Food Becomes You

by Wendy Gordon

Fat is evil, right? Or at least part of a nutritional Axis of Evil, alongside saturated fats and cholesterol?

No. Like just about everything else in the world, the reality of fat is far more nuanced than that. While it is tempting to blame the vilification of fat on a cabal of doctors and pharmaceutical companies, these entities are only reacting to a universal human tendency: to simplify our complex and often contradictory universe and paint it black and white. Let's take a closer look at what we throw around so glibly.

Fat is an integral part of life. To be more exact, it is one of the three primary constituents of food, along with carbohydrates and protein. Fat packs the most energy, providing nine calories per gram as opposed to four for carbohydrates and protein. In times of food scarcity (most of human history), this was a valued commodity. While in Tuscany, I sampled a traditional delicacy known as "lardo," thin slices of rendered pork fat. Unappetizing as that may sound today, for centuries it provided valuable calories to peasants laboring on the steep hillsides of western Tuscany. Along with providing calories, fat is the primary carrier of flavor in food. It also adds: an appetizing texture; provides essential constituents for brain development, sexual function reproduction and infant development; promotes healthy skin and hair; and carries fat soluble nutrients such as vitamin E.

Fats are composed of chains of fatty acids bound to the alcohol glycerol. These chains vary in length and in the proportion to hydrogen atoms they contain. Depending on the proportion of hydrogen atoms, fats are ranked according to degree of "saturation." The more saturated a fat is, the more solid it is at room temperature. Generally speaking, animal fats are more saturated than vegetable, with the exception of palm and coconut oil. Though the body is capable of making most fatty acids, it cannot synthesize long chain fatty acids which makes them an essential nutrient. Fish is the most complete source, while flaxseed, canola oil, nuts, seeds and leafy vegetables provide a more limited range of this vital nutrient.

For a long time, polyunsaturated fats were assumed to be the healthiest, but beginning in the 1990's, scientists came to realize that monounsaturated fats (found in olives, peanuts and avocado) were the most beneficial for heart health and carried the least risk of adverse effects. They also discovered evidence that saturated fats were not a blanket entity. Certain saturated fats - in particular stearic acid, found in chocolate and red meat - are at worst neutral and may actually be beneficial.

Trans fats are a totally different animal. Unknown in nature, they are artificially created by adding hydrogen atoms to polyunsaturated fats. This solidifies liquid oils, increasing shelf life and flavor stability. Trans fats are found in many shortenings and margarines and thus, the foods made from them such as commercial french fries. First popularized in the 1960's, trans fats have since turned out to be more damaging to heart health than a slab of paté. Mercifully, they are currently, albeit slowly, being phased out of the U.S. food supply.

Since cholesterol contains fat and foods high in saturated fat generally (though not always) are high in cholesterol, the two are bundled together in the public mind. However, cholesterol is actually a distinct substance - a steroid. Cholesterol is an essential component of bile acids, vitamin D, all sex hormones, aldosterone and cortisol. It is essential for brain development and the normal function of cellular membranes. While some cholesterol is ingested via food, the body also manufactures its own cholesterol.

Evidence indicates that people's natural cholesterol baselines vary, and that individuals differ in their susceptibility to dietary cholesterol. Triglycerides are the basic form of digested fat that floats through the bloodstream.

Triglyceride levels vary dramatically with the amount of fat and alcohol ingested within the previous twelve hours, so fasting blood levels are the only ones with any diagnostic value. High fat diets raise triglycerides, but so do diets high in refined carbohydrates and alcohol. Ignored for a long time, triglyceride levels are now recognized as a potentially major factor in heart disease.

Cholesterol is not water soluble, so it must be transported through the blood stream via carriers known as lipoproteins. These come in several forms, of which the primary are HDLs (high density lipoproteins) and LDLs (low density lipoproteins). LDLs carry cholesterol to the cells for deposit, while HDLs carry cholesterol away from the cells to the liver for eventual elimination. Judging from the number of references to "good" cholesterol and "bad" cholesterol, you'd think these two lipoproteins were duking it out in your bloodstream. The reality is far more complicated. While elevated LDL levels are one of a cluster of factors associated with cardiovascular disease risk, there has yet to be one study that points the finger specifically at LDLs. As a natural constituent of the body, presumably they have some legitimate role to play.

Ruptured arterial plaques are believed to cause most heart attacks and strokes, yet no one is certain precisely how these plaques develop and what causes them to break loose. Plaques are not just globs of LDLs. They contain many substances, including smooth muscle cells, calcium, connective tissue, white blood cells, cholesterol and fatty acids, all found in the human body. A variety of factors triggers the aggregation of these substances into a plaque on the arterial wall. These factors include nutrient deficiencies, poor glycemic control (as in diabetes), cigarette smoking, psychological stress, overly high iron levels, trans fats and microbial infection.

Equally unclear is the link between diet and serum cholesterol levels. Some people manufacture more cholesterol than others, regardless of diet. Some could eat egg yolks all day without raising their cholesterol level, while others are born with inherited "hypercholesterolemias" where their body manufactures extremely high levels of cholesterol (again, regardless of diet). A recently reported study indicates that some people transport cholesterol differently than others, in larger sized "particles" that are less likely to clog arteries. Foods that raise LDL levels often raise HDL as well, keeping the ratio even.

Statin drugs, which lower LDL levels, are one of the most popularly prescribed drugs in the United States. They lower mortality rates in men already suffering from heart disease, but not nearly as effective when used as a preventive measure or by women. Also, there's no proof that the LDL-lowering function of these drugs is what makes them effective. Statins, which block an enzyme involved in cholesterol synthesis, show many other effects, such as improved arterial function and anti-clotting activity. Side effects of statins (especially in the elderly) include memory loss, irritability, personality changes, and muscle pain. And (should this be surprising?) the overall reduction in death rates is no greater than that seen with less toxic interventions, such as vegetable-rich diets, omega-3 fatty acid supplementation and exercise.

Since the 1970's mainstream organizations have recommended limiting fat intake to thirty percent of total calories, with only ten percent coming from saturated fats. However, two computer models developed as early as the 1980's indicated that people diligently following these dictates gained minimal benefits: a life expectancy increase of one year for those with additional risk factors such as high blood pressure; a gain of as little as three days for those who didn't. A study of over 28,000 middle-aged Swedes failed to pinpoint any type of fat intake (total, saturated, polyunsaturated or monounsaturated) as a definitive risk factor.

The current prevalence of heart disease is paradoxically the result of triumphs of modern medicine and sanitation. Very few people today die of infectious illness (keep in mind that pneumonia was the most common cause of death as recently as the early 1900's) allowing them to survive long enough to develop chronic conditions like heart disease. Take a look at cookbooks from a century ago, when heart disease ranked significantly lower as a cause of mortality. You'll find an awful lot of eggs, butter and organ meats. And, no one was taking statins. Clearly, there is more to the story.

None of this is to imply that diet does not affect cardiovascular health. It most definitely does. Nor am I recommending you put down this article and cut yourself a big slice of lardo. It's just that fat is far from the only culprit.

An increasing body of evidence suggests that antioxidants and omega-3 fish oils protect against formation of arterial plaques. In several studies, subjects with a higher percentage of oxidized LDL showed a greater incidence of heart disease. Eating antioxidant-rich foods such as fish, fruits, and vegetables also exerts a protective effect. Again, as manufactured trans fats are not found in nature, it makes sense that they would disrupt the body's natural handling of fat and promote disease. Complicating health factors such as obesity, diabetes and high blood pressure increase cardiovascular disease risk. Refined carbohydrates and excess alcohol increase serum triglycerides, another risk factor. Since environmental toxins and psychological stress also cause oxidative damage, they qualify as risk factors. As tempting as it is to look for a black and white solution, the problem of cardiovascular disease can only be seen in shades of gray.

Wendy Gordon is a writer and restaurant reviewer who lives in Portland, Oregon. She has a Masters Degree in Clinical Nutrition from the University of Chicago.