Category Archives: this is your research on mass media

Salt Headlines That Make The Vein In My Forehead Throb

Salt has been all over the news this week because of a study just published in The New England Journal of Medicine claiming that if everyone in the U.S. reduced their sodium consumption by 3 grams/day, there would be 32,000 fewer strokes, 54,000 fewer heart attacks, and 44,000 fewer deaths every year. The story that got my attention was:

Remaining Arctic Ice Seen Melting Away Completely! (...on a computer screen)

That’s surprising, I thought. Everything I’ve read suggests that the relationship between salt consumption and cardiovascular disease is weak, inconsistent, and probably only valid for 20-30% of the population. So I expected the article to refer to some new research where, you know, “big benefits” were “seen.” As in observed. Like, in the world. And, given the claim about the magnitude, probably also measured.

To their credit, the authors of the study claim no such thing. The numbers are projections based on the application of several assumed effects of salt reduction, adjusted for different demographics and then applied to a model of the entire U.S. population. Thus, the title of the study: “Projected Effect of Dietary Salt Reductions on Future Cardiovascular Disease.”

The article seems to grasp the essentially speculative nature of the findings. The very first sentence uses the conditional tense:

…scientists writing in The New England Journal of Medicine conclude that lowering the amount of salt people eat by even a small amount could reduce cases of heart disease, stroke and heart attacks as much as reductions in smoking, obesity, and cholesterol levels.

The headline, on the other hand, seems to have confused the “scientists” with clairvoyants. Never mind doing any checking into the validity of their assumptions.

And the claim about how the benefits compare to smoking and obesity reduction led to a few headlines like this:

webmd salt

This crazypants idea initially sounds a lot like what the study’s lead author claims:

"The cardiovascular benefits of reduced salt intake are on par with the benefits of population-wide reductions in tobacco use, obesity, and cholesterol levels."

But the logic behind the claim is that a small improvement in the health of every single American would be as significant as a large health improvement in the health of every single smoker:

Dr. Bibbins-Domingo said that for many people the decrease in blood pressure would be modest, which is why, she said, “many physicians have thrown up their hands and said, ‘I’m not going to advise my patients to reduce salt because it’s too hard for patients and the benefits for any individual are small.’

“But small incremental changes in salt, such as lowering salt in tomato sauce or breads and cereals by a small amount, would achieve small changes in blood pressure that would have a measurable effect across the whole population,” she said. “That’s the reason why this intervention works better than just targeting smokers.”

For any given individual, there is no question about whether cutting salt is even close to “as good” as quitting smoking. The evidence for the link between smoking and lung cancer and death is strong, reliable, consistent, and has a clear causal mechanism (carcinogens). The link between salt and cardiovascular disease and death is weak, inconsistent, and still poorly understood.

That latter point starts to get at the problems with the study itself, and not just the headlines it inspired. A number of the assumptions the projection was based on are either demonstrably false or simply unsubstantiated. More on this some other time; for now, a few quotes and links to the essays they come from in Esquire and the medical journal Hypertension:

In a more recent statement, the founder of the American Society of Hypertension, Dr. John Laragh, goes further: "Is there any proven reason for us to grossly modify our salt intake or systematically avoid table salt? Generally speaking the answer is either a resounding no, or at that, at best, there is not any positive direct evidence to support such recommendations."

Studies show that 30 percent of the Americans who have high blood pressure would greatly benefit from a low-sodium diet. But that’s about 10 percent of the overall population — the rest of us are fine with sodium. And drastically cutting out sodium may actually hurt some people. ( "Go Ahead, Salt Your Food")

And:

The available data suggest that the association of sodium intake to health outcomes reflected in morbidity and mortality rates is modest and inconsistent. Therefore, on the basis of the existing evidence, it seems highly unlikely that any single dietary sodium intake will be appropriate or desirable for each member of an entire population…. The decision to adopt a low sodium diet should be made with awareness that there is no evidence that this approach to blood pressure reduction is either safe, in terms of ultimate health impact, or that it is as effective in producing cardioprotection as has been proven for some drug therapies. (Salt, Blood Pressure, and Human Health)

Things that won’t kill you Vol. 1: High-fructose corn syrup

Confession: I not only avoided high-fructose corn syrup (hfcs) until about a year ago, I was actually skittish about fresh corn for a while after my first encounter with Michael Pollan in The New York Times Magazine (or it might have been this article). I stopped eating corn tortillas and frozen corn kernels and felt vaguely panicky about the possibility that I was consuming hfcs in condiments and sandwich bread when I ate out, even if it would have only been tiny amounts.

Now that I’m over it, I sometimes have a hard time remembering what was so scary about the idea that there was corn in everything I was eating, an idea that was obviously ludicrous anyway because I was a vegetarian who mostly ate food prepared at home from whole, fresh, non-corn ingredients. But looking back at the articles linked above, they are pretty ominous. Even though Pollan notes that a corn-based diet has been the norm in Mexico for centuries without any apparent ill effects, and the story he tells about the "cornification" of the American diet is too complex to be a nefarious plot designed to kill us all, it’s clear that he thinks the amount of corn Americans eat on average is a Bad Thing. Sure, it may rely on innocent accidents of nature, like the uniquely efficient way corn fixes carbon during photosynthesis and and the great distance corn pollen has to travel to reach the style, but it’s also reliant on much more insidious developments: synthetic pesticides and fertilizers, an arcane federal farm subsidy systems that turned corn into "a welfare queen," agribusiness giants with seed patents on genetically-modified strains, giant livestock feeding operations that use antibiotics to keep cows alive because eating corn makes them sick, and food manufacturers who profit from getting people to buy cheap food in ever-increasing quantities. Eating corn in any form may seem like a way of giving in to all of that or even supporting it.

So although I did a fair bit of eye-rolling when I read about people avoiding sweet corn at their farmer’s markets this summer or feeling "corn guilt" when they eat popcorn, it’s worth remembering that I was one of them not so long ago.

HFCS paranoia is not primarily an issue of ethical consumption

It’s not that many of those concerns are invalid—it’s true that most corn relies on a lot of synthetic fertilizers and pesticides, that much of it is grown using genetically modified seeds with patents held by huge corporations that have been known to sue farmers when corn with their patented genes end up in their fields, that cows fed diets of corn get sick and are more susceptible to diseases like e coli that can threaten humans. But it’s also far from clear that refusing to eat ketchup containing high fructose corn syrup is an effective means of changing any of that or even primarily motivated by the desire to change those things.

Although people like Pollan have made a big deal about corn sweeteners being artificially cheap due to farm subsidies, the actual farm cost of hfcs in the food products we buy is so minimal that even if subsidies were eliminated entirely, it might not affect portion sizes or consumer demand at all. Even in soft drinks, which are by far the most demonized hfcs delivery system, hfcs represents just 3.5% of the total cost of manufacturing. The corn content, the only part actually affected by farm subsidies, is only 1.6 percent of the price (based on US Department of Commerce data). A comparison between the U.S., Australia, the UK, and France, all of which have different sugar policies but similar consumer prices, show no pattern in the relationships between how cheap sugar is, how much of it people eat, or how fat on average they are (which most people wrongly assume is a reliable measure of health outcomes, but I’ll tackle some other time).

Pollan’s formal case against hfcs relies primarily on arguments about price and prevalence, but that doesn’t really explain the kind of paranoia his books and articles have helped inspire about eating corn and/or hfcs. Not buying and eating something because it’s too cheap just isn’t the kind of consumer behavior that spreads the way hfcs-phobia has. Nor is this some sort of mass avoidance of all added or refined sugars, or brands like Snapple and Pepsi wouldn’t be running huge campaigns to advertise soft drinks containing only "natural sugar."

Instead, people have latched on to the implication, which isn’t supported by any data I can find, that hfcs is nutritionally worse than other sugars. The hfcs paranoia isn’t caused by the idea that hfcs might be unwisely or unfairly subsidized or that pesticides used to produce corn are poisoning waterways or anything related to feeding corn to cows. The fear is that hfcs might be some kind of demon poison that makes people fat.

The confusing part: "high fructose" isn’t actually high fructose

The idea that hfcs is worse than other sugars seems to be primarily reinforced by research about how fructose is metabolized. Just last April, an article about a study comparing drinks sweetened with fructose and  glucose in the New York Times began:

Some research has suggested that consumption of high-fructose corn syrup, used as a sweetener in a wide variety of foods, may increase the risk of obesity and heart disease. Now, a controlled and randomized study has found that drinks sweetened with fructose led to higher blood levels of L.D.L, or "bad" cholesterol, and triglycerides in overweight test subjects, while drinks sweetened with another sugar, glucose, did not.

Things like this get reported all the time. However, the very last sentence of the article quotes another biochemist:

The study did not test high-fructose corn syrup, he said, and judgments should not be made about it from the findings.

Not that that stopped the author from leading with the useless, ambiguous claim about a supposed link between hfcs and obesity, but surely this deserves a little more attention: yes, fructose alone seems to cause more insulin resistance and weight gain in both rats and people than glucose alone. But high fructose corn syrup is only "high fructose" relative to normal corn syrup, which is 100% glucose.

The kind of hfcs used in most food processing, including soft drinks, is hfcs-55, which is approximately 55% fructose and 45% glucose, or almost identical to sucrose, which is about 50/50. Another kind, hfcs-42, is used in the manufacture of some baked goods, and if fructose is really worse, that would make that kind of hfcs healthier than cane sugar. Indeed, studies comparing the consumption of hfcs to sucrose have shown no differences in metabolic responses (or energy or macronutrient intake) at all.

The argument that hfcs is somehow responsible for the obesity epidemic relies entirely on correlations between the rise of hfcs in food manufacturing in the 1980s and the rise in national rates of overweight/obesity (and the exponential rise in concern about fatness). Pollan’s case against hfcs amounts to a gut suspicion that:

It’s probably no coincidence that the wholesale switch to corn sweeteners in the 1980’s marks the beginning of the epidemic of obesity and Type 2 diabetes in this country.

Of course, this fails to account for the simultaneous increases in obesity in many other countries, perhaps most notably Australia, where obesity rates rival or even exceed those in the U.S., but sugar is the primary sweetener. It’s not that he’s totally wrong; it does seem probable that U.S. farm subsidies and the cheap price of highly-palatable, nutrient-poor, calorie-rich, primarily carbohydrate-based foods is one factor driving the relatively small increases in the average American’s weight since the 1970s. And the history of corn cultivation and agricultural policy has something to do with that. But there’s no reason to think that hfcs is uniquely responsible for the "obesity epidemic." After all, if it weren’t for subsidies and tariffs that keep the price of sugar artificially inflated, which are the result of a different set of biological, historical, and political contingencies, it would be just as cheap. 

Ultimately, hfcs is just another source of sugar, nutritionally no different from cane sugar, and way better than agave nectar if you’re concerned about fructose. It might be slightly worse than things like honey (esp. raw) and maple syrup (esp. grade B or lower) if you’re interested in vitamins and minerals. (This is all assuming the hfcs in question contains mercury, but that’s sort of another story altogether).

That doesn’t mean hfcs is  "natural," a word which has virtually no meaning when it comes to food labeling anyhow, but then, if "natural" is the alternative to "processed," no sweeteners are. Agave nectar must be filtered, hydrolyzed, re-filtered, and concentrated before it can be used as a sweetener. Refined cane sugar is purified with phosphoric acid and calcium hydroxide, and sometimes whitened using bone char which is why some vegetarians and vegans refuse to eat it.

The upshot is there’s no reason to believe that hfcs is any worse for you than sugar or much worse for you than any other sweeteners, and there’s certainly no reason to believe that a little bit here and there in a favorite condiment or even the occasional soda is going to hurt you.

Later in this series: I’ve gotten a request to weigh in on fruit juice, and will try to do that soon. And someday I’ll get around to msg, as promised before.