Natural Foods Merchandiser

Nutrition Q&A with Dan Lukaczer

Q: Customers with carpal tunnel syndrome have asked if taking vitamin B6 is safe and effective. Is it?

A: It depends on what dose they are taking. Very high dosages of vitamin B6 (pyridoxine) can cause sensory neuropathy, a numbness or tingling in the arms or legs. However, this is quite rare and is usually reversible if B6 is discontinued at the first appearance of these symptoms. Doses exceeding 1,000 mg a day pose the most risk. Generally, if you stay under 100 mg per day, you are unlikely to have any problems.1

The idea of using B6 in carpal tunnel syndrome has a long history, though it is quite controversial. The most recent research suggests that people with CTS do not benefit from pyridoxine supplements.2 However, other studies suggest some people with CTS may have a vitamin B6 deficiency, so a subset of people with CTS may benefit from B6 supplementation.3,4 It seems reasonable that if someone takes B6 at levels between 50 mg and 100 mg per day, that person could continue supplementation and feel comfortable about its safety.

Q: How can someone tell if he's getting enough potassium?

A: Severe potassium deficiency can be tested by a common and simple blood test. However, subacute potassium insufficiency is much harder to discern and may be much more prevalent than we think. The estimated safe and adequate daily dietary intake of potassium is quite broad, between 1.9 g and 5.6 g daily. The Food and Drug Administration restricts the amount of potassium in supplements to 99 mg per dose because of potential health issues, such as kidney dysfunction, associated with too much potassium in the body.

High-dosage potassium supplementation is only available by prescription. Thus, for the most part, we need to get potassium from our diets. With the exception of people with kidney disorders, it is difficult to get too much potassium from food sources. All fruits and vegetables have an abundance of potassium, and are great for people seeking to boost their levels. Stars in my book are bananas, cantaloupe, honeydew, beet greens, spinach, potatoes, sweet potatoes and winter squash. All these sources have more than 350 mg per serving.5

Likewise, potassium deficiency is typically caused by a diet low in fresh fruits and vegetables. Deficiency can also be caused by excessive fluid loss from sweat, vomiting, diarrhea, diuretics or laxatives. Symptoms of potassium deficiency may be fatigue, muscle weakness, confusion and irritability—all of which are fairly nonspecific.

Potassium is an important nutrient for health. It is the major positive ion inside cells and is thus important for maintaining fluid and electrolyte balance in the body. It is also important in neuron function. Diets higher in potassium have been shown to ease hypertension and decrease the risk of stroke.6,7

Q: Does magnesium help low-back pain?

A: Low-back pain has many causes including ligamentous strains, disc protrusions, spinal misalignment and stress. I've not heard of magnesium deficiency as a cause of low-back pain. However, magnesium may be useful in conditions where there are muscular spasms, and the supplement has been used intravenously with some success in that regard.8 Because low-back pain sometimes can be exacerbated by muscle spasms, there is some thought that magnesium might help, although I've seen little research on this subject specifically.

A study a few years ago did hypothesize that latent, chronic acidosis (too much acid in the blood) might contribute to low-back-pain symptoms. Researchers tested a supplement with alkaline minerals—including magnesium—in low-back-pain patients. In this noncontrolled trial, the patients' low-back pain did seem to improve with supplementation of a multimineral product given over a period of four weeks. The authors suggested that a disturbed acid-base balance may contribute to the symptoms of low-back pain.9 When researchers assessed mineral levels inside cells, only magnesium increased after supplementation, and not potassium, calcium, iron, copper or zinc. Certainly if chronic low-back pain seems to be associated with spasm, I might suggest magnesium at 300 to 400 mg daily as a therapy to try.

1. Yates AA, et al. Dietary Reference Intakes: the new basis for recommendations for calcium and related nutrients, B vitamins, and choline. J Am Diet Assoc 1998;98(6):699-706.
2. Goodyear-Smith F, Arroll B. What can family physicians offer patients with carpal tunnel syndrome other than surgery? A systematic review of nonsurgical management. Ann Fam Med 2004;2(3):267-73.
3. Fuhr JE, et al. Vitamin B6 levels in patients with carpal tunnel syndrome. Arch Surg 1989;124(11):1329-30.
4. Aufiero E, et al. Pyridoxine hydrochloride treatment of carpal tunnel syndrome: a review. Nutr Rev 2004;62(3):96-104.
5. U.S. Department of Health and Human Services, U.S. Department of Agriculture. Dietary Guidelines for Americans 2005. Appendix B-1. Food Sources of Potassium. Available at: Accessed Jan 29, 2008.
6. McCarron DA, Reusser ME. Are low intakes of calcium and potassium important causes of cardiovascular disease? Am J Hypertens 2001;14(6 Pt 2):206S-12S.
7. Whelton PK, et al. Effects of oral potassium on blood pressure. Meta-analysis of randomized controlled clinical trials. JAMA 1997;277(20):1624-32.
8. Gaby AR. Intravenous nutrient therapy: the "Myers' cocktail." Altern Med Rev 2002;7(5):389-403.
9. Vormann J, et al. Supplementation with alkaline minerals reduces symptoms in patients with chronic low back pain. J Trace Elem Med Biol 2001;15(2-3):179-83.

Natural Foods Merchandiser volume XXIX/number 3/p. 124

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