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Many studies or reports I come across in my research blame "fat" for this or that ill or unhealthy effect, and the one below is a good example:
QUOTE: ...The incidence of cancer of the proximal stomach has been increasing over the last 20 years for which environmental factors, such as diet, certainly play a part.
Nitrite, which is present in our saliva and is derived from nitrate in our diet, is thought to be a pre-carcinogen for gastric cancer. When it is swallowed and enters the acidic environment of the stomach, nitrite spontaneously forms nitrosating species able to convert a range of targets, such as secondary amines and bile acids, into carcinogenic N-nitrosocompounds.
Antioxidants such as ascorbic acid protect against the formation of these nitrosocompounds by converting the nitrosating species back into nitric oxide (NO). However, NO diffuses rapidly to lipids, where it reacts with oxygen to reform nitrosating species. The presence of lipids therefore overrides the protective effect of vitamin C against the formation of harmful compounds. UNQUOTE.
However, what they hardly ever mention is that this increase over the last couple of decades has gone hand in hand with the demonization of "saturated fat" and the declaration of the "healthful" qualities of either "polyunsaturated fats" or "monounaturated fats" (now, mostly, people are told to eat PUFAs as "essential fatty acids"). With a diet very rich in saturated fatty acids and very low in unsaturated fatty acids (I am assuming a very low dietary cholesterol intake, for the sake of simplifying the argument here), the dangerous effects they describe would not happen, as saturated fatty acids cannot participate in these kinds of reactions.
Source of the quoted passage: http://www.sciencedaily.com/releases/2007/04/070402102023.htm |
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Another too common statement these days:
SOURCE: http://www.drmirkin.com/nutrition/healthful_fats.html
QUOTE: How can I tell which fats are healtful and which are unhealthful?
Gabe Mirkin, M.D.
Fat is classified into saturated fats, polyunsaturated fats, and monounsaturated fats. Saturated fats appear to increase your risk for heart attacks when you take in more calories than you burn.
Monounsaturated fats are considered healthful because they form LDL cholesterol that is resistant to oxidation; plaques are formed by oxidized LDL. Good sources include olive oil and avocados.
We used to think that all polyunsaturated fats help to prevent heart attacks when they replace saturated fats, but now we have different information. Polyunsaturated fats are classified by their structures into omega-3s and omega-6s, and you need both types; these are called the essential fatty acids because you cannot make them in your body and must get them from your food.
For most of the time humans have been on earth we have eaten foods that contain omega-6's and omega-3's in a ratio of about 2:1. However, over the last 50 years in North America, the ratio has changed; it now ranges from 10:1 to 20:1. Today our diet includes huge amounts of oils that are extracted from plants and used for cooking or in prepared foods. These oils (such as corn oil, safflower oil, cottonseed oil, peanut oil, soybean oil) are primarily omega-6s. We have decreased our intake of omega-3's, found primarily in whole grains, beans and other seeds, and seafood. Eating too much omega-6 and too little omega-3 causes clots and constricts arteries to increase risk for heart attacks, increases swelling to worsen arthritis, and aggravates a skin disease called psoriasis. It may block a person’s ability to respond to insulin, causing high insulin and blood sugar levels and obesity. It increases hormone levels of insulin like growth factor-1 that causes certain cancers. To get your ratio on omega-6s to omega-3s back to a more healthful 2:1, eat seafood, whole grains, beans and other seeds, and reduce your intake of foods made with or cooked in vegetable oils.
The most unhealthful fats are the polyunsaturated oils that have been processed to form trans fats (partially hydrogenated vegetable oils); see reports #N198 and #N185. UNQUOTE.
Now, after trans fats they are going to blame the interesterified fats for a change:
QUOTE: What are interesterified oils?
We have known for many years that trans fats increase
risk for heart attacks and some cancers. Laws requiring trans fats
or partially hydrogenated oils to be listed on nutrition labels went
into effect last year, so food manufacturers are finally eliminating
them from their products. One substitute that is appearing in
some foods is a new type of fat made with a process called
interesterification or fatty acid randomization. Interesterified oils
have saturated fatty acids, usually from plants, inserted into other
vegetable oils. A study from Brandeis University shows that both
interesterified fats and partially hydrogenated oils raise the bad
LDL and lower the good HDL cholesterol much more than the
plant saturated fats found in palm, palm kernel and coconut oils.
(Nutrition & Metabolism, January 2007).
For more than 60 years, scientists have blamed saturated
fats found primarily in meat, chicken and whole milk diary products
for the high incidence of heart attacks in the United States and
other countries that eat the so-called "Western diet". This study
supports others that show that saturated fats in plants may be
safer than saturated fats in animal tissue. However, scientists
generally agree that the safest fats are those that are liquid at
room temperature: oils that contain primarily polyunsaturated or
monouunsaturated fats. Substituting polyunsaturated fats for
saturated fats lowers LDL cholesterol, and the monounsaturated
fats produce a more stable LDL cholesterol that helps to prevent
heart attacks. UNQUOTE. |
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One major problem is that many "experts" today are only interested in "markers," but, for example, since only oxidized LDL is a problem, that is what should be tested, not LDL which is not distinguised into oxidized and non-oxidized portions. For me, the bigger problem is that many of these people ignore the molecular-level evidence (or don't understand it). It appears that trans fatty acids are healthier than cis unsaturated fatty acids, all other things being equal. The problem is that this is not the way food occurs naturally, that is, trans fatty acids are found in only trace amounts in some foods, whereas now omega 6s, for example, are found in large amounts in many foods. Those who eat more trans fatty acids are more likely to be eating very unhealthy diets than those who eat less, so the "experts" blame the trans fatty acids. Guilt by association, as the saying goes. In science, you have to isolate all variables and then do identical experiments so that there are proper controls for these variables. This is not easy to do, because people don't eat fatty acids, but foods that contain fatty acids in triglyceride form, meaning it is a complex mix of just fatty acids alone (along with all kinds of other substances, such as ones that have antioxidant properties). So because no experiments properly control for all variable in this "trans fat" issue, we get all kinds of misleading information. I buy food based upon the overall fat content versus the saturated fat content. If the product is about 70% or more saturated fat, such as a cookie (or if it is fat free), then I will consider eating it. The "trans fat" content is therefore largely irrelevant (to me, at least). |
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