Ethanol alters the metabolism of protein, fat, and carbohydrates. It inhibits plasma protein and complement synthesis so its allowance in the diet of a bariatric surgery patient increases the risk of malnutrition. As Di Salvo reports, alcohol affects the brain and the body through its effect on neurotransmitters . He outlines the alcohol reward effect with a clear explanation as to why alcohol abuse among postoperative bariatric patients is so widely reported [24-27].
Steffen et al. provide new information on the rapid rate of absorption of alcohol after RYGB. They report that within minutes after consumption, a RYGB patient achieves a very high-blood alcohol concentration that could affect legal driving limits .
Caffeine (1,3,7-trimethylxanthine) has been consumed in coffee, tea, and chocolate for hundreds of years and soft drinks for more than 120 years . Caffeine content of foods and beverages varies with the type of product and the method of preparation with the major sources of caffeine in the American diet being coffee, soft drinks, and tea . Caffeine is rapidly absorbed from the GI tract and metabolized in the liver.
Ground roasted coffee contains 85 mg caffeine per 5 oz. and is the primary source of caffeine in the diet. Instant coffee has 60 mg caffeine per 5 oz. and decaffeinated coffee equals 3 mg caffeine in a 5 oz. cup. Colas are the second most consumed source of caffeine with 18 mg per 6 oz. serving. Black tea contains 30 mg per 5 oz. steeped cup or 20 mg per 5 oz. serving of instant tea. Chocolate/cocoa has 4 mg per 5 oz. serving.
Caffeine has been reported in numerous studies to have ergogenic affects to increase athletic performance, endurance, and mental clarity but for bariatric patients, detrimental effects, such as gastric upset, withdrawal symptoms, sleep disturbance, and interaction with mineral supplements can outweigh the benefits.
Attention on safety of caffeine has been focused on energy drinks and beverages that contain caffeine and other stimulants. The Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) have warned about the dangers of mixing alcohol and energy drinks because the high amounts of caffeine in the energy drinks can mask the intoxicating effects of alcohol while having no effect on alcohol metabolism, which could increase the risk of alcohol-related injuries .
Caffeine is not recommended during early stages of post-op bariatric surgery because of its effect on the central nervous system. The stimulating effects of caffeine could affect blood pressure, disrupt sleep, and exacerbate psychiatric conditions.
Coffee has been called “chemistry in a cup” because it contains almost 2,000 compounds . The Journal of Agricultural and Food Chemistry reports that dark roast coffee produces a chemical that helps prevent the production of excess stomach acid  and another study  in 2011 found that coffee led to significant body weight reduction in preobese volunteers. That may help bariatric surgery patients decide whether to include coffee in their diet.
For many, making coffee is a morning routine. It is much easier to make bad coffee than good coffee with health benefits. For the most nutritive benefits, grind the coffee beans just before brewing to get the best flavor and healthy polyphenols. Ground coffee loses flavor and nutrient benefits upon exposure to air.
Tea use has been associated with improved cognition according to a study in the American Journal of Clinical Nutrition  with green tea offering high levels of catechin (antioxidants). The polyphenol L-theanine in tea has neuroprotective effects for calming and stress reduction.
The methylxanthine in cocoa or theobromine as some biochemists like to call it, can have detrimental effects for those with GERD and migraines .