Drug-Nutrient Interactions: Is a Drug You Take Blocking Vitamins?
Drugs and nutrients have so many interactions that whole books have been written on the topic. It’s important to know how the drugs you’re taking affect your nutritional status, so that you can prevent any negative side effects.
Some drugs deplete nutrients by interfering with their absorption. Others increase the excretion of nutrients through the kidneys, and some prevent the nutrient from being converted to its active form in your body. Plus, some drugs simply work better, or have fewer side effects, if you get enough of a particular nutrient.
Below are some common drugs and their nutrient interactions. To check a drug not listed here, use the Physician’s Desk Reference. It’s a book updated yearly, and is available by subscription online. Your local hospital library or pharmacist should have it.
A good multivitamin can help you avoid some of these deficiencies, but you may need more support. For example, potassium is best obtained from lots of fruits and vegetables, and calcium, vitamin D and magnesium may require separate supplements. If your vitamin B12 levels are really low, you may need injections. If you’re taking diuretics, your doctor needs to monitor blood levels of electrolytes, including magnesium.
- Diuretics. Loop diuretics such as furosemide (Lasix) and bumetanide (Bumex) increase the excretion of potassium, magnesium, sodium, chloride and calcium. Thiazide diuretics such as hydrochlorothiazide (HCTZ) increase excretion of vitamin K, potassium, magnesium, zinc and iodine, but reduce excretion of calcium. Potassium-sparing diuretics such as spironolactone (Aldactone) and triamterene (Dyrenium) increase excretion of sodium, chloride and calcium, but reduce excretion of potassium.
- Cholesterol-lowering statin drugs deplete CoQ10, an energy-producing biochemical. Replacing CoQ10 reduces the muscle-damaging side effects of these drugs. Plus new research shows CoQ10 also enhances the drugs’ cholesterol-lowering ability.
- Cholesterol-lowering drugs called bile acid sequestrants, such as Questran, deplete fat-soluble vitamins A, D, E and K, as well as folic acid.
- Antibiotics and oral antifungals such as metroniazole (Flagyl) kill the good bacteria that keep your gastrointestinal tract healthy. To counter this, take a probiotic while taking these drugs, and for at least two weeks after you have stopped. Long-term antibiotic use also depletes biotin, B12, fat-soluble vitamins A, D, E and K, and possibly calcium and magnesium.
- Fat-blocking weight loss drugs Orlistat and Alli reduce absorption of fat-soluble vitamins A, D, E and K.
- Corticosteroids such as cortisol, prednisone and dexamethasone reduce calcium and phosphate absorption, increase urinary calcium, potassium, ascorbic acid, zinc and nitrogen excretion, and increase requirements for vitamins B6 and D.
- Antacids and GERD drugs such as Pepcid, Zantac and proton pump inhibitors such as Prilosec interfere with absorption of B12, calcium, iron, zinc, folic acid and beta-carotene.
- Colchicine, a dug used to treat gout, depletes vitamin B12.
- Anticonvulsant drugs phenobarbital and phenytoin deplete vitamins D, K and folic acid, while Tegretol (carbamazepine) depletes biotin, vitamin D and folic acid.
- Digoxin causes increased urinary excretion of calcium, magnesium and zinc.
- INH, an antituberculosis drug, and levodopa, a Parkinson’s drug, both prevent vitamin B6 from converting to its active form.
- Methotrexate (MTX or Rheumatrex), used to treat rheumatoid arthritis and cancer, prevents folic acid from converting to its active form.
- Chemotherapy drugs such as cisplatin can cause serious malabsorption and kidney damage, leading to low levels of many nutrients. One study found that low magnesium levels persisted for months or even years after treatment with the chemotherapy drug cisplatin.
- Blood thinners such as warfarin and coumadin work by inhibiting the conversion of vitamin K to its active form. Recent research has found that it is easier to maintain a stable dosage of blood thinner if person gets some vitamin K daily.
The Anti-Aging Bottom Line: If you have to take a drug, and especially if you take it long-term, find out its potential nutritional side effects and how you can prevent them with proper use of nutritional supplements. You’ll fare much better in the long run.