Water‐Soluble Vitamins in People with Low Glomerular Filtration Rate or On Dialysis: A Review

Abstract

People with low glomerular filtration rate and people on dialysis are spontaneously at risk for vitamin deficiency because of the potential for problems with decreased appetite and decreased sense of smell and taste, leading to decreased intake, and because decreased energy or decreased cognitive ability results in difficulties in shopping and cooking. Imposed dietary restrictions because of their renal dysfunction and because of comorbidities such as hypertension and diabetes exacerbate this problem. Finally, particularly for water-soluble vitamins, loss may occur into the dialysate. We did not identify any randomized trials of administering daily doses close to the recommended daily allowances of these vitamins. In people who are eating at all, deficiencies of B5 and B7 seem unlikely. It is unclear whether supplements of B2 and B3 are necessary. Because of dialyzability and documented evidence of insufficiency in dialysis patients, B1 supplementation is likely to be helpful. B6, B9, and B12 are implicated in the hyperhomocysteinemia observed in patients on dialysis. These vitamins have been studied in combinations, in high doses, with the hope of reducing cardiovascular outcomes. No reductions in patientimportant outcomes were seen in adequately powered randomized trials. Because of their involvement in the homocysteine pathway, however, supplementation with lower doses, close to the recommended daily allowances, may be helpful. Vitamin C deficiency is common in patients on dialysis who are not taking supplements: lowdose supplements are warranted. Vitamins for dialysis patients contain most or all of the B vitamins and lowdose vitamin C. We are not aware of any medical reasons to choose one over another.

Association of serum vitamin B12 and folate with mortality in incident hemodialysis patients

“…As folate is not stored in the body in large amounts, deficiency can develop within a few weeks [3]. Previous studies have shown that serum folate concentrations are lower in HD patients in comparison with that of the general population [3]. In contrast, serum B12 concentrations in HD patients have been reported as being similar to or higher than that of the normal range due to B12's larger molecular size and its subsequent difficulty in being cleared during HD [5,6].…”

“…This may be due to several reasons: HD patients have reduced appetite and restricted diets, which increase the possibility of inadequate folate intake. In addition, a large proportion of HD patients have a high comorbidity burden and consume multiple medications, some of which may interfere with the absorption of nutrients and vitamins including folate [3]. Furthermore, folate is a relatively small watersoluble molecule with relatively low protein binding, and it is thus readily cleared during HD [4].…”

“…Patients with end-stage renal disease (ESRD) are at higher risk for nutritional deficiencies due to medication interactions, dietary restrictions and malnutrition [3,4]. Furthermore, the dialysis procedure itself may lead to vitamin B deficiencies, especially in the case of folate where its molecular size renders it capable of being cleared during hemodialysis (HD) [3].…”

“…Furthermore, the dialysis procedure itself may lead to vitamin B deficiencies, especially in the case of folate where its molecular size renders it capable of being cleared during hemodialysis (HD) [3]. As folate is not stored in the body in large amounts, deficiency can develop within a few weeks [3].…”

“…B12 is a coenzyme involved in the catabolism of methylmalonic acid and homocysteine (Hcy) and B12 deficiency is also associated with megaloblastic anemia as well as neurologic and cognitive sequelae [1,2]. Given the importance of these vitamins in cell metabolism and their relationship with adverse outcomes, the use of vitamin supplements or food fortification, especially for folate, has been recommended in many countries including the United States [3].…”