Posts Tagged ‘dietary guidelines’

“The truth?  If I wanted the truth, I would have called Sixty Minutes.”

— Spiros Focás in Jewel of the Nile.

Sugar is an easy target. These days, if you say “sugar” people think of Pop-Tarts® or Twinkies®, rather than pears in red wine or tamagoyaki the traditional sweet omelet that is a staple in Bento Boxes.  Pop-Tarts® and Twinkies® are especially good targets because, in addition to sugar (or high fructose corn syrup (HFCS), they also have what is now called solid fat (the USDA thinks that “saturated” is too big a word for the average American ) and the American Heart Association and other health agencies are still down on solid fat.  Here’s a question, though: if you look on the ingredients list for Twinkies®, what is the first ingredient, the one in largest amount?  (Answer at the end of this post).

The Threat

What went wrong in the obesity epidemic?  There is some agreement that by focussing on fat, the nutritional establishment gave people license to over-consume carbohydrates. The new threat is that by focusing now on fructose, the AHA and USDA and other organizations are giving implicit license to over-consume starch — almost guaranteed since these agencies are still down on fat and protein.  The additional threat is that by creating an environment of fructophobia, the only research on fructose that will be funded are studies at high levels of total carbohydrate where, because of the close interaction between glucose and fructose, deleterious effects are sure to be found. The results will be generalized to all conditions.  Like lipophobia, there will be no null hypothesis.

The latest attack on sugar and on fructose itself (sugar and HFCS are half fructose) comes from Robert Lustig, a pediatrician at University of California San Francisco. His lecture describing fructose as a virtual poison got more than a million and a half hits on YouTube.  The presentation has an eponymous style (Lustig, Ger. adj., merry, amusing, e.g. Die Lustige Witwe, The Merry Widow) and includes a discussion of the science bearing on fructose metabolism. While admitting the limitations of that science, even Gary Taubes was worried. Comments on YouTube and other sites say they liked the science but did not agree with his recommendations — it will turn out that he now wants government control of sugar consumption, especially for my kid and yours.

The presentation of the science is compelling but, while it has a number of important points, it is clearly biased and, oddly, a good deal of it is totally wrong, some of it containing elementary errors in chemistry that border on the bizarre — how hard would it have been to open an elementary organic chemistry text?  In trying to draw parallels between alcohol and fructose, Lustig says “ethanol is a carbohydrate.” Ethanol is not a carbohydrate.  A horse is not a dog. If you said that ethanol is a carbohydrate in sophomore Organic Chemistry, you would get it wrong. Period. No partial credit. Such elementary errors compromise the message and raise the question in what way Lustig is an expert in this field.  It gets worse.

It is biological function that is important and ethanol is not processed like fructose as Lustig says. There is very little chemical sense in saying that ethanol and fructose are processed biologically in similar ways.  And a metabolic pathway is shown in which glycogen is absent. Glycogen is the storage form of glucose and is generally taken as a good thing because of its relation to endurance in athletes but, like fat, glycogen is a storage form of energy and having a lot is not always a good thing.  In any case, it is not true that fructose does not give rise to glycogen.  In fact, fructose is generally better at forming glycogen than glucose is.  This is especially true when you consider the effect of exercise which is why Gatorade® may actually be a good thing if you are in a football game rather than watching one. This is the general error in Lustig’s talk.  Metabolism is not static and has evolved to deal with changing conditions of diet and environment. A metabolic chart, like any map only tells you where you can go, not whether you go there. And the notable absence in Lustig’s talk is data.

It is possible that  sugar and ethanol have behavioral effects  in common but this is not due to similarities in metabolism.  And even the behavioral effects are not settled within the psychology community; alcoholism is far different from “sugar addiction,” if there is such a thing; polishing off the whole container of Häagen-Dazs® may not technically qualify as addictive behavior.

The Threat of Policy

All of this might be okay — Lustig’s lecture was not a scientific treatise — except that he has gone to the next step.  Convinced of the correctness of his analysis, he wants government intervention to control sugar and sweeteners in some way .  There is an obvious sense of deja-vu as another expert attempts to use the American population as Guinea pigs for a massive population experiment, like the low fat fiasco under which we still suffer. It is not just that we got unintended consequences (think margarine and trans-fats) but rather that numerous people have pointed out that the science was never there for low-fat to begin with (brilliantly explained in Fat Head).  In other words leaving aside the question of when we should turn science into policy, is the science any good?

Fructose

It is important to understand that fructose is not a toxin. It is a normal metabolite. If nothing else, your body makes a certain amount of fructose.  Fructose, not music (the food of love), is the preferred fuel of sperm cells. Fructose formed in the eye can be a risk but its cause is generally very high glucose. Fructose is a carbohydrate and is metabolized in ways similar to, if different in detail, from glucose but a substantial amount (can be 60 %) of fructose is turned to glucose — that is why the glycemic index of fructose is 20 and not zero.

The extent to which fructose metabolism has a uniquely detrimental effect is strongly dependent on conditions.  Fructose may be worse than glucose under conditions of very high carbohydrate intake but its effect will change as total carbohydrate is lowered. And since carbohydrate across the board is what is understood to be the problem — Lustig states that clearly in his YouTube — policy would suggest that that is the first line of attack on health — reduce carbohydrate (emphasizing fructose if you like) but as carbohydrate and calories are reduced, any effect of fructose will be minimized.  In the extreme, if you are on a very low carbohydrate diet, any fructose you do eat is likely to be turned into glucose.

The Opportunity

Lustig makes his case against fructose in terms of fundamental biochemistry which is really how it should be.  Can biochemistry be explained to the general population?  Can the problem be explained in a simple but precise way so that we really have the sense of talking about science and not politics?  So what is needed is somebody who actually knows biochemistry.  Maybe somebody with experience in teaching biochemistry to future doctors.  Hey, that’s my job description.  In fact, I’m going to try that in the next few blogs and on YouTube. I and others have  taught courses that try to reduce the three year sequence that professional chemists follow: general chemistry-organic chemistry-biochemistry.  I will try to give everybody a window into organic chemistry, biochemistry and metabolism. In fact, that might be a good focus for government intervention. Instead of punishing the patient, how about funding for teaching biochemistry to the public. For the moment, though, let’s look at some population data.

Sweetener Consumption.

What about sweeteners?  Well, of course, consumption has gone up. Surprisingly, not as much as one would have thought.  According to the USDA about 15 %.  One question is whether this increase is disproportionately due to fructose. The figures below show that, in fact, the ratio of fructose to glucose has remained constant over the last 40 years.  (The deviation from 1:1 which would be expected for pure sucrose or HFCSA, is due to a  relatively constant 20 % or so of pure glucose that  is used in sweetening in the food industry). It is possible that, although the ratio is the same, that the absolute increase in  fructose has a worse effect than the increased glucose but, of course, you would have to prove it.  The figures suggest, however, that you will have to be careful in determining whether the effect of increased sweetener is due to fructose or glucose, or the effect of one on the other, or the effect of insulin and other hormones on both.  An unrestrained, lustige, lack of anything careful is exactly the current threat.

Answer to “puzzler:” The main ingredient in Pop-Tarts® and Twinkies® is flour. Some people say that if you add up the different forms of sugar that will be greater but like all ideas derived from Lustig, there is an advantage in looking at the data: 38 g. of carbohydrate, 17 g. of sugars.

In 1985 an NIH Consensus Conference was able to “establish beyond any reasonable doubt the close relationship between elevated blood cholesterol levels (as measured in serum or plasma) and coronary heart disease” (JAMA 1985, 253:2080-2086).

I have been making an analogy between scientific behavior and the activities of the legal system and following that idea, the wording of the conference conclusion suggests a criminal indictment. Since the time of the NIH conference, however, data on the role of cholesterol fractions, the so-called “good (HDL)” and “bad (LDL)” cholesterols and, most recently, the apparent differences in the atherogenicity of different LDL sub-fractions would seem to have provided some reasonable doubt. What has actually happened is that the nutrition establishment, the lipophobes as Michael Pollan calls them, has extended the indictment to include dietary fat, especially saturated fat at least as accessories on the grounds that, as the Illinois Criminal Code put it “before or during the commission of an offense, and with the intent to promote or facilitate such commission, … solicits, aids, abets, agrees or attempts to aid… in the planning or commission of the offense. . . ..”

A major strategy in the indictment of saturated fat has been guilt by association.  The American Heart Association (AHA), which had long recommended margarine (the major source of trans-fats), has gone all out in condemning saturated fatty acids by linking them with trans-fats.  The AHA website has a truly deranged cartoon film of the evil brothers: “They’re a charming pair, Sat and Trans.  But that doesn’t mean they make good friends.  Read on to learn how they clog arteries and break hearts — and how to limit your time with them by avoiding the foods they’re in.”. While the risk of trans-fats is probably exaggerated — they are a small part of the diet — they have no benefit and nobody wants to defend them; dietary saturated fat, however, is a normal part of the diet, is made in your body and is less important in providing saturated fatty acids in the blood, than dietary carbohydrate.  Guilt by association is a tricky business in courts of law — just having a roommate who sells marijuana can get you into a good deal of trouble — but it takes more than somebody saying that you and the perpetrator make a charming pair.

The failure of the diet-cholesterol-heart hypothesis in clinical trials as been documented by numerous scientific articles and especially in popular books that document the original scientific sources. It is unknown what the reaction of the public is to these books.  However, amazingly, there is only one book I know of that takes the side of the lipophobes and that is Daniel Steinberg’s Cholesterol Wars. The Skeptics vs. the Preponderance of Evidence. A serious book with careful if slightly biased documentation and an uncommon willingness to answer the critics,  it is worth reading.  I will try to discuss it in detail in this and future posts.  First, the title indicates a step down from criminal prosecution.  “Preponderance of the evidence” is the standard for conviction in a civil court and is obviously a far weaker criterion.  One has to wonder why it is that the skeptics have the preponderance of the popular publications — if the scientific evidence is there and health agencies are so determined that the public know about this, why are there so few —  maybe only this one — rebutting the critics.

The Skeptics vs. the Preponderance of Evidence

In any case, what is Steinberg’s case?  The indictment on page 1 is somewhat different than one would have thought.

“….the [lipid] hypothesis relates to blood lipids not dietary lipids as the putative directly causative factor. Although diet, especially dietary lipid is an important determinant of blood lipid levels, many other factors play important roles. Moreover, there is a great deal of variability in response of individuals to dietary manipulations. Thus, it is essential to distinguish between the indirect “diet-heart” connection and the direct “blood lipid — hard” connection failure to make this distinction has been a frequent source of confusion. (his italics)”

What?  Are we really supposed to believe that diet is an incidental part of the lipid hypothesis?  Are we supposed to believe that our cholesterol is just a question of the variability of our response to diet.  Has the message really been that diet is not critical and that heart-disease is just the luck of the draw (until we start taking statins)?  This is certainly the source of confusion in my mind.  Of course by page 5, we are confronted with this:

“In 1966, Paul Leren published his classic five-year study of 412 patients who had had a prior myocardial infarction. He showed that substitution of polyunsaturated fat and saturated fat-rich butter-cream-venison diet favored by the Norwegians reduced their blood cholesterol by about 17 per cent and kept it down.  The number of secondary current events in the treated group was reduced by about one-third and the result was significant at the p < 0.03 level.”

In a future post, I will describe Paul Leren’s classic five-year study which, by 1970, had a follow-up to eleven years and the results will turn out not to be as compelling as described by Steinberg.  For the moment, it is worth considering that, given the strong message, from the AHA, from the American Diabetes Association, from the NIH Guidelines for Americans, the criterion really should be beyond a reasonable doubt. There shouldn’t be even a single failure like the Framingham Study or the Women’s Health Initiative. In fact, the preponderance of the evidence when you add them all up, isn’t there.

The phrase “Evidence-based Medicine” (EBM) guarantees its proponents a certain degree of protection. After all, who would be against medicine that is based on the data, on hard facts rather than opinion. On the other hand, a study that needs to cloak itself in such a self-aggrandizing phrase must raise a few eyebrows; as usual, the Dietary Guidelines, moves to the top of the list in that category but there are many examples.  Martin Tobin, professor of Medicine at Loyola College provided an excellent deconstruction of evidence based medicine [1]. Some of his points were that the grading system has divorced itself from basic science.  For example, he points out that:

  • “ homeopathy uses drugs in which less than one molecule of active agent is present. … A meta-analysis of 89 placebo-controlled trials revealed a combined odds of 2.45 in favor of homeopathy. EBM grades meta-analysis as level 1 evidence but completely ignores scientific theory. There is nothing necessarily wrong with this particular meta-analysis, but the example illustrates how a system that grades findings of all meta-analyses as level 1 evidence is inherently flawed.  A grading system that ranks homeopathy as sounder evidence than centuries of pharmacologic science commits the reductio ad absurdum fallacy in logic.” [1]

Among the things that we found in our critique of the USDA dietary guidelines Report [2] was that the cited evidence did not meet their own standards. They were critical of low-carbohydrate diets on the basis of studies that their own analysis gave a “neutral” quality rating, even those that took dietary assessment at baseline and then assessed  cardiovascular mortality up to 12 years later.

But it is really the idea that there is some set of systematic definitions of science that everybody agrees on. My last post mentioned, by analogy with courts of law, the Frye standard which accepts as evidence, opinions supported by  “general acceptance’ in the scientific community.  While still accepted in some state courts, the federal courts have tried to go beyond trust in such narrow descriptions of science. In 1975, Congress established Federal Rules of Evidence.  The rules are quite general and the major impact is to broaden the range of evidence that could be considered.  Rule 401, defined relevance as  “evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence,”  in other words, whatever works.  In a future post, I will discuss Daubert v. Merrell Dow, Inc. (pr. Dow-burt as in English), an outgrowth of the Rules of Evidence and generally considered the key judgment in the modern interaction of science and the law.  In the real world of jurisprudence, ideas on what constitutes scientific evidence have become problematical and Daubert may have had the paradoxical effect of restricting admissible data but, in the analogy with evidence in medicine, the Federal Rules of Evidence and Daubert have better captured the real quality of science in recognizing the need for flexibility. The kinds of absolute criteria — association does not imply causality, random controlled trials are a “gold standard,” etc. are at least different from the spirit of Daubert.

More important, nobody in any physical science would recognize the tables of levels of evidence.  A random controlled trial may be good for one kind of experiment but not for another and EBM is critical of “observational studies” but all of astronomy is observational.  In the end, most scientists would agree with the physicist Steven Weinberg, echoing Judge Potter Stewart’s famous take on pornography:

  •  “There is no logical formula that establishes a sharp dividing line between a beautiful explanatory theory and a mere list of data, but we know the difference when we see it — we demand a simplicity and rigidity in our principles before we are willing to take them seriously [3].”

So where do these arbitrary guidelines in EBM come from?  They were set up by the  medical community, a community that is stereotyped as being untrained in science. I hate stereotypes, especially medical stereotypes since I think of myself as coming from a medical family (my father and oldest daughter are physicians) but stereotypes come from someplace and, of course, it is well known that physicians never study nutrition.  In the end, it makes me think of the undoubtedly apocryphal story about Mozart.

  • A man comes to Mozart and wants to become a composer.  Mozart says that they have to study theory for  a couple of years, they should study orchestration and become proficient  at the piano, and goes on like this.  Finally, the man says “but you wrote your first symphony when you were 8 years old.”  Mozart says “Yes, but I didn’t ask anybody.”

Bibliography 

1. Tobin MJ: Counterpoint: evidence-based medicine lacks a sound scientific base. Chest 2008, 133(5):1071-1074; discussion 1074-1077.

2. Hite AH, Feinman RD, Guzman GE, Satin M, Schoenfeld PA, Wood RJ: In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition 2010, 26(10):915-924.

3. Weinberg S: Dreams of a final theory, 1st edn. New York: Pantheon Books; 1992.

Coincidence.  My daughter Mimi’s school was debating whether chocolate milk, skim or otherwise, is really a good thing — whole milk of course is not a choice.  At the same time, her first grade class was studying states of matter, specifically solids and liquids.  According to Mimi, they learned that solids do not change shape and liquids flow.  These two topics come together in the bizarre world of the USDA Dietary Guidelines.  Whole milk, it seems, is not a choice because it may be a solid.

Stepping back, the logic of the USDA recommendations is that

1) we now know that  total dietary fat poses no risk for cardiovascular disease (CVD), but

2) saturated fat  is a risk for CVD and therefore Americans must

3) reduce total dietary fat intake and drink skim-milk or fat-reduced milk.  If you are confused about this syllogism, not to worry.  The Guidelines have made it simple. The Advisory Committee has always had a concern for the ability of the public to think.  Dr. Xavier Pi-Sunyer (pr. Pea-soon-yay), a member of the committee wrote an editorial about a scientific report that showed no difference in the effect of different diets (never mind that, in practice, what people ate was about the same, regardless of the “diet” to which they were assigned.) He suggested that it “seems unwise at this point to burden type 2 diabetes patients with trying to pick and choose among different high- and low-GI foods.”  Also, in unveiling the new Guidelines, secretary of Agriculture Tom Vilsack said that he had not read the previous versions.  So, any simplification is welcome. The Dietary Guidelines has, as one of its latest innovations, the introduction of the term SoFAS, which stands for Solid Fats and Added Sugar and was in line for a SAY! Award (Stupidest Acronym of the Year).  So, we simply have to understand what they mean by solid.

If there is anything in science that is well understood and should not be open to conjecture, it is the states of matter.  Outside of the extreme conditions that produce plasmas and other exotica, the idea of solids, liquids and gasses seems pretty much, well, solid.  It turns out, though, that since the term saturated fat is, after all, a chemical term, it is necessary to make things simple for the consumer who is now advised to look for something “solid” instead.  To do this, the DGAC explains: “To determine whether foods contain oils or solid fats, consumers can read the ingredients list to make sure that fats in the foods are oils containing primarily unsaturated fatty acids and that solid fats are not one of the first few ingredients…. Examples of solid fats that may be used in the ingredients list are provided in Table A4-1.” But, of course, labels don’t list “solid fats.”  Got it? To find out if foods contain solid fats, see if it says solid fats on the ingredient list, but since labels don’t list “solid fats” you only have to use Table A4-1 which is shown below.  The table, however, has some surprising entries.  The presence of cream and vegetable oils certainly seems a little strange.  Not to worry.  It is easy to understand if you remember that those oils “are high in saturated fat…therefore, for nutritional purposes, these oils are considered solid fats.”  In other words: when is a solid not a solid?  When the USDA says so.  Not to milk this idea too much, we have to figure out how the consumer is to deal with the fact that “fat in fluid milk also is considered to be solid fat; milk fat (butter) is solid at room temperature but is suspended in fluid milk by the process of homogenization (p. 27).”  Apparently, the simple process of distilling the fluid from milk is all that is required for the consumer to find out whether the fat is solid.

For Mimi, this is not a problem because, the fat has been reduced or removed from the milk that she is offered at school and if there is some added sugar  (8 oz. Nesquik® has 29 g.) at least we know that removal of the fat will make the milk more nutrient dense (p. 5).  In a future post, I will explain how removing nutrients can make food more nutrient dense. For the moment, I think understanding that sometimes a liquid is a solid is enough new information.  Now, for the evidence.

“That which is not”

In one of the countries visited in Gulliver’s Travels, the inhabitants referred to “That which is not” because their language did not have a word for lying.  Now the Guidelines prides itself on transparency and evidence-based conclusions so, at the meeting on saturated fat in Detroit, I asked the representative from the USDA where the evidence was on solid fat.  The literature is large but as far as I knew, there were no studies at all that specifically looked at solid fat. He said he would get back to me on that. That was a while ago.

So in the first grade, we learned that solids hold their shape.  My question: are the USDA Dietary Guidelines solid science?

Nutrition & Metabolism Society

Charles Darwin, in his autobiography described

“the oddest case which I have known. A gentleman (who, as I afterwards heard, is a good local botanist) wrote to me from the Eastern counties that the seed or beans of the common field-bean had this year everywhere grown on the wrong side of the pod. I wrote back, asking for further information, as I did not understand what was meant; but I did not receive any answer for a very long time. I then saw in two newspapers, one published in Kent and the other in Yorkshire, paragraphs stating that it was a most remarkable fact that ‘the beans this year had all grown on the wrong side.’ So I thought there must be some foundation for so general a statement.”

I had read this passage a while ago but it suddenly popped up in my mind on reading the new USDA Dietary Guidelines. The Guidlines have a strong recommendation to choose “nutrient dense” food.  Since all the food you ingest contains some kind of macronutrient or micronutrient  and having a food dense in one or another would depend on how much you thought was good I could not really understood what was meant.  I pretty much forgot about it until I saw in a video from a TV broadcast making the same recommendation suggesting that it was intelligible to the general population. I still couldn’t understand what could be meant. The guidelines say, on page 3, “Energy-dense forms of foods, especially foods high in SoFAS, should be replaced with nutrient-dense forms of vegetables…” SoFAs stands for “solid fats and added sugars.” It would be hard to find two more nutrient dense but different substances. So at least nutrient dense is not calorie dense but it is not obvious what it is.  Note added in 2013:when I first posted this, I genuinely did not know that nutrient-dense now means micronutrient-dense but I think the critique of the USDA still stands and for a description of currency of an idea that has no real meaning at all, Darwin’s story is still the best. (And, of course, vitamin deficiencies may be the least of our nutritional problems).

Darwin described how he

“went to my gardener, an old Kentish man, and asked him whether he had heard anything about it, and he answered, ‘Oh, no, sir, it must be a mistake, for the beans grow on the wrong side only on leap-year, and this is not leap-year.’ I then asked him how they grew in common years and how on leap-years, but soon found that he knew absolutely nothing of how they grew at any time, but he stuck to his belief. After a time I heard from my first informant, who, with many apologies, said that he should not have written to me had he not heard the statement from several intelligent farmers; but that he had since spoken again to every one of them, and not one knew in the least what he had himself meant. So that here a belief–if indeed a statement with no definite idea attached to it can be called a belief–had spread over almost the whole of England without any vestige of evidence.”

(In case you think that there is any botanical meaning at all: it is not just the leap-year. It is that there is no right or wrong side of the pod at all).  Is it possible that the USDA guidelines, put together by the famous 13 experts have made a recommendation that was completely devoid of meaning?  Page 11 says that “A nutrient-dense total diet has multiple health benefits and can be implemented in various ways” but what is nutrient-dense?  Although never defined, examples are given on pages 19-20.

• Vegetables, fruits, high-fiber whole grains

• Fat-free or low-fat fluid milk and milk products

• Seafood, lean meat and poultry, eggs, soy products, nuts, seeds, and oils

• Very low in solid fats and added sugars (SoFAS)

• Reduced in sodium

The remarkable thing is that in five out of six, the nutrient density is attained by absence of nutrients: fat-free, low-fat, lean, very-low SoFAS, reduced sodium — and is there anything less dense than skim-milk?  Paraphrasing Darwin, then, here is a dietary recommendation –if indeed a statement with no definite idea attached to it can be called a recommendation — will be spread over almost the whole of the country without any vestige of evidence.