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 patient-important 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: low-dose supplements are warranted. Vitamins for dialysis patients contain most or all of the B vitamins and low-dose vitamin C. We are not aware of any medical reasons to choose one over another.

There are five main reasons why dialysis patients may have vitamin deficiencies: appetite is reduced, diet is restricted, medications and co-morbidity may interfere with absorption, uremia may alter metabolic pathways, and intradialytic losses may occur [1]. Diets restricted in potassium will often be low in vitamin C, and protein-restricted diets are quite likely to be associated with intake of vitamins below the recommended daily allowance (Table 1) [2].

Table 1. Relationship between estimated vitamin contents of diets with different protein intake and recommended dietary allowances
VitaminUnitsRecommended dietary allowanceDaily protein intake g/day
406080

  1. Adapted from [2] with permission.
Vitamin B1 mg 1.2–1.6 0.6 1.0 1.1
Vitamin B2 mg 1.2–1.8 0.8 1.2 1.8
Vitamin B6 mg 1.6–2.2 1.0 1.2 1.5
Vitamin B7 (Biotin) mcg 100–200 13.4 17.8 15.8
Vitamin B9 (Folic acid) mcg 400 260 290 320
Vitamin B12 mcg 3 2.3 3.2 5.1
Vitamin C mg 40–60 86 87 88

The magnitude of body stores compared with the recommended daily allowance (RDA) varies for different vitamins, and the impact of duration of dietary restriction (whether spontaneous or therapeutically imposed) and of dialysis will depend to some extent on this factor (Table 2) [2].

Table 2. Estimated duration of vitamin stores in humans
Vitamin 

  1. Adapted from [2] with permission.
Vitamin B1 4–10 days
Vitamin B2 3–4 months
Vitamin B6 3–4 months
Vitamin B9 (Folic acid) 1–1.15 years
Vitamin B12 3–5 years
Vitamin C 3–4 months

While frank scurvy, beriberi, and Wernicke's encephalopathy have been reported in dialysis patients, there is concern that subtle vitamin deficiencies, particularly in patients on dialysis, may, in some patients, account for some of the general uremic symptomatology, or for more specific dialysis-associated syndromes such as anemia or peripheral neuropathy [2].

The 2005 KDOQI guidelines do not provide specific recommendations for vitamin supplements to patients on maintenance hemodialysis, but indicate that routine B-vitamin supplementation is needed to replace the losses from dialysis and to prevent rises in serum homecysteine concentrations that result with deficiency in folate, riboflavin, vitamin B6, or B12. Based on DOPPS data, there is a wide variation in vitamin prescription across countries ranging from 3.7% use in the United Kingdom to 71.9% in the United States. A 16% reduced risk of mortality was indentified in individuals taking water-soluble vitamins. In 2007, European Practice Guideline recommended a water-soluble vitamin containing 1.1–1.2 mg of thiamine, 1.1–1.3 mg of riboflavin, 14–16 mg of niacin, 10 mg of pyridoxine and 2.5 μg of vitamin B12, 1 mg of folate, 30 μg of biotin, and 5 mg of pantothenic acid as well as 75–90 mg of vitamin C daily [2b].

Here, we present a narrative review of a large literature. We conducted literature searches using medical subject headings and synonyms for each vitamin combined with terms for chronic kidney disease or dialysis. We supplemented this with our working knowledge, with reference lists of review articles and textbooks, and with references in articles that we found relevant. For each vitamin, we provide a brief background, discuss deficiency in the general population, and then focus on findings in people with low GFR or on dialysis. Most information was on patients on hemodialysis. Where information was available in patients with nondialyzed chronic kidney disease or peritoneal dialysis, we have included this; however, this information was not always available.

Water soluble vitamins (summary)

Vitamin B1 (thiamine)

Vitamin B2 (Riboflavin), Vitamin B3 (Niacin = nicotinic acid; niacinamide = nicotinamide)

Vitamin B5 (Pantothenic acid), Vitamin B6 (pyridoxine, pyridoxal, or pyridoxamine, or pyridoxine hydrochloride)

Vitamin B7 (biotin), Vitamin B9 (folic acid, folate)

Vitamin B12

Vitamin C

Clase, C. M., Ki, V. and Holden, R. M. (2013), Water-Soluble Vitamins in People with Low Glomerular Filtration Rate or On Dialysis: A Review. Seminars in Dialysis, 26: 546–567. doi: 10.1111/sdi.12099