Bittman changes his tune on Sugar Study, while Mother Jones Doubles Down

There’s been an interesting edit in Marc Bittman’s sugar post, as he has now changed his tune on the PLoS one sugar study, now Bittman acknowledges obesity too is important. That was big of him, it is after all, the most important factor. Maybe my angry letter to the editor had an effect, but he’s grudgingly changed this statement:

In other words, according to this study, obesity doesn’t cause diabetes: sugar does.

To:

In other words, according to this study, it’s not just obesity that can cause diabetes: sugar can cause it, too, irrespective of obesity. And obesity does not always lead to diabetes.

The second sentence is totally unnecessary. Of course obesity doesn’t always cause diabetes, or heart attack or whatever. Nor do cigarettes always cause lung cancer. Nor does sugar intake always lead to obesity or diabetes. But obesity is the primary cause of type two diabetes, just as cigarettes are the primary cause of lung cancer, and who knows what sugar is doing.

Mother Jones, sadly, has decided to double down, calling the PLoS One study the “Best. Diet. Study. Ever.” It’s not, of course. It’s merely interesting and suggestive of an effect. It is not nearly proof of causation. They also laud the Mediterranean diet study (maybe it was supposed to be the Best. Study. Ever.?), however, they again show they’re not actually reading these papers because if you read our coverage of the study you’d know they didn’t actually study the Mediterranean diet! In a case of the blind leading the blind, they quote Bittman’s misinformed piece on the Mediterranean diet study

Let’s cut to the chase: The diet that seems so valuable is our old friend the “Mediterranean” diet (not that many Mediterraneans actually eat this way). It’s as straightforward as it is un-American: low in red meat, low in sugar and hyperprocessed carbs, low in junk. High in just about everything else — healthful fat (especially olive oil), vegetables, fruits, legumes and what the people who designed the diet determined to be beneficial, or at least less-harmful, animal products; in this case fish, eggs and low-fat dairy.

This is real food, delicious food, mostly easy-to-make food. You can eat this way without guilt and be happy and healthy. Unless you’re committed to a diet big on junk and red meat, or you don’t like to cook, there is little downside

Except for one critical fact. The subjects assigned to the Mediterranean diet did not have lower consumption of red meat, sugar and hyperprocessed carbs, or other junk! If you look at the supplementary data, you see that the subjects took the positive recommendations of the diet (olive oil, nuts, fish), and more or less ignored the negative recommendations (less meat, less spreadable fats/butter, less baked goods). If you look at figures like supplementary S6, the study groups did not change their diets in these categories relative to the controls, so the effects on their cardiovascular events relative to controls aren’t likely to be from the diet recommendations. When there were changes relative to baseline, even when statistically significant, the changes were tiny.

The participants in this study actually had a very high fat intake, about 35-40% of calories across all groups. And while there was a statistically-significant decrease in cardiovascular events like stroke and heart attack in both study groups (Med + olive oil, Med + nuts), only one arm of the so-called Mediterranean diet (Med + Olive oil) had a non-significant decrease in mortality, while the other arm (Med + Nuts) had a similar curve compared to the “do nothing” control. My interpretation of this, and it’s fine to be critical of it, is that this isn’t that meaningful. If anything, the only variable correlating with decrease in mortality was excess olive oil consumption (> 4 tbsp/day), not the Mediterranean diet. Either that, or eating nuts cancels out the beneficial effects of the diet on mortality.

This is why people always dump on nutrition science when it appears to change every 10 years. Results get overblown, and when the inevitable regression towards the mean occurs, we get blamed for it. The reality is, the press coverage of science is extremely poor, and there is not adequate critical analysis and presentation of results to their audience.

No, It's Not the Sugar – Bittman and MotherJones have overinterpreted another study

Diet seems to be all over the New York Times this week, with an oversell of the benefits of the Mediterranean diet, and now Mark Bittman, everyone’s favorite food scold, declaring sugar is the culprit for rising diabetes. His article is based on this interesting new article in PLoS One and begins with this wildly-inaccurate summary:

Sugar is indeed toxic. It may not be the only problem with the Standard American Diet, but it’s fast becoming clear that it’s the major one.

A study published in the Feb. 27 issue of the journal PLoS One links increased consumption of sugar with increased rates of diabetes by examining the data on sugar availability and the rate of diabetes in 175 countries over the past decade. And after accounting for many other factors, the researchers found that increased sugar in a population’s food supply was linked to higher diabetes rates independent of rates of obesity.

In other words, according to this study, obesity doesn’t cause diabetes: sugar does.

No! Not even close. I hate to repeat his misstatement, because I’d hate to reinforce this as a new myth, but it’s critical to see his full mistake here. This is a wildly inaccurate summary of the authors’ findings, and one they don’t even endorse in their discussion. Bittman has actually just said “obesity doesn’t cause diabetes”, and now has proven himself a deluded fool.

Let’s talk about this paper. This is what is called an “ecological study”, which means it studies populations as a whole, rather than individual patients. Using data from the United Nations Food and Agricultural Organization, the International Diabetes Federation, and various economic indicators from the World Bank, the authors compared populations of whole countries, in particular the prevalence of diabetes correlated to other factors such as GDP, urbanization, age, obesity, and availability of certain varieties of food like sugar, meat, fibers, cereals and oil. Using the rise, or fall, of diabetes prevalence over the last decade in various countries, they correlated this increase with increasing availability of sugar, obesity, urbanization, aging populations etc., and found a few interesting things. For one, increases in GDP, overweight and obesity, tracked significantly with increasing diabetes prevalence. But interestingly, when those factors were controlled for, increasing availability of sugar also tracked linearly with increasing diabetes prevalence, and the longer the duration of the exposure, the worse it got.

However, this does not mean that “obesity doesn’t cause” diabetes, if anything, it’s further support for the exact opposite. While a correlative study can’t be a “smoking gun” for anything, the data in this paper supports increasing modernization/GDP, obesity, and sugar availability are all correlated with higher diabetes prevalence. Even if the sugar relationship is causal, which is no guarantee, the increase in sugar availability could only explain 1/4 of the increase in diabetes prevalence. Obesity is still the main cause of diabetes, which can be demonstrated on an individual level by increases in weight resulting in loss of glycemic control, and subsequent weight loss results in return of euglycemia. In particular, the results of studies of bariatric surgery, in both restrictive and bypass procedures, weight loss is accompanied by improvement in diabetes. The attempts of toxin paranoids like Bittman to reclassify sugar as a diabetes-causing agent, and to dismiss obesity as a cause, are highly premature.

Mother Jones, has a slightly more balanced read, but it still oversells the results.

This is a correlation, of course, and correlation does not always equal causation. On the other hand, it’s an exceptionally strong correlation.

Well, that’s another overstatement. Want to see a picture?

http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0057873.g002&representation=PNG_M

Article Source: The Relationship of Sugar to Population-Level Diabetes Prevalence: An Econometric Analysis of Repeated Cross-Sectional Data

Basu S, Yoffe P, Hills N, Lustig RH (2013) The Relationship of Sugar to Population-Level Diabetes Prevalence: An Econometric Analysis of Repeated Cross-Sectional Data. PLoS ONE 8(2): e57873. doi:10.1371/journal.pone.0057873

Figure 2. Adjusted association of sugar availability (kcal/person/day) with diabetes prevalence (% adults 20–79 years old).

I wonder what the R-squared is on that line fit. Now, consider a comparison with obesity rates by diabetes prevalence:

Figure 1. Relationship between obesity and diabetes prevalence rates worldwide.

Obesity prevalence is defined as the percentage of the population aged 15 to 100 years old with body mass index greater than or equal to 30 kg/meters squared, from the World Health Organization Global Infobase 2012 edition. Diabetes prevalence is defined as the percentage of the population aged 20 to 79 years old with diabetes, from the International Diabetes Federation Diabetes Atlas 2011 edition. Three-letter codes are ISO standard codes for country names.
doi:10.1371/journal.pone.0057873.g001

Hmm, they didn’t fit a line here, but I can bet the fit would be better. Diabetes strongly correlates with BMI, this has been shown time and again using national survey data like NHANES or SHIELD. And before people start whining about BMI as an imperfect measure of obesity, it is perfectly appropriate for studies at a population level, and other metrics such as waist size, hip/waist ratios etc., all show the same thing. Diabetes risk increases linearly with BMI, with as many as 30% of people with BMI > 40 having diabetes, and further, we know from cohort and interventional studies that weight loss results in decreased diabetes. Much of this data is correlative as well (with the exception of the weight-loss studies), and the study that would prove this for certain – dividing people into diets providing excess fat, vs sugar, vs mixed calories, vs controls, with resultant measurement of diabetes rates, would be unethical. Either way, declaring sugar the enemy is both incomplete, and premature. While this paper provides interesting correlative evidence for increased sugar availability increasing diabetes prevalence, it is still subject to risk of confounding errors, it is correlative, and the link does not explain away other known causes of type II diabetes such as obesity. It is a warning however, and we should dedicate more study towards determining if sugar consumption (rather than mere availability) is an independent risk factor for type II diabetes.

Bittman has wildly overstated the case made by this article. He should retract his claims, and the title and false claims should be corrected by the editors. This is a terrible misrepresentation of what this study shows.