Food moods.

In a study of 106 healthy volunteers, researchers found that participants who had lower blood levels of omega-3 polyunsaturated fatty acids were more likely to report mild or moderate symptoms of depression, a more negative outlook and be more impulsive. Conversely, those with higher blood levels of omega-3s were found to be more agreeable.

"A number of previous studies have linked low levels of omega-3 to clinically significant conditions such as major depressive disorder, bipolar disorder, schizophrenia, substance abuse and attention deficit disorder," said Sarah Conklin, Ph.D., a postdoctoral scholar with the Cardiovascular Behavioral Medicine Program in the department of psychiatry at the University of Pittsburgh School of Medicine. "However, few studies have shown that these relationships also occur in healthy adults. This study opens the door for future research looking at what effect increasing omega-3 intake, whether by eating omega-3 rich foods like salmon, or taking fish-oil supplements, has on people's mood."

See this post, Something Fishy, that discusses mercury in fishes, omega-3, beef and dairy.

Drinking just half a pint a day of organic milk as part of a healthy balanced diet gives a useful additional source of this Omega 3 fatty acid, as it could provide approximately 10% of the UK’s Daily Reference Value3 of essential n-3 fatty acid, alpha-linolenic acid.

Organic cheese is an even better source, with a matchbox sized piece of organic cheese providing up to 88% of your RDI of this Omega 3 fatty acid.

Organic isn't the issue since you could have certified organic grain fed animals and thus low omega-3. The issue is grass fed since the omega-3 comes from greens. That's where the little fishes get it and eating the little fishes is where the big oily predator fishes get it. Somebody needs to eat their greens, though some nuts (such as walnuts) have good amounts too.

People can't eat and digest enough greens to get a significant amount, but fishes or ruminants can concentrate it for them. Ruminants do this directly from the foods they eat while most oily fishes are predators that concentrate previously concentrated oils. This is the problem with toxins since each level up the food chain concentrates toxins as well as omega-3. The older a fish is and the higher in the food chain the greater the chance of concentrated toxins.

It seems possible to get non-toxic fish if you are careful. It seems possible to get omega-3 rich meat and dairy if you are selective and specify grass fed. If you do then it's easy to get the RDI of omega-3 while eating a varied diet.