A while back I wrote a couple of essays expressing my skepticism about the notion that supplementing with plant compounds – resveratrol, acai, “antioxidants” - was a plausible route to improved health.
In the second essay I said:
Look, I don't read everything but I read a lot. I am not interested in dying early. The minute I see plausible evidence of some magic supplement working or an essential plant that is not common to all humans, I'll be the first one to promote it.
I've also expressed my skepticism that we could be evolved to be dependent on any particular plant or plant compound, inasmuch as the requirement for animal products at some level is an absolute, but probably not for plants, and in any case there is no one type of plant that has been consistently available across the variety of biomes occupied by humans.
At the same time, in posts like this, I have rejected the absurd idea that humans are not designed to eat any carbohydrate or plants. Note that this was written in August of 2009, so my agnosticism on macronutrient ratios and my emphasis on avoiding the putative NAD (neolithic agents of disease) has been a matter of record from the beginning.
I eat a VLC nearly carnivorous diet. The most important elements of this are no wheat or other grains, zero plant oils and very low fructose. Whether the carb level is 2% or 10% or even 20% with preservation of these more important parameters, I have not seen evidence there is a difference.
PaNu is proscriptive (don't eat that food!) because the way to the EM2 is to avoid the neolithic agents of wheat, linoleic acid and fructose, not through duplicating a particular dietary composition from the paleolithic period - there was too much variety to even do that, and much of what I read about what “paleo man” ate is pure conjecture if not paleofantasy.
At the same time as I’ve scoffed at the cultural obsession with fruits and vegetables, it has always seemed plausible to me that eating some plant matter along with your animal products is probably healthier than otherwise. It’s just that most of the usual justifications for fruit and vegetables don’t ring true, and the few intervention trials where subjects have been exhorted to eat more fruit, vegetables or fiber have failed to show benefit. Such as:
2) WHEL Trial
Note that these trial results leave open the idea that eating some vegetables or fruits is healthier than none. They only refute the conventional wisdom that the more you eat of them, the better.
Analyses of RDA percentages, where vitamin requirements have been derived from the SAD, have never been convincing to me. I have tended to agree with Dr. Bernstein that eating some veggies is a hedge against going without unspecified beneficial compounds.
As I find meals garnished with and flavored by veggies more enjoyable, I’ve eaten plenty of veggies and some fruit even when I’ve been eating VLC. My addition of starchy vegetables (and limited rice) 6 months ago was purely for reasons of physical performance due to increased physical activity.
So to date I’ve felt that animal products should generally be favored over plants (If forced, take the steak over the potato) but eating some plant based whole foods has had two benefits besides the obvious one of palatability:
1) Eating some starch/ sugars avoids chronic deep ketosis and improves physical performance and work capacity
2) Eating a variety of plants should be a hedge against micronutrient deficiencies in our Neolithic/industrial food environment
I’ve so far read nothing to change my thinking about these intuitions, but now Stephan has recently posted a two part series, replete with up-to-date references, which provide some scientific backing for my rejection of the “magic compounds” meme.
At the same time, he has provided an additional highly plausible reason to include a moderate variety of colorful plants in your diet, besides starch for fuel and the micronutrient hedge.
I’ve clipped some key quotes from these excellent essays, and followed with comments of my own in roman:
Polyphenols are a diverse class of molecules containing multiple phenol rings. They are synthesized in large amounts by plants, certain fungi and a few animals, and serve many purposes, including defense against predators/infections, defense against sunlight damage and chemical oxidation, and coloration. The color of many fruits and vegetables, such as blueberries, eggplants, red potatoes and apples comes from polyphenols. Some familiar classes of polyphenols in the diet-health literature are flavonoids, isoflavonoids, anthocyanidins, and lignins.
Polyphenols are often, but not always, defensive compounds that interfere with digestive processes, which is why they often taste bitter and/or astringent.
So we are not forgetting that plants can’t run. Plants elaborate defensive secondary compounds, some of which are specifically designed to mess with “plant predators” like herbivores, vegans and even normal people like us.
Polyphenols that manage to cross the gut barrier are rapidly degraded by the liver, just like a variety of other foreign molecules, again suggesting that the body doesn't want them hanging around.
Things that are rapidly arrested by the liver police should not be recruited en masse – this argues against taking antioxidant supplements or try to “load up” on one particular substance.
The most visible hypothesis of how polyphenols influence health is the idea that they are antioxidants, protecting against the ravages of reactive oxygen species.
This is the mainstream view of “antioxidants”. You can’t turn around without seeing an article advocating that we load up on blueberries, or red wine, or green tea, or whatever, for the supposed “antioxidant” effects.
For a good discussion of the basis for this meme - the idea that we need to fight the damage caused by leakage of free radicals from our mitochondrial furnaces with supplements - I recommend Sex, Power, Suicide by Nick Lane. This book is a must-read.
Suffice to say this antioxidant supplementation idea increasingly seems not just implausible, but totally back-asswards.
Here are a few references that show the perverse effects of trying to fight oxidation by eating excess antioxidants.
The body treats polyphenols as potentially harmful foreign chemicals, or "xenobiotics"
Both radiation and polyphenols activate a cellular response that is similar in many ways. Both activate the transcription factor Nrf2, which activates genes that are involved in detoxification of chemicals and antioxidant defense**(9, 10, 11, 12). This is thought to be due to the fact that polyphenols, just like radiation, may temporarily increase the level of oxidative stress inside cells.
In other words, the benefit of low doses of radiation – the kind we get naturally all the time from cosmic rays and naturally occurring radioactive isotopes – and the slightly toxic colorful compounds called polyphenols found in fruits and vegetables, is that both act through hormesis.
Hormesis is when a small stress induces a healthy response in an organism, such that the organism is healthier than without the stress exposure. Any stress that we have defenses for, that we would expect to encounter on an evolutionary basis, is a candidate to be hormetic. Think of this as a necessary, but not sufficient, set of conditions, though.
The perfect example of hormesis is exercise. Exercise creates oxidative stress, and resistance exercise in particular literally destroys muscle tissue. Hormesis explains the “paradox” (which is no paradox at all) that marathon running and other extreme endurance sports could be quite bad for your health, but that more moderate exercise is much better than no exercise at all. This explains why I write posts like this and this, yet I continue to run about 8-10 K per week in addition to strength training twice a week.
Are you starting to see a pattern here?
Run 10-15 K/ week. Don’t run 100 K/week.
Lift weights 1-2 x per week. Don’t lift weights every day.
Go hungry or fast now and then. Don’t be in ketosis 24/7
Eat a moderate variety of colorful plants. Don’t take Resveratrol pills.
We can extend this principle to some other areas once we understand hormesis.
Don’t freak out about dental or medical xrays if you need them.
Don’t obsess about unavoidable “microtoxins” in the food supply. The natural ones outnumber the unnatural ones, and we are designed to deal with them. Focus on the macrotoxins – the NAD (Neolithic agents of disease).
And more speculatively, we might think about other environmental exposures that are, or could be hormetic. A little is good, lots more might be bad.
UV A and B from Sunshine – Non-burning exposure makes vitamin D and improves mood. Excess sun on white skin causes skin cancer and wrinkles.
Fructose – Creates oxidative stress and we’ve been exposed to it for millions of years. Our liver and gut defend us against large doses. In larges doses, fructose is a NAD. Could it be beneficial in small doses?
Just as in the case of radiation, high doses of resveratrol are harmful rather than helpful. This has obvious implications for the supplementation of resveratrol and other polyphenols.
I think that overall, the evidence suggests that polyphenol-rich foods are healthy in moderation, and eating them on a regular basis is generally a good idea. Certain other plant chemicals, such as suforaphane found in cruciferous vegetables, and allicin found in garlic, exhibit similar effects and may also act by hormesis (27). Some of the best-studied polyphenol-rich foods are tea (particularly green tea), blueberries, extra-virgin olive oil, red wine, citrus fruits, hibiscus tea, soy, dark chocolate, coffee, turmeric and other herbs and spices, and a number of traditional medicinal herbs. A good rule of thumb is to "eat the rainbow", choosing foods with a variety of colors.
My food color palette is probably smaller than Stephan’s, but I do consume dark chocolate, coffee, tea and green tea in pretty decent amounts, in addition to colorful veggies like sweet potato, tomato and "Atkins vegetables" like salad greens, and limited citrus fruits.
Note the variety of plant matter mentioned, some of which (tea) does not even have caloric value. Remember, these are “plant poisons and other rotten stuff” and any particular substance will likely not be tolerated by everyone.
People say they don’t tolerate white potatoes. I believe them. People say they can’t eat tomatoes. I believe them. Some people are sensitive to coffee. Some people are lactose intolerant. Some people really are allergic to casein, shellfish, eggs or beef proteins.
So just like we are on theoretical and practical thin ice saying no one should eat dairy, or everyone should eat beef or shellfish, we can’t reasonably say everyone should eat any particular plant, only more so.
I say everyone should include some, if not a preponderance, of animal foods, and I even say for most people that ruminant products are the best, but I don’t really specify beef or lamb.
In the case of plants, because the beneficial compounds providing the hormetic effect are toxins, the effects on you personally are even more likely to be highly idiosyncratic. So how can I recommend which toxin will be best for you?
So I feel confident now making the following recommendation about plant consumption.
Eat enough plant material to keep you out of constant ketosis. Favor plants as whole foods rich in starch over fructose for caloric value, but try to include a moderate variety of colorful plants as well, for the likely hormetic effects. After these criteria, pick the particular plants you eat based on palatability and your individual tolerance.
Back to a final summary comment from Stephan:
Supplementing with polyphenols and other plant chemicals in amounts that would not be achievable by eating food is probably not a good idea.
I sometimes think Stephan may be more British than French.
William Munny would re-phrase this sentence to say:
“If you take antioxidant supplements, you have rocks in your head”
Thanks to Sean for a good laugh over dubbing me the “Clint Eastwood of Nutrition” with the following imagined quote on his blog:
"I've killed just about everything that walks or crawled at one time or another. And I'm here to kill you, Ancel Keys, for what you done to the nutrition".
- William Munny is the retired gunfighter in Unforgiven, played by Clint
Thanks to several of my friends - Peter for providing links and further background on antioxidants and vegetables. - Dr. Mike and Dr. Emily for providing full text papers to a man isolated at ice station zebra.
NOTE: Comments are OPEN for this post. I've decided to try opening comments on selected posts when I feel I have time to moderate and read them. We'll see how it goes....