Do you know how Drugs, Herbs and Vitamins interact?
01/29/2016 / By Greg White / Comments
Do you know how Drugs, Herbs and Vitamins interact?

Consumers find themselves drowning in a monsoon of information about the health benefits of natural vitamins. But not all vitamins are created equal. Some vitamins work better together than others, and some vitamins, if consumed with pharmaceutical drugs, can lead to ill side‑effects.

In an effort to steer through the murky waters, Alan R. Gaby documents in his book When Pills Collide: A Doctor Approved Safety Guide to to Drug, Herb, and Vitamin Interactions, how drugs, herbs and vitamins interact. The following includes various exerts taken from the book, which note the health benefits of vitamins and minerals, and how they mix with pharmaceutical compounds.

Vitamin C

One study has shown that 500 mg of vitamin C could increase the absorption of tetracycline. Another study found that 2,000 mg vitamin C in combination with the antibiotics trimethoprim-sulfamethoxazole (page 218) improved the efficacy of the antibiotics in people with cystic fibrosis.’ Given the preliminary nature of these studies and the differences in how different antibiotics may act when administered with vitamin C, people should consult with a doctor of natural medicine before combining them.

Taking aspirin has been associated with increased loss of vitamin C in urine and has been linked to depletion of vitamin C. People who take aspirin regularly should consider supplementing at least a few hundred milligrams of vitamin C per day. Such an amount is often found in a multivitamin.

Vitamin E

Anthralin can cause inflammation of the skin. A preUminary study found that topical use of vitamin E was able to protect against this side effect. This report used a tocopherol form of the vitamin rather than tocopheryl. This makes sense, as there is no conclusive proof that the tocopheryl forms (which require an enzyme to split vitamin E from the fatty acid to which it is attached) have any activity on the skin.
Although vitamin E is thought to act like a blood thinner, very little research has supported this idea. In fact, a double-blind study found that very high amounts of vitamin E do not increase the effects of the powerful blood-thinning drug warfarin (page 224). Nonetheless, a double-blind trial found that the combination of aspirin plus 50 lU vitamin E led to a statistically significant increase in bleeding gums compared with taking aspirin alone (affecting one person in three versus one in four with just aspirin). The authors concluded that vitamin E might, especially if combined with aspirin, increase the risk of bleedings.

Vitamin K

Vitamin K is important for healthy blood clotting. Antibiotics may interfere with the action of vitamin K in the body or, especially when taken by mouth, may kill friendly bacteria in the large intestine that produce vitamin K. With short-term (a few weeks or less) antibiotic use, the antibiotic actions on vitamin K are usually mild and cause no problems. Vitamin K, (phylloquinone) is now found in some multivitamins.


A magnesium- and aluminum-containing antacid (page 13) was reported to interfere with azithromycin absorption in a study of ten healthy people. People can avoid this interaction by taking azithromycin 2 hours before or after any aluminum/magnesium-containing products. It has not yet been shown that magnesium compounds typically found in supplements affect absorption of this drug.


A study found that adding 200 mg zinc per day to AZT treatment decreased the number of Pneumocystis carinii pneumonia and Candida infections in people with AIDS compared with people treated with AZT alone. The zinc also improved weight and CD4 cell levels. The amount of zinc used in this study was very high and should be combined with 1 to 2 mg of copper to reduce the risk of immune problems from the zinc long term.

In a study of thirty-four people with hypertension, 6 months of captopril  or enalapril (ACE inhibitors related to benazepril) treatment led to decreased zinc levels in certain white blood cells, raising concerns about possible ACE inhibitor-induced zinc depletion. While zinc depletion has not been reported with benazepril, until more is known, it makes sense for people taking benazepril long term to consider, as a precaution, taking a zinc supplement or a [multi mineral] tablet containing zinc. (Such multiminerals usually contain no more than 99 mg of potassium, probably not enough to trigger the above-mentioned interaction.) Supplements containing zinc should also contain copper, to protect against a zinc-induced copper deficiency.

To make informed decisions about daily vitamin and mineral needs, a copy of the book, When Pills Collide: A Doctor Approved Safety Guide to to Drug, Herb, and Vitamin Interactions, can be purchased by visiting this link.

Sources include:

(1) Gaby, Alan. When Pills Collide: A Doctor Approved Safety Guide to to Drug, Herb, and Vitamin Interactions. Prentice Hall. 1999.

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