After finishing a big programming project this weekend, I spent a good chunk of today reading the last big section of the 2010 Dietary Guidelines, a 65-page document titled Fatty Acids and Cholesterol. The final 30 pages or so were dedicated to reviewing evidence that nuts, omega-3 fats from fish, and chocolate might be good for your heart. The committee’s conclusion: Maybe, but we can’t really say.
But in the first 30-plus pages, the committee makes it clear they’re pretty darned positive saturated fat and cholesterol will kill you. Saturated fat, as it turns out, will not only clog your arteries and stop your heart, it will give you type 2 diabetes as well.
For more than 30 years now, we’ve been told to limit saturated fat to no more than 10% of our calories. We’ve actually come pretty close: according to the committee’s data tables, saturated fat makes up 11.4% of the average American’s intake. Since we’ve also become fatter and more diabetic in the past decades, the committee put their academic heads together and came up with the obvious answer: we’re still consuming too much saturated fat. So in the 2010 guidelines, they tell us to reduce saturated fat to just 7% of our calories. The committee even suggests putting kids on fat-restricted diets to protect them from diabetes:
The growing data to support a risk of T2D from SFA consumption indicates the need for fat-modified diets in persons with pre-diabetes, including those with metabolic syndrome, and with established diabetes. Since the ages of onset of T2D now include childhood, studies from adolescence through middle age would be useful to define when SFA-reduced diets would be most effective.
I found the whole document so biased and contradictory, I managed to get the entire Dietary Guidelines Advisory Committee (DGAC) on the phone so I could ask them to explain themselves. Here is a transcript of the conversation:
Fat Head: Thank you for taking the time to answer a few questions.
DGAC: No problem. We’re glad to help.
Fat Head: Wow … I’ve never heard a roomful of people say the exact same words at the exact time before.
DGAC: So you don’t attend Sunday mass anymore?
Fat Head: I, uh … I mean I’ve never heard people do that without knowing the words ahead of time. It’s pretty amazing.
DGAC: Well, as we made clear in our document, it’s important for policymakers to speak with one voice on nutrition. We’ve been practicing.
Fat Head: You’re very good at it.
DGAC: Thank you.
Fat Head: To get started, I want to just clarify your overall position on dietary fat. You stated that the federal government should continue recommending we limit our fat intake to 30% of total calories. But in your document, you also made these statements:
Currently, several lines of evidence indicate that the type of fat is more important in decreasing metabolic and CVD risk than the total amount of fat in the diet.
The effects of dietary fat, as well as the other macronutrients, and intermediate risk factors, are diverse and highly dependent on other factors such as physical activity and life style habits, and, importantly, individual genetic predisposition that is based on underlying genetic polymorphisms.
However, in the 2002 IOM report on macronutrient requirements there was the adoption of an AMDR of fat intake of 20-35 percent of calories because there were no clear differences in health outcomes in populations consuming dietary fat within this range.
DGAC: Sounds like you’re speaking Italic.
Fat Head: I am, but only when I’m quoting you directly. It’s for the benefit of my readers.
DGAC: Fair enough.
Fat Head: The point is, you gave a pretty specific limit for fat intake, then stated elsewhere that it’s the type of fat that really matters, and that there are wide variations in fat intake within healthy populations. So why give us a limit, then more or less say the amount of fat isn’t all that important?
DGAC: Because we wanted to work the term underlying genetic polymorphisms into the text.
Fat Head: But that doesn’t seem–
DGAC: We’re highly educated and like using a fancy term like that, but just try dropping it into a casual conversation. It’s nearly impossible.
Fat Head: Let me try this another way: Why recommend a 30% limit at all? What would happen if a large population consumed, say, a diet that was 40% fat?
Fat Head: Geez! I’ve never heard people scream in unison like that.
DGAC: What about the first Halloween movie?
Fat Head: Yeah, but not as a reaction to a simple question.
DGAC: Well, the very idea! Don’t you know eating fat causes diabetes?! A population that eats that much fat would have so many amputees, they’d look like a reunion of Civil War veterans.
Fat Head: Or like a bunch of Americans when I was in grade school.
DGAC: Don’t be silly. The last Civil War veteran died in 1956.
Fat Head: I’m merely pointing out that according to your own data tables, the average American diet was more than 40% fat in the 1970s. So where was all the type 2 diabetes?
DGAC: Well … obviously it was sitting there, like a bomb waiting to explode. Look what’s happened since then.
Fat Head: You mean since we started eating less fat and more carbohydrates?
DGAC: Clearly a case of too little, too late.
Fat Head: Diabetes in America has doubled in the past 10 to 15 years. You stated that according to the evidence, saturated fat makes us more likely to develop heart disease and diabetes, while monosaturated fats and polyunsaturated fats appear to prevent both. Here’s how you put it:
In contrast to CVD, T2D is clearly increasing in prevalence and incidence. T2D is a strong risk factor for atherosclerotic disease, but also carries a high burden of disability and healthcare costs, with diabetic nephropathy, retinopathy, and neuropathy as major sequelae. Because of this, T2D and T2D risk were included as disease outcomes related to fatty acid and cholesterol consumption.
Strong evidence indicates that intake of dietary SFA is positively associated with intermediate markers and end point health outcomes for two distinct metabolic pathways: 1) increased serum total and LDL cholesterol and increased risk of CVD and 2) increased markers of insulin resistance and increased risk of T2D. Conversely, decreased SFA intake improves measures of both CVD and T2D risk. The evidence shows that 5 percent energy decrease in SFA, replaced by MUFA or PUFA, decreases risk of CVD and T2D in healthy adults and improves insulin responsiveness in insulin resistant and T2D individuals.
DGAC: Yes, according to the studies that met our criteria, that’s true.
Fat Head: But I’m looking at the report here, and you also said this:
The consumption of harmful types and amounts of fatty acids and cholesterol has not changed appreciably since 1990.
Fat Head: Meanwhile, according to your data tables, the only fats we increased in our diets during the span when diabetes went through the roof were monosaturated and polyunsaturated. Since you’re big fans of observational evidence, what do you make of that observation?
Fat Head: Why not?
DCAG: Because we didn’t make that observation.
Fat Head: I see. Well, here’s another one for you: Compared to Americans, the French consume far more saturated fat, but far less polyunsaturated fat. They also have a lower rate of heart disease, and according to what I can find online, their rate of diabetes is less than half of ours. How do you explain that?
DGAC: It’s got to be the wine.
Fat Head: I knew you’d say that, but as it turns out, there are other countries where people drink just as much wine, but have a lot more heart disease than the French.
DGAC: Do the people in those other countries drink French wine?
Fat Head: Well … I don’t think so.
DGAC: There you go.
Fat Head: All throughout your document, you write about saturated fatty acids and trans fatty acids as if they’re the same. Here are a few examples:
The potential negative effects of dietary cholesterol are relatively small compared to those of SFA and trans fatty acids.
The relationship between dietary saturated fat, trans fat and cholesterol and deleterious health outcomes at the population level has long been recognized, with recommendations for modification of total fat, SFA, and cholesterol dating back to the 1980 Guidelines.
Strong and consistent evidence indicates that dietary PUFA are associated with improved blood lipids related to CVD, in particular when PUFA is a replacement for dietary SFA or trans fatty acids.
DGAC: What’s your point?
Fat Head: You are aware, aren’t you, that saturated fat and trans fat are two completely different substances? In your search for all the relevant data, did you notice that heart disease didn’t become an epidemic until we started replacing lard and tallow with Crisco and corn-oil margarine and other trans fats?
DGAC: Look, saturated fat and trans fat are both solid at room temperature. And if they’re solid at room temperature, they’re solid inside your body, so they clog your arteries.
Fat Head: How do you know that?
DGAC: Dr. Oz explained it on Oprah.
Fat Head: But–
DGAC: And saturated fat intake is clearly associated with heart disease.
Fat Head: The American Journal of Clinical Nutrition published a study recently concluding that there’s no association whatsoever between saturated fat and heart disease.
DGAC: That one didn’t meet our selection criteria.
Fat Head: Yeah, I noticed you didn’t mention it. So what exactly were your selection criteria?
DGAC: Well, if you read the report carefully, you’ll see a lot of sentences that begin something like “A systematic review identified 12 studies that met the selection criteria …”
Fat Head: Which means?
DGAC: It means we selected the studies we identified, okay? Including several that showed an association between saturated fat and heart disease.
Fat Head: I wanted to ask you about those. Elsewhere in the document, you listed the top sources of saturated fat in the American diet. That list included pizza, grain-based desserts, dairy desserts, Mexican dishes, pasta dishes, corn chips, potato chips, candy and fried potatoes. So isn’t it fair to say that in the observational studies that met your criteria, people who ate more saturated fat also ate more pizza, grain-based desserts, dairy desserts, Mexican dishes, pasta dishes, corn chips, potato chips, candy and fried potatoes?
DGAC: Uh … yeah, but … all that fat, you see … it’s …
Fat Head: I’ve never heard people stammer in unison before. That’s freaky.
DGAC: The takeaway here is that people who eat a lot of saturated fat have more heart disease.
Fat Head: Perhaps because they also eat a lot of junk that’s full of refined carbohydrates?
DGAC: Carbohydrates have nothing to do with it!
Fat Head: That’s strange. Let me quote your document:
In all cases of isocaloric SFA or trans fatty acid substitution, there is a decrease in CHD risk. However, it should be noted that when MUFA or PUFA are substituted by any kind of carbohydrates, CHD risk increased.
Fat Head: So replacing two different types of fats with any kind of carbohydrate increased the risk of heart disease. It’s right there in your report. And so is this:
High MUFA intake, when replacing a high carbohydrate intake, results in improved biomarkers of glucose tolerance and diabetic control.
DGAC: Those monosaturated fats are truly wonderful.
Fat Head: Don’t you think maybe reducing carbohydrates figured into it?
DGAC: Of course not. Carbohydrates are good for you. It’s the fat intake you need to watch.
Fat Head: But you stated in your report that carbohydrate is the only macronutrient that makes up a bigger portion of our diets now than it did 30 years ago. Then you wrote about the dramatic rise in metabolic syndrome, and how it’s characterized by high blood pressure, high triglycerides, high blood glucose, obesity and low HDL. You quoted research that fat raises HDL. And a ton of other research shows that carbohydrates raise blood pressure, blood sugar and triglycerides.
Fat Head: So I’m trying to figure out why you’re still recommending we limit our fats and eat a lot of carbohydrates. That was your big conclusion in another section of the report: Healthy diets are high in carbohydrates.
DGAC: That’s right.
Fat Head: What?!
DGAC: Correct. You got it, Mister.
Fat Head: So you’re still saying–
DGAC: Cut th fat. Eat your carbohydrates. Live long and prosper.
Fat Head: And you don’t see any contradictions there?
DGAC: No. That’s why we’re speaking with one voice.
Fat Head: Thank you for clearing things up.