Interactions with Dietary Supplements

Folic acid
Sulfasalazine decreases the absorption of folic acid.¹ Biochemical evidence of depletion of folic acid has been reported in people taking this drug,² although available evidence remains mixed.^{3 4}

Folic acid is needed for the normal healthy replication of cells. Perhaps as a result, there is evidence that folic acid can reverse precancerous changes in humans.⁵ Ulcerative colitis, a disease commonly treated with sulfasalazine, is associated with an increased risk of colon cancer. Folate deficiency has also been linked to an increased risk for colon cancer.⁶ It is plausible that some of the increased risk for colon cancer in people with ulcerative colitis may be related to folate depletion caused by sulfasalazine.

Folic acid supplementation may help protect against colon cancer.⁷ One study found that people who have ulcerative colitis and who supplement with folic acid have a 55% lower risk of getting colon cancer, compared with ulcerative colitis patients who do not supplement with folic acid (although this dramatic association with protection did not quite reach statistical significance).⁸ Researchers at the University of Chicago Medical Centre reported a 62% lower risk of colon cancer in folic acid supplementers.⁹ They suggested that the link between folic acid supplementation and protection from colon cancer may well be due to overcoming the folic acid deficiency induced by sulfasalazine.

Many doctors believe that it is important for all people taking sulfasalazine to supplement with folic acid. Folic acid in the amount of 800 mcg can be found in many multivitamins and B-complex vitamins. People wishing to supplement with more—typically 1,000 mcg per day—should consult their doctor.

Iron
Iron can bind with sulfasalazine, decreasing sulfasalazine absorption and possibly decreasing iron absorption.¹⁰ This interaction can be minimized by taking iron-containing products two hours before or after sulfasalazine.

PABA (Para-aminobenzoic acid)
PABA may interfere with the activity of sulfasalazine. PABA should not be taken with this drug until more is known.

Probiotics
A common side effect of antibiotics is diarrhoea, which may be caused by the elimination of beneficial bacteria normally found in the colon. Controlled studies have shown that taking probiotic microorganisms—such as Lactobacillus casei, Lactobacillus acidophilus, Bifidobacterium longum, or Saccharomyces boulardii—helps prevent antibiotic-induced diarrhoea.¹¹

The diarrhoea experienced by some people who take antibiotics also might be due to an overgrowth of the bacterium Clostridium difficile, which causes a disease known as pseudomembranous colitis. Controlled studies have shown that supplementation with harmless yeast—such as Saccharomyces boulardii¹² or Saccharomyces cerevisiae (baker’s or brewer’s yeast)¹³ —helps prevent recurrence of this infection. In one study, taking 500 mg of Saccharomyces boulardii twice daily enhanced the effectiveness of the antibiotic vancomycin in preventing recurrent clostridium infection.¹⁴ Therefore, people taking antibiotics who later develop diarrhoea might benefit from supplementing with saccharomyces organisms.

Treatment with antibiotics also commonly leads to an overgrowth of yeast (Candida albicans) in the vagina (candida vaginitis) and the intestines (sometimes referred to as “dysbiosis”). Controlled studies have shown that Lactobacillus acidophilus might prevent candida vaginitis.¹⁵

Vitamin K
A few cases of excessive bleeding have been reported in people who take antibiotics.^{16 17 18 19} This side effect may be the result of reduced vitamin K activity and/or reduced vitamin K production by bacteria in the colon. One study showed that people who had taken broad-spectrum antibiotics had lower liver concentrations of vitamin K2 (menaquinone), though vitamin K1 (phylloquinone) levels remained normal.²⁰ A few antibiotics appear to exert a strong effect on vitamin K activity, while others may not have any effect. Therefore, one should refer to a specific antibiotic for information on whether it interacts with vitamin K. Doctors of natural medicine sometimes recommend vitamin K supplementation to people taking antibiotics. Additional research is needed to determine whether the amount of vitamin K1 found in some multivitamins is sufficient to prevent antibiotic-induced bleeding. Moreover, most multivitamins do not contain vitamin K.