Are You Inviting Health Problems if You Combine These Supplements?

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Are You Inviting Health Problems if You Combine These Supplements? about undefined

What if the supplements you take every day in hopes of preventing cancer turn out to be the reason you get it? It’s a disturbing thought, and if proven – a big if -- it could disrupt the $37 billion-a-year supplement industry.

So I thought I’d look into whether there’s any truth behind some hair-raising claims that have been made...

Stay away from this supplement combination

Here’s what we know: Oxidative stress can cause cancer. So when a group of researchers hypothesized that antioxidant supplements would reduce the incidence of gastrointestinal cancer and lower overall mortality, it seemed like a reasonable idea.

What they found told a different story.

They analyzed seven high-quality trials on gastrointestinal and related cancers. What they found was that people who took beta-carotene supplements combined with vitamin A or vitamin E significantly increased mortality (incidence of death).

Taking beta-carotene alone increased mortality by only a little. In contrast, taking selenium reduced the risk of gastrointestinal cancer.

Controversial for a long time

So where does that leave us? How do you know what’s okay to take in combinations, and what’s not? I was not too surprised to learn there’s a cloud hanging over beta-carotene and vitamin A, or that the combo with E raised questions. These supplements have been under fire for a long time.

Just for the record, I don’t take a beta-carotene supplement. I supplement with vitamin A once or twice a week, and in a very small dose – 10,000 i.u.

The body converts beta-carotene to vitamin A when the latter is needed. Meanwhile, the body stores beta-carotene, and most of us have an ample supply. From what I’m told by my personal nutritionist, beta-carotene is used up slowly. You’re not going to run out.

These supplements are toxic in large doses, yet most standalone beta-carotene and A supplements contain horrifyingly huge amounts. Doses of 25,000 or even 50,000 i.u. are common.

Why are large doses toxic? This is not well understood. A possible reason is that your body requires hundreds of antioxidants to function, and all of these antioxidants need to work together synergistically so your body efficiently gets rid of free radicals.

When you take high doses of only a few antioxidants, you might be upsetting the balance. As a result, you wind up hurting your own ability to fight off cancer.

“Synergistic effects” happen, too

There’s a flip side, of course. A 2011 study published in Food and Chemical Toxicology showed a synergistic effect between antioxidant mixtures at least 92% of the time. In other words: almost always.

In many cases, vitamins are more effective when taken in combination. For example, a lot of the B-complex vitamins are more potent when mixed together.

Supplements often give us tremendous benefits in cases where a very large dose – larger than you’re ever likely to get from food – produces a medicinal effect – the sort of strong, obvious response you’d expect with a medical treatment. You just need to make sure the large dose is safe.

The most familiar example is vitamin C, where you can take as much as ten or twelve grams – that is, 10,000 or 12,000 milligrams – per day. The limit is that eventually people get GI upset and diarrhea. Cancer doctors bypass the GI tract problem by giving cancer patients much bigger doses intravenously. And it’s one of the best cancer treatments ever found. In contrast, such a treatment with vitamin A is unthinkable.

Here’s another case of safe use of large doses: I’m not going to eat pomegranates or drink pomegranate juice every day. For one thing, it contains too much sugar. But every day I take a large dose of the beneficial compounds found in pomegranates. Likewise, I take a powdered capsule containing extracts of cruciferous vegetables like broccoli and cabbage.

It’s a noble idea to eat enough cruciferous vegetables so you don’t need the supplement, but I think I’ll take the supplement just in case. Especially considering that the large doses are safe and the benefits are gigantic.

Dangerous supplement combinations you need to know about

The bottom line is that food and the thousands of compounds in it are just as powerful as a lot of the drugs out there. Just as you shouldn’t mix certain drugs, you also shouldn’t mix certain food compounds when they’ve been extracted and packed into a capsule in a big dose. It’s hardly surprising that there’s potential for interactions and toxicity when it comes to supplements.

Here’s what I can tell you about known supplement interactions and supplement-drug combinations:

1. Fish oil combined with herbs that are meant to slow blood clotting, like ginkgo biloba, may lead to bleeding. Much more dangerous is to combine fish oil or ginkgo with a powerful blood-thinning drug like Plavix. You should also avoid combining fish oil with drugs that lower blood pressure. Even NSAID drugs like aspirin, ibuprofen, or naproxen can thin the blood when taken daily for a long period.

2. Melatonin shouldn’t be taken with any supplements that have sedative effects, like St. John’s wort or valerian. You should also avoid combining it with sedative drugs, or medicine used to control blood pressure. Melatonin is one of the most difficult supplements to use correctly. Read up on it in depth before taking the plunge.

3. Vitamin D in high doses combined with any kind of diuretic medication can lead to elevated calcium levels in your body, which may lead to kidney problems. Vitamin D also doesn’t get along well with cholesterol-lowering drugs and high blood pressure medications. As high doses of D have become popular – and rightly so -- because of their huge benefits, there may be a risk for some people on these meds.

4. Echinacea shouldn’t be combined with drugs that inhibit your immune system, like prednisone, because the point of taking echinacea is to stimulate your immune system.

5. Calcium doesn’t appear to have any negative supplement combinations, but you don’t want to mix it with blood pressure meds or prescription drugs for osteoporosis. Calcium also neutralizes stomach acid, and I don’t think it’s a good supplement to take with a meal. Many people, especially seniors, are deficient in stomach acid.

6. Zinc supplements make it harder for your body to absorb antibiotics that contain quinolone or tetracycline, so you’ll want to make sure you take the two types of pills at least two hours apart.

7. Vitamin E, when taken in the presence of a vitamin K deficiency, can increase your chance of hemorrhaging.

8. Calcium and magnesium actually compete for absorption with each other if you exceed 250 mg per dose. If you need to take larger amounts, take them at different times or split your dose into combinations of smaller amounts.

9. Vitamin B1, if you’re taking it in large doses for diabetic neuropathy, chemotherapy side effects, or other conditions, should not be taken with grape seed, pine bark, or green tea extract. These three supplements decrease the absorption of vitamin B1, so you’ll want to take them at least two hours apart.

As you may have noticed, most of these warnings involve drug and supplement combinations. They rarely involve combos of two supplements. My attitude would be to try to get off the drug and continue taking the supplements – and that can be done in many, many cases.

Best way to choose your supplements

The ideal step is to consult with an able alternative practitioner who can look at the whole picture – all the supplements and medications you’re taking. He or she can identify dangerous combos, if there are any, and point you toward safe, natural solutions to the medical conditions that forced you onto the drugs in the first place.

Finally, while mixing vitamin supplements together may be harmful under certain rare conditions, it’s never harmful to mix whole foods that contain different vitamins. So if you’re eating a diversity of foods, and particularly if most of those foods are plant-based, you don’t have to worry about the different vitamin and nutrient combinations you’re creating in your stomach.

In a perfect world we’d all be getting all the nutrients we need from the food we eat. In the real world where we all live, that rarely happens. I recommend careful, well-informed use of supplements combined with a determined effort to eat the healthiest diet you can.

 Best regards,

Lee Euler,


  1. “Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis.” By Bjelakovic G., et al. Lancet. 2004 Oct 2-8;364(9441):1219-28.
  2. “Dietary antioxidant supplements: Benefits of their combined use.” By Ivone M.C. Almeida, et al. Food and Chemical Toxicology, Volume 49, Issue 12, December 2011, Pages 3232-3237.
  3. “Food synergy: the key to a healthy diet.” By David R. Jacobs, et al. Proceedings of the Nutrition Society, Volume 72, Issue 2, May 2013, pp. 200-206.
  4. “How to Take Supplements.” Dr. Sam Russo, Q&A. 1 March 2011.
  5. “Is it OK to take different supplements at the same time?” HSIS, retrieved 5 March 2018.
  6. “Is it Safe to Mix Vitamins?” By Naomi Parks for LiveStrong, 3 October 2017.
  7. “Warning: Do Not Mix These Supplements.” For, 23 May 2013.,,20439590,00.html#st-john-s-wort

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