Fish oils come from fatty fish, also known as oily fish, specifically the tissue of fatty fish, such as trout, mackerel, tuna, herring, sardines, and salmon.
Fish oils are of interest to nutritionists and health care professionals because of two main ingredients: DHA (docosahexaenoic acid), and EPA (eicosapentaenoic acid) - both types of Omega-3 fatty acids.
The fillets of oily fish contain up to 30% oil; this figure may vary. White fish, on the other hand, only contain high concentrations of oil in the liver, and have much less oil. Apart from omega-3 fatty acids, oily fish are also good sources of vitamins A and D. Whitefish also contain these nutrients, but at much lower concentrations.
Health experts commonly tell people that oily fish have more health benefits than white fish. However, their recommendations have never been compellingly proven scientifically in large population studies.
Many health authorities around the world advise people to consume either plenty of oily fish or to take supplements, because of their supposed health benefits. Studies over the last ten years have produced mixed results regarding the benefits of the dietary intake of fish oils.
Possible health benefits of fish oils
Over the last ten years, there have been dozens of studies on fish oils and omega-3 oils. Some have backed up these claims, while others have not.
Fish oils are said to have several health benefits if they are included in a human diet, including:
Multiple sclerosis (MS)
Fish oils are said to help people with MS. However, a study carried out by researchers from University Hospital in Bergen, Norway, in April 2012 found that omega-3 fatty acids do not help people with MS.1
Fish oils reduce men's risk of developing prostate cancer if they follow a low-fat diet, one study found, while another linked omega-3 levels to a higher risk of aggressive prostate cancer2.
A study published in the Journal of the National Cancer Institute found that omega fish oils raise prostate cancer risk. The authors, from the Fred Hutchinson Cancer Research Center reported that high fish oil intake raises the risk of high-grade prostate cancer by 71% and all prostate cancers by 43%.3
Post-natal (post-partum) depression
Fish oils protect from post-partum depression - Dr. Michelle Price Judge, of the University of Connecticut School of Nursing, said after carrying out a study in 2011 "DHA consumption during pregnancy at levels that are reasonably attained from foods has the potential to decrease symptoms of postpartum depression."4
Mental health benefits
fish oils help young people with behavioral problems, especially those with ADHD.5
Working memory can improve in healthy young adults if they increase their Omega-3 fatty acids intake, researchers reported in the journal PLOS One (October 2012 issue).6
Protection from Alzheimer's disease
Claims were made for many years that regular fish oil consumption would help prevent people from developing Alzheimer's disease. However, a major study in 2010 found that fish oils and a placebo were no different in Alzheimer's prevention.
In contrast, a study published in Neurology in 2007 reported that a diet in fish, omega-3 oils, fruit and veggies reduces dementia and Alzheimer's risk.7
Protection from vision loss
Adequate dietary consumption of DHA protects people from age-related vision loss, Canadian researchers reported in the journal Investigative Ophthalmology & Visual Science.8
Benefits for the fetus
omega-3 consumption boosts fetal cognitive and motor development - scientists from L'Université Laval Laval found that omega-3 consumption by the mother during her last three months of pregnancy improved her baby's sensory, cognitive and motor development