While there are sometimes trace amounts of mercury in fish oil supplements derived from salmon, it isn't likely enough to lead to mercury poisoning. Just being exposed to this element doesn't mean you'll develop this condition. In fact, you're exposed to some level of mercury each day. It's in the ground, it's in the air and it's in the water. When it comes to any supplement, it's best to talk to your doctor to determine if it'll adversely affect your health.
Evidence
Researchers from the Division of Laboratory Medicine at Massachusetts General Hospital conducted a study in 2009 to determine the level of mercury in five over-the-counter fish oil supplements. Three of these supplements -- Nordic Ultimate, Sundown and Kirkland -- contained no mercury at all, whereas the other two fish oil supplements -- Omega Brite and CVS -- contained 12 mcg/L and 10 mcg/L, respectively. Although mercury was found in these two supplements, it isn't enough to cause mercury poisoning. They pose minimal risk of mercury toxicity. In fact, most people are exposed to low levels of this element each day.
Mercury Levels
Another study, this one published in the 2005 edition of the "Journal of Automated Methods and Management in Chemistry," analyzed 40 available dietary supplements for mercury. Of all the supplements, the highest amount found was in a concentrated salmon oil sample, coming in at 123 nanograms per gram, or ng/g. When taken as directed each day, this is equivalent to 7 mcg per week. Using the previous study as a guide, this should pose only a minimal risk of mercury toxicity.
Mercury Ingestion
When mercury is ingested, it's quickly absorbed within the gastrointestinal tract. It's then moved to the kidney and liver, where it slowly eliminated in your urine, saliva and sweat. It's also expressed in milk and some of it is also expelled in your stool. Mercury poisoning doesn't usually occur until you've been exposed to this element for prolonged periods of time, unless you ingest large quantities at one time.
Symptoms
Long-term exposure to mercury can lead to a number of neurological symptoms. Some people develop tremors or trouble walking, while others may suffer blindness or double vision. You may also experience seizures, memory problems or numbness. Severe cases may even lead to death. During pregnancy, exposure to mercury can lead to brain damage of the child. The amount of mercury needed to cause these symptoms varies from person to person. There isn't a standard level that causes problems. Your best bet is to get as little as possible.
References
- MedlinePlus; Mercury; February 2009
- Archives of Pathology and Laboratory Medicine; Measurement of Mercury Levels in Concentrated Over-the-Counter Fish Oil Preparations: Is Fish Oil Healthier Than Fish?; Stacy Foran, et al.; December 2003
- Journal of Automated Methods and Management in Chemistry; Determination of Mercury in an Assortment of Dietary Supplements Using an Inexpensive Combustion Atomic Absorption Spectrometry Technique; K.E. Levine, et al.; 2005
- Michigan Department of Natural Resources: Mercury Poisoning
