RYGB is the most common bariatric procedure performed in US. The procedure is meant to: (1) restrict food space in the gastric and intestinal region by creating a smaller pouch for food to enter the stomach (other restrictive approaches include gastric banding and sleeve gastrectomy);
(2) to disallow absorption of food also called malabsorptive procedures. The biliopancreatic diversion with duodenal switch (BPD/DS) is a less-common weight-loss procedure.
The surgical changes from the RYGB that cause nutritional effects include:
- Reducing the size of the stomach
- Shortening the length of the small intestines in contact with nutrients
- Disrupting accessory organ function - bile and pancreatic enzyme release
- Possible bacterial overgrowth in the bypassed segments
Macro-nutrients:
Protein deficiency
- Inadequate protein intake
- Reduced gastric acid secretion (normally facilitates protein denaturation and pepsinogen activation)
- Insufficient amino acid absorption (reduced absorptive surface)
- Extreme weight loss prior to surgery
- RX:
- Protein intake of 1.1-1.5 g/kg per ideal body weight totaling 60-120 g daily
- Leucine supplements - shown to promote protein synthesis
Fat deficiency
- Malabsorption if the common channel below the bilio-pancreatic and Roux limb anastomosis is too short.
- Malabsorption leads to deficiencies of fat soluble vitamins
- Insufficient bile (no longer directed into the sphincter of Oddi) and bypassing of jejunum where most fat soluble vitamins are absorbed is problematic
Vitamins:
Water Soluble Vitamin Deficiency
- Thiamine
- Seen with excessive emesis
- Reduction of intake
- Reduced absorption from proximal small intestines
- RX: with neurological symptoms, parental, otherwise 50-100 mg daily.
- Vitamin B12
- Insufficient intrinsic factor made by Parietal Cells in stomach, then binds to vitamin in duodenum so it can be absorbed in the ileum
- Insufficient HCl from stomach assists in release of vitamin from food
- Bacterial overgrowth will consume vitamin for own use
- RX: parental.
- Folate
- Inadequate intake
- Insufficient absorption
- RX: PO 800-1000 ug daily for several months
Fat Soluble Vitamin Deficiency
- Vitamin D
- Greater amount of subcutaneous fate store more of the vitamin
- Low serum 25-hydrocyvitamin D and high PTH suggest impaired vitamin D status
- RX: 3,000 IU (75 mcg) to 10,000 IU (250 mcg) or higher until levels greater than 30 ng/mL.
- Vitamin A
- Low serum retinol and vision problems
- RX: 5,000-25,000 IU daily for 6-12 months
Minerals:
Calcium deficiency
- Best absorbed from a slightly acidic environment in the proximal small intestines and requires adequate vitamin D status
- 2 g of elemental calcium along with vitamin D supplement daily for those with bypass
Iron deficiency
- MOST WELL STUDIED and DOCUMENTED DEFICIENCIES of RYGB
- Reduced acid production and rerouting of proximal intestines are problematic
- Inflammation (with obesity) can diminish intestinal iron absorption
- Iron intake often poor as meat not frequently tolerated
- DX:
- low serum ferritin
- increased soluble transferrin receptors
- low transferrin saturation
- elevated total iron-binding capacity
- low serum iron
- low mean cell volume (MCV) - MCV may be normal if there is co-presence of vit B12/folate deficiency.
- RX:
- parenteral iron
- 300 mg daily PO
Zinc and Copper deficiency
- Poor dietary intake
- Reduction in gastric acid
- Better absorbed in slightly acidic environment in proximal small intestine
- S/S:
- poor wound healing
- hair loss
- DX:
- Low serum Zinc
- Low 24-hours urine Zinc
- RX:
- 10-40 mg elemental Zn daily
- More than 40 mg daily can impair Cu status
- 1-2 mg of elemental Cu recommended with Zn
- If Cu deficiency suspected 2-5 mg daily or parental
