The right way to take supplements

As I was preparing my last post about misconceptions surrounding the safety of supplements, I came across an online article about 15 supplement ingredients to “always avoid,” because they “…can cause organ damage, cardiac arrest, and cancer.”

Their list included comfrey, green tea extract powder, Kava, and red yeast rice — supplements I’ve recommended for years and taken myself. Let me comment on the safety of these and other supplements.

Common sense medicating and supplementing

The online article by Consumer Reports, July 27, 2016 was entitled, 15 Supplement Ingredients to Always Avoid 1 and included some familiar supplements. Their first reason these could be dangerous is because of the ingredients that could potentially interact with prescription medications such as statin drugs (to lower cholesterol and heart attack risk) or warfarin (blood thinner).

Clearly it is important to know both prescription medications and natural supplements. There are numerous drug-to-drug interactions that have potentially adverse effects. And herbs can influence certain higher risk medications.

For example, warfarin (blood thinner) is a dangerous medication if not monitored with blood testing. That’s because many prescription and over-the-counter medications with influence it gets metabolized through your liver. Herbs need to be metabolized too, and therefore will also likely influence warfarin metabolism.

But rather than scare people away from nature’s medicine, I prefer to ask the question, “Which medications could react with your supplements” — not the other way around.

Factors that influence supplement risk

Furthermore, the article warned that a danger of taking supplements depends on your pre-existing medical conditions. Well of course it does! For example, if you have liver disease, heart disease, or fragile lungs, you should take caution with any medication — natural or prescription.

Additionally, the potential harm from taking supplements depends on how much you take and for how long. Of course you can overdose on an herb — as you can any prescription or over-the-counter medicine… but does that qualify it for a list of herbs to “always avoid?”

In the article, their panel of doctors and dietary supplement researchers claim that none of these supplement ingredients give sufficient health benefits to justify the risk of taking them. That’s not what I have learned. Let’s look at the evidence…


Comfrey has a longstanding reputation as a therapeutic herb. Used topically, it treats a wide variety of ailments from lung problems and stomach ulcers to skin burns, acne and musculoskeletal injuries. Several randomized controlled trials demonstrate safety and efficacy of comfrey root extract for the topical treatment muscle and joint pain of degenerative arthritis, acute back strain, contusions and other sports injuries. 2

It is also a skin healing agent. That’s mostly due to the ingredient, allantoin, an active ingredient in over-the-counter cosmetics that gives a moisturizing effect and also enhances exfoliation to increase skin smoothness. By stimulating cell growth while also suppressing inflammation, it promotes skin cell proliferation and wound healing.

There are some precautions to be aware of with green tea comfrey. When ingested, it can be dangerous. That’s because in addition to its healing ingredients it also contains pyrrolizidine alkaloids, which if taken in the right dose, can cause liver damage. 3 4 Comfrey has been implicated but not proven to be the cause of one death. 5 In 2001, the FDA banned internal use of comfrey, and a recommends topical use for only 10 consecutive days, or a total of 6 weeks in a year. 6 With these precautions, comfrey is still a valuable and safe herb for topical use.

Green tea extract powder

Made from the shrub Camellia sinensis, green tea extract is 90 percent total polyphenols. Just one capsule equals five cups of tea and has many undisputed health benefits for:

  • Cardiovascular disease 7 8 9 10
  • Skeletal muscle strength as well as heart health 11
  • Contains L-theanine is used to reduce mental and adrenal fatigue
  • Weight loss 12
  • Helps prevent metabolic syndrome (pre-diabetes) 13
  • Helps regulate blood sugar plus has beneficial anti-oxidant effects 14
  • Has cancer-reducing effects 15 for skin, lung, mouth, esophagus, stomach, small intestine, colon, liver, pancreas, mammary glands, plus breast 16 and prostate. 17

The online Consumer Report highlighted the dangerous possible side effects of green tea extract: “Dizziness, ringing in the ears, reduced absorption of iron; exacerbates anemia and glaucoma; elevates blood pressure and heart rate; liver damage; possibly death.”  Please be aware that green tea extract, taken alone in the recommended doses, is very safe. Therefore, it is best to take precaution regarding any interaction this may have with certain prescription medications, see the Precautions section at this link:

The American College of Gastroenterology has found evidence that green tea extract could cause a rare adverse drug reaction known as idiosyncratic drug-induced liver injury (DILI). 18 I still do not see why you should “always avoid” this herbal supplement.


Kava has several uses. For examples, it:

  1. Improves sleep 19
  2. Reduces anxiety 20
  3. Boosts immune system 21
  4. Fights cancer as a chemo-preventative or chemo-therapeutic agent; 22 may reduce prostate tumor size 23 and breast cancer 24 25

The reports that it can damage your liver can be traced to the time of preparation of kava extracts. 26 Toxicity is likely attributed to poor quality raw materials that cause liver hepatotoxins, and rigorously testing the kava raw material must be done to meet Pan-Pacific manufacturing quality standards.

Red yeast rice

We know that red yeast rice lowers LDL (“bad”) cholesterol and in this way helps prevent heart disease. It also improves circulation and improves digestion.

But it is the active natural ingredient Monascus purpureus, or more specifically, monacolin K that has been proven to have the desired health effect. It is identical to the active ingredient responsible for the effectiveness of the cholesterol-lowering drug lovastatin. The challenge is that some red yeast rice products contain substantial amounts of monacolin K, while others don’t, because the FDA has determined that if a red yeast rice product contains more than trace amounts of monacolin K, it cannot be sold as a dietary supplement, but should be considered a drug.

If you have liver disease, kidney disease, thyroid imbalance, musculoskeletal conditions, or a high cancer risk, simply avoid red yeast rice. Also avoid red yeast rice if you have a weakened immune system, are fighting a chronic infection, or have a transplanted organ. If you take a prescription medication, read here about the “Interactions and Depletions” involving red yeast rice.

Be aware that supplements can have great therapeutic effects.  Also take precautions if you take prescription medications or have known diseases as described. But certainly don’t “always avoid” these supplements any more than you should “always avoid” prescription medications, which also come with precautions.

To feeling good, and healthy,
Michael Cutler, M.D.

[2] Staiger C. Comfrey root: from tradition to modern clinical trials. Wien Med Wochenschr. 2013 Feb;163(3-4):58-64.
[4] Larrey D.  [Liver involvement in the course of phytotherapy]. Presse Med. 1994 Apr 16;23(15):691-3. [Article in French]
[5] Yeong M.L.; Swinburn, Boyd; Kennedy, Mark; Nicholson, Gordon; et al. (1990). Hepatic veno-occlusive disease associated with comfrey ingestion. Journal of Gastroenterology and Hepatology. 5 (2): 211–214.
[6] Stickel, F; Seitz, HK (2000). The efficacy and safety of comfrey. Public Health Nutr. 3 (4(A)): 501–508.
[7] Stephen J. Duffy, MB, BS, PhD; John F. Keaney Jr, MD; Monika Holbrook, MA; Noyan Gokce, MD; Peter L. Swerdloff, BA; Balz Frei, PhD, “Short- and Long-Term Black Tea Consumption Reverses Endothelial Dysfunction in Patients With Coronary Artery Disease”; Joseph A. Vita, MD From Evans Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Mass, and Linus Pauling Institute, Oregon State University, Corvallis.
[8] Grassi D, Mulder TP, et al. Black tea consumption dose-dependently improves flow-mediated dilation in healthy males.  Journal of Hypertension 2009 Apr;27(4):774-81.
[9] Hodgson JM, Woodman RJ, Puddey IB, Mulder T, Fuchs D, Croft KD. Short-term effects of polyphenol-rich black tea on blood pressure in men and women. Food Funct. 2013 Jan 19;4(1):111-5. Epub 2012 Oct 5.
[10] Theaflavins from Black Tea, Especially Theaflavin-3-gallate, Reduce the Incorporation of Cholesterol into Mixed Micelles. Mario A. Vermeer, Theo P. J. Mulder and Henri O. F. Molhuizen, J. Agric. Food Chem., 2008, 56 (24), pp 12031–12036.
[11] Siamwala JH, Dias PM, et al. l-Theanine promotes nitric oxide production in endothelial cells through eNOS phosphorylation. J Nutr Biochem 2012 Jul 20. [Epub ahead of print] found online at:
[12] Vernarelli JA, Lambert JD. Tea consumption is inversely associated with weight status and other markers for metabolic syndrome in US adults. Eur J Nutr. 2012 Jul 10.
[13] Kubota K, Sumi S, et al. Improvements of mean body mass index and body weight in preobese and overweight Japanese adults with black Chinese tea (Pu-Erh) water extract. Nutr Res. 2011 Jun;31(6):421-8.
[14] Chen H, Qu Z, Fu L, Dong P, and Zhang X.  Physicochemical Properties and Antioxidant Capacity of 3 Polysaccharides from Green Tea, Oolong Tea, and Black Tea. Journal of Food Science, June 30, 2009 Volume 74 Issue 6, Pages C469 – C474. Abstract online at
[15] Yang CS, Maliakal P, Meng X. Inhibition of carcinogenesis by tea. Annual Review of Pharmacology and Toxicology 2002; 42:25–54.
[16] Shrubsole MJ, Lu W, et al.  Drinking green tea modestly reduces breast cancer risk. J Nutr. 2009 Feb;139(2):310-6.
[17] Oct. 18, 2012 — Men with prostate cancer who consumed green tea prior to undergoing prostatectomy had reductions in markers of inflammation, according to data presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held in Anaheim, Calif., Oct. 16-19, 2012. Accessed online Jan 7, 2013 at:


Dr. Michael Cutler

By Dr. Michael Cutler

Dr. Michael Cutler is a graduate of Tulane University School of Medicine and is a board-certified family physician with more than 20 years of experience. He serves as a medical liaison to alternative and traditional practicing physicians. His practice focuses on an integrative solution to health problems. Dr. Cutler is a sought-after speaker and lecturer on experiencing optimum health through natural medicines and founder of the original Easy Health Options™ newsletter — an advisory on natural healing therapies and nutrients. His current practice is San Diego Integrative Medicine, near San Diego, California.