FN 225: Nutrition
Teresa McFerran, M.S., R.D.
Health Professions Division
Lane Community College
There is an EXAM this week (Week 5) on the material from Weeks 3 and 4.
1. What did you learn in this chapter that makes you think more positively or more negatively about fats?
2. Read "Nutrition myth or fact? Is Margarine More Healthful Than Butter?" What do YOU think, and WHY?
LECTURE 5A: Week 5: The Lipids: Fats, Oils, Phospholipids and Sterols
First look through the major headings of this Lecture Outline in your packet:
II Where do lipids come from?
IV Recommendations regarding lipids & heart health
V Digestion and Absorption
I The THREE types of LIPIDS
A. Triglycerides (or fats)
B. Phospholipids (lecithin is the main one)
C. Sterols (an example is
Fill in your lecture outline
while viewing the following:
Now watch the Video Clip below to learn more about the structure of triglycerides.
Next in your lecture outline it outlines the different types of fatty acids. What I want you to know for each fatty acid is a little bit about its chemistry, what foods you predominately find these fatty acids in, and how they affect heart health. Click on the following link to view a Powerpoint presentation to help you fill in the lecture outline on the different types of fatty acids.
The power point presentation had this image and said that the liquid oil would be polyunsaturated and the yellow fat would be monounsaturated. That is not completely correct. A highly mono or polyunsaturated fat would be liquid at room temperature. For example olive or corn oil. However a fat that is more saturated, but still contains high amounts of monounsaturated fatty acids (like chicken fat) would look like the yellow fat below. And a fat that is highly saturated, like coconut oil would look like the white fat below.
Acids are a stable and compact way
for a plant or an animal to store fat for
later use as energy. Animals in the wild don't have a chance to
store very much fat since they constantly need
an energy source to live. On the other
hand, animals that spend much of their time on
feedlots, such as
beef cattle, are inactive and therefore store
a lot of saturated fat. So while deer
meat is a very small source of saturated fat,
most beef purchased in a grocery store is high
in it. Foods that have mostly saturated
fatty acids, like butter, are solid at room
temperature and can raise risk
of heart disease because they increase
blood cholesterol, specifically the LDL
or "bad" cholesterol. (More on this
later). Food sources of
saturated fatty acids include most animal
fats, tropical oils (like coconut and palm
oil), and partially or fully hydrogenated
Omega-6 Unsaturated Fatty Acids (PUFAS) - This is the type of fatty acid made by plants for storage. People take in plenty of the essential linoleic acid (an omega 6) when they eat the oil of seeds, such as corn oil or soybean oil that we often find in margarines and salad dressings.
Omega-3 Unsaturated Fatty Acids (PUFAS) - In the last decade, we have come to a much deeper understanding of this kind of unsaturated fatty acid. An omega-3 fatty acid is even more unsaturated than other unsaturated fatty acids and has special functions in our body.
Some plant foods like flax seed have one type of beneficial essential omega-3 fatty acid called alpha-linolenic acid (ALA,) while some wild fish (like salmon) have another type of beneficial (not essential) omega-3 fatty acid, called EPA and DHA.
Most people associate omega-3 fatty acids with fish, but fish get them from green plants (specifically algae), who use them during photosynthesis.
Research does NOT support that there is a beneficial ratio between omega-6 and omega-3 to support health. Most people need to simply increase omega-3s in their diet because they already get plenty of omega-6s.
|As you can
see from the illustration below, there is a mixture of
all fatty acids in fats, and oils, and therefore
foods. It can be confusing when we say that olive
oil is a monounsaturated fat because that makes it seem
like there are no saturated or polyunsaturated fatty
acids present. What would be more correct is to
say that olive oil is predominately a monounsaturated
fat, but it does contain other fatty acids as well as
you can see from the illustration.
Looking at the illustration below, which dietary fat is the most saturated?
Click here to see answer.
As you can see from the label below 12g out of the total 14g of total fat (in 1Tbsp. of coconut oil) are saturated. Notice that there is 0mg of cholesterol. That is because only animal fats contain cholesterol, not plant fats.
|The two essential fatty
acids are linoleic acid and linolenic
acid. Below is linoleic acid,
which is an omega-6 fatty
Linoleic acid (above) is more common in the seeds of plants. The first double bond is after the 6th carbon starting on the left. Below is another way of representing linoleic acid:
Below is the other essential fatty acid, linolenic acid, which is an omega-3 fatty acid.
|The fatty acids
represented below are not officially considered essential
because we can make them from the essential
ones. But new research supports a recommended
intake of at least 250 mg per day of EPA+DHA. Having
good levels of them in your DIET appears to decrease the
risk of heart disease.
By no means is it important to know the names of all of the fatty acids in the following table. This table was made to illustrate a little about the wide diversity of fatty acids in foods, and how those fatty acids affect blood cholesterol.
The first four fatty acids are saturated fatty acids. Notice that the first three (Lauric, Myristic, and Palmitic) have a negative impact on blood cholesterol levels (increasing LDL levels), but they ALSO have a positive impact as well (increasing HDL levels). Saturated fats get a bad reputation for being unhealthy, but recently there has been evidence that demonstrates that the link between saturated fat and heart disease may not be as strong as we once thought.
In an article from Tufts University Health & Nutrition Letter (May 2010), Links Between Saturated Fat, Blood Cholesterol & Heart Disease Prove Complex, a researcher from Children's Hospital Oakland Research Institute, Ronald M. Krauss, MD stated that, "Our meta-analysis showed that there is insufficient evidence from prospective epidemiological studies to conclude that dietary saturated fat is associated with an increased risk of cardiovascular disease (CVD)."
Researchers state that one reason reducing saturated fat intake may not decrease CVD risk is because people tend to replace saturated fat with processed carbohydrates.
"An overall eating pattern that emphasizes whole grains rather than refined carbs such as white flour, along with foods high in polyunsaturated fats, such as fish, seeds, nuts and vegetable oils, is of more value for reducing coronary heart disease risk than simply aiming to further reduce saturated fat," states Krauss.
The message really is to
displace saturated fat with unsaturated fat, and to
eat a balanced diet with a variety of whole foods.
Trans Fatty Acids
More About Hydrogenated Fats:
In an attempt to find an inexpensive
substitute for butter, as far back as 1903,
Britain was adding hydrogen gas to liquid
(polyunsaturated) oils in a process called
hydrogenation. This hydrogen reacted with
the double bonds in the structure of the
unsaturated fatty acids of the corn oil.
Hydrogenation creates both saturated and trans
fatty acids. Not only did this make the
at room temperature (so margarine and shortening
were possible from oils like corn oil), it also preserved them
by making the oil more stable and less likely to
(so baked goods like cookies and chips would have
a longer shelf life).
So why is the above flaxseed meal especially prone to rancidity, leading to a distasteful smell for my colleague Roger Hecht?
Flax seed contains a fatty acid that has 3 double bonds. As said above, rancidity is when oxygen attacks double bonds. With more double bonds, more rancidity happens.
Flaxseed meal is a wonderful food but it should be refrigerated to keep it from going rancid.
When concerns arose in about the 1970s and 1980s about the saturated fats in the palm and coconut oils used in baked goods and margarine (in part because they were cheaper than butter) they were often replaced with these hydrogenated fats made from oils from corn and soybeans. When used in cookies or potato chips instead using an oil like corn oil that contains polyunsaturated fats, the product had a longer shelf life. And products like margarine made with corn oil were solid similar to butter. McDonald's and Kentucky Fried Chicken found the hydrogenated fats gave a wonderful crispness to their French fries and chicken that was difficult to replace. Jif liked the smooth “mouth feel” small amounts of it added to their peanut butter.
|Video Clip for
the Lecture Outline about
approximately 7 minutes
Trans Fatty Acid video
|As the Lecture Outline
says, plants make sterols, but not cholesterol. An
article in the journal Nutrition Today about pistachios said
"Among tree nuts, pistachios are the richest source of phytosterols, particularly beta-sitosterol and campesterol."
"Phytosterols are plant sterols, which compete with cholesterol in the intestinal lumen for uptake into the bloodstream, and phytosterols may reduce cholesterol levels."
"The Pistachio: A Surprising and Colorful Nut"
David Hever, MD, PhD
Susan Bowermanm MS, RD
The article said that pistachios are botanically related to cashews and mangos (!).
Although they are native to the high deserts of West Africa and the Middle East, our neighbor California now grows them.
which fat is best to eat?
The best way to get fatty acids is in WHOLE foods, as you're also getting a variety of vitamins, minerals, phytochemicals and sometimes fiber and protein. And consuming a lot of refined fats, whether it be in butter, olive oil or margarine can lead to an excess of a particular fatty acid and does not come packaged with other nutrition.
There are definitely times, though, when we may prefer something that is not whole, like when we have a nice slice of toast or we're wanting to stir-fry vegetables.
For bread and toast, what I prefer is butter, and the first reason for that is a personal preference for the taste of butter. Just a little bit goes a long way and I don't think a little bit of butter is going to raise my risk of heart disease, especially when there are also plenty of fruits, vegetables and whole grains in what I eat.
For sautéing and other uses, I like to use canola oil. It can be heated to a high temperature, plus it does not have any flavor so you can use it for baking. It also contains Omega 3's which can help balance out the Omega 6's you find in soybean and corn oil that is the main oils used in a lot of processed foods. For salads and other uses, olive oil is great and we always have it on hand. I buy the less refined "Extra Virgin" olive oil that has a green color and a stronger flavor from the phytochemicals that are present.
Since margarine companies want to advertise their product as having no hydrogenated fat and no trans fat, they have been using other ways of making their margarine solid and spreadable. What some companies are choosing to use are things like palm "oil", which is high in saturated fat.
|These lectures have often said that WHOLE foods
are usually the best way to get nutrients.
Just look at the nutrients in
pistachios, listed in the previously
Using the "MAGIC DV", which nutrients would a serving of these pistachios be a good source of?
Our local filberts are just as nutrient dense as these pistachios are.
CORRECT. Saturated fat is part of one of the 3 types of lipids.