Food is a common topic of conversation. Newspaper articles about food are written almost every day.
Magazines completely dedicated to the preparation of food are amongst the most frequently purchased, and
radio and television programs about food and cooking are probably the most popular of all the lifestyle
programs.
Perhaps all this should come as no surprise. Food is important not only for its nutritional value; it has very real
social aspects as well.
Of course, it has become clear in recent years that we don't always eat the right kind of food. Doctors and
nutritionists tell us our diet doesn't have quite the right balance. And, generally speaking, we just eat too much
of everything. Overweight and obesity affects more than 50% of the Australian population. The consequences
are a greater risk of diabetes, heart disease and possibly some cancers.
All these facts are well documented. But somewhat less attention is given to the effect certain foods might
have on the medicines we take; in fact what we eat and when we eat may actually determine whether or not
our medicines work.
These issues are the subject of an article written by Professors Andrew McLachlan and Iqbal Ramzan from the
Faculty of Pharmacy at the University of Sydney and published in this month's edition of Australian Prescriber,
an independent journal for health care professionals. As the authors say, understanding the possible
implications of taking medicines with or without a meal is important for getting the best possible benefit and
equally important for minimising adverse effects.
The absorption of the active ingredients of medicines usually takes place in that part of the gastrointestinal tract
known as the small intestine – not the stomach. The larger a meal the slower its passage from the stomach to
the intestine. Fatty meals pass even more slowly, so when taken with food, drug absorption is delayed.
If rapid onset of action is desired from a medicine, then it may be recommended that the medicine be taken on
an empty stomach – that means at least one hour before or two hours after a meal. On the other hand, for
most medicines, especially those used to treat chronic conditions; a delay in absorption is of no clinical
consequence as long as the total amount absorbed is unaffected.
Indeed to ensure that medicines are taken at the desired frequency for the appropriate length of time it is often
recommended that doses be taken when they best fit with your normal daily routine – and that may mean meal
times.
Nevertheless there are certain foods and food ingredients or so-called micro-nutrients which can seriously
affect the action of some medicines. For instance foods rich in vitamin K can affect the action of the
anticoagulant medicine warfarin. Calcium-rich foods might reduce the effect of some antibiotics. Potassium-
rich foods in conjunction with some high blood pressure medicines can cause side effects.
One of the most important and widely documented food/drug interactions involves grapefruit juice. A single
glass of grapefruit juice is sufficient to increase the effects and possibly the adverse effects of many medicines.
Theoretically we should be able to use grapefruit juice to enhance the effect of some medicines; but the effect
of the juice is so variable from brand to brand and batch to batch that complete abstinence might be the only
option.
In any event, be aware it's not only alcohol and drugs which don't mix, the combination of meals and
medicines can occasionally cause problems.
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