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From The January 2001 Issue of Nutrition Science News
Nutrition Q&A
with Dan Lukaczer, N.D.
Gauging the Bs
Q: I'm aware that elevated homocysteine levels are associated with heart disease, and that vitamins B6, B12 and folic acid help, but how much of the vitamins should I recommend to my customers?
A: As you know, hyperhomocysteinemia has been associated with increased risk for heart disease.1 The best way to tell if you need extra B vitamins is to get a serum test, which measures homocysteine levels in your blood. If they are elevated, you can then take vitamins B6, B12 and folic acid—the three vitamins most studied for lowering homocysteine levels. A repeat test can then determine if the dose is sufficient. Aside from testing, you can't be completely sure that you have decreased blood levels of homocysteine.
Having said that, most people who have elevated levels, which may be 10 to 20 percent of the general population, will probably lower those levels by daily ingesting 1020 mg B6, 5001,000 mcg B12, and 8001,000 mcg folic acid. These doses are well above the RDA, but there is no literature to indicate long-term harm in taking this combination of nutrients at these levels, probably because they are water-soluble and will not accumulate in the body. While not everyone has a problem with elevated homocysteine levels, unless you know what your level is, supplementation at literally pennies a day seems prudent as insurance medicine. A good book to read on the subject is The Homocysteine Revolution (Keats, 1997) by Kilmer McCully M.D., who pioneered the concept of homocysteine and heart health.
Do Drugs and Supplements Mix?
Q: Should customers take prescription medications separately from supplements?
A: Interactions between drugs and nutrients are increasingly an issue as more studies bring signs of caution. A nutrient can interfere with the absorption of a drug and affect the drug's efficacy.
One example of a nutrient's effect on a drug can be found with a thyroid medication. A recent 20-patient coed study at the Veterans Affairs Medical Center in Los Angeles showed that calcium carbonate appears to impair the absorption of levothyroxine, a hormone-replacement drug analogous to thyroxine (T4)—a principal hormone secreted by the thyroid gland—and commonly prescribed for hypothyroid patients.2
Researchers measured patients' levels of thyroxine four times: at baseline while taking levothyroxine alone; at two and three months while taking both calcium carbonate and levothyroxine; and two months after discontinuing just the calcium carbonate. Levels of both mean free T4 and total T4 were significantly reduced from baseline levels with calcium supplementation. These changes were reversed when calcium supplementation was discontinued.
This study indicates that when taken together, calcium carbonate has a significant effect on thyroid function by blocking levothyroxine absorption. The bottom line: Calcium supplements and this thyroid medication should be taken at separate times during the day so the body can properly absorb the thyroid drug.
Lead Toxicity
Q: If someone was exposed to lead some time ago, can that cause problems down the road?
A: Yes, it appears even low-level lead exposure that had no noticeable effect at the time can have long-term consequences. A recent study at Johns Hopkins School of Hygiene and Public Health in Baltimore reported that adults with past exposure to lead—in this case on the job—suffered a progressive decline in memory and brain function starting when they left the business nearly two decades before.3
This is the first data I've seen to suggest that cognitive function can progressively decline due to long-past occupational exposures to a neurotoxin. The researchers suggested the effect of the average level of bone lead found in former lead workers was equivalent to five years of aging on the brain. That declines continued during interim testing and were seen long after lead exposure had stopped, suggests that the effect of lead on the brain is progressive.
Animal studies suggest that a possible mechanism involved in lead toxicity is oxidative damage. One review says Vitamin C may protect against lead toxicity.4 A study at the Department of Environmental and Occupational Health in Taiwan found vitamins C and E reduce oxidative damage-related lead toxicity in rat sperm.5 An adequate amount of both of those nutrients is a good precaution. Cleaning up the environment, though, is obviously the most important step.
Dan Lukaczer, N.D., is director of clinical research at the Functional Medicine Research Center, a division of Metagenics Inc., in Gig Harbor, Wash.
References
1. Boushey CJ, et. al. A quantitative assessment of plasma homocysteine as a risk factor for vascular disease: probable benefits of increasing folic acid intakes. JAMA 1995 Oct 4;274(13):1049-57.
2. Singh N, et al. Effect of calcium carbonate on the absorption of levothyroxine. JAMA 2000;283:2822.
3. Schwartz BS, et al. Past adult lead exposure is associated with longitudinal decline in cognitive function. Neurology 2000;55(8):1144-50.
4. Houston DK, Johnson MA. Does vitamin C intake protect against lead toxicity? Nutr Rev 2000 Mar;58(3 Pt 1):73-5.
5. Hsu PC, et al. Effects of vitamin E and/or C on reactive oxygen species-related lead toxicity in the rat sperm. Toxicology 1998 Jul 17;128(3):169-79.
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