**6. n-3 PUFA specific factors that make a difference: Source, purity and EPA: DHA ratio**

If the general question on n-3 PUFA and PCa surrounds whether or not there is an increase or decrease in PCa cancer risk, then consideration of confounding factors for n-3 PUFA intake, including source, purity and ratio, should be addressed primarily. The foremost sources of essential fatty acids for the majority of studies are fish derived. Consider that both animal protein [201] and accumulated environmental pollutants [202] both have been linked to prostate cancer. In this regard, it is fitting that the development of n-3 PUFA as a pharma‐ ceutical is already underway for other indications as the approval process normally removes the risk of contamination by methyl mercury, arsenic or other pollutants that are often seen in ocean or land based food sources protein [201]. Currently, there are three commercially significant formulations of pharmaceutical grade n-3 PUFAs and numerous over the counter supplements available for potential use in PCa. The noted differences between all of these formulas are purity, source and/or the ratio of EPA to DHA. Lovasa has received United States Food and Drug Administration (USFDA) approval to lower very high triglyceride levels (hypertriglyceridemia) [203]. In other major markets outside the United States, including Europe, Lovasa is known as Omacor, and can be prescribed to patients as a montherapy for hypertriglyceridemia, in combination therapy with a statin for mixed dyslipidemia, or as a secondary preventative therapeutic following myocardial infarction [204]. The expiration of GlaxoSmithKline's patent for Lovasa in September [2012] will likely increase availability of generic replacements. Such equally effective, but lower priced versions could supply markets for already proven indications as well as for subsequently approved disease indications, including for example, PCa. AMR-101, also marketed as Vascepa, received USFDA approval in July, 2012 [205]. Similar to Lovasa, this approval was based on effective treatment of hypertriglyceridemia but with the added ability to impact people with high triglycerides; the latter indication has been filed and is under review pending outcomes in clinical trials [206]. Epanova, another promising n-PUFA formula, is undergoing clinical trials for similar indica‐ tions as previously mentioned for Lovasa, and USFDA approval is forthcoming [207]. Other dietary supplements, containing various amounts and ratios of n-3 PUFA which are sold over the counter in the United States and Canada would likely be based on values issued by the Institute of Medicine and National Academies as described below. Such unregulated formu‐ lary preparations do not undergo clinical trials. Studies relating to n-3 PUFA pharmaceutical preparations have focused on treating cardiovascular disease with no clinical consideration for PCa. Albeit, men diagnosed with PCa have accepted the use of such nutraceuticals and thus there is a role in ensuring that this approach constitutes safe and effective therapies. Although studies around the prescription formulas have demonstrated a very good safety and tolerability profile, the focus has been in treating cardiovascular disease and thus there has been no concern over potential adverse effects for other diseases.

Another proposed explanation for inconsistent findings in the role of n-3 PUFA in prostate cancer relates to absolute intake versus ratio of n-3 to n-6 PUFA. The latter may be more relevant for prostate cancer risk considering that the recommended dietary ratio of n-6/n-3 PUFA for health benefits are variable and range from 1:1-4:1, yet dietary intake in such studies, relative to the Western diet could contain 10 or more times the amount of n-6 compared to n-3 PUFA [208]. Also consider that in gathering and thoroughly reviewing all information toward this chapter, we were unable to find an *official* recommended daily allowance for n-3 PUFA for adults or children. In Canada and the United States, the general public and health professionals (including healthcare policy makers and public health officials) use a set of five nutrient based reference values issued by the Institute of Medicine and National Academies for a wide variety of food and dietary applications [209]. These dietary reference intakes (DRI), are inclusive of components including: estimated average requirements (EAR), recommended daily allowance (RDA), adequate intake (AI), tolerable upper intake level (UL) and an acceptable macronutrient distribution range (AMDR). Considered to be the official standard for federal agencies, these values are used to issue dietary guidance or policy directives for the health and well-being of individuals. In the absence of a DRI specific to EPA and DHA, the National Academies have recommended an AMDR of 10% for another n-3 PUFA, namely alpha-linolenic acid (ALA) to be consumed as EPA and/or DHA equating to a much lower value (about 100 mg/day) than currently recommended by many groups worldwide. For example, a number of nutritionist and physicians recommend as much as 450 milligrams of n-3 PUFA in either DHA or EPA form per day to promote a healthy diet [79, 210], a fact alone which warrants further studies to determine DRI, specifically UL. More importantly, if the effects of n-3 PUFA represent different disease specifications, then it is crucial to establish DRIs for DHA and EPA individ‐ ually, and in combination. Considering the contradictory evidence that excessive DHA may be a possible cause for some types of aggressive prostate cancer, the expansion of this field of research may want to revisit the incorporation of such basic factors as the ratio of EPA to DHA as a beginning to rationalize some existing data. Altogether, in proceeding with such studies, it would be important to consider all forms of n-3 PUFA, as well as a variety of ratios and then proper incorporation of such into cell-culture media or animal models; all while considering relevant study models to reflect relevance to human disease. However, while supplementation in cell based and animal studies may produce positive results, such may not be relevant to actual human therapies.

The existing results for n-3 PUFA and prostate are contradictory, especially in the absence of consistent epidemiological data. Therefore, incorporation of n-3 PUFA related factors such as source, purity and EPA/ DHA ratios are crucial while employing *in vitro* and *in vivo* models representative of the entire PCa cascade.
