A couple days ago, Charlie Bell, the former McDonald’s CEO, died of colorectal cancer at the age of 44. About a year ago, the CEO before him died of heart attack at the age of 60. Many people keenly pointed out that it is McDonald’s hamburgers that killed them. Well, maybe. The free meals that all McDonald’s employees enjoy during the work are fat loaded fast foods. They are not healthy foods. We all know that. But how bad the McDonald’s fatty foods are?

Today I took my family to the infamous McDonald’s simply because both my wife and I didn’t want to cook the lunch. I ordered a Big Mac (without French fries) and my son ordered a chicken nugget Happy Meal. My wife, a health-conscious person, ordered a salad. It was a quite joyful meal and everybody felt stuffed. Out of my professional curiosity, before I walked out of the McDonald’s, I started wondering how much bad stuff I had eaten today. I looked around and discovered some nutrition brochures just right beside the door. I have to admit that I never noticed them before. Well, it wouldn’t hurt me if I grabbed a few brochures.

The McDonald’s nutrition fact booklet looks very professional. There is a huge table similar to the nutrition labels required by FDA. The table lists major nutrients for all foods McDonald’s currently serves. In this big messy table, I quickly located the line for my Big Mac. A Big Mac weights about 219 grams and has 560 kcal. Well, it sounds just fine for my 2000 kcal daily allowance. The next column shows that 270 kcal are from fat in the Big Mac (total fat: 30 grams, half of my daily allowance, FYI, the DV% column, daily value, tells how much your daily allowance has been spent by eating this meal.). Hmmm, 50% seems too much.

I moved my fingers to the next column which is the bad fat–saturated fat. It is about 10 grams, again accounting for half of my daily allowance (total allowance 20 grams). Gee, after gobbling down some tasteless beef patties and low grade cheeses, all of a sudden I had lost half of my bad stuff allowance. This created some internal conflicts when I was trying to enjoy some delicious pork chunks during the dinner.

The next column is a very interesting one. Trans-fats are about 1.5 grams in a Big Mac. Although 1.5 grams don’t seem a lot, my daily allowance for trans-fats is 0, as the new dietary guideline almost prohibits eating trans-fats. I quickly searched down the trans-fat column to see which food has the largest amount of trans-fats. Not surprisingly, it is the large French Fries: 6 grams of trans-fats per serving! Thank goodness, I was lucky leaving French fries out of my order (because I knew it before. :-)).
I asked my wife whether she knew the differences among saturated, unsaturated, and trans-fats. She looked somewhat embarrassed. She admitted that she knew something about saturated and unsaturated fats. But the “trans-fats” was a new word for her. This was not surprising. Her biochemistry knowledge was pretty rusty after so many years of not mentioning the word “biochemistry”.

Well, I haven’t done any lab work for years either. To be more scientifically learned, I decided to entertain my wife and myself with the joy of sharing knowledge. I grabbed my old medical biochemistry textbook only to be disappointed that there was no mention of trans-fats at all. My not-so-old nutrition textbook didn’t help me much either. Nevertheless, Google is always available to satisfy my curiosity.

Fatty acid is essentially a long chain of carbon atoms attached with lots of hydrogen atoms. In saturated fat, every carbon atom binds two hydrogen atoms (except at ends). In unsaturated fat, a couple carbon atoms have only one hydrogen atom, thus creating a double bond between two neighboring carbon atoms, i.e., unsaturated. There are monounsaturated or polyunsaturated fatty acids depending on the number of double bonds. Naturally, the two neighboring hydrogen atoms in these unsaturated sites stay at the same side of carbon chain, i.e., cis alignment. These unsaturated sites can be saturated by hydrogenation– adding hydrogen atoms onto carbon atoms. Most unsaturated fats (for example vegetable oils) are liquids and easily oxidized (when oil has disgusting smells, it is oxidized). Food industry commonly uses partial hydrogenation to create half-liquid half-solid fats. For some reasons, the two nicely aligned hydrogen atoms along the double-bonds sometimes move to opposite side, make a trans (opposite) alignment.

Recent knowledge suggests that trans-fats are as bad as saturated fats. Studies found that trans-fats can increase the risk of heart disease. Unfortunately, one study estimated that 2.6% of our total energy intake was from trans-fats. Cakes, cracks, animal products, margarines, shortening, and fried potatoes contain high trans-fat. Gosh, by saying this, I realized that I might have to throw away a pack of preserved cheese, a big bottle of shortening, two boxes of Oreos, and some of my son’s favorite cracks.

I once talked to someone who proposed labeling trans-fats. There were indeed some struggles between academics and industry. At the beginning, the food industry was very angered by this discovery. They complained that labeling trans-fats might confuse customers. For example, we used to recommend margarine over butter as healthy foods. Now we are saying what we said before is not 100% correct. In addition, the facility adjustment can also cost food industry a significant amount of money about which they care the most. Nevertheless, FDA recommended adding trans-fat content to food labels in July 2003.

Trans-fats are bad, but there is more bad stuff. The next column in the McDonald’s nutrition table is cholesterol. How much cholesterol does a McDonald’s Big Mac have? 80 mg, about one fourth of my daily allowance (300mg). My goal is to reduce cholesterol intake to a minimal level (say less than 300mg according to the dietary guideline). As a matter of fact, our human body can make cholesterol from carbohydrates in the liver. A high load of cholesterol in body can lead to atherosclerosis, in which arteries are fattened by the excessive deposit of cholesterol esters in blood vessel cells. The blood vessels may be blocked by the disruption of plaques. These plaques are the consequences of repeated inflammation within endothelium. If the blockage happens in heart vessels, it creates a heart attack; if it happens in brain, it creates a stroke.

Furthermore, human body only needs seven nutritionally essential fatty acids which our human body can’t synthesize. All these essential fatty acids are unsaturated fatty acids. DHA and EPA are among them. On the other hand, those saturated fatty acids can be synthesized within human body, for example, by liver cells. So they are not essential. People can live with very little saturated fat intake, as monks have practiced for thousands of years.

The take home message is this: vegetable oils and fish oils have a large amount of unsaturated fatty acids, while animal oils have lots of saturated fats. The new guideline further informs us that processed foods and oils are bad for you too because of trans-fats.

Another related message is a rule of thumb for your own benefit: the total cholesterol should be below 200 mg/dL; the low density lipoprotein (LDL), below 100 mg/dL; fasting triglyceride levels, below 150 mg/dL; and the high density lipoprotein (HDL), the good lipoprotein, ABOVE 40 mg/dL. I assume you have heard of these terms before.

There is other bad stuff in a Big Mac such as high sodium content. But I will leave it for my future post when talking about sodium, potassium, calcium, hypertension and the role of kidney in our body.