Micronutrient and Macronutrient Needs in Roux-en-Y Gastric Bypass Patients

| March 10, 2008

by Dana Swilley, RD

Ms. Swilley is with the Section of Minimally Invasive and Bariatric Surgery, UCLA Division of General Surgery

Thiamine. Thiamine deficiency has commonly been reported in RYGB patients. Risk factors included poor intake, intestinal loss, and also losses through vomiting, disordered eating, dialysis, and excessive alcohol intake. Thiamine deficiency outside of the Roux-en-Y patient population comes in three different forms, dry, wet, and cerebral Beriberi. A new form of thiamine deficiency has been defined for the weight loss surgery (WLS) population as bariatric beriberi.1 It is defined as being caused by alcohol intake, lack of supplementation, and poor eating habits associated with WLS. A deficiency is often identified through thiamine blood level results and possibly signs and symptoms. Treatment can be initiated before lab results are obtained if thiamine deficiency is suspected. Being that thiamin is a water-soluble vitamin, there is no tolerable upper limit (UL) set by the Food and Nutrition Board of the Institute of Medicine. It is therefore viewed as safe to supplement without a confirmed deficiency. Recommended treatment levels are 50 to 100mg given orally, or intravenously 1 to 2 times daily until symptoms resolve. Dietary sources of thiamine include fortified grains, whole grains, legumes, nuts, fish, and lean meats (especially pork).

Folate. Folate deficiency is not often seen with RYGB patients. This may be partially secondary to the abundance of foods fortified with folate and folic acid. A well balanced multivitamin will also provide a good quality source of folic acid, easily absorbed in both the duodenum and the jejunum. It is considered beneficial to include serum folate levels among regular follow-up of these patients for reasons other than detecting a folate deficiency. Elevated folate levels and supplementation above the UL of 1000mcg can mask a B12 deficiency. Elevated folate may also indicate small intestine bacterial overgrowth or blind loop syndrome. A deficiency in folate could result in elevated homocysteine levels. Treatment of 1 to 5mg twice a day will correct deficiencies within 2 to 3 months.2

B12. Cobalamin (B12) plays an important role in creating cellular energy and hemoglobin production. The route of absorption for B12 is unique and complex. The Roux-en-Y procedure puts patients at risk for B12 deficiency for several reasons. The use of proton pump inhibitors, common for ulcer prevention in RYGB, inhibits absorption of B12 because of the decrease in HCl acid. Decreased stomach function, decreased intake, and malabsorption due to loss of intrinsic factor (IF) also contribute to the risk of B12 deficiency. There is also an increase in physiologic demand for B12 during rapid weight loss. A deficiency may not be seen until several months of low intake and/or absorption because, unlike most water-soluble vitamins, B12 is stored and recycled in certain organs in the body. Symptoms of deficiency are generally neurological in nature, including numbness and tingling of extremities, difficulty walking, memory loss and disorientation. Because of the possibility of a masked deficiency with folate or a folate deficiency causing a falsely low serum B12, it is recommended that homocysteine and monomethylamine (MMA) be tested as well.3 When both homocysteine and MMA are high, supplementation of both B12 and folate is indicated. If homocysteine is normal, but MMA is high, B12 supplementation is indicated. If homocysteine is elevated and MMA is normal, this is an indication for folate levels to be tested. Recommended treatment for B12 deficiency is 2,000mcg sublingual B12 daily for 2 to 4 weeks or intramuscular injections (IM) 1000mcg daily for 1 to 2 weeks. Though the RDA for B12 is 2mcg and the daily reference value (DRV) is 6mcg, an easily found and inexpensive dose available in drug stores is 500 to 1,000 mcg. This is likely the driving force for the commonly recommended maintenance dose of 500 to 1,000mcg per week via effective absorption route (i.e., sublingual tablet, nasal gel, or B12 patch) or 1,000mcg IM once a month. If labs values have not corrected themselves after 2 to 3 months, a repeat course of therapy may be indicated. Permanent damage from B12 deficiency can occur if treatment is initiated too late.

Vitamin A. Vitamin A uses hydrolysis with pepsin in the stomach and pancreatic enzymes in the proximal small intestine for its route of absorption and is therefore at risk for deficiency in RYGB patients. Being a fat-soluble vitamin, approximately one year’s supply can be stored in the liver, making deficiencies show up relatively late postoperatively. This stored vitamin A also means that toxicity is possible. The risk for developing deficiency may be associated with the length of small intestine bypassed. Increased length of bypassed small intestine may increase risk for deficiency of vitamin A, as well as other fat-soluble vitamins, protein, and zinc. Symptoms of vitamin A deficiency include pathology of the eye, problems with skin, mucous membranes, dry hair, broken nails, and increased risk of infections. Vitamin A and iron are interdependent on each other, and several studies have shown resistant iron deficiency corrects more easily with vitamin A supplementation.4 Other studies have also indicated that vitamin A deficiency may contribute to developing iron deficiency. Serum retinal levels accurately identify vitamin A status. Treatment for deficiency has been recommended as 100,000IU oral or IM daily for three days, then 50,000IU for two weeks, then tapering to 20,000IU daily for 2 to 3 months. Oral doses should be preformed vitamin A, not beta-carotene. Water-miscible vitamin A palmitate has been shown to be better absorbed, but also showed a higher risk for toxicity.5,6 Once labs have been rechecked and show normal levels of vitamin A, a maintenance dose of 5,000 to 10,000IU is recommended for RYGB patients. This dose is usually met with a balanced multivitamin, but a lab result will determine if a separate supplement is needed for individuals. The RDA is 3,000IU, with the UL set at 10,000IU.

Vitamin D. Vitamin D is often called the “sunshine vitamin” for its complicated transformation into active vitamin from UV rays through skin. Risk for deficiency comes from decreased intake, fat malabsorption, age, and low sun exposure or darker skin. One study has reported vitamin D as one of the most common deficiency states in RYGB.7 Symptoms of deficiency include rachitic tetany, muscle pain and spasms, weakness, bone pain, and a range of other symptoms. Vitamin D has seven identified forms, and new functions are continuously being discovered. Lab results for D25 and parathyroid hormone(PTH) can accurately identify vitamin D status. Recommended treatment for vitamin D deficiency is 50,000IU per week in conjunction with 1,000 to 1,500mg of calcium daily. Maintenance levels are recommended between the Adequate Intake level (AI) per age group (200–600IU) and the UL of 2,000IU set by the Institute of Medicine, though it should be noted that there is evidence that levels up to 10,000IU are unlikely to produce toxicity in adults.8 800IU has been suggested to promote adequate vitamin D status and prevent deficiency.9 A set protocol is difficult to determine secondary to differences among individuals of age and skin color.

Calcium. Calcium’s main route for absorption is in the small intestine and can be malabsorbed to a degree in Roux-en-Y patients. The increased risk of calcium deficiency and bone loss comes from this malabsorption and decreased intake. Naturally occurring barriers to calcium absorption include oxalate and phytate in foods, which decrease the bioavailability of calcium. Caffeine causes an increase in calcium loss through urine and the gut. Because serum calcium levels are so closely regulated, any changes will result in either removal from bone or increased absorption in the gut and more or less excretion in urine. Therefore, if a RYGB patient’s intake of calcium is inadequate and absorption is compromised, bone loss can occur. In the chronic absence of adequate calcium intake metabolic bone disease can present as osteoporosis, osteomalacia, hyperparathyroidism, or a combination of these. Other symptoms of deficiency include muscle cramping, hypotension, and bone pain. Roux-en-Y surgery, as well as other types of weight loss surgery, have been shown to increase bone turnover and promote loss of bone mass.10-12 A large amount of weight loss, as well as individual factors, such as diet, exercise, and peak bone mass achieved, can also contribute to bone loss. Lab tests used to clearly identify a calcium deficiency generally include serum calcium, serum ionized calcium, PTH, vitamin D, and possibly magnesium and serum protein levels. For treatment of calcium deficiency in RYGB patients, calcium citrate has been shown to be significantly more bioavailable than calcium carbonate due to the decrease in stomach HCl needed for calcium carbonate absorption.13 The general recommendation for prevention and maintenance is 1,000 to 1,500mg of supplemental calcium citrate with vitamin D.1 It is best to divide doses into 500mg or less at one time and should be in a chewable or liquid form initially. Good dietary sources of calcium include dairy products, fortified soy or rice milk, fortified juices, and edible fish bones. A recommendation for maximal intake of calcium for RYGB patients is 2,500mg per day. Iron, calcium, zinc, and phosphorus all decrease each other’s absorption. A balanced ratio of phosphorous to calcium is needed. Products containing phosphoric acid may increase calcium excretion, such as dark colas, some bottled teas, and flavored waters.

Iron. Iron functions in hundreds of human proteins, most commonly known for its role in hemoglobin carrying oxygen. Iron deficiency is relatively common in RYGB patients.14 Patient risk for iron deficiency is due to the decrease in stomach HCl and decreased intake, and individual risk is associated with heavy menstruation. Symptoms of iron deficiency include anemia, fatigue, hair-loss, feeling cold, pagophagia (significant chewing and eating ice), and decreased immune function. Lab tests for determining iron deficiency should include serum ferritin levels, serum iron, transferrin saturation, total iron binding capacity (TIBC), (MCV), and hemoglobin (Hb). Typical presentation of iron deficiency with anemia will show elevated TIBC and all other results will be low. In the absence of anemia, Hb and MCV can be normal. Treatment and resolution can be difficult secondary to outside factors affecting absorption and patient noncompliance because of constipation and stomach irritation. A commonly suggested recommendation is to give 100 to 200mg of iron per day to treat deficiency.1 Some studies have shown greater outcomes and compliance with doses given every 5 to 7 days.15 Iron taken with vitamin A may be more effective in resolving iron deficiency, even if there’s been no vitamin A deficiency identified.16 There is no agreed upon protocol for prevention or maintenance largely because of the risk of iron toxicity. The UL for iron has been set at 45mg per day for adults. Symptoms of toxicity include gastrointestinal (GI) irritation, nausea, vomiting, diarrhea, or constipation. Chronic toxicity can present with heart palpitations, fatigue, joint and muscle pain, and depression.

Zinc. Zinc is a trace mineral whose rate of deficiency in RYGB patients is not yet known. One study found that zinc levels fell postoperatively, but that zinc intake fell as well.17 Fat malabsorption puts patients at risk for deficiency, as well as competition between zinc and other minerals, such as iron, calcium, and phosphorus. Symptoms of zinc deficiency include a decreased sense of smell, altered taste, poor wound healing, poor appetite, hair loss, low libido, and lethargy. Common recommendation for prevention is to take a multivitamin that includes the RDA level of zinc—12mg for women and 15mg for men.

Copper. Copper deficiency can occur in RYGB patients if there is high supplementation of iron and zinc when copper intake is already low.18 Copper also relies on stomach acid for absorption, making the RYGB procedure a risk for developing copper deficiency. The Dietary Reference Intake (DRI) for copper is 900mcg and the UL is 10,000mcg. Dietary sources, such as organ meats, shellfish, nuts, grapes, beans, legumes, dark chocolate, dried fruit, mushrooms, and avocados, are recommended for prevention of deficiency.

Magnesium. Magnesium is the fourth most abundant mineral in the human body. The main factors putting WLS patients at risk of deficiency are diabetes, chronic diarrhea, malabsorption postoperatively, and protein deficiency. There is virtually no literature or reports of magnesium deficiency in WLS patients; however, its relationship to bone health and mineralization makes it worth mentioning. A basic multivitamin will provide 100 to 250mg. Magnesium-rich food sources include whole grains, nuts, seeds, oysters, corn, avocados, and green vegetables. RYGB patients may take less magnesium than average due to food choices.19 The typical American diet falls short of RDA by 25 percent.20 However, patients consuming a variety of foods in combination with a complete multivitamin will easily meet the RDA of 350mg/day for men and 280mg/day for women. Toxicity results in diarrhea due to a laxative effect. A safe recommendation for an upper limit of magnesium from supplements is 350mg.

Selenium. Selenium’s main absorption site is the duodenum, and therefore RYGB patients are theoretically at risk for a deficiency. However, reports of selenium deficiency in the gastric bypass patient have been largely undocumented. This may be because food sources of selenium are generally well absorbed outside of the duodenum. Selenium is important for its association with thyroid hormones related to growth, development, and metabolism. It is found in plant sources where soil is rich in selenium and in animal sources when fed a selenium-rich diet. The RDA is 55mcg for women and 70mg for men. Food sources include Brazil nuts, seafood, meat, milk, and brown rice. Acute toxicity symptoms include headache, nausea, and abdominal pain. If chronic, toxicity can cause nail and hair changes, as well as nerve damage.

Phosphorus. Phosphorus is the second most abundant mineral in the body. Eighty-five percent of phosphorus is found combined with calcium in the crystals of the bones and teeth. Animal protein provides an excellent source of phosphorus. The needs for phosphorus are easily met with almost any diet, particularly one supplemented with a multivitamin. The recommended ratio of phosphorus to calcium is 1:1. The RDA for phosphorus is 800 to 900mg.21 Excess phosphorus can cause calcium excretion, a particularly undesirable effect for RYGB patients who are taking supplemental calcium to make up for bypassed receptor sites.

Sodium. No known human diet lacks sodium.22 For this reason, no RDA has been set. However, the RDA committee estimated the minimum sodium requirement for adults to be 500mg, an amount provided by a diet of plain foods with no salt added.23 The DRV for sodium is 2,400 mg. It is important for RYGB patients to obtain adequate intake of sodium to maintain proper fluid balance in the body because of the fluid shifts associated with rapid weight loss.24 Excess sodium is commonly associated with water retention, unless well diluted with increased water intake. A more serious side effect of excess sodium, particularly as we age, is the effect of net acid production that occurs with natural decrease of renal function. This in combination with its increased body fluid acidity may contribute to development of osteoporosis, renal stones, and loss of muscle mass.25

Potassium. Potassium plays a major role in fluid balance in the body. RYGB patients, as a known consequence of the surgery, are at risk for vomiting and diarrhea, dehydration, and rapid weight loss. These same risks are associated with potassium loss as well. Some research has suggested that being obese causes a disruption in the roles of potassium and sodium in fluid distribution that does not completely correct itself, even after sustained weight reduction.24 Potassium is found in fresh foods of all kinds. The DRV for potassium is 3,500mg. Potassium toxicity is rare but the presence of excess potassium often induces a vomiting reflex. It is therefore not viewed as life-threatening, unless a person is otherwise compromised.

Chromium. Chromium’s relationship with insulin and the incidence of diabetes preoperatively in the RYGB patient population makes it worth mentioning. Persons with common forms of diabetes cannot cure their diabetes with chromium supplementation, but a person consuming a diet lacking in chromium may worsen the diabetes.26 A diet high in simple sugars can deplete a body’s supply of chromium.27 Fortunately, a high simple sugar diet is generally poorly tolerated in RYGB patients. Chromium can be absorbed from foods if the compound is in a biologically active chromium form. It is estimated that 90 percent of US adults consume less than the recommended minimum intake of 50mcg per day.28 With limited dietary volume, RYGB patients are theoretically at risk for low chromium intake, though research documenting chromium deficiency in RYGB patients is virtually absent. The RDI for chromium is 120mcg. Good food sources of chromium include liver, whole grains, nuts, and cheeses. A balanced multivitamin taken daily in combination with the good food sources mentioned adequately meet the needs of the RYGB patient.


Total daily caloric intake needs to meet the basal metabolic rate (BMR) of a patient in order to avoid stimulation of starvation mechanisms that can prevent weight loss. There are several formulas for estimating BMR, which can vary individually based on age, gender, height, weight, and body composition. Indirect calorimetry devices may provide more insight into accurately calculating basal energy expenditure (BEE) and body composition. Most RYGB programs recommend a range of 1,000 to 1,400 calories per day as lifelong guidelines for weight maintenance. Less than 900 to 1,000 calories per day is generally not recommended due to stimulation of fasting and starvation hormones, which have the effect of decreasing BMR as a compensatory mechanism. However, the best method for determining a daily caloric level for an individual is for the patient to closely monitor his or her food intake, daily activity, and weekly weights.

Protein. Protein digestibility and quality are important factors that the RYGB patient must take into account when making food or supplement choices. The digestibility of a protein depends in part on the health of the user. Digestibility of protein is increased when accompanied by a full array of vitamins and minerals. Protein quality is largely determined by the amino acid content, which affects the usefulness of the protein to the body. Foods rated the highest on the Protein Digestibility Corrected Amino Acid Score (PDCAAS) are egg whites, non-fat milk, beef, chicken, and tuna. The RDA for protein is 0.8g/kg/day, the DV is 50g per day for a 2000-calorie diet, and the WHO lower limit for daily protein is 10 percent of total calories, with the upper limit stated as 15 percent of total calories. The National Academies’ Institute of Medicine recommends 10 to 35 percent of total calories come from protein. Protein intakes and recommendations for RYGB patients are generally higher than recommendations for other adults due to increased needs based on rapid weight loss and a degree of malabsorption. The effects of excess protein are not well understood, but there are no benefits to a diet with excess protein.29 High protein diets over a lifetime are known to worsen existing kidney problems.30 Excess protein may also accelerate adult bone loss because of increased calcium excretion with increased protein intake from animal sources,31 though bone depletion is largely dependant on intake ratio of calcium to protein.32,33 Symptoms of protein deficiency include lethargy, headaches, easy fatigue, and muscle wasting. Measurement of albumin levels will reflect past month’s intake and may be inaccurate during inflammatory processes, but is generally an effective tool for assessing adequate protein status in the RYGB patient. Common recommendation for daily protein intake among RYGB programs is 60 to 105g (20–35% of 1,200-calorie diet). Excess provides no benefit and possibly harm, but more likely the liver will convert all extra energy compounds into fat.

Carbohydrate. Carbohydrate provides the body with its preferred source of fuel and is the only source of energy for the brain, central nervous system, red blood cells, kidney, and retina. In the Roux-en-Y procedure, there is an emphasis on choosing complex carbohydrates versus simple carbohydrate. This is to avoid an overload of simple carbohydrate or sugar entering the small intestine and blood stream too quickly, often called “dumping syndrome.” Symptoms of dumping syndrome are immediate onset of heart palpitations, sweating, weakness, and nausea. It is common practice to recommend patients not take more than 5 to 10g of sugar per meal or snack. The tolerance of simple sugars varies per individual. The WHO recommends 50 to 75 percent of the diet come from carbohydrate. The newest report on recommendation for healthy eating from the National Academies’ Institute of Medicine recommends 45 to 65 percent of an adult’s calorie intake come from carbohydrate. Based on a 1,000 to 1,400-calorie diet, 45 percent carbohydrate would require a minimum intake of 113g of carbohydrate. A deficiency of carbohydrate can be characterized by fatigue, low energy, decreased concentration, decreased endurance and energy with exercise, and possibly acetone breath in the state of ketosis. If the body is not provided with adequate dietary carbohydrate, protein is broken down for energy and ketones are produced, causing acetone breath. Ketosis can be identified with a ketone urine test. Therefore, meeting carbohydrate requirements prevents protein breakdown, or has a protein sparing action. Complex carbohydrates are also a source of fiber. The RDA for fiber is 25g per day or 11.5g per 1,000 calories and the WHO recommends 27 to 40g. Fiber is needed to prevent constipation, diverticulosis, help lower cholesterol, maintain health of the digestive tract, and improve the body’s handling of glucose. Food sources of complex carbohydrates and fiber include fruits, vegetables, legumes, and whole grains.

Fat. Fat is necessary in the body for growth and development and provides the basic components for hormones, skin, hair, transportation of fat-soluble vitamins, and insulation and cushion for the body and internal organs. The American Heart Association (AHA) recommends 10 to 14g or less saturated fat per day. RDA recommends 15 to 30 percent of calories from fat. The National Academies’ Institute of Medicine recommends 20- to 35-percent calorie intake come from fat. Based on 1,200 calories for a Roux-en-Y patient, this would include a minimum 27 to 47g of fat per day. Due to the degree of malabsorption with RYGB, the higher end of this range may be beneficial for increased absorption of fat-soluble vitamins. The AHA recommends a diet rich in mono- and polyunsaturated fats. Food sources include avocado, tuna, salmon, olive oil, flaxseeds, canola oil, nuts (nut butters), and seeds.


Products for supplementation should be selected based on bioavailability, quality, and nutrient content. Recommendations for RYGB patients are the following:
• Chewable, liquid, or powder multivitamin containing RDA levels of iron and zinc taken daily.
• Sublingual B12 (500–1,000mcg) once per week, IM injection (1,000mcg) once per month, or nasal gel or B12 patch (1,000mcg) once per week; increase based on follow-up labs.
• Chewable, liquid, powder, or lozenge 1,000 to 1,500mg calcium citrate with vitamin D in divided doses; increase based on follow-up labs.
• Some programs may also recommend a separate daily B-complex or thiamine.
• 1,000 to 1,400 calories depending on the individual and activity level.
• 60 to 100 grams of protein depending on the individual and activity level.
• 27 to 47 grams of fat based on 20 to 35 percent of a daily
1,200-calorie intake.


Roux-en-Y surgery creates an increased risk for deficiency of certain nutrients. Decreased intake in combination with varying degrees of malabsorption presents unique challenges to achieving the macronutrient and micronutrient status needed to thrive. Lifelong preventative actions, such as supplementation, regular follow-up, and thorough patient education are mandatory for accomplishing all the benefits and avoidance of the health risks involved in Roux-en-Y gastric bypass surgery. Given the nature of the procedure and the individuals undergoing the procedure, no clear protocols have been determined. The focus, therefore, is on risk reduction and careful monitoring and follow-up, versus risk elimination.


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Category: Nutritional Considerations in the Bariatric Patient, Past Articles

Comments (2)

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  1. Catherine says:

    Is there any connect to RYGB and developing seizures?

  2. terri says:

    I have had two seizures since my roux en y 7 months ago. Has anyone else had this issue?