Effects of fish oils and fish on cardiovascular disease

Original Research: Effect of various dietary fats on fatty acid profile in duck liver: Efficient conversion of short-chain to long-chain omega-3 fatty acids

Omega-3 fatty acids, especially long-chain omega-3 fatty acids, have been associated with potential health benefits for chronic disease prevention. Our previous studies found that dietary omega-3 fatty acids could accumulate in the meat and eggs in a duck model. This study was to reveal the effects of various dietary fats on fatty acid profile and conversion of omega-3 fatty acids in duck liver. Female Shan Partridge Ducks were randomly assigned to five dietary treatments, each consisting of 6 replicates of 30 birds. The experimental diets substituted the basal diet by 2% of flaxseed oil, rapeseed oil, beef tallow, or fish oil, respectively. In addition, a dose response study was further conducted for flaxseed and fish oil diets at 0.5%, 1%, and 2%, respectively. At the end of the five-week treatment, fatty acids were extracted from the liver samples and analyzed by GC-FID. As expected, the total omega-3 fatty acids and the ratio of total omega-3/omega-6 significantly increased in both flaxseed and fish oil groups when compared with the control diet. No significant change of total saturated fatty acids or omega-3 fatty acids was found in both rapeseed and beef tallow groups. The dose response study further indicated that 59-81% of the short-chain omega-3 ALA in flaxseed oil-fed group was efficiently converted to long-chain DHA in the duck liver, whereas 1% of dietary flaxseed oil could produce an equivalent level of DHA as 0.5% of dietary fish oil. The more omega-3 fatty acids, the less omega-6 fatty acids in the duck liver. Taken together, this study showed the fatty acid profiling in the duck liver after various dietary fat consumption, provided insight into a dose response change of omega-3 fatty acids, indicated an efficient conversion of short- to long-chain omega-3 fatty acid, and suggested alternative long-chain omega-3 fatty acid-enriched duck products for human health benefits.

Polyunsaturated fatty acids and their effects on cardiovascular disease

Dietary polyunsaturated fatty acids (PUFAs) affect a wide variety of physiological processes. Much attention has been given to the n-3 PUFAs and their role in the prevention and treatment of cardiovascular disease, stemming from evidence obtained through a number of epidemiological studies and clinical trials. Investigators are now focused on elucidating the pathways and mechanisms for the biological action of n-3 PUFAs. Dietary intervention is recognized as a key measure in patient therapy and in the maintenance of human health in general. This review provides a summary of several important clinical trials, and while the exact modes of action of n-3 PUFA are not known, current viewpoints regarding the mechanisms of these fatty acids on atherosclerosis, circulating lipid profile, cell membranes, cell proliferation, platelet aggregation and cardiac arrhythmias are discussed.

Does fish oil prevent preterm birth?

A literature review was performed on the effect of fish oil on preterm birth in observational and randomized studies. The only weak effect on preterm birth found in meta-analyses could be caused by the low compliance, and the fact that many women stop supplementation before term together with a fast acting effect on fish oil.

A framework and information needs for the management of the risks from consumption of self-caught fish

Governmental agencies deal with the potential risk from consuming fish contaminated with toxic chemicals by issuing fish consumption advisories. Yet such advisories are often ignored by the general public, who continue to fish and consume self-caught fish that are the subject of advisories and are from contaminated waters. Further, people are often unaware of specific warnings (which species to avoid, who is vulnerable, when they are vulnerable). In this paper we propose a more inclusive framework for examining consumption behavior of self-caught fish and identify information needs for effective communication. We include not only the usual variables that are used for calculating risk from fish consumption (meal frequency, meal size, contaminant levels) but also other aspects of behavior that contribute to risk. These include attitudes (trust, risk aversion, environmental concerns), behavior (sources of information, cultural mores, personal preferences), exposure (physical proximity, ingestion rates, bioavailability, target tissues), contaminant levels, individual host differences, and hazards (levels of contaminants). We suggest that attitudes and behavior shape risk as much as exposure and hazards and that all four of these factors must be considered in risk management. Factors such as gender, age, pregnancy status, and nutrition all influence who is at risk, while other consumption factors affect these at-risk populations, including meals/week, meal size, cooking method, fish species and sizes eaten, and years of fish consumption. Similarly, contaminant levels in fish vary by fish species, fish size and age, part of the fish, and collection location. Elucidating the risk to individual consumers involves integrating this range of factors, and managing the risk likewise involves incorporating these factors. We suggest that development of appropriate advisories and compliance with advisories will occur only if managers, risk assessors, and public policy makers consider this whole range of factors and not just the traditional fish consumption rate (often underestimated) and contaminant levels in fish (often undersampled). Merely informing the public of contaminant levels or the risk from contaminants will not ensure a public that has enough information to make informed decision, or to be in compliance with consumption advisories, or to effect changes in consumption behavior where public health is at risk.

Are omega-3 fatty acids the most important nutritional modulators of coronary heart disease risk?

With each passing year, the evidence linking an increased risk for coronary heart disease (CHD) death with a chronic dietary deficiency in long-chain omega-3 (n-3) fatty acids (FAs) grows stronger. Recently, a federally mandated evidence-based review in the United States concluded that n-3 FAs, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have clear cardioprotective effects, and national and international expert panels and health organizations have begun to call for increased EPA and DHA intakes. Consumption of between 450 and 1000 mg/d is recommended for those without and with known CHD, respectively. Based on animal and isolated cell studies, these FAs were presumed to have antiarrhythmic effects. The first direct evidence for this in humans was recently published, as were new data linking low n-3 FA intakes with risk for developing atrial fibrillation. The strength of the n-3 story has now led to a proposal that blood levels of EPA plus DHA be considered a new, modifiable, and clinically relevant risk factor for death from CHD.

The role of fats in the lifecycle stages. Adulthood--prevention: cardiovascular disease

Coronary heart disease (CHD) risk is positively linked with dietary saturates and negatively linked with polyunsaturated fatty acids (PUFAs). Consumption of omega-3 fatty acids, such as in fish, appears highly protective against CHD. PUFAs (linoleic acid or omega-6) lower low-density lipoprotein (LDL) cholesterol levels most, and saturates, especially butter fat, raise LDL levels most. Fish oil fatty acids (omega-3) lower triglyceride and raise high-density lipoprotein (HDL) cholesterol levels. A higher ratio of dietary omega-3 to omega-6 fatty acids than is currently consumed in our population may be desirable, and can be achieved by increasing consumption of fish and alpha-linolenic acid in canola, soy and flaxseed oils. Large prospective trials show that people who experience least CHD have a pattern of eating that is rich in fish, PUFAs, whole-grain cereals, fruits and vegetables and low-fat dairy foods, and low in saturates from dairy fat, meat fat and fried foods.