Principles of healthy eating. Part 5.
By Roman Pawlak, Ph.D, RD
Healthy diet should be exclusively or primarily based on foods of plant origin. Meats, especially red meat should be avoided. One area of confusion regarding healthy diet has to do with intake of dietary fat. There are those that advocate adherence of very low-fat diet. Both vegetable oils and animal fats have been used in food preparation. In the Bible, for example, olive oil is mentioned as a blessing for those consuming it. Animal fats, on the other hand, is prohibited for consumption. In the 7th chapter of the Book of Leviticus, we read God’s command to Moses, the leader of the Israelites: “Speak to the children of Israel, saying: ‘You shall not eat any fat, of ox or sheep or goat.’” Pork intake is prohibited in the Bible and thus pork fat such as lard was prohibited as well. In the Book of Deuteronomy we read regarding olive oil: “For the LORD your God is bringing you into a good land, a land of brooks of water, of fountains and springs, that flow out of valleys and hills; a land of wheat and barley, of vines and fig trees and pomegranates, a land of olive oil and honey; (...).” Olive oil is also mentioned elsewhere in the Scriptures. Some of these references refer to its use in olive lamps. In other passages, such as in the fragment of the Book of Numbers, its use is clearly referred to food preparation: “Now the manna was like coriander seed, and its color like the color of bdellium. The people went about and gathered it, ground it on millstones or beat it in the mortar, cooked it in pans, and made cakes of it; and its taste was like the taste of pastry prepared with oil.” Some foods are naturally rich in fat and/or oils. These include meats, milk and dairy products, nuts and avocado. Also, a variety of different types of fats and oils are currently available to consumers in grocery stores. In addition, both fats and oils are added in various amounts to commonly consumed products, usually in food preparation. These products include
salad dressings, mayonnaise, French fries, many baked deserts, pizza and many others. How and to what extend fats and oils affect our health depends on several factors, especially the quantity and kind of fat ingested. There are several types of fatty acids. These include saturated fatty acids, trans-fatty acids, monounsaturated and polyunsaturated fatty acids. Cholesterol is perhaps one of the best example of fats commonly consumed. Trans-fatty acids occur naturally in foods such as meats and dairy products and also can be made when unsaturated fatty acids (either monounsaturated or polyunsaturated) and artificially converted to saturated fatty acids. This conversion is done using heat and a catalyst. The artificially made trans fatty acids along with saturated fatty acids and dietary cholesterol when consumed in excess are harmful. On the other hand, unsaturated fatty acids are necessary for the proper functioning of the body, and protect us from the onset of certain diseases. Trans-fats, saturated fats and cholesterol increase the risk of cardiovascular diseases and other health problems, such as diabetes and certain cancers. They also increase serum cholesterol level. For many years it has been known that elevated serum cholesterol level increases chances of developing cardiovascular disease. Recent studies showed that individuals with elevated serum cholesterol level have a higher risk of developing Alzheimer's disease and dementia. Monounsaturated and polyunsaturated fatty acids are generally beneficial to our health. Polyunsaturated fatty acids are divided into those that belong to the omega-3 and those from the omega-6 group. The omega-3 fats are considered to be particularly beneficial for health. It is also believed that the majority of people who live in Europe and North America do not consume the recommended amounts of these fatty acids. The health effect of monounsaturated fatty acids depends on the source of this fat in our diet. If they are mainly derived from meats and foods of
animal origin they do not seem to have the same protective effect as when they are consumed from plant foods. Animal products contain mainly saturated and monounsaturated fats. However, vegetable products, with a few exceptions, mainly contain unsaturated fatty acids. A healthy diet should be comprised of a small or no amount of fat of animal origin, including saturated fat and cholesterol, as well as a minimum amount of or no trans fat. At the same time, a healthy diet should include a sufficient amount of unsaturated fats, preferably from unrefined plant products, such as nuts and from virgin olive oil. Fats, like carbohydrates and proteins are a source of energy. One gram of fats and oils contain 9 kcal (1 gram of carbohydrate and protein contains 4 kcal). The recommendation for fat and oil intake varies somewhat depending on the organization that issues such recommendations. In the United States, the dietary guidelines issued by the U.S. Department of Health and Human Services and U.S. Department of Agriculture call for intake of between 20 to 35 percent of calories from fats and oils per day. According to the European Society of Cardiology such intake should be between 25 and 35 percent of calories. These ranges refer to a total fat consumed including fats and oils naturally found in foods and fat and oils that were added during processing and food preparation. According to data from the U.S. Department of Agriculture, Americans consumed, on average, about 32 percent of their calories from added fat alone. While this percentage is within the recommended range, it does not account for fats and oils found naturally in foods such as meats. This suggests that Americans should make a major cut in the amount of fats and oils they consume. Furthermore, our health not only depends on whether the number of ingested fats and oils is within the recommended range, but also on the type of fatty acids we consume. In order to
reduce the risk of chronic health conditions, intake of trans fats, saturated fats and cholesterol should be limited. These items should be replaced by products that are a good source of unsaturated oils, including primarily monounsaturated and polyunsaturated omega-3 oils. In the best case scenario, the majority of ingested fats and oils should come from products such as avocado, nuts and seeds, less from refined vegetable oils and the least from animal products. Cardiovascular disease constitutes the number one cause of death in the United States and many other countries. In fact, it is the leading cause of death in the world. One of the most detrimental fats in terms of cardiovascular disease is trans fatty acids. According to the U.S. National Academy of Sciences trans fatty acids are not necessary for human health and there is no evidence that they provide any benefits. As such, the same organization recommended limiting their intake to “as little as possible.� The recommendation of the World Health Organization is more specific and says that their intake should be limited to no more than 1 percent of calories. The European Society of Cardiology recommends the consumption of trans fatty acids together with the consumption of saturated fatty acids should not exceed 7 percent of calories. In the United States, trans fatty acids intake is more than two and a half times higher than the World Health Organization’s recommendation (about 5.6 grams per day or 2.6% of calories). In comparison, intake of trans fatty acids in Poland is about 3.3 to 6.9 grams per person per day, in Norway, it is 4.0 grams, 1.1 grams in Belgium, 3.8 grams in Germany, 1.6 grams in Italy and just 0.3 grams in Japan. According to estimates calculated by Dr. Mozaffarian and colleagues, if intake of these fats was reduced to 1.1 percent of calories, 72,000 deaths due to cardiovascular disease could be avoided annually. If such intake dropped to just 0.1 percent, as many as 228,000 deaths could be prevented. The table below provides a list of products that provide the greatest
amount of these fatty acids in the diet of Americans. This data clearly indicates that the best way to reduce trans fatty acids intake can be achieved by reducing or eliminating intake of cakes, margarine, chips, candy bars and other sugary products.
Table 1. Products containing trans fatty acids. Product
Percentage of total intake
Baked products, cakes, waffles, crackers, bread
40
Meats and animal products
21
Margarine
17
Fried potatoes
8
Chips and popcorn
5
Added fats
4
Other (cereal, candies)
5
Adopted from: Federal Register: „Food Labeling; Trans Fatty Acids in Nutrition Labeling; Consumer Research To Consider Nutrient Content and Health Claims and Possible Footnote or Disclosure Statements; Final Rule and Proposed Rule�, vol. 68, no. 133, p. 4143341506 (July 11, 2003).
Meats, including red, white and processed meats are the main source of saturated fat. It is estimated that about 40 percent of the overall saturated fat intake in America comes from meats. Fats added to food (e.g. butter, lard) account for about 34 percent and dairy products (especially cheese) provide about 22 percent. Thus, together these three categories provide more than 90 percent of saturated fat ingested by Americans. Cheese is the biggest single contributor to the
overall saturated fat intake (about 9 percent), followed by pizza (about 6 percent), grain and dairy based deserts (about 6 percent each), chicken (about 6 percent) and sausages, franks, bacon and ribs (about 5%). Saturated fat provides about 11 percent of calories in the American diet, which is more than the recommended amount. Cholesterol is found only in meats and animal products such as eggs and dairy products. Eggs are the main source of cholesterol from foods commonly consumed (organ meats such as liver or kidneys are higher in cholesterol content but are not widely consumed). Depending on the size, one egg contains at least 200 and may have as much as 300 mg of cholesterol. This means that consuming only one egg per day will provide more or less as much cholesterol as the amount defined as the maximum daily amount, which should not be exceeded (300 mg/day). Many scientists with expertise in nutrition and chronic disease prevention believe that this recommendation is too high, and therefore, a much lower intake of cholesterol should be recommended for the prevention of cardiovascular disease. In fact, to achieve the best results, cholesterol intake should be as low as possible. Since the body makes its own cholesterol, humans have no need to ingesting cholesterol-containing foods. Thus, ideally, no cholesterol should be ingested with foods. One of the best examples of the impact of the consumption of fats and oils on human health comes from Poland. Up until the year 1990, intake of saturated fat as a percentage of calories had been increasing from year to year. Thereafter, it has been decreasing, mainly due to lower intake of foods of animal origin such as butter. Consumption of butter, for example, was about 6 kg per person, per year in 1970. It increased to about 9 kg per person in 1990. Subsequently, it decreased and in the year 2000 was reduced by about half. Between 1990 and 2000, the consumption of vegetable oils doubled. Data from the same period of time showed that
the mortality (death) due to cardiovascular diseases, increased in proportion to the increase in intake of saturated fat (up to 1990). Mortality rates due to cardiovascular disease began to decline since the early 1990 in proportion to the decreased intake of saturated fat and also as intake of vegetable oils increased. Dietary changes in Finland constitute another good example of the impact that fats and oils have in terms of disease prevention and development. The region of Finland known as North Karelia had higher rates of heart disease than almost any other European countries between 1940 and 1960. In 1970, the Finnish government made efforts to promote replacing the use of foods high in saturated fat with foods made with and containing vegetable oils. For example, people who consumed regular cow’s milk were encouraged to switch to either reduced fat milk or to soy milk. Similarly, those who used hard margarines and butter were urged to use soft margarines (soft margarines have much lower content of saturated fat compared to hard margarines). In the spring of 1972, 86 percent of men and 82 percent of women used mainly butter as a spread on bread. In early 2000, only about 10 percent of men and 4 percent of women use butter for the same purpose. While in the early 1970s the use of soft margarine was not very common at the beginning of 2000 about 42 percent of men and 47 percent of women used reduced fat margarines (fat in such margarines provided less than 60 percent of calories). In the spring of 1972, only about 2 percent of people used vegetable oil for frying, and at the beginning of 2000 this number increased to about 40 percent. These dietary changes over time resulted in a change in the ratio of intake of unsaturated fat and saturated fats from 0.25 to 1.48. During this period of time, the average serum cholesterol level decreased from 267 to 226 (15.4 percent) in men and 275 to 249 (9.9 percent) in women. Although the serum cholesterol level should be much further reduced for the most protective effect, preferably to below 150 mg/dl, these
changes practically instantaneously resulted in reduced the rates of death due to cardiovascular disease and cancer. Mortality due to cardiovascular disease dropped by 80 percent, and a 67 percent drop in mortality due to cancer was seen. Lower mortality rates were observed in each of the studied age groups. For example, among those between 65 and 74 years of age, a 69 percent lower mortality was reported in men and an 82 percent lower mortality was reported in women. Similarly, among those between 55 and 64 years old, an 80 percent lower mortality in men and 92 percent lower mortality in women was reported. These examples illustrate the profound impact that replacing animal fat with vegetable oils has in terms of disease prevention. In 2009, the American Journal of Clinical Nutrition published a manuscript describing the effect of fat intake on the occurrence of coronary heart disease. The conclusions of this article were based on 11 studies, which included a total of nearly 350,000 participants. According to the results, the risk of death from coronary heart disease would be reduced by 26 percent if 5 percent of calories from saturated fats were replaced with the same amount of unsaturated fatty acid. As already mentioned, meats, added fat, dairy products, eggs, baked goods, cheese, margarines and fries contribute more to the overall trans fats, saturated fat and cholesterol intake than any other items. Thus, the best way to reduce fat intake is by limiting or eliminating these products and consuming a diet that is primarily based on unrefined plant foods. People who are not willing to eliminate these products can significantly reduce intake of these detrimental fats by eating fat-free dairy products, soft margarines, or lean meat (preferably fish). It would be best if people who eat meat reduce its consumption to specific days (such as holidays or birthdays) or to no more than one day a week. Unfortunately, in many households, meat in its
various forms is not only consumed daily, but also in almost every meal. The same is true of foods of animal origin and refined plant foods. The following are good examples of different types of high fat products and in some case lower fat alternatives are suggested. Just 30 grams (about 1 oz.) of cheddar cheese contains about 6 grams of saturated fat, while the same amount of cheddar made of skimmed milk, only 1 gram. One glass of regular milk contains 4.5 grams of fat, while skim milk contains only 1.5 grams. A cup of regular ice cream contains 5 grams of fat and ice cream made of zero fat milk contains no fat at all. One type of croissant contains more than half of the daily recommended amount of saturated fat. About the same amounts of fat is found in a large portion of popcorn chicken. An extra-large serving of fries contains about 30 percent of the daily recommended amount of saturated fat. Most of the burgers offered in fast food restaurants contain from two-thirds to more than 200 percent of the recommended daily amount of saturated fat. Unfortunately, saturated fat in fast food restaurants can be found not only in the burgers. For example, a strawberry shake (medium size) comprises about 150 percent of the recommended daily amount of fat. Pizza is another example of a product with a high content of saturated fat. For example, a personal pizza with pepperoni contains more than 60 percent of the daily recommended amount of saturated fat. Just one slice of vegetarian pizza contains a similar amount. Fruits and vegetables (including beans) and grains generally contain a small amount of fats and oils. One of the exceptions is avocado, which, like most other plant products such as nuts and seeds, contain mostly beneficial oils, especially monounsaturated fat. Plant foods do not contain cholesterol, but contain plant sterols and stanols, which are associated with reduction in risk factors of heart disease, such as serum cholesterol. In the table below a few additional ways to reduce the amount of saturated fat consumed are
suggested.
Table 2. Tips for Reducing Saturated Fat Intake. 1.
Limit eating fast food.
2.
Limit the amount of fat used in frying. Instead of frying, bake or cook.
3.
Do not use butter, lard or other visible fat.
4.
Use herbs and spices in place of butter, mayonnaise and salad dressings.
5.
Limit your intake of pastries including croissants, donuts, biscuits and cakes.
6.
Use reduced fat in place of the regular dairy products.
7.
Use soy products such as soy milk in place of cow's milk.
8.
Use soy products in place of sour cream and mayonnaise.
9.
Remove visible fat from meats before cooking and drain off any fat after cooking.
10. Reducing or eliminating meat intake altogether. 11. Remove skin from poultry before cooking products. Fat is usually under the skin. 12. Eat vegetarian meals at least a few times a week.
Olive oil Of all the oils available in grocery stores, olive oil is one of the most beneficial to human health. Research clearly shows that the frequent use of olive oil helps in reducing the risk of many chronic diseases such as heart disease, cancer, stroke, and hypertension. For example, a study published in the medical journal Archives of Internal Medicine showed that olive oil is effective in reducing blood pressure. In this experiment, patients were divided into two groups. One group was instructed to add olive oil (men 4 tablespoons and women 3 tablespoons) to their
diet and the other was advised to add the same amount of sunflower seed oil. After 6 months, 8 of the11 patients who consumed olive oil no longer needed to take antihypertensive medication. However, none of those ingesting the sunflower seed oil discontinued using medications. In another study, it was estimated that individuals who used olive oil had a 47 percent lower risk of coronary heart disease compared to those who did not use it. The researchers who conducted the study stated that “exclusive use of olive oil during food preparation seems to offer significant protection against CHD (coronary heart disease – author), irrespective of various clinical, lifestyle and other characteristics of the participants.” Modern research also indicates that olive oil can help prevent cancer. One such study was carried out with 755 women living in the Canary Islands. The women, who consumed the highest amount of olive oil, had a 48 percent lower risk of developing breast cancer compared to women consuming the least amount of olive oil. A study conducted in Italy and Switzerland, assessed the impact of olive oil consumption on risk of developing cancer of the colon (large intestine) and rectum. This time, the researchers assessed risk based on the amount of olive oil used in frying. From other studies, it is known that carcinogenic compounds (e.g. oxygen radicals) can develop when fats and/or oils are heated to a high temperature. Researchers compare the risk among 886 individuals with to 4,765 individuals without cancer. The results indicated that the use of olive oil reduced the cancer risk by 11 percent. At a conference about the impact of olive oil on human health held in Cordoba in Spain, an organization, the Centro de Excelencia Foundation sobre Aceite de Oliva y Salud stated that the use of olive oil reduces the risk of cardiovascular disease, probably protects against agerelated decline in cognitive abilities and Alzheimer's disease, is associated with healthier aging and longevity. In the conference’s report we also read: “The protective effect of virgin olive oil
can be most important in the first decades of life, which suggests that the dietetic benefit of virgin olive oil intake should be initiated before puberty, and maintained through life.” These statements are consistent with the recommendations of the Advisory Committee of the American Heart Association, which concluded that “a diet high in MUFA (monounsaturated fatty acids, olive oil predominantly contains this type of fat – author) (versus a high-carbohydrate diet) improves glycemic control in individuals with NIDDM (none-insulin dependent diabetes mellitus – author) who maintain body weight. Individuals with elevated triglycerides or insulin levels also may benefit from a high-MUFA diet.” Another study conducted in Greece showed that those with the greatest long-term consumption of olive oil (consumption of almost every day in a lifetime) had about 4 times lower risk of developing arthritis compared to those who consumed olive oil, on average, only about six times per month. The same researchers showed that increasing the consumption of olive oil to two times a week, reduced the risk of developing arthritis by half. In most countries the most frequently consumed oils are the omega-6 group. Sunflower oil or soybean oil are examples of oils from the omega-6 family. Unfortunately, excess intake of refined oils from the omega-6 family increases the risk of certain chronic diseases. A study published in the European Journal of Clinical Nutrition conducted in Spain showed that people who consumed the highest amounts of omega-6 had a 3 times greater risk of fractures due to osteoporosis, compared with those with the lowest intake of these oils. The same study revealed that people who had the greatest ratio of olive oil to omega-6 had an 80 percent reduced risk of fractures. Thus replacing vegetable oils with virgin olive oil can further protect individuals from developing certain health conditions. One of the most common questions asked about olive oil is regarding its use in frying and
baking. This is because in some sources, including many websites, one can find information that says that olive oil should not be using for frying or baking due to the fact that this oil has relatively low smoking and burning temperatures. According to the International Olive Oil Council the smoke temperature of olive oil is 210 degrees C (410oF), and according to the Institute of Shortening and Edible Oils, it is 215 degrees C (420oF). In comparison, the smoke temperature of canola seed oil is approximately 205 degrees (400oF). Smoke temperature of oils and fats has been known for many decades. In 1940, two scholars, Detwiler and Markley, published oil burning temperatures in the Journal of the American Oil Chemists Society. The smoke and burning temperatures of selected oils are included in the table below. The values are based on the above mentioned publication.
Table 3. The smoke and burning temperatures of selected oils. Oil
Smoke temperature o
C (oF)
Burning temperature o
C (oF)
Virgin olive oil
199 (390oF)
361 (682oF)
Flax seeds oil
163 (325oF)
353 (667oF)
Corn oil
227 (441oF)
359 (678oF)
Soybean oil
194 (381oF)
361 (682oF)
As can be seen in the table above, smoke and burning temperatures of olive oil are comparable to those of other commonly used oils. Based on this data, we can say that olive oil can be used in place of other vegetable oils for frying, baking and other kind of food preparation. The research reviewed above indicates that the use of olive oil in place of other vegetable
oils and animal fats can reduce the risk of developing the most common chronic health conditions. Thus, the use of olive oil, whether raw or in frying or baking should be recommended in primary prevention. It must be kept in mind, however, that the benefits of olive oil pertain to virgin olive oil and not to other types, such as lite, refined, pure or pomace olive oils. The use of some types of fat including trans fats, saturated fats and cholesterol is detrimental. Thus, in order to reduce a risk of chronic health conditions, the use of meats, lard, butter, mayonnaise as well as milk and dairy products, especially the regular fat variety should be replaced with products such as nuts, seeds, olives and vegetable oils, especially olive oil.
Roman Pawlak, Ph.D, RD is an Associate Professor of Nutrition at East Carolina University in North Carolina. He is the author several books including “Forever young. Secrets of delaying aging and living disease free,” “Healthy diet without secrets,” “In defense of vegetarianism” and “I am the Lord who heals you,” and a co-author of “Vegetarian mother and her baby.”