Thursday, January 27, 2011

Vegetables Are Nutritionally Useless? Try Again Zoe.

Zoe Harcombe, a Cambridge graduate currently studying for a PhD in nutrition, wrote a piece for Mail Online  in which she claims that vegetables and fruits are nutritionally useless.  I consider it worthwhile to examine her “argument” carefully. Here we go:

“People are convinced that fruit and vegetables are a particularly good source of vitamins and minerals.

“For a long time, I too was a believer. I was a vegetarian for 20 years. It is only after nearly two decades of my own research — I am a Cambridge graduate and currently studying for a PhD in nutrition —that I have changed my views.”

Nice stab at an appeal to your own authority. It does not matter to me whether you graduated from Cambridge or taught yourself, and I don’t care about PhDs either, only care whether you use facts and logic properly. I was also a vegetarian for many years, no longer, but being a vegetarian doesn’t make you knowledgable about nutrition or vegetables either.

“The message that fruit and veg are pretty useless, nutritionally, gradually dawned on me.”

Zoe, you can’t rationally talk about the nutritional content of fruits and vegetables generically, because they—particularly vegetables—vary too much in nutrient content.  Its like saying that motorized vehicles are “pretty useless” for traveling to the moon—which motorized vehicles are you talking about?  There's a vast difference in nutrient density between zucchini and collards. Think, Zoe, think.

“The facts are these. There are 13 vitamins and fruit is good for one of them, vitamin C.

“Vegetables offer some vitamins — vitamin C and the vegetable form of the fat-soluble vitamins A and vitamin K1 — but your body will be able to absorb these only if you add some fat, such as butter or olive oil.

“The useful forms of A and K — ­retinol and K2 respectively — are found only in animal foods. As for minerals, there are 16 and fruit is good for one of them, potassium, which is not a substance we are often short of, as it is found in water.”

Whoa….hold on Zoe. The you just said that fruit is "pretty useless," then you say it is good for vitamin C. You can’t have it both ways, both useless and useful. Then, the fact that you need to have some fat with vegetables to absorb carotenoids and K1 does not make vegetables useless. This is like saying that autos are useless because you have to fill them with gasoline to make them work.  Perhaps you forgot that you also have to consume fat with retinol and K2 as well, putting them in that respect on par with K1 and carotenoids.

Next, you state that carotenes and vitamin K2 are the useful form of the A and the K complex, implying that K1 is not useful, which is simply wrong. We need K1 for normal blood clotting function. Moreover, it appears that vitamin K1 can protect arterial elasticity . As for carotenes, perhaps you consider them useless, but I don’t feel so certain, since humans accumulate carotenes in various tissues, they appear associated across species with longevity,  we have evidence that they provide photoprotection, and may have roles in fertility and breast health.

“Vegetables can be OK for iron and calcium but the vitamins and minerals in animal foods (meat, fish, eggs and dairy products) beat those in fruit and vegetables hands down. There is far more vitamin A in liver than in an apple, for instance.”

Again you contradict yourself, after saying vegetables are “pretty useless, nutritionally” you admit that they contain iron and calcium. Then you set up a straw man argument by comparing apples, which contain no vitamin A, to liver, which does contain vitamin A. Since you assert that meat, fish, eggs, and dairy products beat “fruit and vegetables hands down,” let’s compare collards and beef sirloin on a gram for gram basis, first for vitamins:

Click for larger version


• Collards excel in folate (10:1), vitamin C, provitamin A (as carotenoids) , vitamin K1 (400:1), and vitamin E (almost 2:1).
• Beef excels in B1 (1.5:1), B2 (1.2:1), B3 (12:1), B5 (2.4:1), choline (~3:1), B6 (~4:1), and B12.
• Of 12 vitamins, collards excels in 5, beef sirloin in 7.
• Where collards excel, they do so by greater margins than by where sirloin excels.

Consider that the beef supplies nearly 10 times the caloric value of the collards, which means the nutrient density of collards relative to caloric content far exceeds that of beef. Thus, looking at vitamins, I find it hard to dismiss “vegetables” as nutritionally useless. Collards provide far more folate, vitamin C, K1, and E than beef, as well as carotenoids which may or may not have vitamin A value depending on the genetic constitution of the consumer, but which in any case may have functions in photoprotection and fertility. Although we absorb only about 10% of K1 in vegetables if consumed with fat, discounting the K1 in collards by 90% they still deliver amost 30 times more K1 than beef sirloin.

Now for minerals:
Click for larger version


• Collards excel in calcium (8:1) and manganese (44:1).
• Beef clearly excels in iron (1.5:1), phosphorus (almost 7:1), potassium (about 2:1), zinc (20:1), copper (>2:1), and selenium (60:1).
• The value for magnesium is not significantly different (beef:collards = 1.1:1)

Thus, collards equal or exceed beef sirloin as a source of calcium, magnesium, and manganese, while beef provides more iron, etc. Again, I don’t see how one can say that “vegetables” are nutritionally useless compared to animal products until you specify which vegetables and which animal products you want to compare.

If you compare kale and beef sirloin on a calorie for calorie basis, you find something even more remarkable:
Click on image for larger version

So kcalorie for kcalorie kale provides:

• 93 times more calcium

• twice as much iron

• 3.75 times as much magnesium

• five times as much potassium,

• 2486 more units of provitamin A activity (mostly in humans not forming A, but used as carotenoids)

• 2.4 times as much thiamin

• 44 times as much vitamin E

• almost ten times as much folate

• and 86 mg more vitamin C.

If that makes kale nutritionally useless, I don’t know what would make it useful.

If I compared these greens to eggs, milk, liver, or any other animal product, the results would be different.  I'm not claiming that vegetables are superior to animal products, only argue against the headline grabbing claim that vegetables are "pretty useless." 

Comparing apples to liver for vitamin A content makes you, Zoe, look like the inverse of the vegetarians who attack animal products for not supplying fiber and carbohydrates.  Apples aren't useless because they don't provide retinol, and liver isn't useless because it doesn't have fiber or much vitamin C.   Jets aren't useless because you can't drive them on highways, and cars aren't useless because they don't fly. 

“But surely, people ask, even if there is no evidence that increasing our intake of fruit and vegetables will help prevent disease, they remain good things to eat?

“I don’t think so. If people try to add five portions of fruit and veg — let alone eight — a day to their diet, it can be counterproductive. Fruit contains high levels of fructose, or fruit sugar.

“Among dieticians, fructose is known as ‘the fattening carbohydrate’. It is not metabolised by the body in the same way as glucose, which enters the bloodstream and has a chance to be used for energy before it heads to the liver.

“Fructose goes straight to the liver and is stored as fat. Very few people understand or want to believe this biochemical fact.”

Here’s another straw man. One can easily eat 5 portions of vegetables daily (2.5 cups cooked) and avoid your dreaded fructose. Further, the statement “Fructose goes straight to the liver and is stored as fat” is out of context, namely the context of energy expenditure. It will only be stored as fat if that fat is not needed for use as energy.

“Another argument that is often put forward by dieticians on behalf of fruit and vegetables is that they are ‘a source of antioxidants’.”

Funny, just above you are quoting dieticians as the supreme source of knowledge on the metabolism of fructose, but now you put them downs as stupid for believing in plant foods as sources of antioxidants.

Tell us more:

“The biggest tragedy of all is the lost opportunity from this misguided five-a-day campaign.

“If only we had hand-picked the five foodstuffs that are actually most nutritious and spent what the Department of Health has spent on promoting fruit and vegetables over the past 20 years on recommending them, we could have made an ­enormous difference to the health and weight of our nation.

“If you ask me, these foodstuffs are liver (good for all vitamins and packed with minerals), sardines (for vitamin D and calcium), eggs (all-round super-food with vitamins A, B, D, E and K, iron, zinc, calcium and more), sunflower seeds (magnesium, vitamin E and zinc) and dark-green vegetables such as broccoli or spinach (for vitamins C, K and iron).”

WHAT? Zoe, you started this article telling us that vegetables aren’t good sources of vitamins or minerals, and said that K1 in vegetables is useless, and then you even implied that they aren't even "good to eat," but now you tell us we should eat dark-green vegetables of vitamins C, K(1), and iron? Give me a break. You clearly attacked “vegetables” just to grab a headline.

You haven't given me a very good impression of Cambridge graduates or whatever PhD (piled high and dry?) program you're completing.  Try again Zoe.

P.S.  If you like this post and want to see more like it, please consider making a small donation or a recurring subscription payment using the PayPal buttons in the right hand column.  Fighting fallacies is a full time job I love to do, but I need support to continue doing it.  Also consider sending a link to this post to all of your Facebook and other friends.  

Tuesday, January 25, 2011

Study: People Prefer The Carotene Complexion Over The Sun Tan On Evolutionary Basis

Science News reports on an interesting study published in the Journal of Evolution and Human Behavior which found that people prefer the glow of skin that results from eating foods rich in carotenoids over the darker coloration produced by a sun tan.

Left, sun tan; center, neutral; right, carotene-rich
According to the Science News article:

“Dr Ian Stephen, from the School of Psychology, University of Nottingham, Malaysia Campus, led the research as part of his PhD at the University of St Andrews and Bristol University. He said: "Most people think the best way to improve skin colour is to get a suntan, but our research shows that eating lots of fruit and vegetables is actually more effective.”

The article continues:

“Dr Stephen said: ‘We found that, given the choice between skin colour caused by suntan and skin colour caused by carotenoids, people preferred the carotenoid skin colour, so if you want a healthier and more attractive skin colour, you are better off eating a healthy diet with plenty of fruit and vegetables than lying in the sun.’

“Dr Stephen suggests that the study is important because evolution would favour individuals who choose to form alliances or mate with healthier individuals over unhealthy individuals.

“Professor David Perrett, who heads the Perception Lab, said: ‘This is something we share with many other species. For example, the bright yellow beaks and feathers of many birds can be thought of as adverts showing how healthy a male bird is. What's more, females of these species prefer to mate with brighter, more coloured males. But this is the first study in which this has been demonstrated in humans.’”

This research follows up on the team’s previous publication in The International Journal of Primatology, entitled “Facial Skin Coloration Affects Perceived Health of Human Faces”  in which they discussed the health and fertility effects associated with carotenoid consumption and coloration in many species:

“Carotenoid supplementation is associated with improved development of the immune system in human children (Alexander et al. 1985), whereas individuals infected with HIV and malaria have reduced carotenoid levels (Friis et al. 2001). Carotenoid levels may also affect spermatogenesis in boars (Chew 1993), and women who failed to conceive during in vitro fertilization had unusually fluctuating carotenoid levels in their follicular fluid (Schweigert et al. 2003). Brightly colored carotenoid-based ornaments are displayed by many bird and fish species, the size and brightness of which reflect aspects of health and condition. Male greenfinches with brighter yellow breast feathers showed stronger humoral immune responses to a novel antigen (Saks et al. 2003). Male and female yellow-eyed penguins with more saturated yellow eye ornamentation produced more offspring per season (Massaro et al. 2003). Researchers have demonstrated mate choice based on the brightness of carotenoid ornaments in greenfinches (Eley 1991), yellow-eyed penguins (Massaro et al. 2003), and goldfinches (MacDougall and Montgomerie 2003).”

To summarize, the two studies simply show that people prefer (i.e. find more attractive) skin that has more red, yellow, and bright coloration, to skin that has blue, green, and dark coloration.  Stephen et al discuss the fact that redness signifies good blood perfusion, and that red, yellow, and bright coloration associates with fertility and virility in many species.  It appears that they have shown that this applies to humans as well as other species.  In case you wonder, they have also shown that people with naturally dark skin – namely, African ethnics – also prefer skin with a brighter, yellowish and reddish tint.

This research reminds me of earlier work published in the PNAS entitled “Carotenoids and retinol: their possible importance in determining longevity of primate species,”  (full text pdf available here ) in which Cutler showed that serum and brain tissue concentrations of carotenoids positively correlate with maximum life span potential in 13 mammalian species.  That is, he found that longer-lived species have higher serum and brain tissue carotenoid concentrations than short-lived species, with humans having the highest carotenoid concentrations of the 13 species he tested.  Cutler wrote:
“It is not understood what determines the serum and tissue concentrations of carotenoids, but it is likely to be based in part on the quantitative and qualitative aspects of absorption and on the activity of an enzyme found predominantly in the intestinal mucosa cells, ß-carotene 15,15'-dioxygenase (39). This enzyme is responsible for initiating the conversion of carotene to retinol, and low levels would be expected in the longer-lived species.
Indeed, humans do show lower activity of this enzyme; see below.  Continuing the quote from Cutler:
"Humans unselectively absorb both carotenes and xanthophylls into their tissues, whereas the shorter-lived species absorb only the carotenes (16-18). The amount of carotenoids in the diet would of course also play an important role in determining the amount of carotenoids that are absorbed, but not the qualitative aspects. Thus, although all carotenoids are derived from the diet, the amount and type that is absorbed in serum and other tissues is clearly a species-dependent characteristic. [italics added]

During the evolution of increased MLSP in the mammalian species, and particularly in the primates (27, 40), carotenoid concentration in serum and tissues also may have increased. This may have been facilitated by an increased absorption of both the carotenoids and xanthophyll and a decrease in the activity of intestinal ß-carotene 15,15'-dioxygenase.  Thus, the nonselective absorption of the carotenoids in humans may represent an end point to this evolutionary strategy; most of the carotenoid protection attainable through the diet is now being utilized.” [italics added]
It appears that in the course of human evolution, the activity of ß-carotene 15,15'-dioxygenase has declined substantially, such that up to 45% of people do not convert ß-carotene to retinol vitamin A. Hickenbottom et al   found that 45% of 11 men tested did not convert ß-carotene to vitamin A (retinol).  Lin et al  found the same in women. Leung et al identified gene polymorphisms contributing to this variability in carotene conversion capacity. 

These data indicate that in the course of our evolution, humans have shifted from use of ß-carotene as a precursor for vitamin A, to dependence upon animal sources of retinol (vitamin A), such as liver, exerting a negative pressure on the retention of activity of ß-carotene 15,15'-dioxygenase.  This simultaneously gave us opportunity to use carotenoids and xanthopylls for other purposes (as they were no longer needed for retinol production).  As noted by Cutler, we humans absorb these non-selectively, suggesting that the human organism has found uses for most carotenoids.  It appears that this shift facilitated an increase in lifespan, perhaps by virtue of the carotenoids now being available for use primarily as free-radical scavengers and protection against genetic malfunctions leading to cancer, etc.

As an example, consider the photoprotective effects of carotenoids.  You may have noticed that green leaves sit out in the sun all day long without any sunscreen, yet do not become cancerous regularly.  Aside from being a sign of health, the storage of carotenoids in the skin protects the skin from ultraviolet radiation thereby retarding the aging process.  For more support for this assertion, see this, this, this, this, this, and these:

These data appear to provide evidence similar to something I have noted in my experience, namely that a higher skin content of carotenoids may reduce both the tendency to burn and the need and production of melanin in response to UV radiation. When a youth and living in Ohio, I got sun burned many times in the summer sun there.  At the time, my diet had no where near the carotenoid levels of my current diet.  Now I live in Arizona, and I often go out in the blazing summer sun around noon.  In the 10 years I have lived in Arizona, I have never gotten a sun burn anything like I had when a child.  I might turn a little red on my shoulders for 24-36 hours, but I don’t blister and peel, despite the higher intensity of the Arizona sun compared to Ohio.  

Carotenoid Complexion and Sun Tan Not Mutually Exclusive

While Stephen et al may appear to consider sun tans and carotenoid complexion as mutually exclusive, as if one can only have one or the other, I would not agree with this.  Sun exposure is necessary for vitamin D production, not to be avoided.   

However, in my experience, copious consumption of carotenoid-rich food increases skin content of carotenoids to a level that leads to reduction of sun burning AND a reduced melanin response.  In all of the more than 20 years that I have eaten a high carotenoid content diet, my sun tan appears more orange-yellow than brown.

If you don’t believe that carotenoids can modify your response to sun exposure, both in terms of burning and melanin response, don’t look for more data.  I already gave you a dozen references above.  The next step is to try it yourself.  In my experience, even fair skinned (e.g. Scandinavian) individuals can increase their sun tolerance simply by increasing their intake of carotenoids.  Again, the best data comes from your own experience.  Try it. 

I believe that traditional consumption of high carotenoid content foods help explain why our ancestors could spend most of their time outdoors without suffering the type of malignant skin damage found among modern people who spend less time outdoors but consume lower amounts of carotenoids.  This is likely an aspect of dietary influence on skin cancer incidence.  Modern people may consume lower amounts of carotenoids than our ancestors, making modern man's skin more susceptible to sun damage despite less total sun exposure.

I further wonder if by eating both fatty meat and cooked or fermented carotenoid-rich vegetables (more about the cooked and fermented below), humans were able to reduce the use carotenoids for vitamin A and increase their use for photoprotection, which in turn reduced the need for body hair to protect the skin from UV radiation, as in other species.  In other words, I wonder if our unique approach to omnivory made it possible for us to shed most of our body hair and still withstand the African homeland sun.

Carotenoid Absorption and Sources

These authors emphasized eating fruits and vegetables for carotenoids.  However, they did not mention several important facts discussed at length in Carotenoids: Nutrition and Health :

  • Carotenoids are fat-soluble so we must consume fats with carotenoid-rich foods to optimize carotenoid absorption.  [p.136]
  • Fiber present in fruits and vegetables reduces carotenoid absorption:  
“Not only purified fibre, but also fruit and vegetables as sources of this fibre, cause reductions in carotenoid bioavailability.  Dietary fibre, lignin, and resistant proteins found in green leafy vegetables inhibited the release of ß-carotene and lutein [129] and citrus pectin reduced the plasma ß-carotene responses [126].” [p.138]

  • By rupturing plant cells in which carotenoids are stored, cooking and/or pureeing carotenoid-rich vegetables dramatically increases bioavailability of carotenoids. 
“In healthy women, feeding heat-processed and pureed carrots and spinach cause serum ß-carotene to be three times higher than when the same dietary level of ß-carotene was consume in the raw food sources [102].  In a population of women at risk for breast cancer, serum concentrations of lutein and a-carotene, but not of ß-carotene, ß-cryptoxanthin, or lycopene, were higher in women consuming vegetable juice, rather thatn cooked or raw vegetables [103].” [p.134]
  • Fake-fats (sucrose-polyesters) inhibit carotenoid absorption. [p.136]
  • Statin drugs and plant sterols reduce carotenoid absorption. [p.137]

Some people may suggest that animal fats from grass-finished animals supply substantial amounts of highly bioavailable carotenoids.   

  • Duckett et al found that meat from grass-finished cattle contains 54% more ß-carotene than meat from corn-finished animals. 
  • Mother Earth News reported that pastured chickens produce eggs that contain 7 times as much ß-carotene as conventional eggs.

This photo from my collection shows the difference in color between an egg yolk from a chicken fed a supplemented grain concentrate (purchased at a Wild Oats natural food store) and one from a chicken raised on pasture (purchased from A Bar H Farm), a difference caused by carotenoid concentration:

Egg yolks:  L, from grain-fed hen; R, from pastured hen.

However, these numbers and photos may mislead.  According to Duckett et al, conventional beef and grass-finished supply only 29 and 44 mcg ß-carotene per 100 g serving, respectively.  One pound of grass-finished beef thus provides about 200 mcg of ß-carotene. The Mother Earth News study found that one egg from a pastured hen supplies 79 mcg of ß-carotene.

 In comparison, 100 g of cooked carrots contains 8332 mcg of ß-carotene, more than 40 times what we could get from an entire pound of grass-finished beef.   Hedren et al produced data on absorption of carotenes from carrots suggesting a maximum extraction of about 3% of the ß-carotene if we eat it raw, and 39% if we cook the carrots to a soft texture and consume them with fat. 

The raw supplies less than the cooked, because in raw vegetables, all of the carotenoids lie inside the plant cell walls, which consist of cellulose, and we can't digest cellulose. Cooking explodes the cells, allowing the juice to flow out for utilization. 

Thus, 100 g of raw carrot would deliver  about 250 mcg of ß-carotene, 25% more than a whole pound of grass-finished beef and about 3 times as much as an egg yolk from a pastured egg.   One hundred grams of carrot cooked soft with fat would provide 3250 mcg of ß-carotene, more than 16 times what one would get from a whole pound of grass-finished beef, and 40 times what we could get from one egg yolk from a pastured hen.

Carotenoid-rich Primal Food:  Beef with carrots, squash, and greens.

Since it appears that people prefer carotenoid complexions (which in my experience can manifest in concert with a sun "tan"), and people with high blood levels of carotenoids have better health than those without, and this also occurs across ethnic groups as well as in other primate species, and high carotenoid levels of plasma and brain correlate with longevity across mammalian species, this strongly supports the idea that humans evolved to attain long lifespans on diets containing high amounts of both vitamin A and carotenoids, i.e. dark green leafy and deep orange or red vegetables or fruits such as kale, collards, spinach, carrots, winter squashes, and tomatoes, and not exclusively carnivorous diets. 

Ethnographic data (see Guts and Grease:  The Diet of Native Americans ) even largely carnivorous tribes of humans such as Inuit and Blackfoot recognized the value of deep green plant foods and got some carotenoids by consuming the partially fermented grasses found in the foreguts of ruminants such as buffalo and caribou.  As reported by Enig and Fallon  in "Guts and Grease," according to John (Fire) Lame Deer, the eating of guts in his tribe had evolved into a contest:

"In the old days we used to eat the guts of the buffalo, making a contest of it, two fellows getting hold of a long piece of intestines from opposite ends, starting chewing toward the middle, seeing who can get there first; that's eating. Those buffalo guts, full of half-fermented, half-digested grass and herbs, you did not need any pills and vitamins when you swallowed those." [1]
Again, I suggest you to test this in your own experience.  Dark green leafy vegetables and carrots have negligible carbohydrate content yet deliver large amounts of carotenoids.  If you are sun sensitive, or want to see how increasing the carotenoid content of your skin affects your sun tan or untanned appearance, all you have to do is eat more high carotenoid foods to find out.  It takes about 10 weeks of high carotenoid consumption to produce a change. 


1. John (fire) Lame Deer and Richard Erdoes, Lame Deer Seeker of Visions, Simon and Schuster, 1972, p. 122.

Wednesday, January 19, 2011

Study: Strength Training Lowers Blood Pressure Equal to Medication or Aerobics

A study published in the Oct 2010 issue of the Journal of Strength & Conditioning Research by Collier et al [1] reports that resistance training (3 sets, 10 reps; upper and lower body at 65% 1 repetition maximum) produces greater increases in limb blood flow and a greater reduction of blood pressure  at (40 minutes postexercise) when compared to aerobic exercise.

According to Kathleen Blanchard writing for,  the study found a 20 percent reduction in blood pressure at 45 minutes after a resistance training session.  This reduction persisted for 24 hours and is equal to or greater than what can occur after use of blood pressure medication, but without side effects.

1. Collier, SR, Diggle, MD, Heffernan, KS, Kelly, EE, Tobin, MM, and Fernhall, B.  Changes in Arterial Distensibility and Flow-Mediated Dilation After Acute Resistance vs. Aerobic Exercise. Journal of Strength & Conditioning Research: October 2010 - Volume 24 - Issue 10 - pp 2846-2852

Saturday, January 1, 2011

Study: Strength Training Improves Flexibility, Equal To Or Better Than Stretching

Conventional wisdom maintains that stretching improves flexibility and that strength training makes people "muscle bound"--i.e. less flexible.   I have known for years through self-experimentation that this is hogwash, and have often maintained that properly performed strength training improves flexibility on par with stretching. 

Yesterday I learned that a pilot study presented at the American College of Sports Medicine’s 57th Annual Meeting on June 4, 2010 has confirmed my observations.  The report states:

Researchers compared the two techniques’ effect on flexibility of the same muscle/joint complexes in a five-week intervention.
“The results suggest that carefully constructed, full-range resistance training regimens can improve flexibility as well as—or perhaps better than—typical static stretching regimens,” said James R. Whitehead, Ed.D., FACSM, presenting author of the study.
Twenty-five college-age volunteers were randomly assigned to groups performing either resistance training or static stretching. A 12-person control group remained inactive. All were pre-tested on hamstring extension, hip flexion and extension, and shoulder extension flexibility, as well as peak torque of quadriceps and hamstring muscles. The resistance training and stretching programs focused on the same muscle-joint complexes over similar movements and ranges. Post-tests measured flexibility and strength.

The results—which may surprise advocates of stretching to improve flexibility—showed no statistically significant advantage of stretching over resistance training. Resistance training, in fact, produced greater improvements in flexibility in some cases, while also improving strength. [Italics added]

Although this was a "preliminary" study, I have no doubt that the larger study planned will have the same outcome.  Properly performed, strength training can give you strength, flexibility, and cardiovascular fitness as well.