Warfarin and Supplement Interactions – and What About Food?

Way back in 1988 I was Editor of a book called The Medicine Chest which was a straightforward examination of the interactions between drugs, supplements and foods. It had a lot of good advice that hasn’t changed much over the years so I was surprised to receive a ‘news’ item that warned that Warfarin when taken with vitamin E and large doses of vitamin C can decrease effect of the drug.

I was not surprised at the effect because I was writing about it over 20 years ago, but that it was news came as a surprise. However, it never hurts to repeat a good piece of information and scientists never turn up a chance for a grant to research something we already know.

This time it is researchers at the Intermountain Medical Center Heart Institute in Salt Lake City, Utah who want to point out the dangers. Warfarin is a commonly prescribed drug used to prevent blood clots from forming and given to people with certain types of irregular heartbeat, those with prosthetic heart valves, and those who have suffered a heart attack.

The study consisted of interviews with 100 atrial fibrillation patients to determine their understanding of potential interactions between supplements and medications such as Warfarin. This is not really a study about interactions but of people’s understanding of them and generally people do not know enough about how supplements, and everyday foodstuffs react with their medication.

In this study more than half were unaware of potential interactions and they also found that of the 100 most-used supplements (vitamins, glucosamine/chondroitin, fish oil and coenzyme Q10) 69 percent interfere with the Warfarin’s effectiveness.

Warfarin and herbal and dietary supplements “compete” in the liver and this competition changes the way the blood thinner works — either intensifying its active ingredients, thereby increasing the risk of bleeding, or by reducing its effectiveness, increasing the risk of stroke.

All true, and the lead researcher is urging that doctors do a better job of teaching patients about the dangers of mixing Warfarin with these products. Now I entirely agree with him, but what he doesn’t mention is that this particular drug is also seriously affected by certain foodstuffs and other drugs.

Given what the average doctor knows about nutrition I hold out little hope they will also pass on this advice so that instead of increasing or decreasing their drug prescription they could suggest changes to their patients diet. In addition, the effectiveness of Warfarin is impacted by other drugs – particularly antifungals, barbiturates and beta blockers which all decrease the drugs effectiveness.
Conversely, antibiotics, some diabetes drugs, gout medicines, tricyclic antidepressants and asprin and paracetamol – among others – all can increase the drug’s effectiveness, making it more potent.

On Warfarin? Avoid These:
Warfarin is affected by large doses of vitamin E, vitamin C, bioflavanoids and calcium and a large intake of fats or oils. If the diet is also high in vitamin K rich foods this can cause an imbalance in the body which could decrease the anticoagulant effect.

Vitamin K is needed to allow your blood to clot normally, to protect your bones from fracture and postmenopausal bone loss, to prevent calcification of the arteries and provide possible protection against liver and prostate cancer.

Vitamin K is a fat soluble vitamin and only a small amount is able to be stored in the body. It is destroyed by light and acids and alkalis such as vinegar or baking soda. A deficiency of it can lead to increased blood clotting time, easy bruising and excessive bleeding.

Significant food sources include: green leafy vegetables including spinach, Brussels sprouts, Swiss chard, green beans, asparagus, broccoli, kale and also cauliflower, cow’s milk, eggs, fish liver oils, green vegetables, kelp, liver, molasses, polyunsaturated oils, tomatoes

Everyone responds differently to drugs, foods and supplements so if you have any concerns, or if your diet is high in vitamin K rich foods, then you should discuss with your doctor how this is affecting your medication.

Diabetes and memory loss solution

Another story that interested me this week, also came from Canada and the Baycrest Center. This time they were reporting on the link between diabetes, high-fat foods and memory loss.

Apparently, adults with type 2 diabetes who eat unhealthy, high-fat, meals can suffer from some reduction in their ability to remember things immediately after eating such a meal. Possibly because they have fallen asleep while digesting such a heavy meal, but there is hope as the temporary memory loss can be offset by taking antioxidant vitamins C and E with the meal.

It is already known that diabetes is linked to the ability to retain information, but now it seems that adults with type 2 diabetes are especially vulnerable to acute memory loss after eating unhealthy foods. The new findings appeared in a recent issue of Nutrition Research, a professional peer-reviewed journal, and suggests that taking high doses of antioxidant vitamins C and E with the meal may help minimize those memory slumps.

Type 2 diabetes is associated with chronic oxidative stress, a major contributor to cognitive decline and Alzheimer disease. If you have an unhealthy diet, then that raises your level of free radicals and those unstable molecules can damage tissue, including brain tissue. These destructive molecule reactions typically occur over a one-to-three hour period after you have eaten but don’t think that popping a supplement pill will do the trick on its own. It’s a place to start, and the study used vitamin C of 100mg and vitamin E of 800 mg taken with the meal, but do check with your doctor as there are contraindications for taking high doses.

Specifically, tell your doctor if you are taking warfarin as you may not be able to take vitamin E without special monitoring during treatment, and also consult your doctor if you are pregnant or breast-feeding a baby.

Ideally you will change your diet to one that is high in antioxidants to chase down those free radicals – look back at the article on the Mediterranean Diet as it is generally accepted to be one of the most health-giving there is.

Warning on fruit juice and drug interactions

Sorry to be still on the fruit juice trail, but news this week had a real deja-vu quality about it for me. In the 1980′s, I was involved with a naturopath in the writing of a book called ‘The Medicine Chest’ which looked at the relationship and interaction between foods, vitamins and medicines. One of the things we flagged up then was how food can affect your medication. One example of this is the drug warfarin which interacts with vitamin K, which we get from food, and from the bacteria in our gut. Vitamin K is involved in the formation of special liver proteins, known as coagulation factors, which reduce the risk of haemorrhage or bleeding. Conversely, if you are susceptible to blood clotting, warfarin (because of how it interferes with the formation of these vitamin-K-dependent factors) may be prescribed for you. So you can see that if you increase the amount of vitamin K-rich foods then you can alter the effect that the warfarin will have in your body. Such foods include everyday items like spinach, lettuce, beef, broccoli and soy beans – good foods in themselves but to be discussed with your doctor if you are on warfarin.

Now the scientific world seems to have caught up with the research done by naturopaths over the years, which has always treated food as ‘medicine’ and been much more aware of its effects. Recent research presented at a US conference has now suggested that a chemical in grapefruit, orange, and possibly also apple juice, could stop anti-allergy drugs being absorbed properly. Grapefruit juice is already known to interfere with blood pressure drugs and indeed some medicines carry a warning that taking them alongside grapefruit juice could cause an overdose and normally your pharmacist will point this out to you. However, the latest finding shows that grapefruit juice had the reverse effect on fexofenadine, an antihistamine drug, making it less rather than more potent. Volunteers took the drug with either a single glass of grapefruit juice, or just water.

When it was taken with juice, only half the drug was absorbed, potentially reducing its effectiveness. The active ingredient of the juice, naringin, appears to block a mechanism which moves drug molecules out of the small intestine into the bloodstream and this substantially decreases the absorption of certain drugs.

The three juices mentioned have also been found to affect etoposide, a chemotherapy drug, some beta-blocker drugs used to treat high blood pressure, and cyclosporine, taken by transplant patients to prevent rejection of their new organs. Dr David Bailey of the University of Western Ontario, the study’s author, said: “This is just the tip of the iceberg – I’m sure we’ll find more and more drugs that are affected this way.”

An aspirin a day keeps heart attacks at bay?

It is part of the daily routine for many, but is it actually doing you good? Aspirin prevents platelets (a type of blood cell) from forming into clots and it is so effective that a single tablet can increase the tendency to bleed easily for up to a week. That’s fine if all you want to do is thin the blood, but too much blood thinning can be quite dangerous as researchers from McGill University Health Centre in Montreal, Canada found when they examined 4,000 cases of patients suffering from gastrointestinal bleeding. They found that when the anticoagulant drugs warfarin and clopidogrel were taken with aspirin, gastrointestinal bleeding was four to six times higher than in subjects who didn’t combine these drugs. When these prescription blood thinners are prescribed, aspirin use is usually discouraged, but that doesn’t mean that each patient gets the message. Those who don’t may be experiencing much more harm than good.

In a previous study in 2004, UK researchers at the University of Hull produced a Warfarin/Aspirin Study in Heart Failure that divided patients into three groups: one group received 300 mg of aspirin daily, one received a standard daily dose of warfarin, and a third group received a placebo. All the subjects in the study had experienced either heart attack or stroke, prompted by thrombosis. After an average follow up period of more than two years, researchers found that neither the aspirin nor the warfarin therapies provided any greater protection against death, nonfatal stroke, or nonfatal heart attacks than the placebo. In fact, subjects who received aspirin therapy were nearly twice as likely to suffer a heart attack or stroke compared to those who took warfarin or placebo. Gastrointestinal problems were also elevated in the aspirin group, confirming the findings of McGill University.

So if you’re taking a daily aspirin, should you stop? NO. Not before talking to your doctor first. In a 2003 study that reviewed more than 1,200 cases of coronary episodes, researchers found more than 50 cases of heart attacks or other severe coronary problems less than one week after patients discontinued aspirin use.