My head is truly spinning about this. I am confused. I know what works for me personally, but I wonder what you Paleohackers have to say about all this "safe starch stuff?"
Jimmy Moore just released this post on this very subject. Just for further information. If a better question can be gotten from this blog post, please someone have at it!
So it seems that more may be to come on this blog post from Jimmy. Just FYI.
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So he thinks that nearly everyone has diabetes and that glucose is always a glycating poison. OK, so why does the body still force (mostly via the metabolically costly, and one might argue toxic, process of gluconeogenesis) a blood glucose level of 70-100 mg/dL in zero carbers? Is that glycating proteins? Sure, who cares? Whether you're zero carb or zero food, the CNS and RBCs will require glucose and scavenge it one way or another.
Which is worse: A cortisol spike or a postprandial blood glucose spike?
Seems like another example of biochemical reductionism resulting in the demonization of an essential component of our physiology.
Handing your body a preformed version of something it wants (that in excess is toxic) is not the same as poisoning it.
Glycerol accounts for a little over 20% of glucose production during total starvation: http://www.ncbi.nlm.nih.gov/pubmed/7647479
disclaimer: i've been low carb and moderate to high starch and had good experiences with both being that my body was different in each situation. i'm not married to either position- i'm an ideological whore on this subject.
I find KGH a bit more convincing with his analogy that we have evolved to efficiently get energy from two different pathways in the context of a healthy body. i think dr. rosedale, whom i respect and think is right on so much, is overstating by saying everyone is diabetic to a degree. i find it odd how a lot of flailing happens when trying to explain the kitavans and okinawans when an occams razor-type explanation is that the populace is undamaged metabolically so they handle starch fine.
my less than $.02
A few points of info and clarification...
i.e. 'safe starches' and the study "Glycerol accounts for a little over 20% of glucose production during total starvation: http://www.ncbi.nlm.nih.gov/pubmed/7647479"
The following is the main point of that article; "These findings confirm that the contribution of glycerol to glucose production is directly correlated to its release as a consequence of lipolysis and support the notion that the central physiological role of accelerated lipolysis in fasting is the provision of gluconeogenic precursors."
In other words, the main point of the article is that burning fat results in glycerol used to make glucose. This is only after 4 days. The use of ketones and fatty acids as fuel continues to increase, and the need for glucose (and lean mass catabolism) declines as (carbohydrate and protein) starvation continues. Furthermore, eating fat and not starving will provide greater amounts of fatty acids and glycerol to be used as substrates for energy, reducing the need for glucose further than if one was starving..
Also, sometimes (usually? always?) the truth is more hidden than realized. Another main glucogenic precursor is lactate derived from glucose??? I.e. glucose is recycled, such that the glycerol used to make glucose is also used to make lactate that makes glucose??? This is called the Cori cycle. Glycerol use goes further than what appears on the surface.
For point of interest; George Cahill is considered an expert in this field..
Annu. Rev. Nutr. 2006. FUEL METABOLISM IN STARVATION George F. Cahill, Jr.! Department of Medicine, Harvard Medical School
p.9 "After several weeks of starvation??? Many studies suggest human brain cells can survive with little to no glucose"
But again, the major point is being missed; that there is plenty of substrate to provide all of the glucose necessary without having to eat it, if one is adapted to a high-fat, very low non-fiber carbohydrate diet.
A few other points;
It seems that many people have a hard time understanding that I am not advocating that what is ???natural??? is best. Dying soon after our children have a reasonable chance to make it on their own is very natural??? a very long post reproductive lifespan is not. What we are trying to do is live unnaturally long, and that's perfectly fine with me and I am endeavoring to find out how.
What I am talking about is optimal diet for optimal health, not just a better, healthier than SAD diet. If that's all we were talking about, then any diet other than the SAD would do. An optimal diet to me is one that might extend youth and maximal lifespan, not just average lifespan. There are no societies on earth that can reveal how to do this, not the Okinawans, not the Kitavans. However, the science of the biology of aging has powerful clues.
I am not saying that we do not need glucose. I'm saying that we do not need to go out of our way to eat it. I understand that glucose is needed for many functions such as cell recognition, manufacture of mucus, the immune system, etc. However, just eating glucose will not necessarily improve those functions, any more than eating extra protein will build more muscle, and will likely impair those functions. There must be an up regulation in genetic expression of enhanced immune system function for glucose to be utilized, and taking extra glucose will not do this; other factors and hormones regulate this. What glucose is necessary can be supplied without having to eat it and without the concurrent detrimental effects of non-enzymatic glycation and elevated insulin and leptin. That is what I am saying. I have also said that having zero carbohydrate intake is essentially impossible without starving. Cruciferous and other vegetables that I am in favor of, have sugar. Every non-starving animal will have some sugar, for better or for worse. We do not need to go out of our way to have more, as so-called 'safe starch' proponents advocate.
As such, what Jaminet is recommending is a self-fulfilling prophecy; requiring the consumption of glucose forming carbohydrates such as potatoes and rice increases blood glucose and insulin enough to greatly reduce ketone production, necessitating the use of glucose by the brain. This is not good. I have talked decades about the change in brain function when it converts from glucose to primarily ketone use; it becomes much healthier. Studies are now pouring in on the connection between glucose and chronic brain diseases. Jaminet rightly mentions the benefit of increasing ketone use in epilepsy. Epilepsy is an extreme of an over excitable brain. Is it possible that a brain primarily burning ketones as its primary fuel may function better all of the time? I believe strongly that the answer to this is yes- rosedale
Maybe in order to understand starches we have to look at that word itself. STARCHES. Basically, it's made up of two separate words "star" and "ches". What do these words really mean? It's a mystery and that's why so are starches.
On top of that, I tend to agree with Kurt Harris and Paul Jaminet. If I were a caveman, I sure as heck would like to find some potatoes (err, I mean taro) and fill myself up. Underground storage organs rule, as long as you don't need to be low carb for a special reason. Also, I wish Rosedale explained these things more, because they don't make immediate sense to me.:
"Also, there is really no totally safe level of blood sugar that will not cause non-enzymatic glycation or damage."
"...the fact that glucose spikes leptin still places sugars, including glucose from so-called "safe starches" and fructose, at the centerpiece of obesity and disease."
"Though my knowledge of the Kitavans is less, I believe much the same applies to them, and there are similar myths based on poor science and falsities that is being written about them that unfortunately is getting much unwarranted publicity."
@Dr. Harris and for clarifications;
Dr Harris; "It makes absolutely no sense that neurons only start using ketone bodies under nutritional stress- glucose shortage - if that is the "best"
You are making a huge and false assumption; that glucose shortage is equivalent to nutritional stress. The brain's use of ketones may be very natural and likely much more prevalent during much of our evolution, and indeed our human brain did not likely evolve on glucose???see 'Expensive Tissue Hypothesis' cited several times. The brain uses ketones when they are available, i.e.when glucose is not.
You say I said, "It makes sense if excess sugar is poisonous to the body." I do not believe that came from me, though I do not necessarily disagree with the statement.
Dr. Harris; "You are suggesting that the brain only uses glucose as a favor to buffer us from excess glycation?"
I do not know that that is what the statement was suggesting if I didn't say it, however that is not altogether a bad reason???but not the only reason. The brain burns lots of glucose when it is available because it can and when the subsequent toxic effects are not severe enough until after we have had a chance to reproduce, preventing evolution from having selected against it, and where the effects of burning it, such as reduced glycation, offers benefit.
Dr. Harris "If that is so, why does it [ketone burning?] stop at 60% of energy needs."
Dr. Harris; "Why use any glucose at all and why make the liver engage in GNG to provide it - using precious energy while you are starving?"
For the tissues that need it I suppose???it takes energy to stay alive??? Furthermore, I suspect that it takes far less energy to derive the necessary glucose via GNG from glycerol or lactate than having to eat and digest it from starches when not starving.
Dr. Harris; "PP BG increases do not cause hyperinsulinemia."
Wrong. Have you ever measured glucose, insulin and insulin resistance in people before and after eating. If you had, I do not think you would make that statement. Glucose and insulin will spike after eating starch, insulin following glucose, particularly rice and potatoes, in some more than others, in those already quite resistant, and those not very, and will do so often to a greater degree in a child that has not yet had much chance to become insulin resistant. In fact some believe, including myself, that cells become resistant to insulin, partially to help protect from intracellular glycation. The major damage from glycation occurs in those tissues where glucose entry is largely not mediated by insulin such as nerves, endothelium, basement membrane of kidneys, etc seen so regularly in diabetics. And talking about stress; raising glucose raises insulin, raises leptin, and this stimulates the SNS???raising glucose..
Dr. Harris; "Pathological insulin resistance causes hyperinsulinemia [rather than PPBG]."
Incomplete. What causes the pathological insulin resistance? Glucotoxicity of receptors, overuse of insulin receptors that cannot be recycled fast enough, fatty liver secondary to hyperleptinemia, etc..
You say I said, "There are no redundant systems in the body to control for blood sugar except utilisation, so ... you must utilise it to get rid of it."
Where is that said?
Dr. Harris; "The liver is a large and flexible buffer that in normal people can soak up huge amounts of glucose."
Yes???and your point? Isn't the liver utilizing it then?,,,and doesn't it need instructions to do so? and isn't the liver one of the first and main organs that becomes dysfunctional with insulin and leptin resistance?
Dr. Harris; "All of these systems demonizing dietary carbohydrate fatally conflate glucose as a cellular fuel with glucose in the diet. Hyperglycemia and subsequent glycation is caused by failed glucoregulation, not dietary glucose in "spikes"???"
Hyperglycemia happens after one eats starch/glucose. It is made worse by failed glucoregulation that elevated glucose/spikes in glucose, spikes in leptin helps to cause.
Dr. Harris; "Why did we not evolve to be more independent of the need for glucose at the cellular level?"
To have an anaerobic fuel supply???for fight and flight..
Dr. Harris; "it [glucose] is valuable. Our neurons literally die without it. Period.The reason the brain can run partially on ketones is SO THAT IT CAN LAST LONGER ON LIMITED GLUCOSE WITHOUT DYING."
Since you apparently are still misunderstanding what I and others are saying, and since you like so much to capitalize so we can see better; NO ONE IS SAYING GLUCOSE IS NOT VALUABLE OR NECESSARY. All WE ARE SAYING IS THAT WE SHOULDN'T GO OUT OF OUR WAY TO EAT IT.
"It makes absolutely no sense that neurons only start using ketone bodies under nutritional stress- glucose shortage - if that is the "best"
It makes sense if excess sugar is poisonous to the body.
You are suggesting that the brain only uses glucose as a favor to buffer us from excess glycation? So it "prefers" ketones, but only gets to use them when we are avoiding "toxic" glucose in the diet. If that is so, why does it stop at 60% of energy needs. Why use any glucose at all and why make the liver engage in GNG to provide it - using precious energy while you are starving?
" There are no redudant systems in the body to control for blood sugar except utilisation, so ... you must utilise it to get rid of it."
Well, no. The liver is a large and flexible buffer that in normal people can soak up huge amounts of glucose, and as you know even if you never eat a molecule of glucose, it will flood your bloodstream with demonically glycating glucose if for even a minute it stops hearing, or listening to, insulin.
All of these systems demonizing dietary carbohydrate fatally conflate glucose as a cellular fuel with glucose in the diet. Hyperglycemia and subsequent glycation is cause by failed glucoregulation, not dietary glucose in "spikes"...
Why did we not evolve to be more independent of the need for glucose at the cellular level? Neurons and red cells require glucose.
"Insulin is the only hormone that promotes that. If sugar was so valuable we would have some redudancy I guess."
But it is valuable. Our neurons literally die without it. Period.
The reason the brain can run partially on ketones is SO THAT IT CAN LAST LONGER ON LIMITED GLUCOSE WITHOUT DYING.
Nutritional monotheism, all. And what all forms of monotheism seem to require is: a devil, against which to rally and rail.
"May God us keep From Single vision & Newton's sleep." ???Blake
What Rosedale claims is may be even close to truth. That we are all diabetics, he may be right.
In several contexts, there is considerable theoretical and experimental evidence that ascorbate (or ascorbic acid, also called vit. C, although it is not a vitamin) is much more effective if blood glucose is in the low range, i.e., 50-90 mg/deciliter (mg/dL) (2-6). This was normal until the 1900's and is still seen today where the primitive (unrefined) diet prevails but blood glucose is only half the glycemic levels typical of affluence (6,7).
During the Calcutta Diabetes Study, the 2-hour postprandial blood glucose values for non-diabetic humans aged 40 to 70 in India were reported to range from 50 to 90 mg/dl. However, in a long term investigation of 1400 people in the U.S., decadal age group medians for the same 2-hour values were reported to range from 105 to 122 mg/dl in nondiabetic 40 to 70 year olds ; this distribution is completely disjoint from the Indian median values (which clearly must fall inside the 50 to 90 range reported above). In addition, the 2-hour GTT values are observed to rise circa 10% per decade of age in the U.S 
The situation is probably similar to what we know about some other nutrients - for instance vitamin D level that is now accepted as normal is far bellow what many D experts consider healthy.
I don't get the Jaminets conclusion about glucose deficiency. First, if such thing exists, it would be seen via sugar meter. If my blood glucose is between 4-6 (72-108) then I don't have a deficiency as deficieny would cause hypoglicemia - bg less then 3.8 (68.4). Second, its well known that higher CHO content equals to less vitamin C availability:
There exists in the scientific literature a wealth of data that explains the role of ascorbic acid in immune system function and documents its requirement for greater than micronutrient quantities to fight infections. The inhibitory effect by glucose of the actions of ascorbic acid could well explain the lack of beneficial effect of ascorbic administration in many studies reported in the literature because few, if any, such studies controlled for dietary carbohydrates. In light of the current dietary sugar excesses and concomitant obesity epidemic, clinicians should be reminded of the great importance of the long recognized but largely unappreciated inhibitory action of glucose against ascorbic acid. In summary, ascorbic acid is essential for effective immune system function and, further, it can be a potent immune system stimulator when high glycemic dietary carbohydrates are restricted.
I guess it boils down mostly to not eating refined stuff, not eating potatoes or rice with every meal and use moderate quantities and ofc, rarely eat any fruits. This depends a lot on your physical activity also. You can tolerate more carbs if you are more active, particularly ananerobic type of activity.
Lets also not forget that Jaminet might be biased as he has/had fungal infections which might get worse on ketogenic diet. Stubby says also "but he says that we do need some starch because low carb vegetables don't allow the glucose to absorb quickly enough and it gets gobbled up by gut flora.", but gut flora works in the colon and glucose is absorbed in stomach and small intestines which keep far far lesser amounts of gut flora. AFAIK, he actually said that those low amounts of glucose would be used ASAP to power digestion. And again, there is that vitamin c inhibition thing. We now know that glucose can't inhibit it completely though, as another type of receptor for VC is found (SVCT1/2), but some systems don't have it expressed, for instance brain's blood barrier. It seems to get expressed after a stroke though which tells about importance of proper C metabolism.
All this said, I think Rosedale can be very wrong, he for instance claims that saturated fat is "second generation carbohydrate" which is ... well.. nonsense. Everything is 2nd or 3td generation something.
I don't see a point in dissecting isolating communities like Kitawians because you can't ever isolate variables correctly - they live different life, in different world, with different air and water with different environmental toxins with different eating habits with different pregnancies, different activities etc... nothing can be further from city life. I think its best to concentrate on what current state of physiology has to tell us.
At the end, I must say that Fiona summed it up the best possible:
The body needs glucose.. you just don't need to eat it.. ??? Fiona
At issue is whether post-prandial BG spikes are harmful even though it's temporary. In a healthy person, post-prandial BG spikes return to normal (fasting) quickly after 60 minutes and well before 120 minutes. Normally, this would not result in "chronic" insulin nor leptin elevation.
However, Rosedale says that even a temporary BG spike is bad, because it will spike insulin and leptin as well, albeit temporarily. Is the quick deployment of insulin/leptin to deal with spiking BG bad? Is this gonna still result in all the ailments associated with chronically elevated insulin/leptin: cancer, AGEs, glycation, autoimmunity, etc.?
I don't think so. Just about every tribal group (except those Inuits and Masais) have subsisted on starches -- healthy starches that entail insulin spikes. Starch-based diets far outnumber ketogenic diets. Yet, as long as the starches are "safe" they will not lead to diabetes. No one got diabetes by eating potatoes, yams, sweet potatoes, even tropical fruits like watermelon or mangoes. At least not to our knowledge.
What is Rosedale mising? Some of us tend to think it's gluten (white flour) and sugar (fructose), but not endogenous sugar in fruits nor carbs in starchy whole foods.
I think that sites comments are limiting [bad stackoverflow] so let me react in another post.
"that you can game the system is not uncommon in medicine, and not particularly effective either" [Harris]
But if we ignore non-medical interests, medicine did find some valuable gems. Its general failure when chronic disease are in question may have nothing to do with potential ability of the body to be improved in unnatural ways, it means that it sucks at it at the current stage. We are nothing more then complex machines. Every machine can get overclocked the safe way.
"It makes absolutely no sense that neurons only start using ketone bodies under nutritional stress- glucose shortage - if that is the "best" [Haris]
It makes sense if excess sugar is poisonous to the body. There are no redudant systems in the body to control for blood sugar except utilisation, so ... you must utilise it to get rid of it. Insulin is the only hormone that promotes that. If sugar was so valuable we would have some redudancy I guess.
"Ambi, those studies also showed susceptibility to kidney stones and other complications that beset ketogenic diets." [Namby]
Its much more probable that you had Mg or C deficiency. Ketogenic diets can be applied wrong. Since you are T2DM you are surelly C deficient, its well known fact about diabets. Drop from 5.7 to 5.5 A1C is meaningless IMO.
"I agree with PHD 100% on this mainly because I've experienced the very same complications while on a ketogenic diet: constipation due to mucosal dryness" [Namby]
Perceived constipation might be because you have reduced stool content on ketogenic diet becaue nutrients are fully absorbed unlike most of the complex CHO. There is also an option that you didn't eat enough fat.
"fainting spells when getting up from a chair" [Namby]
This is probably mineral disbalance [not enough salt for instance]. You need to supplement because humans mostly eat animal muscles. If you did exercise like all T2DM are suggested then this would make it worse.
"and low LIBIDO" [Namby]
Possible zinc deficiency if you are a man.
As you can see all your problems could be described the other ways. I don't claim its not about lack of CHO, there are beneficial things coming up with CHO, like flavonoids but those are available in vegtables and nuts too.
I think its notoriously easy to get malnourished on any weight loss diet and ketogenic diet further limit food chocices. Industrial animals are also deficient themselves and you can't really be sure how is animal treated.
It seems that many people have a hard time understanding that I am not advocating that what is ???natural??? is best. Dying soon after our children have a reasonable chance to make it on their own is very natural??? a very long post reproductive lifespan is not. What we are trying to do is live unnaturally long, and that's perfectly fine with me and I am endeavoring to find out how. [Rosedale]
Amen! That is true hacking spirit.
Do you know what's kind of scary? I've lived in Sweden and the people there are thinner, eat better, and get more exercise. They have all the appearance of a fairly healthy people. But when Dr. Lindeberg looked at their blood glucose levels compared to Kitavans, the Kitavans have lower blood fasting glucose and maintain this throughout age, whereas in the Swedes it ends up climbing higher and higher. So the evidence is that even somewhat "healthy" Westerners who don't have diabetes experience aging of that system.
In his book Lindeberg emphasizes both the fact that refined sugars screw this up, but that more and more scientists believe it has an autoimmune component. The wheat lectin can also bind to insulin receptors.
In Rosedale's article measuring his diet's effect on what he thinks are markers of aging, his diet did improve their markers, but they don't even approach those of the Kitavans or fish-eating Tanzanians. I know it's not a real study (if doctors and their clinical anecdotes ran science we'd still be bleeding patients for sore throats) and the patients were sick, but there is simply no proof out there that the low-carb high-fat diet has an anti-aging advantage. Ethnographic studies can only tell us so much, but since there already exist cultures eating a high-fat low-carb diet and they are unexceptional in regards to longevity, we can rule out this as the answer to our aging woes.
Don't forget all doctors are not scientists. If I listened to doctors and didn't delve into real scientific data, I'd still be overweight and sick. And guess what? If you are selling a low-carb diet, making your money off of it, it does suck that the pillars of the paleo community are abandoning it.
I'm also really disturbed by Dr. Rosedale's misuse of paleoanthropology. He claims that the Expensive Tissue Hypothesis proves the human brain evolved for a keto optimum and a high-fat diet. I have had the pleasure to study under one of the reviewers of the original Expensive Tissue Hypothesis paper and there is absolutely no consensus on the matter on paleoanthropology and no one I know of believes in a keto optimum, even keto-friendly people working in the area like Stephan Cunnane. The consensus is that high quality food was the fuel for the expensive tissue, but what fuel that is remains under heavy debate. My own research interest is looking into whether fat was high in the ancient paleolithic African diet, but it is a very fringe interest and even I will admit that. Most papers show that African game and the African ancestral environment is low in fat. I'm looking to argue against that, but not because I think keto is optimum, but because I think fat is an important nutrient for humans and I do think our ancestors used both the keto and glucose burning systems on and off. The vast majority of researchers focusing on the high-quality food are looking at protein and that's how I got into it, because Cordain cites that research to advise people to eat lean meats. Richard Wrangham of Harvard is arguing for roots and tubers. Rosedale is playing on people's relative ignorance of this debate and of paleoanthropology in order to espouse an absurd fringe theory and sell his diet books.
In my own experience, I had rather poor blood fasting glucose when I was 17 and now it is much much lower. It has remained low throughout my relatively high and low carb diets. If we truly all had diabetes, our markers of the damage that makes that disease so problematic would be increasing.
This guy loves to put words in your mouth you have never said.
Not diggin his methods even though we agree on most things but a few
One thing is for sure, we need more evidence. That will mean more funding for more studies that are conducted using the proper scientific method and without bias.
Dream on Rhubarb, dream on.
As always it depends on the individual. Humans have existed and thrived on many different diets.
I think it up to us to tweak our diets, and react based on our energy levels and overall health. For example, if you are feeling a bit lethargic, try adding in some safe starches. If you are able to tolerate and it resolves your issue continue.
I don't think we have to be so black or white on this. We should allow a healthy spectrum from low to carb to moderate carb all eating healthy safe foods.
fyi all, i have just seen that Paul Jaminet has posted a reply to Dr Rosedale here;
Well, the evangelist picture/quotation certainly isn't helpful. Whassup wid dat?? We're all different degrees of diabetic? Why must low carbers employ such hyperbole?
There is NO evidence that postprandial insulin spikes and BG spikes cause diabetes. Heck, even the current conversion rate from prediabetes to frank diabetes on the SAD is in the low single digit percents. The progression goes through insulin resistance, and carbs do not cause IR.
As regards glycation, the first step is a reversible equilibrium. A little bit goes down the path with a glucose spike, then hops back off when glucose falls. It's the chronic elevation that causes problems. I can't find the post at the moment on Ned Koch's blog, but the risk curve for HbA1c makes a shallow U around "normal" -- risk is slightly elevated as much for very low than for slightly high. The curve really takes off after that.
Diabetes is not a continuum. There's a clear "switch" from compensators to beta cell dysfunction. We see it in both directions where GBP, intense early insulin therapy, and that crash diet all have been known to restore normal glycemic control in diabetics in rather short timeframes.
I'm going with the "it all depends" stance. There are so many variables within variables so that what is safe for one person is not for another. Of the research cited in these articles, was there a difference between male and female; what about oriental vs. European; what about age differences. Even if the group was really focused such as all male northern European in the age range of 30-35, there are still variables of lifestyle, genetics, etc.
We all know that some foods are going to be better, for example, between a grocery store apple imported from China v. organic from your own tree, your own tree wins. Then we can get into the argument of how well the produce is grown since fertile soil (organic, of course) will produce a better item than worn-out soil.
Then there is what is the basis for this declaration; what were the assumptions in the study; what was the theory did it start with; what other information arose from the study; and even was the entire study valid.
It all comes down to knowing your body, what it needs, and being aware it all changes, then skip over the rest of the noise.
Many low-carb people just don't believe that our ancestors could have eaten carb-heavy diets. We saw this at the 2012 AHS again. These people still cling to the romantic notion that the hunter-gatherers mainly lived off of animal carcasses. All cultures more or less thrived on a starch-based diet. In fact, the new book by the vegan guru, Dr. McDougall, is largely correct that most indigenous tribes and even pre-agricultural civlizations depended on a few staple starches.
Of course, they also ate animal carcasses. (Except perhaps Pacific Islanders, who ate fish and marine life). That's why it's so shocking when confronted with the evidence that the Okinawans ate lots of carbs, mostly their purple sweet potatoes. Many used to claim that the Okinawans ate mainly pork and fiber-rich vegetables. Mention the Kitavans or the Highlanders of New Guinea, and the low-carb camp will still deny that they ate a carb-heavy diet centering on tubers.
As always, the answer is in the genes. It's why Jeanne Calment lived to the age of 122 whilst smoking till 117. She did, however, consume a lot of olive oil. And chocolate. Does this mean if she avoided chocolate and cigarettes she would have lived till 140?
Most of us do not carry her genes and according to actuarial tables can expect to live 65% of her lifespan. There is evidence that paleo-type diets will improve healthspan but no evidence on extending lifespan (other than avoiding premature death due to gross pathology rather than frailty). In fact, for humans, there is no known intervention that has been shown to increase lifespan.
In any case, I intuitively tend to lean towards Rosedale's position. Carbs appear to be problematic for most people, particularly as they get older or become more sedentary, causing metabolic dysregulation. Also, many types of carbs end up as food for gut bacteria and this is another dimension to the carb problem when you take into account that people also have different gut bacteria populations.
However, the unavoidable fact is that people like eating carbs and - in a world of endless abundance and variety of carb based foods - will continue to consume them and find ways of rationalising their consumption. Therefore Jaminet's position is the more pragmatic.
Looking towards the future, it's more likely we will end up altering our genome (ala The Bourne Legacy) and that of our gut bacteria to accomodate carb intake rather than eliminate from our diet.
and so it goes.. new debates now with Kresser and Rosedale.. http://drrosedale.com/blog/2012/08/18/a-conclusion-to-the-safe-starch-debate-by-answering-four-questions/
Of COURSE our ancestors ate low carb/high fat. I have no doubt that Grok probably chowed down on things like this - http://livinlavidalowcarb.com/blog/jimmy-moores-n1-experiments-nutritional-ketosis-day-61-90/15125.