There are different types of dietary fat with differing implications for health based
on their varying impact on blood levels of triglycerides, LDL-C, and HDL-C. Fats
are classified as saturated or unsaturated. Although in a particular food one form of
fat may predominate, foods contain a mixture of the various types of fat.
Saturated fat is sometimes called “bad fat” based on its health effects. Saturated
fat molecules have no chemical double bonds between carbon atoms because
they are filled or “saturated” with hydrogen. Saturated fats are usually solid at
room temperature and tend to raise LDL-C, the unhealthy form of cholesterol in
the bloodstream. Saturated fats come mainly from animal sources, including meat
(beef, lamb, pork, lard, poultry) and dairy products (butter, cream, cheese, whole
and reduced-fat milk). Meats that are highest in fat content include ground beef,
bacon, liver, and other organ meats. Tropical oils such as coconut, palm kernel, and
palm oil may come from plants, but they have a high content of saturated fatty acids
and are solid or semi-solid at room temperature. Saturated fatty acids are also found
in some other plants, such as nuts.
Unsaturated fats are sometimes called “good fats” based on their relatively benign
health effects. Unsaturated fats are classified as monounsaturated or polyunsaturated
depending on if they have a single or multiple unsaturated chemical bond.
Unsaturated fats are usually the predominant form of fat found in vegetable oils that
are liquid at room temperature.
Trans-fats, also called partially-hydrogenated oils, are a harmful form of unsaturated
fat that is synthesized in a chemical process that adds hydrogen to liquid vegetable
oils to make them more solid. Like saturated fats, trans-fats raise markers of inflammation (interleukin-6 and
C-reactive protein), increase unhealthy LDL-C levels, and lower healthy HDL-C
levels. Studies suggest that a 2% increase in energy intake from trans fatty acids
was associated with a 23% increase in the incidence of coronary heart disease (CHD).
Because they improve taste and shelf life, trans-fats have been used to make
shortening and many commercially prepared baked goods such as pastries, pizza
dough, pie crust, cookies and crackers, snack foods, fried foods, and margarine.
Because they harm health, in 2015, the U.S. Food and Drug Administration (FDA)
ruled that partially-hydrogenated oil is no longer “generally recognized as safe”
(GRAS) and must be phased out of food by 2018 unless approved as food additives
on a case-by-case basis. The FDA labeling rules allow foods that have up
to 0.49 grams of trans-fats to list their trans-fat content as zero. As little as 0.5%
of the total energy intake 10 calories (1 gram) of trans-fat may incur adverse health
effects. The best advice is to completely avoid any food containing trans-fats.
Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs)
are usually liquid at room temperature. They have more favorable blood lipid and
health effects than saturated fats. Plant sources rich in MUFAs include vegetable
oils (e.g., canola, peanut, olive, high oleic safflower, and sunflower), avocados,
peanut butter, and most nuts. Primary sources of PUFAs are vegetable oils (corn,
soybean, cottonseed); some nuts (walnuts, pine nuts); and some seeds (sesame,
pumpkin, flax). When substituted for trans and saturated fats, monounsaturated or
polyunsaturated fats bring about a reduction in LDL-C. They are sometimes called
“good” fats or “healthy” fats.
There are three types of n-3 PUFAs, also called fish oils and omega-3 fatty acids: alpha-linolenic
acid (ALA) is an n-3 fatty acid that the body converts into the other two types,
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are
found in fish and shellfish. ALA sources include some green vegetables (Brussels
sprouts, kale, spinach) soybean oil, canola oil, walnuts, and fl axseed. ALA cannot
be synthesized by humans and, therefore, is considered essential in the diet.
This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in the book or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon). Copyright 2020 by J. Joseph Speidel.
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