Let's take a look at a new study that can be misleading.

Here's the abstract:

Controversy exists over how much linoleic acid (LA) should be consumed in a healthy diet. Some claim that high LA intake promotes inflammation through accumulation of tissue arachidonic acid (AA) and subsequent production of pro-inflammatory lipid mediators. Here the author reviews the current available evidence from human studies that address this issue. The data indicate that high LA in the diet or circulation is not associated with higher in vivo or ex vivo pro-inflammatory responses. Surprisingly, several studies showed that those individuals consuming the highest level of LA had the lowest inflammatory status. Recent findings suggest that LA and AA are involved in both pro- and anti-inflammatory signaling pathways. Thus, within the ranges of intake that are achievable for most human populations, the evidence do not support reducing LA intake below current consumption levels.

Title: Too much linoleic acid promotes inflammation-doesn't it?

Source: Prostaglandins Leukot Essent Fatty Acids. 2008 Nov 4. [Epub ahead of print].

Author: Fritsche KL.

Perhaps the biggest "problem" here is that the author appears unaware of a couple of pieces of crucial evidence from the professional scientific literature. One Asian study found that vegetarians had less oxidized LDL than meat eaters, despite consumed more LA. Another study found that the incidence of certain cancers (now considered due to "chronic inflammation") increased significantly once one reached a certain level of LA consumption, but consuming more than that amount did not result in even more cancers. In other words, there is a threshold amount for LA consumption and certain cancers. Why might this be the case?

First of all, if you eat a certain amount of LA, your body will replace the natural Mead acid (if you were born with it in your cells - it depends upon your mother's diet) with AA, and then "chronic inflammation" is possible, even if only minor stressors are present. Again, above that amount and you are not going to incorporate more AA. The author doesn't tell us how many calories were being consumed. It could be that those with higher LA intake also consumed less calories. They could also have consumed more antioxidant-rich foods, and less cooked meat, etc. There is also no mention of people who consume hardly any LA, such as myself, and the author doesn't even explain why this is the case. Basically, what we see in this study is someone who has not considered that multiple factors might be at work. Instead, it's the same old "nutritional science" game, which is to create abstract categories, then do "epidemiological" studies (originally designed for infectious diseases, not dietary studies) that only control for one or more of these categories. Instead, I've suggested for years now that studies be done on actual diets that people are consuming now. By doing so, investigators can then "work backwards" and determine what is healthy and what is not. Of course, they should have studied the scientific literature (including biochemical) that appears to be relevant, such as:

J Natl Cancer Inst. 2005 Oct 5;97(19):1458-65.

"...Intake of total and saturated fat from meat was associated with statistically significant increases in pancreatic cancer risk but that from dairy products was not. CONCLUSION: Red and processed meat intakes were associated with an increased risk of pancreatic cancer. Fat and saturated fat are not likely to contribute to the underlying carcinogenic mechanism because the findings for fat from meat and dairy products differed. Carcinogenic substances related to meat preparation methods might be responsible for the positive association."

Because they have not used my type of approach, what the public sees, especially now with almost all adults having internet access, are all kinds of contradictory "studies." Even in the study directly above, the phrase "saturated fat" is used, which is sometimes used in a misleading way. The authors should have said "saturated fatty acids" (the actual molecules) because "saturated fat" is yet another potentially misleading abstract concept. For example, lard is classified as a "saturated fat" (and is unhealthy, generally-speaking), but is only about 40% saturated fatty acids. It also contains quite a bit of LA, as well as cholesterol, which can get oxidized during cooking. Coconut oil is about 92% saturated fatty acids and is a healthy food item (so long as it's not going rancid), as the best "natural" nutritional study of al time demonstrates (that is, the documented good health of many millions of Asian people consuming diets rich in coconut products).

As I said, if "nutritional scientists" would not ignore this kind of evidence, which is undeniable and direct, unlike their "epidemiological" studies of abstract categories, they would realize that classifying both lard and coconut oil as "saturated fats" makes no sense at all, and that dietary saturated fatty acids are not likely to be unhealthy (since there is no unhealthy biochemical mechanism that they are involved in, unlike LA and AA). This unfortunate situation illustrates how "science" can go terribly wrong, leading to dangerous advice being given to the general public. And now that you have this information, you can confront various "experts" yourself, and you will likely find that they are not willing to talk to you at all or else their responses don't make sense or don't address the issue. One "expert" told me he didn't have time to learn the basic biochemistry involved and could not speak to the point I was raising, which concerned oxidized cholesterol. Many people ask me how such a situation could have occurred, but as a historian I realize that it's too complex to reduce to a simplistic explanation, one that would require a major investigation in its own right.