If you're a fish lover, or someone who's eating more in an effort to stay healthy, you do not need to worry so much about mercury found in fish and risks of heart disease according to recent research. The only limit in terms of fish consumption that still holds for young children, pregnant women and nursing mothers – as for the rest of us, experts can now insure us that at the exposure level most common in the US there's no evidence of harm.

Fish, loaded with good-for-you omega-3 fatty acids, has long been associated with a reduction of both stroke and heart disease. This is thought to be due to the anti-inflammatory properties of those omega-3s that are capable to reduce dangerous inflammation all through the body.

The concern for many is that fish also poses us to mercury and that low levels of this toxin have been tied to delays in brain development in babies. This is the reason behind the warning against too much fish for pregnant or nursing mothers.

For adults, the main worry was trouble for the cardiovascular system that might come from all that mercury. This study was prompted by the confusion over this risk. The research involved almost 7,000 adults. The team started by evaluating data from two more larger studies that included over 54,000 men (average age 61) and over 121,000 women (average age 53).

At two-year intervals the participants provided information on their medical history, diseases, risk factors and lifestyle. The team focused on 3,427 subjects who did not develop heart disease and an additional 3,427 who were diagnosed with the condition.

The mercury levels of the subjects were obtained from toenail clippings, considered an accurate biomarker for mercury because it attaches tightly to toenail protein. They also looked at selenium levels, a trace nutrient that might protect against the toxicity of mercury.

Those with the highest levels of mercury did not have a higher risk of heart problems. What's more, levels of selenium were not a factor.

When the team compared the highest mercury levels to the lowest, there was a trend towards lower heart disease risk with the higher mercury levels. This may be because of the other helpful effects of eating fish.

US government guidelines suggest that adults eat more seafood, pointing out that 8 ounces a week is a number associated by earlier studies as having an impact on cardiac death. The American Heart Association has long recommended that people eat fish with omega-3s at least two times per week. The concerns about mercury (or other contaminants) have been a source of debate, with many wondering if the benefits of fish outweigh the risks.

Thanks to this latest research, we can now say that they do.

If you decide to add more fish to your diet, it's a good idea to eat a variety of different kinds. The varieties with the higher mercury levels are king mackerel, swordfish, shark and tilefish. Those with the lowest levels of mercury in fish include sardines, salmon, scallops and shrimp.