What should I know about drug interactions with St. John's wort?
Drug interactions are extremely common, so it's no surprise interactions between herbs and drugs keep coming to light. Probably the best-known interactions occur with St. John's wort (Hypericum perforatum), an extremely popular remedy for mild to moderate depression. One activity of St. John's wort, probably independent of its mood-altering actions, is increasing the CYP3A4 enzyme activity of liver and intestinal-wall cells. The enzyme helps metabolize various drugs including cyclosporine, an immunosuppressive medication used to prevent transplanted organ rejection. Taking St. John's wort with cyclosporine can "up-regulate" the enzyme, stimulating the metabolism, breakdown and excretion of cyclosporine, so much so that the herb was shown to decrease plasma levels of the drug.1 In fact, a recent review suggests taking both cyclosporine and the herb led to several cases of transplant rejection.2 Clearly, not all herbs pose such dangers, but customers and health care professionals alike must be aware of potential interactions and know when to be cautious.
What are the facts about banaba, an herb said to help control blood sugar in diabetics?
Banaba is the common name of the herb Lagerstroemia speciosa. It has been used traditionally in the Philippines as a diabetes remedy, and was studied most recently by Japanese researchers. Banaba leaf extracts are reported to reduce diabetic symptoms in mice, and have also been shown to slow weight gain in genetically obese mice.3,4 More recent cell-culture studies suggest the effects may be caused by banaba extract components that enhance glucose uptake into cells.5,6 Despite numerous claims that banaba has similar effects in humans, there are no published human clinical studies on banaba extract in scientific journals. (Extract manufacturers cite unpublished human studies showing blood sugar improvements.) Although banaba is an interesting herb that may help control hyperglycemia, at this point, evidence of its effectiveness is slim.
Is it true vitamin B-2 helps prevent migraine headaches?
Yes. Riboflavin, or vitamin B-2, was shown to prevent migraine headaches in two recent trials. Both the open study and the placebo-controlled study showed positive results.7,8 In the placebo-controlled trial, 400 mg of riboflavin per day resulted in a 59 percent positive effect compared with only 15 percent for the placebo group. How riboflavin works to prevent migraines is unclear, although it appears from other studies it works differently than beta-blockers, which are commonly used to prevent migraines.9 Riboflavin, even at these very high dosages, appears to be safe, well tolerated and inexpensive. Along with the herb feverfew (Chrysanthemum parthenium) and eliminating potential food allergies, I think riboflavin is one of the most important natural treatments for preventing migraines.
Dan Lukaczer, N.D., is director of clinical research at the Functional Medicine Research Center, a division of Metagenics Inc., in Gig Harbor, Wash.
1. Ioannides C. Pharmacokinetic interactions between herbal remedies and medicinal drugs. Xenobiotica 2002;32(6):451-78.
2. Ernst E. St. John's wort supplements endanger the success of organ transplantation. Arch Surg 2002;137(3):316-9.
3. Kakuda T, et al. Hypoglycemic effect of extracts from Lagerstroemia speciosa L. leaves in genetically diabetic KK-AY mice. Biosci Biotechnol Biochem 1996;60(2):204-8.
4. Suzuki Y, et al. Antiobesity activity of extracts from Lagerstroemia speciosa L. leaves on female KK-AY mice. J Nutr Sci Vitaminol (Tokyo) 1999;45(6):791-5.
5. Liu F, et al. An extract of Lagerstroemia speciosa L. has insulin-like glucose uptake-stimulatory and adipocyte differentiation-inhibitory activities in 3T3- L1 cells. J Nutr 2001; 131(9):2242-7.
6. Hayashi T, et al. Ellagitannins from Lagerstroemia speciosa as activators of glucose transport in fat cells. Planta Med 2002;68(2):173-5.
7. Schoenen J, et al. High-dose riboflavin as a prophylactic treatment of migraine: results of an open pilot study. Cephalalgia 1994;14(5):328-9.
8. Schoenen J, et al. Effectiveness of high-dose riboflavin in migraine prophylaxis. A randomized controlled trial. Neurology 1998;50(2):466-70.
9. Sandor PS, et al. Prophylactic treatment of migraine with beta-blockers and riboflavin: differential effects on the intensity dependence of auditory evoked cortical potentials. Headache 2000;40(1):30-5.