Can You Get Too Many Plant Polyphenols?

cup coffee and cream

Are all plant polyphenols created equal? Read on for my thoughts on that topic.

Polyphenols: The Right Dose

Several of the supplements in this section [of the book], including resveratrol, green tea, curcumin, quercetin, and berberine, are polyphenols, a class of chemicals found in plants. In addition, coffee, black tea, chocolate, and red wine contain relatively large amounts of these phytochemicals. If you consume these foods/beverages and also supplement, is it possible to get too many polyphenols?

Consumption of polyphenols is robustly associated with better health and 37% lower death rates,  as well as a 46% reduction in cardiovascular disease risk. However, these studies were based on the polyphenol content of foods, such as coffee, fruits and vegetables, etc., as well as a spot urine test for polyphenols, not supplement use. The highest intakes of polyphenols, that is, those associated with the lowest death rates, averaged about 1235 mg a day.

Polyphenols in food

To get a handle on this, it helps to know the polyphenol content of some common food items, notably those high in them as we’ve discussed. I’ve listed the total polyphenol content, by serving, in the following, calculated from the amount in 100 grams or in 100 ml from “Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database”.

  • Dark chocolate: ~500 mg
  • Coffee: ~300 mg
  • Black tea: ~150 mg
  • Green tea: ~120 mg
  • Red wine: ~150 mg

Someone who drinks two regular-size (6-ounce) cups of coffee daily, eats a serving of dark chocolate, and drinks two glasses of red wine (for example), will have a polyphenol intake of around 1400 mg. (Rough calculation.) That’s about the level seen in the highest category of polyphenol consumption and the category with the lowest death rates. Using some different assumptions, it would appear to be relatively easy to get total daily polyphenol uptake into the several-thousand-milligram daily range. In fact, a 20-ounce coffee of the kind sold in chain coffee shops may alone have 1200 mg of polyphenols.

For comparison, some of the doses of supplements we’ve discussed, such as berberine and curcumin, are 500 mg. Resveratrol suggested doses are lower, at 100 mg or less.

Could you get too many plant polyphenols? Or is there even such a thing as too many?

Hormesis and polyphenols

Unfortunately, the answer is not known. It may or may not follow that, because those who consumed 1250 mg of polyphenols a day had the lowest death rates, those who consumed 2500 mg a day have even lower death rates. Maybe they do, maybe they don’t.

A point of diminishing returns likely exists somewhere. Furthermore, not all polyphenols are the same and some have greater effects than others and/or use different mechanisms of action, so adding them into all one basket for purposes of calculating total intake may be of limited value.

Stilbenes and lignans

The study that found 37% lower death rates also reported, “Among the polyphenol subclasses, stilbenes and lignans were significantly associated with reduced all-cause mortality [HR 0.48 and 0.60, respectively], with no significant associations apparent in the rest (flavonoids or phenolic acids).”

If polyphenols cause lower death rates (not mere association), then only certain classes of them count for much.

The two classes of polyphenols that mattered were stilbenes, which include resveratrol, pterostilbene, and other compounds in grapes, wine, and cocoa; and lignans, the richest source of which is flaxseed.

Since polyphenols most likely work through hormesis, the process by which low doses of toxins or stressors produce beneficial health effects, it follows that at some dosage, polyphenols may become overtly toxic, and damage health.

The point I wish to make is to be aware of what you’re taking and not to overdo it. Don’t indiscriminately take large amounts of different polyphenol supplements in the quest for ever better health, especially if you already drink coffee, tea, and wine, and eat chocolate. Not to mention berries (another source of large amounts of polyphenols) or if you cover your food with cloves (just kidding, but that’s the number one food for polyphenols).

Although we don’t know at what, if any, level that polyphenols become a problem, and overt toxicity in animals seems to occur only at very high doses, if you tally up your polyphenol intake and find it at, say, over a couple thousand milligrams daily, you might consider cutting back. These considerations may not apply to those with special health needs, such as someone taking berberine several times a day for blood sugar control, but such people should have cleared their use of supplements with their doctor first.

PS: Check out my Supplements Buying Guide for Men.


Tresserra-Rimbau, Anna, et al. “Polyphenol intake and mortality risk: a re-analysis of the PREDIMED trial.” BMC medicine 12.1 (2014): 77.

Tresserra-Rimbau, Anna, et al. “Inverse association between habitual polyphenol intake and incidence of cardiovascular events in the PREDIMED study.” Nutrition, Metabolism and Cardiovascular Diseases 24.6 (2014): 639-647.

Pérez-Jiménez, J., et al. “Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database.” European journal of clinical nutrition 64 (2010): S112-S120.

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  1. Rob H says:

    Hi Dennis, this is a fascinating area and as you say very little research seems to exist at the moment. I’m not sure if you read my recent comment under you curcumin post? I unearthed something that seemed to reinforce what you are saying in this post, ie turmeric in food has been shown to be beneficial but higher doses of curcumin were shown to cause cell death. Also who was that guy Seth Roberts is it who was famous for trying nutrition hacks – he died very young and unexpectedly and some say it was not unrelated to his very high intake of flaxseed products – I’m sure you can find out more if you are interested. Again, very little evidence exists, all we can do is make conjecture and try to join up the dots..:

    • P. D. Mangan says:

      Hi Rob, yes of course, I read all comments. I spoke to Seth Roberts several times and corresponded with him; his death was a real shock. I attended his memorial too, bright side of that being that I met Paul Jaminet and John Durant, and heard Gary Taubes speak. The cause of Seth’s death was listed as a myocardial infarction, I believe, so the flax seed thing, which I’ve read, doesn’t seem to pan out. As for the polyphenols/curcumin, yes, there’s just so little to go on. Those toxic effects of curcumin that you noted, I’m guessing those are from concentrations that would be difficult to attain in vivo.

      • Herman Rutner says:

        Flax seed products, presumably oil and whole seeds, contain about 50% alpha linoleic fatty acids, both C16 and C18 and precursors for EPA and DHA in inefficient in vivo enzymatic 2-step elongations at about 10% conversion, further reduced in the presence of far larger amounts of competing dietary omega 6 plant oil precursors forming inflammatory arachidonic acid etc. Hence flaxseed oil is no substitute for fish oils are not equivalent to the biologically active fish oil omega 3, C20 EPA and C22 DHA from fatty fish. All omega 3, less so other unsaturated fatty acids, are subject to free radical oxidation to toxic products responsible for off odors or bitterness of damaged or improperly stored omega 3 oils. I personally believe refined molecular distilled cod liver oil, free of mercury, colorless, odorless and nearly tasteless, is a better source of EPA and DHA at higher levels in 1 teaspoon than found in several fish oil capsules of generally poor quality (suggest you open one to taste and smell). And it should be kept frozen, best stabilized with Vitamin E. Concurrently taking Vitamin E and sacrificial anti oxidant Vitamin C with codliver oil is advised to protect it in oxygen rich blood before metabolism. Codliver oil contains some cholesterol, but also beneficial Vitamin A and D. I suspect numerous clinical studies used commercial fish oils of uncertain purity or quality, hence yielding conflicting results or else did not co administer anti oxidants..
        Seth’s death of cardio disease is tragic but may not have been caused by flaxseed consumption, unless excessive since it may variable amounts of a toxic cyano glycoside, linamarin.

  2. Coincidentally, a few weeks ago I decided that I was going to consume the following daily:
    1) 1 cup of coffee (8 oz)
    2) 1 cup of green tea (8 oz)
    3) 1 cup of black tea (8 oz)
    4) 1 glass of red wine (8 oz)
    5) 2 squares of 85% dark chocolate (20 grams).

    It may be healthy, but I do it partly because I enjoy caffeine, red wine, and dark chocolate. 🙂

    • P. D. Mangan says:

      Hey Mark, that’s 1.6 glasses of wine!

      • Joshua says:

        The more the merrier! (But, yes, watch your placement in the U-curve..)
        Jeanne Calment (longest lived human ever) was reputed to eat 2 pounds of chocolate a week. I’m wondering if she just had fantastic genes (maybe…I think she smoked earlier in life, too), or if the large dose of polyphenols from the chocolate were indeed very beneficial. Meanwhile, I guess I’ll hedge my bets by having a mere half pound of dark chocolate a week. 🙂

        • P. D. Mangan says:

          AFAIK, Calment smoked well past age 100. You could be right that huge amounts of polyphenols may have made the difference, and that there’s no upper limit to intake. That would be a good thing.

      • Mark Cancellieri says:

        8 ounces fits in one glass. 🙂

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