Nutritional Issues in Inflammatory Bowel Disease…
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Multivitamin supplements contain adequate amounts for daily requirements of watersoluble B vitamins, and can be used for the prophylaxis against deficiencies of these micronutrients. Treatment of macrocytic anemia in IBD patients does not differ from the general population (intramuscular injections of hydroxycobalamin in vitamin B12 deficiency or folinic acid orally in folate deficiency). Hyperhomocysteinemia may be present in IBD patients and has been associated with thromboembolic complications. Cattaneo et al. [131] found that hyperhomocysteinemia in IBD patients could be corrected by the administration of folate, vitamin B12 and vitamin B6. Many other studies assessing the homocysteine and “vitamin B complex” status in IBD patients suggested the daily administration of folate, vitamin B12 and vitamin B6 for prophylaxis against hyperhomocysteinemia and thrombotic complications [17,21,39], since studies have shown a lowering effect on serum homocysteine levels by daily administration of “vitamin B complex” supplements [132-135]. It is hoped that lowering homocysteine towards normal serum levels would reduce the risk for thrombosis, but a recent study, the VITRO trial [135], showed that homocysteine lowering by “vitamin B complex” supplementation did not prevent recurrent venous thrombosis. Finally, previous studies have linked folate deficiency with increased cancer risk in UC patients [104-106]. Evidence from small clinical studies suggests that folate supplementation in UC patients may have a protective effect against colorectal cancer since it has been associated with a dose-dependent reduced risk [106] or with an improvement of surrogate markers of colorectal cancer (DNA repair defects or rectal cell hyperproliferation) [136,137]. However, folate supplementation for colorectal neoplasia chemoprevention should be regarded with great caution. Animal studies have shown that the protective effect of folate is dose and timing related, since folate supplementation reduces the risk of colorectal cancer in normal colorectal mucosa, whereas folate supplementation has a promoting effect on the progression of established microscopic neoplasmatic foci in the colorectal mucosa and colorectal neoplasms [138]. Large prospective studies are needed to clarify the chemopreventive role of folate against colorectal cancer in ulcerative colitis.
CONCLUSION • •
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Nutrition-related issues are important components of the global assessment in the management of patients with inflammatory bowel disease. Several nutrient deficiencies, including the “vitamin B complex” members, are frequently observed in IBD patients. The aetiology of nutrient deficiencies is multifactorial and clinicians should be aware of the malnutrition existence and its clinical consequences in IBD patients. Nutritional status and nutrient intake should be regularly assessed in all IBD patients. Children, adolescents, perioperative patients, patients with severe disease or complications and patients with extended small bowel resection, need special attention.