why you have problems staying awake after a large meal is a phenomenon called the alkaline tide. After a meal, your stomach produces more hydrochloric acid to digest whatever you’ve eaten. To make hydrochloric acid, the cells lining your stomach use salt. During the process, bicarbonate, an alkaline substance, is produced. If this bicarbonate were to build up, it would raise the pH of the stomach. So instead, some of it enters the bloodstream, creating what we call the alkaline tide.
So, why does a rise in blood pH (alkalinity) make you feel sleepy? As bicarbonate enters the bloodstream and the pH of the blood drops (become more alkaline), it suppresses the release of a peptide called orexin that helps you stay awake and alert. Without the activating effects of orexin, you start to feel sleepy, groggy, and less productive. The alkaline tide usually lasts for around two hours after a meal.
What You Can Do about It:
The best way to reduce the alkaline tide after eating is to avoid eating a large meal. If you always feel sleepy after you eat, eat smaller meals throughout the day rather than a few large ones. If you’re at work, it’s probably not a good idea to eat a large lunch and then head back to the office Your productivity may suffer. Don’t eat too much at one setting, especially if you have to be productive after that meal.
Activation of the Parasympathetic System
The alkaline tide isn’t the only reason you feel non-productive after a meal. When you eat something, your body’s priorities shift. You now have food in your stomach and it needs to be digested and absorbed. This turns on the parasympathetic nervous system, the “rest and relax” component, so that blood flow is shifted toward the digestive tract and digestion and away from skeletal muscles and the brain. The shift in blood delivery to the brain can temporarily make you feel sleepy. The parasympathetic nervous system opposes the sympathetic nervous system that keeps you alert and active by increasing your heart rate, breathing, and blood flow to your muscles. When one is active, the other is quiescent. Your body wants you to be in a relaxed state when you’re trying to digest your food and that can cause you to feel sleepy.
What You Can Do about It:
As mentioned, don’t eat a large meal as meals larger in size create more of a parasympathetic response. Also, take a 10-min. brisk walk after a meal to boost blood flow to your brain. Walking, especially at a brisk pace, also revs up your sympathetic nervous system so you don’t feel as sleepy.
Post-Meal Inflammation
We hear so much about inflammation these days and the role it plays in a variety of health problems. Did you know every time you eat, you get a bump up in inflammation? However, this inflammatory response is actually protective in some respects. Each time you eat, you potentially take in harmful bacteria. To counter this, your immune system ramps up to keep harmful bacteria from gaining a foothold. The other positive is the temporary inflammation boosts the production of insulin to help get glucose inside cells where it can fuel the production of energy. The downside is this inflammatory response blocks the activity of the peptide mentioned earlier, orexin, the one that helps you stay awake and alert. The inflammatory response to a meal is greater in people who are overweight or obese and if you eat inflammatory foods, like a fast food meal, or foods that you’re sensitive or allergic to.
What You Can Do About It:
Avoid eating pro-inflammatory foods, like fast food, refined carbs, and sugary fare. Also, avoid foods you’re sensitive to as this can elicit an inflammatory response after a meal. Stick to whole, unrefined foods since they don’t contain additives that your body might not recognize and react to.
Increase in Leptin
Leptin is an appetite hormone that signals your brain that you have enough stored energy and that you can stop eating. Not surprisingly, leptin rises after a meal as your energy stores increase. Research links a rise in leptin with fatigue. Leptin increases more with a meal high in carbohydrates, so you’re more likely to feel sleepy after a carby meal over one high in protein or fat.
What You Can Do About It:
Choose healthy, whole foods and skip the refined carbs and sugar as these foods cause a greater rise in leptin. Make sure to include a healthy source of protein and fat with each meal too.
Rapid Spikes in Glucose
Eating a meal high in rapidly absorbed carbs from sugar and refined food sources causes a rapid spike in glucose. This rise in glucose blocks orexin, the “keep you awake” protein, so that you feel sleepy. One of the best ways to feel less like taking a nap after a meal is to eat fiber-rich carbs from natural sources rather than refined ones. There’s another reason to avoid refined carbs and sugar. The spike in glucose and insulin from eating these foods can lead to a subsequent blood sugar fall that triggers hunger. So, watch those refined carbs! Instead, choose high-fiber carbs sources such as vegetables, whole grains, legumes, and lentils to help stabilize your blood sugar and prevent a rapid post-meal spike. It’s better for your metabolic health too!
The Bottom Line
Now, you know some of the reasons why you feel sleepy after a meal. However, it’s a good idea to check with your healthcare provider if it’s a persistent problem. An underactive thyroid, anemia, or a problem with blood sugar regulation could be a factor. Otherwise, give these tips a try!
References:
J Clin Gastroenterol. 2002 Jul;35(1):5-8.
Science Daily. “Every meal triggers inflammation”
Journal of Translational Medicine201311:93 https://doi.org/10.1186/1479-5876-11-93.
American Journal of Clinical Nutrition. 85(2): 426-30.
