This may seem like a strange thing to argue about, because the popular consensus still seems to be that juice is healthy. Jamba Juice markets itself as "the category-defining leader in healthy blended beverages, juices, and good-for-you snacks." They even use Jamba as an adjective to mean the opposite of high fructose corn syrup and trans-fats (adding those things to juice ""just wouldn't be Jamba"), which again, constructs the brand as healthy vs. the demon poisons that make people fat. Even if it's foolish to go looking for truths in advertising, I don't think Jamba Juice's branding generally occurs to people as a massive irony or lie. Advocates of banning or restricting soda vending machines in schools often claim that the soda should be replaced with 100% fruit juice with no added sugars, and for many people, a glass of orange juice still represents "part of a nutritious breakfast" strongly with desirable nutrients like Vitamin C.
The Case Against Juice
But a number of health trends have begun cast suspicion on juice, especially the (impartial and incomplete) shift from primarily low-fat to primarily low-calorie and low-carb dieting in mainstream weight-loss culture, and the growing concern about the role sugars (especially fructose) play in personal and national obesity.
On the low-calorie front, people who believe that losing weight or maintaining a healthy weight is all about the basic algebra of calories-in vs. calories-out often end up axing all caloric beverages from their diets because they have a bad satiety-to-calorie ratio—I mean, obviously, right? Fruit juice is just fruit with some or all of the filling fiber removed. If the goal is maximum satiety on minimum calories, you're better off eating whole fruit and drinking water or artificially sweetened beverages.
On the low-carb front, people who believe that what's important is not how many calories you eat but what kind are also going to see juice (and sometimes most fruits and vegetables as well) as "unhealthy." It does seem to be true that diets high in carbohydrates drive up insulin levels, slowing metabolism and encouraging the body to store fat. And the overwhelming majority of the calories in most fruit juices are in the form of carbohydrates. Some green vegetable juices have protein content approaching 50% of the carbohydrate content, but that just makes it 75% bad rather than 100% bad, at least as true carbophobes are concerned.
And finally, there are some non-carbophobes who might avoid juice because they're wary of sugar qua sugar, rather than sugar qua carbohydrate. The carbohydrates in fruit juice primarily take the form of fructose—wikipedia has a handy chart of the kinds of sugars in common plant foods. It doesn't seem like there's a true consensus yet about whether or not fructose is especially bad—despite recent studies linking fructose to obesity, even within the medical community, some people still advocate fructose as a "low glycemic" sugar that's better for diabetics. It basically all comes down to whether you think the fact that fructose is digested in the liver and doesn't trigger insulin production is a good thing or a bad thing. To link it to other sugar purveyors: pro-agave nectar people should also think that fruit juice is healthy and people who think hfcs is bad because they think it's "high fructose" compared to other sugars are, well, a) wrong, but b) should also be advocating hfcs-sweetened sodas over fruit juices, which are even richer in sugar.
Personally, I think the evidence that fructose in large amounts causes equivalent blood sugar spikes to other sugar, increased "bad" cholesterol and triglycerides and signs of insulin resistance compared to glucose, and can cause non-alcoholic fatty liver disease consumed in vast quantities suggests that it is certainly no better and possibly much worse for human health than glucose or sucrose. But "worse for human health" is relative, not absolute, and depends a lot on amount, kind, and context.
What is health?
I'm generally convinced by the argument made by people like Gary Taubes that a diet composed of almost-exclusively proteins and fats might better represent the pre-agricultural, hunter-gatherer diet (as would cyclical feast and famine) and prevent carbohydrate-induced insulin resistance and fat storage. Jared Diamond makes some of the same points in Guns, Germs, and Steel. But the benefits of agriculture ultimately outweighed the costs—both for the species as a whole and measured by individual health metrics. In the immediate aftermath of the transition to agriculture, lifespans and average height decreased, but after a few thousand years, people depending on rice, corn, and wheat began to get healthier again.
Does that mean carbohydrates are a healthier basis for a diet than proteins and fats? No. But it does mean that people can (and do) live very long lives uninterrupted by diet-based disease during which they are strong and energetic enough to physically do anything they want to do while eating a diet consisting substantially of carbohydrates. And I think that's not a bad working definition of "healthy."
It seems to me that the debate comes down to a difference between ideas about nutritional "health" based on what might be theoretically optimal (for a very limited set of criteria), ideas about health based on potential pathology, and ideas about health based on actual health outcomes.
Fear of juice is based on the first two—the idea that either people should eat as few carbohydrates as possible in pursuit of some sort of optimal diet, or that the fructose in juice will cause fatness (an aesthetic problem, not a medical problem) or disease and eventually death. Based on actual health outcomes, I think it would be almost impossible to make a case for the claim that drinking fruit juice—occasionally or regularly—is categorically unhealthy or the direct cause of disease or death.
In fact, things like fruit juice and hamburgers and Doritos, which can each be constructed as "unhealthy" are hard to entirely rule out of a "healthy diet." Even proponents of a soda tax generally agree that the only reason soda is a reasonable target is because it has no identified nutrients (what would happen if they fortified them, I wonder?).
The nutrient-density of juice is the primary reason for the long tradition of juice being regarded as a health food. If your concern is about essential vitamins and minerals (like many older models of nutrition, which people like Marion Nestle stand by) or consuming carbohydrates for fuel, which many physically active people still do, it's hard to argue with the healthfulness of juice. I agree with Michael Pollan's claim that popular beliefs about health often fall prey to "nutritionism," or the attempt to reduce food and nutrition to scientifically-identified nutrients and vitamins. At the same time, I don't think you have to be brainwashed by the continued prevalence of nutritionism to believe there's good evidence that many of the nutrients that scientists have identified are actually valuable or promote health and well-being (even if they're not the only valuable aspects of food).
All juices are not created equal
The person who requested this entry was concerned specifically about fresh juices being portrayed as unhealthy, because they seem to have been smeared by concerns about packaged juices being just other source of dietary sugar.
While not all fruits lend themselves as readily to the production of refined sugars as sugar beets, some like apples, pears, and grapes can be turned into a nutrient-poor sweetener without most of the fruits' color, flavor, or minerals and many fruit juices marketed as 100% natural fruit juices, like Juicy Juice, are sweetened with fruit juice that's basically been turned into a sugar syrup. The nutritional distinction between those drinks and hfcs-sweetened soda is probably negligible regardless of whether your primary concern is calories, carbohydrates, sugar, or vitamins.
But the reason packaged juices often combined with fruit-based sugar is that many fruit juices aren't actually that sweet on their own, or their sweetness is offset by the intensity of the flavor, as anyone who's ever tried 100% cranberry or concord grape or cherry or blueberry juice knows. The fresh juices you can get at juice bars or make at home are calorie-dense, but they're also extraordinarily nutrient dense and not likely to be consumed in quantity or alongside meals. They're more often enjoyed on their own, like a snack, particularly after a workout—basically just like fruit. When you leave in some of the pulp, it becomes even less nutritionally distinct from fruit, and when you include vegetable juices or the juices of things like wheatgrass and ginger which are difficult or unpleasant to eat raw, you may be enjoying something that could, by some criteria, be healthier than a piece of fresh fruit.
Some juices even have pretty well-established medicinal uses. Cranberry juice, for example, can help prevent and cure urinary tract infections (that study notes the existence of "diet" cranberry juice, which I'd never heard of, but now that I have I wonder why there aren't more "diet" juices sweetened with artificial sweeteners rather than pear or grape juice-sugar. Not that those would necessarily be "healthy" by everyone's standards, especially given the links between saccharin and cancer and suspicions about the healthfulness of aspartame and sucralose…)
Ultimately, while I don't think even the occasional hfcs-sweetened Capri Sun is incompatible with a "healthy" diet and life, I think it's unreasonable to conflate fresh juice without added sweeteners with juices sweetened with refined juice-sugar. I guess people trying to eat an "optimal" diet a la Gary Taubes should avoid all juices, fresh or no, but I don't envy them their carbohydrate-less life, nor am I convinced that the total deprivation of many foods that have aesthetic, gustatory, social and/or cultural value is necessarily "healthy" or "optimal" either. For the vast majority of people who think fruit and vegetables are part of a healthy diet, fruit juice and especially fresh fruit juice should also pass muster as a "healthy" choice especially when consumed in moderation, which I suspect fresh fruit juices usually are.
I share your praise of Pollan
I share your praise of Pollan and for that reason--the key to eating successfully (whether in terms of health or enjoyment) seems to lie in a constant variety--different food groups, different nutrients, with carbs just as necessary as any others (and a carb-free diet a bizarre idea). I always thought the argument against fruit juices seemed more aesthetic and cultural than purely scientific (although I may be prejudiced as I love grape juice)--the idea that you aren't getting the "natural" experience either by drinking juice in the first place or by drinking pulp-free varieties. Of course, there often seem to be the same kinds of people who tout an imaginary past (culinary or otherwise) as a plausible or desirable future.
Did I ever tell you about the Steven Seagal energy drink ("drink his juice and gain his power!")?
Asian Experience in a can!
yeah, the construction of what is and isn't "natural" often relies on romantic fantasies of the past.
I had to google the Seagal energy drink. A-ma-zing. One of the flavors is "Asian Experience." Unbelievable.
To be fair, no one has ever
To be fair, no one has ever said that one needs to completely expunge carbohydrates from one's diet (though it does seem that they are nutritionally unnecessary). The issue is more a matter of the health consequences of the drastic change in carbohydrate (and especially sugar) intake in the last couple of centuries. As of the middle of the 18th century, we were consuming on average 10-20 pounds of sugar per year; currently it is about 150 pounds per year. To bring juice into the equation, if someone drinks 12 oz of orange juice a day that already amounts to roughly 30 pounds of sugar a year. You'd have to eat 4 or so oranges to get the same amount of sugar. Obviously, this doesn't mean you should never have juice, but it seems fair that people should know what the consequences of consuming their food may or may not be--this does not change if the effects are relative to context. Lions may only be a danger in the context of an African savannah, but I still need to know as much if I live in an African savannah.
My understanding is that the notion that fructose does not induce insulin production is not quite true--it can do so in an indirect fashion: when a relatively high fructose diet is consumed, the fructose can block the metabolism of glucose in the liver, and prevent its storage as glycogen; this causes the pancreas to secrete more insulin to take care of the excess glucose that is thus blocked from leaving the bloodstream.
Also, someone wanting to lose weight for whatever reason would I think certainly appreciate the knowledge that certain things that they were told were a part of a "healthy" lifestyle were actively impeding that weight loss. (Incidentally, I have to add my own anecdotal statement to the efficacy of low carb diets--I've lost 30 pounds over the summer, and without once trying to limit my total caloric intake, and while simultaneously being much lazier at exercising than I had been formerly while maintaining a constant weight; I haven't even been too strict about eating carbful meals occasionally. And, oddly enough, I used to feel cravings fpr bread/potatoes--those have almost disappeared.)
I've got a disagreement or two about the notion of "healthy", but I think I'll leave that for another time--this comment is already too long.
As noted, I agree that
As noted, I agree that carbohydrates may be nutritionally unnecessary but I don't think that makes them "unhealthy." I'm glad low-carb seems to be effective as a weight-loss diet for you and that you seem to have gotten over a potential carb addiction--I hope your experience with weight loss ends up being statistically anomalous and lasts over 1-3 years.
I think most people have a much, much harder time breaking carb addictions and there's other research Taubes left out of his book that challenges the notion that the kind of calories really matters more than the quantity, which this reviewer mentions: http://www.nytimes.com/2007/10/07/books/review/Kolata-t.html Most research on low-carb diets suggests that when people eliminate carbohydrates they also end up eating many fewer calories than previously, which would at least contribute to their weight-loss. Also, it appears difficult or impossible for most people to maintain over long periods of time. But many people may have a more complex emotional attachment to what Kessler calls "highly palatable foods" than you do/did and require continual applications of willpower to avoid carbohydrate-rich food, meaning they're pretty much doomed to fail over the long run.
I think demonizing foods can also complicate the emotional relationship to food--for example, children who are outright forbidden from drinking soda and juice and eating candy at home may binge when at friends' houses and often carry a sense that some foods are "bad" and guilt-inducing but highly desirable into adulthood when they have a much harder time eating things in moderation or respond to emotional traumas by binging on carbohydrate-rich foods.
I also think people who think they ought to lose weight might also appreciate knowing that obesity is not itself a disease or a cause of disease and people who are active but obese have much better health than people who are "normal" but sedentary, that weight-cycling is strongly correlated with negative health outcomes.
There's another issue with low-carbohydrate diets neither of us has mentioned: the question of just how many people could be fed on a diet composed almost exclusively of fat/protein. Even if carbohydrates aren't optimal for individual health, they've certainly enabled many more people to survive in smaller areas than was possible in pre-agricultural societies.
I don't think they must be
I don't think they must be unhealthy because they're unnecessary. I think they can be unhealthy because I've become convinced of their important causal role in many western/chronic diseases.
The evidence that Taubes "left out" does not really seem to be relevant. I'd actually already seen the Gina Kolata piece, as well as Taubes' response to it here: link. To me she seems to come off pretty badly in the exchange. She makes multiple factual errors, bizarrely responds to a charge Taubes did not make ("Jules Hirsch, who in fact says he did do the study"--Taubes had even called it the "Leibel-Hirsch paper" in his reply) and fails to address the points he does make. She also basically ignores what he is interested in--the way in which fat storage is regulated by hormones--and just focuses on why people often don't stay on low-carb diets--which is completely beside the point.
Note also that there is a datum to be explained--why our average weight has increased in the recent past. If not carbs, what explains it? And why is obesity so often associated with the same conditions that produce malnutrition?
The fact people often in fact eat fewer calories when they go on low-carb diets is also beside the point. The question is: why, if they eat the same reduced quantity of a diet including a fair number of carbs, do they not lose weight as easily? And why is their cholesterol generally improved most on the low-carb diet?
I'm not suggesting that people ought not be told whatever the facts bear out about obesity and health, or about the world food situation, or about the difficulties of making permanent changes to one's weight. Rather that as autonomous human beings they deserve to know the truth about the effects of dietary carbs too--e.g. about fat storage, insulin resistance, heart disease, etc. I'm only saying that we need to respect their autonomy and give them the information they need to make their own rational decisions--not attempt to manage their emotions for them.
Thanks for the "encouragement", by the way. It's nice to know you don't think it's a completely foregone conclusion that I will fail.
I didn't know Taubes had
I didn't know Taubes had disputed the study Kolata mentions.
I don't think you will necessarily or even likely fail at losing weight and maintaining that--you seem to have had a much easier time reducing the carbohydrates in your diet than most people seem to. If you are not strongly compelled to eat carbohydrate-rich foods now, I don't think there's any reason to expect that you will be. What I'm saying is that almost all long-term studies of people following all kinds of diets show that people regain the weight they lose initially. And not just "most" of them as in 50% or more or a regain of only some of the initial weight lost--nearly all the people in most studies gain nearly all of the weight they lost back, and many gain more, ending up weighing more than people who didn't diet in the first place. Again, I don't think the fatness is necessarily a medical concern, but the weight cycling is.
And people have been consuming carbohydrate-rich diets for literally millenia. Why would carbohydrate consumption, which was driven by the development of agriculture, explain the weight increases in the "recent past"? The "obesity epidemic" is usually dated to the 1980s, but Americans were eating carbohydrate-rich diets in the 1970s, and the 1930s, and the 1850s. People in many countries with much lower rates or obesity also eat carbohydrate-rich diets.
So what else would explain it? Increased caloric intake, primarily. There are a few indicators that Americans are eating more calories on average now than in the 1970s and that that increase alone can explain the amount of the average weight gain (http://www.sciencedaily.com/releases/2009/05/090508045321.htm). But I agree that not all calories are equal and weight gain isn't as simple as calories-in>calories-out. The fact that the increasing caloric intake has been composed primarily of carbohydrates is likely a factor in weight gain. And I think the reasons some people may be consuming more calories are also complex--the falling relative cost of food, the increasing consumption of food outside of the home, more "snacking" which may be related to more time spent working outside the home and decreasing time spent cook, and weight-loss dieting that ultimately results in greater long-term weight gain are all likely factors.
I'm not proposing that we attempt to manage peoples' emotions for them or withhold information about the relationship between carbohydrates and insulin resistance, fat storage, heart disease, etc. However, I think the decisions people make about food are not necessarily "rational," and that demonizing foods often does more to make them desirable than prevent people from consuming them. The upshot is not that people shouldn't seek to inform people, but that they should take care how dietary advice is framed.
The entry was prompted not by Taubes' advice, which may in fact make room for the consumption of some carbohydrates, but by someone claiming that fresh fruit juice is "not good for you" because it's "just sugar." That's the kind of oversimplification and moralization that I think should be avoided.
If my understanding of
If my understanding of Taubes' take on the studies done by Ahrens is correct, it's basically that they were not designed to find, and were not capable of finding, effects that would be relevant to his claims. It occurs to me that this part of the discussion is a little odd, considering that you already claim to disbelieve the claim that Kolata wants to make based on it--namely that a calorie is a calorie, and weight gain can be explained by calories in being greater than calories out.
I knew what you meant by the comment. It just sounded quite back-handed and disparaging.
When it comes to the diet of Americans prior to the doubling of our population near the end of the 19th century, I've heard just about the opposite of what you say; there was apparently even a USDA estimate that Americans were consuming 178 pounds of meat a year per capita in the 1830s. I have no idea how reliable that estimate would have been, but it does make clear that non-carb food was fairly prevalent. Even in the early years of the republic, Americans apparently also had a very strong reputation as a meat-eating people. There's also the matter of the types of carbs. As I mentioned earlier, the amount of sugar consumed by Americans has increased by an order of magnitude since around the time of country's birth. Finally, the proportion of carbohydrates in the American diet has in fact been growing steadily since the 70s.
Something that I don't understand: given that it seems that people are eating more calories now, and about 90% of the added calories are in the form of carbs (meaning that people are almost eating the same number of additional carb calories as additional calories period) why is it fine to say that the weight gain is because of additional calories, but somehow a terrible sin to say that it is from additional carbs? Especially considering that you seem to admit that the carbs may well be the primary causal factor in weight gain. It is, after all, not at all clear that we would have seen the same increase if the additional calories had come from protein or fat. If it's a matter of whether or not carbs are present, calling it "increased caloric intake" just seems like a figleaf to protect the nakedness of the calorie-is-a-calorie model.
I suppose another thing I don't understand: what is the difference in your mind between demonizing a food and saying that it has negative health consequences X, Y, and Z? How would you inform without demonizing, if you think that people should in fact be informed of such things? Assuming that the sugar in fruit juice can contribute to certain health problems, what would one say to the juice drinker?
According to the USDA, per
According to the USDA, per capita consumption of meat in 2000 was 195 lbs. Consumption of cheese increased nearly 300 percent from 1950 to 2000. It's true that carbohydrates as a percentage of calories produced and consumed has increased, but I'm not sure it's true that the diet in the 1970s, 1950s, or 1830s was not still a carbohydrate-rich diet. Do you know or does Taubes say what the tipping point is and why so many American diets reached it in the 1980s-1990s? Or why other countries and populations whose diets consist substantially of carbohydrates have lower rates of obesity and heart disease?
I agree that it's not clear at all that weight and health outcomes would have been the same if the additional calories had all come from protein or fat. I agree completely that calories-in/calories-out doesn't explain *everything*. However, it's also true that when people increase or decrease their total caloric intake even without changing the composition of macronutrients, they gain or lose weight accordingly. Part of the amazing sticking power of the theory of caloric arithmetic is that most dieters experience conforms to it--if they decrease their consumption or increase their activity levels to generate a deficit of approximately 500 calories/day, they lose approximately 1 lb/wk. It's not perfectly consistent because the kind of calories and various other factors that might influence metabolic rate interact, but it's also not a complete myth.
I don't think it's a "terrible sin" to say the weight increase is due to carbohydrates. But I think it's impossible to know whether or not the same increases in weight gain would have been seen if national caloric consumption had remained steady and the increased consumption of carbohydrates had displaced proteins and fats. And if the increase in caloric consumption explains the increased weight entirely, I don't know why it makes more sense to insist that it's been caused by carbohydrate consumption, especially given that many people (in the U.S. and elsewhere) whose diets are heavily carbohydrate-dependent are not obese.
What I would tell people about fruit juice is precisely what I've written above: if you wish to avoid sugars because they can contribute to certain health problems, you should avoid juice. On the other hand, if you are looking for a very rich source of vitamins and minerals, if you enjoy the taste of juice, or if wish to consume sugars to fuel a highly active lifestyle, you should enjoy juice in moderation. Furthermore, I think people should distinguish between fresh or unsweetened juices and juice blends. I don't think juice has *exclusively* negative health consequences, and think nutritional advice should strive to reflect the complexity of health goals.
Being not sure it wasn't a
Being not sure it wasn't a carbohydrate rich diet that was consumed in those periods is not enough to use them as evidence.
Why would there have to be a specific tipping point? Western countries have experienced a greater degree of diseases in which carb consumption is implicated compared to native populations with relatively low-carb diets for a long long time. Those diseases have become more prevalent at the same time as the carb consumption has risen.
I don't know what other countries and populations you're referring to. Give me an example, and we can take a look at it.
It's not the case that most dieters' experiences conform to the theory of positive/negative caloric balance. Most dieters find that they lose a few pounds quickly, and then the loss soon slows to a crawl, making the loss of even 20 pounds quite rare. Similarly, while cutting daily calories by a small amount (say 100 calories per day) would be expected to lead to a loss of 11 pounds in a year, this just doesn't seem to occur. A third sort of counter-example comes from low-carb dieting, in which it is often reported that even when the dieters are known to be consuming more calories than would formerly have been necessary to maintain their weight, they still often lose significant amounts of weight (typically 3 or so pounds a week—this is also actually my situation, and when I'm sticking strictly to the diet I usually lose about 3 pounds in a week).
The study that claims that "the increase in caloric consumption explains the increased weight entirely" is using the notion that it's merely net energy balance that drives weight loss/gain as an initial presupposition; the possibility that it was caused by something other than activity levels or food intake is assumed out of existence. (Note also that the gained weight for adults did not actually quite match the prediction, despite what the headline would have you believe. They say: "That suggests that excess food intake still explains the weight gain, but that there may have been increases in physical activity over the 30 years that have blunted what would otherwise have been a higher weight gain." All sheer assumptions based on the notion that net energy balance must be what drives changes in weight.)
I think a confusing aspect of this is that conservation of energy has to be observed; when someone gains weight, it's certainly true that more calories have been taken in than were let out. But this in no way implies that taking in extra calories is the effective cause of weight gain. The arrow of causality can just as easily point the other way: weight gain causing a net positive energy balance. The importance of the difference can be seen by considering a growing child. It would be perverse to say that children grow because they start taking in a surplus of energy. Rather, they are taking in a surplus of energy as a necessary result of hormone-triggered growth. The analogy is strong for weight gain/loss, right down to the influence of hormones on the process.
The carbohydrate hypothesis has the additional advantages of being quite simple, easy to test, and with an explicit mechanism for its action. The alternative hypothesis—that people were driven by miscellaneous outward effects to have the desire to eat more calories per day—has none of these properties; this suggests that the default hypothesis if all else is equal should be the carb one.
China and Japan are the most
China and Japan are the most frequently-cited examples. Average carbohydrate consumption in both countries is much higher than in the U.S. (75% or higher compared to 45-50% in the "Western diet"), but rates of obesity, heart disease and diabetes are much lower.
More broadly, the carbohydrate consumption as a percentage of diet is generally much lower in "developed" countries with higher incidence of chronic diseases associated with diet than "developing" countries. http://www.fao.org/docrep/w8079e/w8079e0g.htm.
Undoubtedly the percentage of carbohydrates consumed in the form of simple sugars and refined starches in "developed" countries has increased, but that's a different issue than carbohydrate consumption as a whole.
I think part of what the carb hypothesis is missing is an account of how nutrients affect each other. So, for example, everything I've read suggests that fats and especially saturated fats and fiber can slow the rate of glucose absorption. And that linoleate, present primarily in refined vegetable oils, can increase the oxidizability of LDL cholesterol, which is what promotes atherosclerosis (not LDL levels themselves). And carbohydrates also cause changes in blood lipid levels that promote oxidation --> atherosclerosis. So eating saturated fats in the context of a very high-protein, very-low carbohydrate diet doesn't promote factors in coronary heart disease, whereas in the context of a typical "Western" diet, they do.
Again, the point is that just like all juices are not the same, all carbohydrates are not the same and all fats are not the same and context matters.
Re: China and Japan-- But
Re: China and Japan-- But you know the answer to this: differing types of carbs will have different types of effects. For example, in China and Japan sugar consumption has typically been much much lower than in the US. I've never claimed that all carbohydrates are the same. Just that carbohydrates are an effective causal agent with respect to a number of conditions.
For some of the same reasons, the study you quote does not include enough information about what is going on to make any determination. You also would have to match relatively specific information about consumption with relatively specific information about disease incidence to be able to make any conclusions. We have no idea from the studies about which types of carbs are being eaten by which groups, and what health results those particular groups have.
The examples of interactions you give have, as far as I can tell, no relevance to whether or not carbohydrates are a primary causal factor in the set of conditions we're discussing. Feel free to tell me how, if I'm wrong.
I'm getting the strong impression that despite the necessary causal role carbohydrates have in the conditions under discussion, you just don't want to call it the carbohydrate hypothesis, even though you believe its conclusions. If that's what this is about, I am done.
So I think where I've been
So I think where I've been confused is that because it's been referred to as the "carbohydrate hypothesis," I didn't realize that the hypothesis makes a distinction between types of carbohydrates. I thought the effects posited were supposedly the result of carbohydrates qua carbohydrates, not specific "types of carbs." Just like I wouldn't expect a theory about the effects of trans-fats to be characterized as a "fat theory."
If the effective causal agent is sugar, or sugars, or refined carbohydrates or some other category, why conflate that with the entire category of carbohydrates?
If people can and do get more of their total caloric intake from carbohydrates without suffering from the conditions under discussion, then it seems like it's got to be more complex than simply the consumption of carbohydrates --> those conditions.
I only used the "carbohydrate
I only used the "carbohydrate hypothesis" to signify the general idea that carbohydrates play a (practically) necessary causal role in a set of conditions. I think where you're getting confused is that you're conflating a scientific theory with potential dietary recommendations you might want to give.
So, for example, in the past Japan has had a low incidence of certain types of cancer (though not all). However, their rates still seem high compared to many native peoples eating diets much lower in all carbohydrates. If we're trying to determine the potential enabling role of carbohydrates in certain cancers, are we to say that complex carbohydrates do not play a role, because the Japanese at least do better than Americans? That's scientific gibberish. On the other hand, it might in some circumstances be reasonable to give dietary advice like "limit intake of (specifically) refined carbs."--That might make the most practical sense in the given situation.
Finally, you've got the logic backwards in your last paragraph. It's the condition which implies the (practical) necessity of the carbohydrate consumption, not carbohydrate consumption which implies the (practical) necessity of the conditions. The logical form of your statement would be like saying "If people can and do smoke their whole lives without getting lung cancer, how could it be that lung cancer is caused by smoking?"
yeah, you're right, that does
yeah, you're right, that does actually seem to be the cause of my confusion. the idea that carbohydrates --> disease makes it seem as though the recommendation would be to stop eating carbohydrates. and i sort of think it's more complex than that--which you've also indicated above.
the reason i brought up the interaction of nutrients thing earlier is because it seems to suggest that some of the diseases that might in some cases be caused by carbohydrate consumption could also be caused by the consumption of dietary fats along with vegetable oils.
a traditional hunter-gather diet would rarely combine carbohydrates with meat and has virtually no sources of linoleate, so the fats would not as often be oxidized, which seems to be what causes atherosclerosis.
but a more contemporary diet that frequently mixes carbohydrates with meat and often contains vegetable oils (even more so since the olive oil fad), eating more meat might in fact lead to atherosclerosis.
i'm not saying the latter is a *better* explanation than the "carbohydrate hypothesis." i actually think what's most likely is that various dietary changes interacted--so carbohydrates on their own have some effects, and their interactions with other foods have other effects, etc.
part of the problem, then, with a recommendation to simply reduce carbohydrate consumption is that it doesn't take those kinds of interactions into effect. transitioning to a diet of, say, lots of meat and olive oil, might also create risk factors for coronary heart disease, even though it might eliminate the risks associated with a very-high-carbohydrate diet.
It is definitely one of the
It is definitely one of the essential dangers of dietary recommendations that you have to make sure that what people avoid will not be replaced with something just as bad—or worse.
I have to emphasize again, though, that the idea is that carbohydrates have a necessary causal role in the various conditions (or as close to necessary as makes it practically so) whether or not they are sufficient in themselves to cause the conditions. Removing a practically necessary cause has to prevent the conditions; that's what it means to be a necessary condition.
This is obviously an empirical statement that needs showing, but the evidence seems strong, whatever other elements may also have a helping hand.
To address the particular case you mention, consider also the case of the Masai, in Africa. They subsisted on a diet composed basically exclusively of meat, blood, and milk. They were found to have extensive atherosclerosis, and yet also did not suffer from heart attacks or other symptoms—until they moved into cities and started eating a more westernized diet. The point being that their atherosclerosis was extensive without causing heart disease; I've read that there is some decent evidence that there are other major factors necessary for coronary heart disease to manifest itself. As you might imagine, in Good Calories, Bad Calories presents some evidence that it may be an effect of carbohydrate.
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