Fats are important to the taste and texture of foods. Fats contribute flavor and aroma and influence the texture by adding creaminess, smoothness moistness or crispiness. In addition, they help make foods tender and most importantly they help us absorb the fat soluble vitamins, A, D, E, and K. Fats also give us satiety, which is very important in weight maintenance. Fats have received a really bad rap in the past, but are they making a comeback?
Because fats provide 9 kcal/g of energy, it takes less by weight to provide the same amount of calories as a protein or carbohydrate source. By practicing balance, variety and moderation, fats too can be part of a healthy diet.
The 2010 Dietary Guidelines recommend limiting our intake of solid (saturated) fats. Solid fats are fats that are solid at room temperature, like beef fat, butter, and shortening. Saturated fats have no double bonds and are straight chains, allowing them to pack together-thus making them solid at room temperature. Saturated fats mainly come from animal foods and can also be made from vegetable oils through a process called hydrogenation. Some common solid fats are:
- milk fat
- beef fat (tallow, suet)
- chicken fat
- pork fat (lard)
- stick margarine
- hydrogenated and partially hydrogenated oils*
- coconut oil*
- palm and palm kernel oils*
* The starred items are called “oils” because they come from plant sources. Even though they are called “oils,” they are considered to be solid fats because they are high in saturated or trans fatty acids.
Now, this is where we are going to deviate from the Dietary Guidelines recommendations. Solid fats are high in saturated fatty acids. For years, top governmental agencies and other health authorities have recommended that we reduce our intake of saturated fatty acids, as they have been linked to cause heart disease. This recommendation was derived from a study done in the 1950’s by a researcher named Ancel Keys. Dr. Keys studied the eating habits of seven countries and made the association that saturated fat and cholesterol lead to heart disease. Studies that showed results opposite to this theory were in part, ignored. This theory, called the lipid hypothesis theory, has taken root in our nation, and has been embraced by food companies, governmental agencies and health agencies.
Saturated fat and cholesterol from foods on the supermarket shelf were replaced with carbohydrate laden ingredients-mostly of the refined type. In addition, natural products, like beef tallow and pork lard, were replaced with synthesized oils-hydrogenated oils full of trans fatty acids. We know now that trans fatty acids have a deadly effect on heart disease, there is no dispute about this and no controversy. Synthetically produced trans fatty acid intake should be 0. In fact, entire cities are banning trans fatty acids from use in their restaurants, such as New York and Chicago. To read more about the trans fatty acid ban, click on this link: http://www.nytimes.com/2006/12/06/nyregion/06fat.html?_r=0
Now, back to saturated fatty acids. Are saturated fatty acids correlated to heart disease? According to new, and not so new, research, no-they are not linked to heart disease. “More than 20 studies have shown that people who have heart attacks don’t eat more saturated fat than healthy people,” says Swedish researcher Uffe Ravnskov, MD, PhD. In fact, in France, saturated fat is eaten with gusto (butter, cream sauces, etc.), and they have lower rates of heart disease than Americans. Some believe it is due to their consumption of red wine, or maybe their level of exercise counteracts the effects of the saturated fat. At any rate, they even have a name for this phenomenon-called the French Paradox. Researchers studied over 20 studies, looking at 350,000 people, with study periods ranging from 5-23 years. The findings were published in 2011 in the American Journal of Clinical Nutrition.
Here is an excerpt from the study “No clear benefit of substituting carbohydrates for saturated fatty acids (SFA) has been shown, although there might be a benefit if the carbohydrate is unrefined and has a low glycemic index. Insufficient evidence exists to judge the effect on coronary heart disease (CHD) risk of replacing SFA with monounsaturated fatty acids. No clear association between SFA intake relative to refined carbohydrates and the risk of insulin resistance and diabetes has been shown. The effect of diet on a single biomarker is insufficient evidence to assess CHD risk. The combination of multiple biomarkers and the use of clinical endpoints could help substantiate the effects on CHD. Furthermore, the effect of particular foods on CHD cannot be predicted solely by their content of total SFAs because individual SFAs may have different cardiovascular effects and major SFA food sources contain other constituents that could influence CHD risk.”
What do you make of this contradictory information? How was all of this information so misconstrued? There are many kinds of saturated fatty acids, ranging in chain length from 3 all the way to 36 carbons. “Evidence that SFAs elevate total and LDL cholesterol concentrations is the basis for guidelines to reduce SFA intakes. However, the metabolic aspects of individual SFAs are complex and lack uniformity”(Ramsden, et al, 2009). In addition, overall, saturated fats have been shown to raise LDL cholesterol, which is the bad cholesterol-or is it? The LDL fraction of cholesterol is made up of multiple particle sizes. There is actually “good” LDL and “bad” LDL! “We’ve shown in our own research that in the great majority of individuals, this increase in LDL reflects an increase in pattern A LDL,” explains Dr. Krauss, a lipid specialist and the director of atherosclerosis research at the Children’s Hospital Oakland Research Institute. Pattern A LDL is the good form of LDL.
In fact, saturated fat has also been shown to have an increasing effect on “good” HDL form of cholesterol. Plus, when you reduce your intake of saturated fat, or any fat for that matter, in America, it is typically replaced with refined carbohydrates. “Little will be gained if saturated fat is simply replaced by carbohydrates, especially if these are mainly refined starches and sugar,” says Walter Willett, MD, DrPH, who heads the nutrition department at the Harvard School of Public Health.
There is no doubt that research over the past decade has shown that saturated fats affect heart disease. But, were other factors in these research studies taken into consideration? Yes, the people in these studies were eating saturated fats and contracting heart disease, but, they were also eating refined carbohydrates, trans fatty acids, and, well, just being human.
You might be thinking, yeah, but what about the Chinese, who eat lots of white rice? Wouldn’t that be considered refined carbohydrates? Don’t they have lower incidence of heart disease? They do, and yes, they do eat white rice, pretty much with every meal. What’s important is the food that they are eating with the rice-vegetables, and more vegetables, and some meat, including organ meats. They do not fill their diets with honeybuns, donuts, cheezits, or chips. They don’t drink soft drinks either. One of my graduate students from China told me about her experience at an American grocery store. She said that everyone’s baskets had boxes in them (she was meaning the highly processed packaged foods so commonly sold at American grocery stores). She said in her country, they mostly purchase fresh produce, meats, and, of course, rice.
OK, so what do you need to take from all of this is:
- Nutrition research is always changing, as science and technology becomes more advanced, so does our knowledge of how nutrition and the body interact.
- Food is a complex entity, and should be treated as such. It is very difficult to show cause and effect based on one nutrient-and its interaction in the body. In addition, people are complex. Even though research attempts to control variables, it is still difficult to remove people from their lives. Exercise, stress, genes, emotions, and even the smallest of bacteria residing in the gastrointestinal tract, affect our health.
Another word about omega-3 fatty acids
Americans eat way too much Omega-6 and not enough Omega-3 fatty acids. Most of the omega-6 fatty acids in the American diet come from soybean oil salad dressings and mayonnaise. Omega-3 fatty acids are found in fish such as mackerel, herring, trout, salmon, anchovies, sardines, tuna, and oysters. Less concentrated sources include shrimp, mussels, squid, and scallops. How many of you eat anchovies and sardines on a weekly basis? You can see how our omega-6 to omega-3 intake is so much higher than it should be. (Salmon is a great choice! There is salmon recipe at the end of this module.) The American Heart Association recommends eating fish twice a week. Pregnant women and children need to be careful of the amount of mercury in fish. Best sources for them would be shrimp, canned light tuna, salmon, pollock and catfish. While eating fish is healthy, taking fish oil supplements may not be as good. For one thing, taking too much can have side effects and some supplements contain high levels of mercury. As with any supplement, use caution when taking them.
Unsaturated fatty acids
Unsaturated fatty acids are the mono-and poly-unsaturated fatty acids. The monounsaturated (MUFA) group has one double bond in its structure, while polyunsaturated fats (PUFA) have two or more double bonds. Double bonds cause structural kinks, causing them to stack together loosely, making them liquid at room temperature. MUFA are found in high amounts in olive oil, avocados and canola oil. PUFA are found in nuts and vegetable oils such as soybean, safflower, sunflower and corn oil. Linoleic and linolenic are the most common PUFA and are considered essential, as our body can’t make them.
Cholesterol is so important for our health that our body makes way more than we can eat in our diet. Cholesterol is responsible for making steroid hormones, contributing to the structure of the cell membrane, and it is essential for brain development and function. Many studies show that dietary cholesterol has no effect on heart disease. Eggs have now been exonerated, and it just goes to show, that research and the interpretation of research, is ever changing.
Take Home Message
How do you lower your risk for heart disease? Eat a well-balanced diet filled with fruits and vegetables, practice moderation (not avoidance) with all fats (except avoid trans fat like the plague), focus on omega 3 fatty acids and by all means, reduce your intake of refined carbohydrates. In addition, get plenty of exercise and learn how to manage stress. The more unprocessed, naturally raised, traditional foods you can find, the better!