Here's the great Ray Peat article on fats, starting with why the Eskimo diet misfired. No organ meats, including thyroid, were included. In the body of the article is the mechanism of proteases being blocked by PUFA/EFA, with Iodine neutralizing or "saturating" PUFA, Poly-Unsaturated Fatty Acids, to allow anti-tumor effect of proteases. Great stuff throughout. Take your time with it!
http://raypeat.com/articles/nutrition/oils-in-context.shtml



EXCERPT:

Immunodeficiency and Unsaturated Fats: Intravenous feeding with unsaturated fats is powerfully immunosuppressive [35] (though it often was used to give more calories to cancer patients) and is now advocated as a way to prevent graft rejection. The deadly effect of the long-chain unsaturated fats on the immune system has led to the development of new products containing short and medium-chain saturated fats for intravenous feeding. [36] It was recently reported that the anti-inflammatory effect of n-3 fatty acids (fish oil) might be related to the observed suppression of interleukin-1 and tumor necrosis factor by those fats. [37] The suppression of these anti-tumor immune factors persists after the fish oil treatment is stopped.

As mentioned above, stress and hypoxia can cause cells to take up large amounts of fatty acids. Cortisol's ability to kill white blood cells (which can be inhibited by extra glucose) is undoubtedly an important part of its immunosuppressive effect, and this killing is mediated by causing the cells to take up unsaturated fats. [38]

Several aspects of the immune system are improved by short-chain saturated fats. Their anti-histamine action [39] is probably important, because of histamine's immunosuppressive effects.[40] Unsaturated fats have been found to cause degranulation of mast cells.[41] The short-chain fatty acids normally produced by bacteria in the bowel apparently have a local anti-inflammatory action.[42]

A recent discussion of "tissue destruction by neutrophils" mentions "a fascinating series of experiments performed between 1888 and 1906," in which "German and American scientists established the importance of neutrophil proteinases and plasma antiproteinases in the evolution of tissue damage in vivo." [43] MacCallum's Pathology described some related work:


. . . Jobling has shown that the decomposition products of some fats--unsaturated fatty acids and their soaps--have the most decisive inhibiting action upon proteolytic ferments, their power being in a sense proportional to the degree of unsaturation of the fatty acid. So universally is it true that such unsaturated fatty acids can impede the action of proteolytic ferments that many pathological conditions (such as the persistence of caseous tuberculous material in its solid form) can be shown to be due to their presence. If they are rendered impotent by saturation of their unsaturated group with iodine, the proteolysis goes on rapidly and the caseous tubercle or gumma rapidly softens.[44]


Another comment by MacCallum suggests one way in which unsaturated fats could block the action of cytotoxic cells:


This function of the wandering cells is, of course, of immediate importance in connection with their task of cleaning up the injured area to prepare it for repair. While the proteases thus produced are active in the solution of undesirable material, their unbridled action might be detrimental. As a matter of fact, it is shown by Jobling and Petersen that the anti-ferment known to be present in the serum and to restrict the action of the ferment is a recognizable chemical substance, usually a soap or other combination of an unsaturated fatty acid. It is possible to remove or decompose this substance or to saturate the fatty acid with Iodine and thus release the ferment to its full activity. [45]


Unsaturated Fats Are Essential For Cancer: The inhibition of proteolytic enzymes by unsaturated fats will act at many sites: digestion of protein, "digestion" of clots, "digestion" of the colloid in the thyroid gland which releases the hormones, the activity of white cells mentioned above, and the normal "digestion" of cytoplasmic proteins involved in maintaining a steady state as new proteins are formed and added to the cytoplasm. It has been suggested that inhibition of the destruction of intracellular proteins would shift the balance toward growth.[46] Cancer cells are known to have a high level of unsaturated fats,[47] yet they have a low level of lipid peroxidation;[48] lipid peroxidation inhibits growth, and is often mentioned as a normal growth restraining factor.[49]

In 1927, it was observed that a diet lacking fats prevented the development of spontaneous tumors.[50] Many subsequent investigators have observed that the unsaturated fats are essential for the development of tumors. [51, 52, 53] Tumors secrete a factor which mobilizes fats from storage, [54] presumably guaranteeing their supply in abundance until the adipose tissues are depleted. Saturated fats--coconut oil and butter, for example--do not promote tumor growth.[55] Olive oil is not a strong tumor promoter, but in some experiments it does have a slightly permissive effect on tumor growth. [56, 57] In some experiments, the carcinogenic action of unsaturated fats could be offset by added thyroid, [57] an observation which might suggest that at least part of the effect of the oil is to inhibit thyroid. Adding cystine to the diet (cysteine, the reduced form of cystine, is a thyroid antagonist) also increases the tumor incidence.[58] In a hyperthyroid state, the ability to quickly oxidize larger amounts of the toxic oils would very likely have a protective effect, preventing storage and subsequent peroxidation, and reducing the oils' ability to synergize with estrogen.

Consumption of unsaturated fat has been associated with both skin aging and with the sensitivity of the skin to ultraviolet damage, Ultraviolet light-induced skin cancer seems to be mediated by unsaturated fats and lipid peroxidation.[59]

In a detailed study of the carcinogenicity of different quantities of unsaturated fat, Ip, et al., tested levels ranging from 0.5% to 10%, and found that the cancer incidence varied with the amount of "essential oils" in the diet. Some of their graphs make the point very clearly: [52}


This suggests that the optimal EFA intake might be 0.5% or less.

Butter and coconut oil contain significant amounts of the short and medium-chain saturated fatty acids, which are very easily metabolized,[60] inhibit the release of histamine,[39] promote differentiation of cancer cells,[61] tend to counteract the stress-induced proteins,[62] decrease the expression of prolactin receptors, and promote the expression of the T3 (thyroid) receptor. [63] (A defect of the thyroid receptor molecule has been identified as an "oncogene," responsible for some cancers, as has a defect in the progesterone receptor.)

Besides inhibiting the thyroid gland, the unsaturated fats impair intercellular communication,[64] suppress several immune functions that relate to cancer, and are present at high concentrations in cancer cells, where their antiproteolytic action would be expected to interfere with the proteolytic enzymes and to shift the equilibrium toward growth. In the free fatty acid form, the unsaturated fats are toxic to the mitochondria, but cancer cells are famous for their compensatory glycolysis. CONT'D