Monday, December 31, 2007

Fruit and vegetables re post

It is remarkably widely accepted that fruit and vegetables are good for you. Three a day, five a day, nothing but fruit and vegetables all day..... The problem is that all of the evidence of benefit is epidemiological, and this never proves causation, merely association.

Where does hard science take us? This was the first study I stumbled across, about Polish cyclists.

Effects of a low carbohydrate diet and graded exercise during the follicular and luteal phases on the blood antioxidant status in healthy women.

I only have the abstract of this paper so there is no information as to exactly what comprised the 5% of energy intake which was derived from carbohydrate. Whether it was pure sucrose, apples or bananas, there wasn't a lot there in total. So minimal plant based antioxidants to speak of. End result?

"The 3 days of the L-CHO diet, which had been preceded by glycogen-depleting exercise, resulted in a stimulation of the blood antioxidant defence system in young eumenorrhoeic women both at rest and during the graded cycling exercise to maximal oxygen uptake."

Not bad for three days of dumping the fruit and veg.

The next study, which is an excellent piece of work, was this one:

Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet.

Never mind the green tea bit, that turned out to be irrelevant. It's what happened when almost all fruit and vegetables were removed from the diet of the volunteers for 10 weeks that's interesting. The result being:

"The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defence."

This later study was NOT a low carb study. Potatoes, bread and cake were all included in the sample menus provided in the full text. Please note the DECREASE in oxidative damage to your genes, your protein structure and your lipids. Great stuff fruit, when you put it in the bin.

The conclusion seems to be that there is something nasty in fruit and vegetables, something pro-oxidant. You just have to ask yourself why a plant should manufacture an antioxidant in the first place. You can bet your bottom dollar that it was not for the benefit of herbivores! No, plants hate herbivores and negotiate with substances like strychnine rather than antioxidants.

The most likely candidate for a generic pro-oxidant toxin, produced by plants, is fructose. Plants outside of domestication contain relatively little fructose and appear to use it as a lure, to get their seeds eaten, then use the fruit eater as a transport method. They protect themselves from the fructose with antioxidants. Plants in domestication have been selected, by ourselves, to produce quite unreasonable amounts of fructose (plus glucose and sucrose). Just compare the average Granny Smith to a wild crab apple. A bag of sugar.

Mammals do exactly the same when presented with fructose. They make an antioxidant, in the case of mammals it's uric acid. Uric acid improves the total plasma antioxidant capacity after fruit ingestion. The mechanism is rather well summarised here:

Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: Cause, consequence, or epiphenomenon?

"We conclude that the large increase in plasma total antioxidant capacity observed after the consumption of flavonoid-rich foods is not caused by the flavonoids themselves, but is likely the consequence of increased uric acid levels."

Small studies using intervention strategies show this clearly. Don't forget those marvelous fruits and vegetables in this intervention study too. Oxidised LDL cholesterol anyone?

Or the Dutch study.

So in summary plants produce fructose which is both attractive and damaging to mammals. They protect themselves as best they can with antioxidants.

I don't see any causality between fruit and vegetable consumption and improved health.



Warren Bathurst Gallery said...

That was another eye-opening post. How do we determine what to do next? We can reduce and refine our choice of fruit and vegetables but where do we come out even with their effects on our health? I look forward to your posts. Thanks very much for your efforts!

Peter said...

Hi upload,

I find the Danish Green Tea study pretty convincing. My main problem is that my digestion does not much like starches (mild) and my skin hates grains (badly enough that I avoid even beer, sigh), certainly the gluten based ones. So I tend to use quite a lot of tomatoes, peppers and onions, plus the sucrose in 86% cocoa chocolate as my carb intake, plus occasional chips based on some starches. Still gives a relatively low total fructose load. Fructose without the antioxidants is probably even worse. I just don't accept that fruit in particular is healthy. It certainly tastes nice, so I'm perfectly willing to act as transport for a limited number of blackberry seeds...

There are some great papers from the WHEL (Women's Healthy Eating and Lifestyle) study I stumbled across today, along similar lines. Probably worth a post some time.


Anonymous said...


In the sidebar you state that you: eat a high fat diet, approximately 80% of calories from animal fat. What does this consist of? I think I saw somewhere that you eat a lot of heavy cream. I am considering trying this out with lard. (Your blog and Taubes' book gave me the idea.)

What I was wondering was, out of pure curiosity, what your body fat percentage is and what your cholesterol profile looks like.

Also, do you lift weights or exercise intensely in any manner? As I just recently started your blog, I apologize if I am not familiar with your day-to-day framework. Would love a post on this if possible. Thanks in advance and Happy New Year.

Peter said...

Hi varangy,

There's a reasonable summary of my food about half way down this column of comments, posted as my daughter Liz, as she'd borrowed my lap top and signed in to her own blog...

I'm cautious with UK lard as it often has BHT added as an antioxidant and there was a time when it was partially hydrogenated. In the UK dripping is just dripping (beef fat).

I exercise whenever my 12m old son lets me and it's usually resistance based.Climbing the steepest hill I have easy access to in the highest possible gear on my pushbike is the norm. No time for the gym. Not doing a lot at the moment.

I have access to a bench top clinical chemistry analyser at work and have never had a TC below 7.0mmol/l, whatever diet I was eating. My last full profile was TC 8.6mmol/l, trigs 0.85mmol/l, HDL 1.4mmol/l, LDL by calculation 6.7mmol/l. I get this done privately to avoid arguing with my GP, who is a nice guy but knows nothing about lipids. It came with referral advice to a specialist lipid clinic!

I'm 177cm, 64kg and 11-12% body fat, estimated from lower body by electrical impedence (Tanita scales). Early on in LC eating I dropped to 8-9% body fat and BMI 18.5%, just because I could. My wife complained and sitting around in the car for 4 hour journeys was too sore on the bum. Not healthy.

My HbA1c, probably a better marker for CVD, is 4.4%, low end of normal. That's fine by me.


ttlaitin said...

excelent post.

since so many studies indicate that "fruits are bad", the only way for the fruits to save their "reputation" would probably be hormesis.

for example exercise causes acute stress, which has health-effects in the long term. could the fruits/flavonoids/antioxidants have a similar effect?

and if they did, would be know about it? most studies are probably focusing on the acute effects only. the long-term effects must be very difficult to study.

either way, it's probably wise to avoid "over exercising" and not eat too many fruits.

Peter said...

Hi ttlaitin,

Thanks for that. Yes, hormesis may well apply. There's a post somewhere on Dr Eades' blog which suggests that low dose fructose improves insulin sensitivity. It's pretty obvious what getting 33% of your calories as HFCS does in terms of metabolic syndrome.....


PS Of course some of the time I just get carried away in response to the roaring silence which greets some excellent studies.

Peter said...

Hi varangy,

There's a post up with menu and Fitday analysis


Unknown said...

Hi Peter
Very interesting! I'm a nursing student and up to now all I've heard of uric acid has been it's association with disease.
I didn't know uric acid was an antioxidant too. So I did a quick lookup and wow am I surprised :D.

Uric acid might be (one) of the reasons that humans do not develop scurvy on a plant-free diet. In higher primates it is enzymatically transformed into vitamin c; it's not unreasonable to assume that maybe humans are capable of making limited use of uric acid in a similar way, when vitamin c intake is very very low.

It might be that uric acid follows need. If one eats a diet that is very good about causing oxidative stress (such as being high in carbohydrate, fructose) then uric acid levels rise, antioxidant status rises. Net effect, if the defense mechanism exceeds the damage, is greater protection against disease.

However, uric acid, like vitamin c, is thought to be prooxidative at excessive intakes. If damage is extreme and constant, this might cause very high uric acid, which only further contributes to the damage.

So maybe this is an argument for a "critical carb level"; when carb intake (oxidative damage) is in a certain range, (let's say, 30 to 120 grams hypothetically) then your damage/defense mechanisms are ideal. If the damage (carb intake) exceeds this, your defense system breaks and you're prone to disease.

Of course this assumes that "less is not better"; that the ideal defense against disease is at a low-moderate carb intake.
It might very well be true that the lower your carb intake, the more normal your antioxidant capacity.

Wouldn't it be funny if the association between fruits/veggies and less disease / aging isn't because of the fruits/veg themselves, but because in comparison to a normal way of eating a diet based on fruit and veg is starvation calorie (thus glucose-deficient by definition)?

Peter said...

Hi itsthewoo,

Do you have a ref for the enzymic conversion? I can't see the chemistry here. I realise that uric acid can replace ascorbate as an antioxidant, but that this is in a functional roll rather than a simple (or complex) chemical conversion.

Don't forget that glucose limits the uptake of ascorbate, as they both ride on the same transporter (GLUT4???). In hypeglycaemia you can forget ascorbate uptake from gut to blood or from blood to cells.


Unknown said...

Hi :D
I wikied it real quickly...

"In humans and higher primates, uric acid is the final oxidation product of purine catabolism. In most other mammals, the enzyme uricase further oxidizes uric acid to allantoin.[1] The loss of uricase in higher primates parallels the similar loss of the ability to synthesize ascorbic acid.[2] This may be because in higher primates uric acid (urate) partially replaces ascorbic acid.[3] Both urate and ascorbate are strong reducing agents (electron donors) and potent antioxidants. In humans, about half the antioxidant capacity of plasma comes from uric acid."

I took that to mean animals that make vitamin c turn uric acid to allantoin as part of vitamin c synthesis; but reading it again more carefully it seems like what it actually said is animals who can make vitamin c metabolize uric acid into allantoin as part of elimination (wheras higher primates who do not have the ability to synthesize vit c, also lost the ability to metabolize uric acid, perhaps to use it for an antioxidant). Oops :D
Either way it seems to imply that maybe uric acid can substitute for some of the functions of vit c; why else would loss of c synthesis occur with loss of metabolism of uric acid into allantoin?

Oh the bit about how sugar competes with vit c I knew already, attributed that to one of the reasons why I am a germ fortress and at best get minor symptoms for a few hours.

However I don't think this (lower glucose) can explain how people on no carb diets fail to develop deficiency, it is my understanding vitamin c must be consumed daily because it doesn't stay in the body long. Somehow the body must be compensating for the essential need for vitamin c. I was just wondering maybe other substances we do produce can fill in for these roles.

Doing another quick look up (carefully this time) it appears that eating organ meat will give a person enough vitamin c to meet the RDA. COmbined with the lower need on a carnivorous diet (most energy from fats) then it appears my question has been answered. Even a proper carnivorous diet provides c.

Dave Lull said...

Hi Peter,

Bix, just today, put up a posting titled "Raspberries Ward Off Cancers Of The Gastrointestinal Tract". She prefaces her list of a few studies and her summaries with these statements:

'Most of the abstracts referenced studies conducted previously that documented raspberries' benefits:

'Dietary administration of raspberries in animals "inhibited chemically induced oral, esophageal, and colon carcinogenesis."

'Dietary administration of raspberries in humans "reduced measures of oxidative stress, decreased DNA damage, inhibited cellular proliferation rates, and reduced levels of esophageal and colon preneoplasia in pre-clinical models."'

Are you familiar with the studies she cites?

BTW, she concludes with:

'An aside: None of the hundreds of abstracts found any cancer-fighting effect for meat consumption. (One of our commenters mentioned that Dr. Eades, author of "Protein Power" advocates a high-meat diet for cancer risk reduction.) The ones I did see found that meat consumption increased cancer risk. I have yet to come across any body of peer-reviewed cancer research which supports the hypothesis that a high-meat diet reduces cancer risk.'


Peter said...

Hi Dave,

I like raspberries, I grow the red ones in my garden. They're a tasty way to limit ketosis. They're not intended to save my life.

Perhaps the PPT and WHEL trials, full on intervention trials in real human beings, both of which failed utterly, did so due to a lack of black raspberries?

You know from the inulin post that you can prove almost anything with lab rat carcinogenesis models. Bix's lack of awareness of the bacon trial merely highlights the limitations of her reading. A bit like her lack of in-depth understanding of resistant starches, or any understanding of the gut microbiota for that matter. I presume she's never heard of conjugated linoleic acid from ruminant meat/milk and cancer protection. Just click on "related articles".

She doesn't cite the study you mention, she just talks about it without giving a reference. There are ways around this sort of behaviour. You can get the abstract here.

You'll note that they're again talking high dose carcinogens in rats, isolated cancer cells in petri dishes and some changes in oxidative markers in the urine of seriously ill humans. Well, that's nice, but there is still no suggestion that this antioxidant effect will reverse the precancerous changes in the oesophagi.

Barrett's oesophagus is primarily a complication of acid reflux, a condition I am very familiar with. It was due to having to sort out the VERY severe acid reflux of my wife which got me in to nutrition generally. Simply curing acid reflux by carbohydrate restriction is one of the easiest and most reliable effects of this type of diet. Going grain free, especially avoiding whole grains, is helpful too. There are no studies on this but Atkins/Groves/Lutz and I presume Eades too have written on this. LC cures most acid reflux problems. Better sort the basic problem out completely rather than apply a raspberry sticking plaster to the pre cancerous lesion developed after the failure of omeprazole (that's assuming the black raspberries should turn out to work in the real humans in the real world). You're aware of course that dumping all fruit and veg markedly improves antioxidant status in humans anyway, without raspberries.

BTW I believe Eades suggests a protein intake determined by a formula which ends up fairly close to 1g/kg lean body weight. For me that is only 50% above the absolute rock bottom minimum (about 40g/d). It's roughly what I eat. I've not read Eades' book, just his blog. I have absolutely no doubt that Bix hasn't read either. Doesn't stop her from misinforming her readers. High fat is where it's at, not high protein. Eades is certainly not stupid.

I doubt she has any grasp of the roll of insulin, ILGF1 and glucose in cancer development or progression either.


Dave Lull said...

Hi Peter,

Thanks for taking the time to respond.

Both you and Bix are much more knowledgeable than I am; you both give me a lot to think about.

I don't know whether she's ever seen the bacon research, but she has heard of conjugated linoleic acid in relation to cancer:

". . . some studies show that a certain trans fat called conjugated linoleic acid (CLA) can stem cancer progression. I don't know. But until a body of evidence can be assembled that shows that consuming dairy products (a food source for CLA) can stem cancer progression - a claim the National Dairy Council is chomping at the bit to substantiate by referring to test tube studies and nutrient interventions but not diet studies - then the CLA issue to me is just about a supplement, if it's an issue at all. It's not about food. (Especially when you consider the drawbacks of milk.)"

BTW, she devoted posts to Thoughts on Meat and Cancer and Meat and Cancer Part 2, in which she presents some of what she thinks might be evidence for this connection.

But she's also commented on studies that indicate that "[t]here appear to be benefits associated with saturated fat consumption[,]" though she concludes:

"That said, people differ in their response to fat in the diet. That's a really important piece of the puzzle, individual response. Some people respond better (weight loss, better serum lipids) with a low-fat diet, others with a low-carb/higher fat diet. (For example, the latter may be beneficial for a person with insulin resistance, low HDL and low LDL.) Broad recommendations are risky.

"So, I'm back to where I started. Some amount of saturated fat in the diet appears to be beneficial. But I don't want to take responsibility for someone construing that to mean I endorse a diet of double bacon cheeseburgers and Ben & Jerry's."

My self-experimentation with diet puts me in the responds better to "low-carb/higher fat" camp.


Peter said...

Hi Dave,

I just love that, CLA is a supplement and freeze dried black raspberries are a food!

As for the double bacon cheese burgers and Ben and Jerries: Dump the bun, make sure the cheese is made of old sour milk, not something disgusting processed from Kraft, extract the sucrose and any vegetabble derived fats from the icecream and replace with minimal glucose/honey plus real cream and I'm all for it. If it's all grass fed in origin I'm even more totally all for it. Re hormones etc, you must be aware the the UK banned the importation of american beef years ago. Personally I think this may well be a red herring, but certainly USA beef is not considered fit for human consumption in the UK!!!!!!!! But still much better than a Mars bar made with partially hydrogenated soya oil, or doughnuts fried in stale soya oil.

Re metabolic typing, here's a secret. You're a human. Low carb-high fat works for all of us! There may be some people in some circumstances, Kitava comes to mind, where high carb is OK, but putting a Kitavan on LC would work perfectly well. Putting Bix on a Kitava diet wouldn't (I assume she's a diabetic, presumably type 2). It's sad to see her trapped between her metabolic needs and her belief structures. Any frank diabetic not on Bernstein's plan (or similar) is in trouble. HbA1c must be below 6.0, below 5.0 is preferable. Doing this with a high carb diet risks fatal hypos by minor misjudgments of the industrial doses of insulin needed. Insulin doesn't care where the cabs come from, beans/whole grains or doughnuts are all just sugar. Butter isn't.


Dave Lull said...

Hi Peter,

Bix, in her posting "I have prediabetes," wrote:

"Or at least I thought I did. Last summer my fasting blood sugars were pushing 120 mg/dl. (100-125 is prediabetes, 126 or more is full-fledged diabetes). I went on a very low-carbohydrate, Atkins diet. My fasting sugars came down, hovering near 100.

"I went off the Atkins diet when I experienced some precancer, and when others in my family were diagnosed with cancer. I went on an animal-free, high-carbohydrate diet. Now, over 70% of my calories come from carbohydrate.* And my fasting blood sugars are always in the 70s!"

"* No flour or refined sugar."


Peter said...

An honorary Kitavan! On serious LC I suspect a FBG of 100mg/dl is normal, mine is always there, yet I have an HbA1c of 4.4%. I don't consider myself prediabetic. Again, you have to look deeper in to the physiology. There has been a lot of discussion as the to hows and whys of extreme high carbohydrate eating further up the blog. I don't think any of us seriously consider there is only one answer. In much the same way as I have come to realise that my own diet has done many things by accident (minimal fructose, minimal PUFA (espec omega 6), minimal sugar, zero MSG, no grains and a few more things along those lines. I'm accidentally getting a significant proportion of my calories as CLA. I'm willing to accept that Bix and Barnard are doing good things by accident too, I think Bruce would agree, in the same manner. Her opinions re cancer are her own. If one accepts that the common cancers are an aspect of metabolic syndrome, LC should do nothing but benefit. Unless you eat "healthy oils" rather than lard or butter. Summer to Winter also seems very quick to attribute the development of a pre cancer change to a few months change in diet. If animal fats were that bad that quickly I'd have been dead years ago!

The basic premise for health seems to be to get the sugar and flour out, plus the refined vegetable oils. Whether you go my route or Bix's, these aspects appear to be essential. I just look at the human intervention studies regarding fruit and veg and realise that the health aspects of fruit and vegetables so dear to the more extreme vegetarians are simply wrong.

I've read a little of Barnard but was to unable to continue due to my own personal reaction, acute nausea. From my point of view you can understand, I'm sure. Each to their own.


Feralandroid said...

I'm trying to understand the role of vitamins in a LC/HF diet. If we lower our veggies and fruits, how do we get adequate vitamins such as Potassium and Vit C? Do you feel that we do not need these if we are on a High Sat Fat diet? Do you have any references for this?


Daniel said...

This evidence against fruits and vegetables seems too casual to toss out, or even limit, a class of foods that seems so healthy. Reminds me the "fat is bad" theory used to toss out meat, eggs, cream - as you know, a really healthy class of food that was limited based on a flawed theory. Might it be the case that what good about fruits and vegetables is not their anti-oxidant capacity? Maybe the oxidants, in small amounts, act hormetically. Green tea might be good because it is a low dose of hydrogen peroxide and fruits may be good as a low dose of fructose?

Peter said...

Hi Dan, it's an interesting thought. I would certainly concur that antioxidant provision is no reason to eat fruit and veg. You could argue that damaging your DNA in minor amounts is good for you, as per Xray exposure. You then have to ask at what level of fruit and vegetable intake the toxicity becomes significant, as per Xrays, and should we be investigating the upper tolerable limits of toxicity from fruit and vegetables. A fascinating concept.

The other aspect to the Danish study is to differentiate between statistical and biological significance, this I've not given much thought to. Might be a better way to bring fruit and veg in from the cold here...

Ultimately the WHEL study suggest that huge intake of phytotoxins has no detectable all cause mortality effect, up or down, over seven years. Multivits take 14 years to show a benefit, so it is also possible (but getting tenuous) to argue 7 years is too short for the gifts to work over.

I dunno.

I still feel that small amounts make great flavourings but bulk vegetables are best used as cattle fodder.


Daniel said...

Peter, thanks for the reply in this old thread. I agree that our understanding of antioxidants is incomplete at best. Anyway, I look forward to your return from sabbatical. Best, Dan

robrob said...

interesting post there, tho alot of it makes sense, the part about fruits I have to comment, fruits are meant to be eaten by mammals that is why they are sweet and delicious. second many animals eat plants that other animals cant eat because their bodies can detoxify it. some monkeys I seen on tv eat plant leaves that are toxic to everyone else and do fine. second many veggies use chemicals to deter herbivores but no way does the mean they are bad for us. plants and what they do is not always selfish. my tomatoes and peppers and bean plants are seldom ever touched by anything but they are delicious to me and I would think if they harmed me my body would make them yucky, like kale is yucky no matter how you slice it. the body can use veggies chemicals as messengers or to fight off invasion by worms, microbes oxidation damage that sorta thing. the bible indicates man was allowed to eat the green vegetation and fruits of the trees.

Dragan said...

Hey Peter, this is completely unrelated but I see that you like to keep your vitamin D levels above 100 ng/ml. What do you think of Rhonda Patricks views that the optimal level is 40-60 ng/dl?