The study was published in the March 13, 2007, issue of Neurology®, the scientific journal of the American Academy of Neurology.
 
Weight loss surgery or bariatric surgery manipulates the digestive system in a way that the body could not absorb as much calories as a person normally does.   The adverse effects of this operation include reduced absorption of nutrients such as vitamins and minerals.

Thiamin deficiency can result in Wernicke's encephalopathy, a severe syndrome characterized by loss of short-term memory and caused by damage to the mammillary bodies in the brain.   The syndrome can cause other problems such as rapid eye movements.

The sundrome is often seen in malnourished alcoholics.   But its association with weight loss surgery has not been well known.

The syndrome was found often in patients who have frequent vomiting after the weight loss surgery. It usually occurs within one to three months after the surgery, but one case was diagnosed 18 months after surgery.

The complications of the weight loss surgery were more than Wernicke encephalopathy. The authors found that many of the 32 patients also suffer neurological symptoms that are not typical of the syndrome including seizures, deafness, psychosis, muscle weakness, and pain or numbness in the feet or hands.

“When people who have had weight loss surgery start experiencing any of these symptoms, they need to see a doctor right away,” said study author Sonal Singh, MD, of Wake Forest University School of Medicine in Winston-Salem, North Carolina.

“Doctors should consider vitamin B1 deficiency and Wernicke encephalopathy when they see patients with these types of neurological complications after weight loss surgery. If treated promptly, the outlook is usually good.”

A small number of patients receiving weight loss surgery were treated with vitamin B-1 shots, but only 13 made a full recovery.   Singh was cited by news media as saying that early intervention is important.  Still, many patients in the study continued to have memory problems, weakness, or difficulty coordinating movement.

Physicians already give Vitamin B-1 supplements to patients who receive gastric bypass surgery, but there is no recommended dose, according to Singh.

Singh said further studies are needed to investigate the prevalence of Wernicke encephalopathy. A standard for vitamin B-1 supplementation is also needed.

Weight loss surgery can cause a wide range of complications and risky consequences.

The following are the typical nutritional deficiencies typically experienced by patients who receive gastric bypass surgery (GBP), cited from wikipedia.

Hypoparathyroidism, due to inadequate absorption of calcium, may occur in over 30% of patients receiving weight loss surgery. Calcium is primarily absorbed in the duodenum, which is bypassed by the surgery. Most patients can achieve adequate calcium absorption by supplementation with Vitamin D and Calcium Citrate (carbonate may not be absorbed - it requires an acidic stomach, which is bypassed).

Iron frequently is seriously deficient, particularly in menstruating females, and must be supplemented. Again, it is normally absorbed in the duodenum. Ferrous sulfate can cause considerable GI distress in normal doses; alternatives include Ferrous fumarate, or a chelated form of iron. Occasionally, a female patient develops severe anemia, even with supplements, and must be treated with parenteral iron.

Vitamin B-12 requires intrinsic factor from the gastric mucosa to be absorbed. In patients with a small gastric pouch, it may not be absorbed, even if supplemented orally, and deficiencies can result in pernicious anemia and neuropathies. Sub-lingual B-12 appears to be adequately absorbed.

Thiamine or vitamin B-1 deficiency (also known as beriberi) will, rarely, occur as the result of its absorption site in the jejunum being bypassed. This deficiency can also result from inadequate nutritional supplements being taken post operatively.

Protein malnutrition is a real risk. Some patients suffer troublesome vomiting after weight loss surgery, until their GI tract adjusts to the changes, and cannot eat adequate amounts even with 6 meals a day. Many patients require protein supplementation during the early phases of rapid weight loss, to prevent excessive loss of muscle mass.

GBP also has an impact on nutritional effects, cited from wikipedia.

After weight loss surgery, patients feel fullness after ingesting only a small volume of food, followed soon thereafter by a sense of satiety and loss of appetite. Total food intake is markedly reduced. Due to the reduced size of the newly created stomach pouch, and reduced food intake, adequate nutrition demands that the patient follow the surgeon's instructions for food consumption, including the number of meals to be taken daily, adequate protein intake, and the use of vitamin and mineral supplements.

Protein nutrition

Proteins are essential food substances, contained in foods such as meat, fish and poultry, dairy products, soy, and eggs. With reduced ability to eat a large volume of food, patients   gastric bypass surgery must focus on eating their protein requirements first, and with each meal. Proximal GBP rarely leads to protein deficiency[citation needed] if this simple precaution is followed. Distal GBP is more likely to lead to protein deficiency, particularly if fat intake is excessive, and the position of the Y-connection is farther downstream.[citation needed] In some cases, surgeons may recommend use of a liquid protein supplement.

Calorie nutrition

The profound weight loss which occurs after bariatric surgery is due to taking in much less energy (calories) than the body needs to use every day. Fat tissue must be burned, to offset the deficit, and weight loss results. Eventually, as the body becomes smaller, its energy requirements are decreased, while the patient simultaneously finds it possible to eat somewhat more food. When the energy consumed is equal to the calories eaten, weight loss will stop. Proximal GBP typically results in loss of 60 to 80% of excess body weight, and very rarely leads to excessive weight loss. The risk of excessive weight loss is slightly greater with Distal GBP.

Vitamins

Vitamins are normally contained in the foods we eat, as well as any supplements we may choose to take. The amount of food which will be eaten after weight loss surgery is severely reduced, and vitamin content is correspondingly reduced. Supplements should therefore be taken, to completely cover minimum daily requirements of all vitamins and minerals. Absorption of most vitamins is not seriously affected, after Proximal GBP, although Vitamin B-12 may not be well-absorbed in some persons. Sub-lingual preparations of B-12 will provide adequate absorption. After the Distal GBP, fat-soluble vitamins A, D and E may not be well-absorbed, particularly if fat intake is large. Water-dispersed forms of these vitamins may be indicated, on specific physician recommendation.

Minerals

All versions of weight loss surgery bypass the duodenum, which is the primary site of absorption of both Iron and Calcium. Iron replacement is essential in menstruating females, and supplementation of iron and calcium is preferable in all patients. Ferrous sulfate is poorly tolerated. Alternative forms of iron (fumarate, gluconate, chelates) are less irritating and probably better absorbed. Calcium carbonate preparations should also be avoided; calcium as citrate or gluconate, 1200 mg as calcium, has greater bioavailability independent of acid in the stomach, and will likely be better absorbed.

SOURCES: Singh, S. and Kumar, A. Neurology, March 13, 2007; vol 68: pp 807-811.