FHEA Clinical Pointers:
Drug-Nutrient Interaction

by Margaret A. Fitzgerald, MS, RN, CS-FNP

An important part of our role is counseling our patients to achieve optimal health. We prescribe medications daily. We offer nutritional advice, including information on nutritional supplements and helpful, health-enhancing foods. A newly published book provides great insight into this often overlooked part of practice. Here are some highlights:

  • The first Recommended Daily Allowances (RDA) were published in 1941. The intent of these guidelines is to give the minimum levels of nutrients needed to prevent serious health problems such as scurvy (vitamin C deficiency), pellagra (niacin deficiency), and beriberi (vitamin B1 deficiency). The RDA may not be adequate to ensure optimal well-being, particularly for the person with a chronic health problem and taking certain potentially nutrition-depleting medications. A new set of standards, Dietary Reference Intakes (DRI), tolerable upper level (UL) Estimated Average Requirement (EAR) and Adequate Intake (AI), have been developed to better reflect a range of nutritional needs.

  • Chromium is a trace mineral that plays an important role in the utilization of insulin and activation of enzymes for energy production. Through a complex process, chromium helps form glucose tolerance factor (GTF), an endogenous compound that not only helps with blood sugar regulation but also assists in lowering triglycerides and cholesterol. Found in whole grains, lean meats, cheese, black pepper, and thyme, chromium deficiency is common, with an estimated 90% of diets having inadequate intake. In addition, the intake of refined sugar helps accelerate chromium excretion. Presentation of chromium deficiency includes hyperglycemia, glucose intolerance, numbness and tingling of the extremities. While there are no RDA recommendations, a safe, adequate range is 50-200 mcg/day and is available in nutritional brewer’s yeast, and in picolinate and polynicotinate form. When taken orally, all are reasonably well-absorbed.

  • Coenzyme Q 10, often called CoQ 10, is a fat-soluble, vitamin-like compound. Its nutritional roles are varied, acting as an antioxidant and as a coenzyme for numerous enzymes needed in the production of ATP, an important cellular fuel source. Found in cells in all plants and animals, limited CoQ 10 is obtained from the diet. Human cells, through a complex process requiring the presence of riboflavin, niacin amide, pyridoxine, cobalamin, folic acid, vitamin C, and other micronutrients synthesize it. Since the heart is an energy-demanding muscle, consequences of CoQ 10 deficiency primarily involve the cardiovascular system and include cardiomyopathy, dysrhythmia, angina, and heart failure. Deficiency arises from inadequate intake of these essential nutrients. In addition, depletion can occur from the use of medications that interrupt CoQ 10 synthesis. These include medications often used in the treatment of heart disease, thiazide diuretics, HMG CoA reductase inhibitors (the statins), and beta-blockers. Supplemental CoQ 10 dose range is 30-100 mg daily.

  • Found in vegetable oils, soy beans, leafy greens, and wheat germ, vitamin E is easily destroyed during cooking and food processing; a diet built on prepared and processed foods likely contains little of this important nutrient. With an RDA of 30 IU/day, vitamin E is the body’s most important fat-soluble antioxidant and helps maintain the integrity of cell membranes and body tissue from free-radical damage. Supplementation at =>100 IU/day has been associated with a reduction in cardiovascular risk in part by decreasing platelet aggregation and preventing oxidation of LDL cholesterol to a form easily taken up in an atherosclerotic lesion. Supplemental doses of 150-600 IU have been noted to be helpful in minimizing PMS and perimenopausal symptoms. Natural source vitamin E, usually labeled as d-alpha tocopherol, is more bioavailable than the synthetic form or dl-tocopherol. Due to bleeding risk, high dose supplementation is not recommended with anticoagulant use. Absent of that, vitamin E is a well-tolerated relatively non-toxic nutrient. Approximately 60% of the daily dose are excreted through the feces.

As more and more of our patients use nutritional supplements over a long period of time, attention must be paid to long-term consequences. This topic will be explored more thoroughly during the session entitled "Drug to Drug and Drug-Nutrient Interactions: A Focus on Common Problems" on the Alaskan NP Cruise, August 13-20, 2000.


Pelton, R., LaValle, J., Hawkins, E., Krinsky, D. (1999) Drug-Induced Nutrient Depletion Handbook. Hudson, OH: Lexi-comp.

Posted May 29, 2000


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