Tuesday, October 11, 2011

Get Your Fats Straight

Image Credit: Dawn Huczek

Last week, in an attempt to curb obesity rates and their related health complications, Denmark rolled out what quickly became dubbed the “fat tax” – a price hike targeting foods specifically by saturated fat content. Critics of the tax – and there are many – are taking aim from several directions, including social inequity, the uncertain efficacy of sin taxes in general, and the singling out of saturated fats over other dietary dangers (processed foods, refined sugars etc.). But throughout the reports and editorials, terms like “saturated fats” and “fatty foods” have been used almost interchangeably, as though there were no other fats in existence besides saturated ones. Denmark’s new food rules aren’t the only sign of triglyceride confusion. In my workplace on the other side of the Atlantic, a jar of reduced fat peanut butter has been loitering in the break room for months. Part of a coworker’s good intentioned but misguided attempt to eat healthier, the odious product is another reminder that we could all use a refresher course on our metabolic macromolecules.

Some fats are better than others
Let’s travel back in time (figuratively at least) to high school biology, where we learned that the structure of fats involves fatty acid chains, each composed of a long carbon skeleton decorated by a bunch of hydrogen atoms. The hydrogen to carbon ratio is what makes fats different both in physical form and nutritional function. If the carbons on the skeleton are all single-bonded to one another, this allows for the maximum number of hydrogens to be attached to the chain. The resulting fats are called saturated because the carbon chain is holding as much hydrogen as it can fit. Saturated fats (found mostly in foods from animal sources, such as butter) are solid at room temperature, which makes them desirable ingredient for sandwiches, baked goods, etc. Unfortunately, they have also been widely linked to cardiovascular problems like atherosclerosis. Unsaturated fats, on the other hand, are one or more hydrogens short of a full set. This occurs because at least one pair of carbons in the skeleton is double-bonded. These double bonds create fatty acid chains that have kinks in them. They can’t pack together as tightly as the straight chains of saturated fats and are thus usually liquid at room temperature. Rounding out the list of contrasts, unsaturated fats (found in foods like vegetable oils, nuts and fish) are linked to health benefits, such the lowering of bad (LDL) cholesterol.

This would be easy enough to keep straight if the food industry hadn’t come up with the idea of turning liquid vegetable oils into solid fats by “hydrogenation”, a process that breaks those carbon double bonds and sticks more hydrogens on there. In the best-case scenario, the fatty acid is fully hydrogenated and the consumer is rewarded with a product whose higher saturated fat content renders it solid enough to be applied to toast. But if unsaturated fats are only partially hydrogenated, the process can warp the stereochemistry on any remaining carbon double bonds and the dreaded trans fat is born.* In short, “unsaturated” means safe, whereas “saturated”, “hydrogenated” and “partially hydrogenated” means varying degrees of scary.

Reduced fat peanut butter: the devil’s lunch spread
So what’s so bad about reduced fat peanut butter? Given all the other unhealthy atrocities lurking in your local supermarket – chocolate-covered Oreos, frozen chicken pot pies, 2-liter jugs of soda the color of antifreeze – it may seem odd to single out reduced fat peanut butter for nutritional derision. But what is especially evil about this product is that it takes something that is initially healthy (peanuts are naturally low in saturated fat and high in unsaturated fat) and defiles it with a host of questionable ingredients that render it less so, which is then advertised as an improvement.

And then there's portion size...  Image Credit: Dan McKay
Ideally everyone would wise up and purchase plain, unadulterated peanut butter such as the reasonably affordable Central Market store brand I’m using as a reference point. It contains a single ingredient: peanuts. Pulverized peanuts serve up 190 calories, and 16 grams of fat per 2 tablespoon serving (which is more than enough to make a sandwich).

Because the oil in pure peanut butter tends to separate out after it’s packaged and apparently some people find stirring to be a task too daunting to undertake, many national brands add a dash of hydrogenated vegetable oil to keep things all homogenized. They also add sugar. Go figure.

Sugared and hydrogenated peanut butter is already not great, but let’s have a look at the ingredients of reduced fat Skippy (they own the domain name “peanutbutter.com”, so it seems only fair to pick on their brand): roasted peanuts, corn syrup solids, sugar, soy protein, salt, hydrogenated vegetable oils (cottonseed, soybean and rapeseed), mono and diglycerides, minerals (magnesium oxide, zinc oxide, ferric orthophosphate, copper sulfate) vitamins (Niacinamide, pyridoxine hydrochloride, folic acid).

Oh, peanut butter, what have they done to you? To break things down a bit, many of the additional names are vitamins and minerals (strangely absent from the original Skippy product and not touted on the reduced fat version label). The remainder are additional texturizers and emulsifiers (if you’re going to take out peanuts, you’ve got to fill out the space with something) and even more sweetener, this time in the form of corn syrup solids, the second ingredient, sandwiched between peanuts and sugar. The resulting mess weighs in at 180 calories and 12 grams of fat per serving.

So reduced fat peanut butter shaves of 4 grams of fat (an underwhelming 25%) and 10 calories (pfff) and replaces it with increased sweeteners and fillers. Oh, and they throw in a secret multivitamin pill for your trouble.

What brings this to the level of absurdity is that reduced fat peanut butter is marketed toward those trying to control their weight. However nuts, though high in fat, have been linked to weight loss rather than gain as well as an array of other health benefits.

Something rotten in the state of Denmark
Image Credit: Bryan Ochalla.
Now while replacing unsaturated fats with processed sweeteners is a terrible idea, lowering saturated fat consumption is, in theory, a good one. That’s why, when I first heard about Denmark’s tax on saturated fats, I was totally ready to be on board. Sure, I said, make such foods more expensive and they will be used only as luxury items. Daily staples like butter and cheese will be saved for special occasions and replaced with foods high in healthy fats like olive oil and nuts. But it turns out to be a bit more complicated. The specific form of the Danish tax, as reported in the press, is a price increase equivalent to just under $3 (16 Kroner to be exact) per kg of saturated fat, and affects those foods whose saturated fat content exceeds 2.3%.

That 2.3% struck me as a bit low. While vegetable source fats are generally much lower in saturated fats than their animal derived counterparts, they are not completely absent of such fats. And with something like cooking oil, the calorie content comes exclusively from fat (as opposed to proteins or carbohydrates). A trip to the kitchen and some basic math revealed that both my preferred oils – olive and sesame – were comprised of 15% saturated fat.† But these are not unhealthy foods. The remaining 85 percent of their caloric make-up comes from a mixture of mono and poly-unsaturated fats (remember, unsaturated fats are linked to health benefits).

Where did this 2.3% cut-off come from? It seems so precise and yet so arbitrary. I seriously considered that it might be a typo, the intended figure being 23%. But no, every article thorough enough to report a percentage stated it as 2.3%. If Denmark’s tax is rigidly enforced, many foods considered to be healthful would also be subject to the price increase. Nutritious foods like walnuts and avocados would be too high in saturated fat to make the cut. Yet the okay list would include Cracker Jacks (too few peanuts to tip the scales) pretzels, and gummy bears (as well as every other fat-free candy out there). Considering that a healthy diet should contain some fat (20-35 percent of total daily caloric intake is the usual recommendation) that 2.3% limit seems illogically restrictive – an attempt to cut out not just saturated fat, but all fat.

While obesity is, in part, a problem of too much energy in and not enough out (i.e. lots of calories and little exercise), diseases associated with it are also influenced by the kind of calories input. One would think that the idea behind a tax aimed at saturated fat would be to encourage replacing foods high in saturated fats with those containing mostly unsaturated fats. But if even “good fats” are included in the tax, people might reach for other options. Some may reach for fruits and vegetables (though not avocados, it seems) but others may just follow the example of Skippy’s reduced fat products and replace fat with sugar. Perhaps I’m missing something. Denmark is welcome to check my math but for now I’m just going to go ahead and declare this tax almost as stupid as reduced fat peanut butter, which, by the way, is still too high in saturated fat to escape Danish taxation.

* You probably recall cis/trans isomers more from Chemistry class. It’s about the carbon-to-carbon double bond again and how atoms and molecules can end up on the same or opposite sides of that bond. In this example, both hydrogens on the same side yields a cis fatty acid, whereas hydrogens on opposite sides yields a trans fatty acid. The two isomers have different properties. Long story short, trans fat are bad for you. Very, very bad.

† As butter contains over 60% saturate fat, 15% is relatively low.

‡ Formula: (Grams of fat per serving)(9 [the calorie content of 1 gram of fat])/total calories per serving = percent fat, expressed as a decimal.
For instance olive oil: (2 grams saturated fat)(9 calories/gram)/120 calories = 0.15 = 15%

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