Coffee & Tea Lovers Unite! The Truth About Caffeine Post-WLS

Article By: Maria Tucker, MPH, RDN, LDN, CDCES

Maria Tucker is a Registered Dietitian and Certified Diabetes Educator with over 20 years of experience assisting patients with diabetes, obesity, and nutrition-related conditions. Maria is also the Founder of, a site dedicated to healthy recipes and kitchen shortcuts.

If you’ve had bariatric surgery, you are probably pondering this question. Why is caffeine prohibited after bariatric surgery? Let’s take a deeper dive into coffee, caffeine, and the reasons why caffeine is not recommended post-bariatric surgery.

Caffeine is a naturally occurring, bitter-tasting compound found in the leaves and seeds of many plants. The most common source of caffeine is the coffee bean, but it can also be found in cacao beans, tea leaves, guarana berries, yerba mate, and kola nuts. It contains polyphenols and other beneficial compounds. Synthetic caffeine is also found as an additive in sodas, energy drinks, and even some food items and pain relievers. It is the most widely used psychoactive stimulant drug around the world. Caffeine affects the central and peripheral nervous system, influencing cognitive performance by making one more alert and awake. This is why most people have to have their coffee first thing in the morning. It is fat and water soluble and can easily cross the blood-brain barrier, causing antagonism of the adenosine receptor A2a, which results in the wakefulness effects of caffeine. It is typically consumed orally, is totally absorbed in the small intestine in less than one hour, and quickly gets into other tissues. Consumption of caffeine with food can somewhat delay its absorption. The onset of caffeine’s effects will typically occur within 45 to 60 minutes and can last 3 to 7 hours in adults which is why it is typically recommended for caffeine to be avoided later in the day as it can alter sleep.

Although caffeine has been studied for its potential positive effects on lowering blood sugar and has been shown to increase alertness, it does have several adverse effects. According to a review of literature regarding caffeine from the National Center for Biotechnology Information or NCBI, these adverse effects can range from mild to severe, relative to the dose consumed and a person’s sensitivity to caffeine. The most common side effects of caffeine are increased restlessness, increased urination, tremors, irritability, increased blood pressure, and increased heart rate. It may also cause hallucinations, arrhythmias, and disorientation. Although the typical dose of caffeine is around 70 to 100 mg. per drink, and there is no recommended daily allowance for caffeine, the Food and Drug Administration considers doses of up to 400 mg. as safe.

After bariatric surgery, caffeine is typically not recommended for the first 30 days due to its effects on hydration status and gastrointestinal function. Several studies have found no adverse consequences of consuming 4 and 6 mg/kg body weight per day of caffeine in healthy adults who drink coffee regularly. This amounts to ~309 and 463 mg caffeine for a 170 lb. adult. However, since maintaining good hydration can be a problem after bariatric surgery, it is still good practice to avoid caffeine during the immediate post-surgery stage. Caffeine stimulates gastric, biliary, and pancreatic secretions as well as colon motility. You may feel the need to go to the bathroom right after drinking caffeine. According to a review of several studies, caffeine may be a contributing or additive factor to GERD risk factors like obesity and poor eating habits but does not directly cause GERD.

As a bariatric surgery nutritionist, it is not uncommon for me to encounter patients who report adverse effects of caffeine or develop intolerance to it in the first 3 months after bariatric surgery. Some patients complain of more frequent urination, acidic taste in their mouth, and even bloating, abdominal pain, constipation, or diarrhea after ingestion of caffeine. The bottom line, though, is that caffeine has both positive and adverse effects, but limiting consumption of caffeine to no more than 8 ounces in the morning, especially during the first month post bariatric surgery, won’t hurt and will allow you to enjoy your morning cup of Joe you’ve waited so long to taste again.

BariMelts provides general recommendations, not to be construed as medical advice. Please consult your doctor.

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