Gastric Band and Nutrient Absorption
Gastric banding does not delay nutrient absorption—it functions exclusively through mechanical restriction of the stomach without any malabsorptive component, meaning once food passes through the band and reaches the small intestine, absorption proceeds completely normally. 1
Mechanism of Action
The adjustable gastric band operates through a purely restrictive mechanism:
An inflatable silicone band is placed around the upper stomach, creating a small pouch with a narrow outlet that reduces stomach capacity and slows gastric emptying, but does not alter the absorptive function of the small intestine. 1
The band slows food passage through the restricted outlet, but once nutrients reach the small intestine, the entire absorptive surface remains intact and functional. 1
No intestinal bypass or rearrangement occurs with gastric banding, unlike malabsorptive procedures. 1
Critical Distinction from Malabsorptive Procedures
Understanding the difference between restrictive and malabsorptive bariatric procedures is essential:
Roux-en-Y gastric bypass (RYGB) bypasses the duodenum and proximal jejunum, creating true malabsorption by diverting nutrients away from key absorptive sites. 2, 1
Biliopancreatic diversion creates a short "common channel" where digestion and absorption occur, resulting in profound malabsorption and severe nutrient deficiencies. 2, 1
Sleeve gastrectomy is considered primarily restrictive with reduced negative impact on nutrient absorption. 2
Gastric banding, vertical banded gastroplasty, and laparoscopic adjustable gastric band are purely restrictive procedures that reduce proximal stomach volume capacity without interfering with normal digestion and absorption. 2
Clinical Implications
Micronutrient Deficiencies
Micronutrient deficiencies after gastric banding are primarily due to reduced oral intake, not malabsorption, unlike RYGB or biliopancreatic diversion. 1
Vitamin D deficiency is common in bariatric patients, but postoperative reductions are particularly marked in malabsorptive procedures rather than purely restrictive ones like gastric banding. 2
Medication Management Considerations
While absorption is not impaired, gastric banding does create important medication considerations related to altered gastric emptying:
Extended-release and delayed-release formulations should be avoided entirely due to the small upper pouch and restricted outlet disrupting the prolonged gastric residence time required for proper dissolution. 1
Switch to immediate-release alternatives using liquid formulations, chewable tablets, or crushed immediate-release tablets when possible. 1
Oral contraceptives should be switched to non-oral methods due to concerns about unreliable absorption from altered gastric emptying patterns. 1
Altered gastric emptying can affect the rate (but not extent) of drug absorption, as drugs are absorbed primarily from the small intestine rather than the stomach. 3
Common Pitfalls to Avoid
Do not confuse delayed gastric emptying with impaired intestinal absorption—these are distinct physiological processes. The band slows how quickly food leaves the stomach but does not affect how well nutrients are absorbed once they reach the small intestine. 1
Do not assume all bariatric procedures have the same nutritional consequences—gastric banding has fundamentally different effects than RYGB or biliopancreatic diversion. 2
Once nutrients or medications pass through the band and reach the small intestine, absorption capacity remains normal. 1