This article is more than 5 years old. Information may no longer be current.
Mercury from fish consumption linked to positive antinuclear antibodies in women
Click Here to Manage Email Alerts
Women of reproductive age with high blood, hair or urinary levels of mercury from fish consumption were more likely to show positive serum antinuclear antibodies.
Additionally, women with systemic lupus erythematosus, scleroderma and Sjögren’s syndrome should limit consumption of certain types of fish, according to researchers.
Emily C. Somers
The researchers analyzed data from the National Health and Nutrition Examination Survey (NHANES) collected between 1999 and 2004. Cross-sectional associations between blood, hair and urinary mercury and positive antinuclear antibodies (ANA) were studied in 1,352 women between the ages of 16 and 49 years enrolled in the NHANES. Hair samples were 1 cm in length and represented about 2.5 months of growth. Mercury levels were too low to be detected in 6% of hair samples.
Sociodemographic data were collected, along with BMI, blood chemistry data and serum polychlorinated biphenyls (PCBs). Dietary intake of seafood was estimated based on participant recall of fish or shellfish in the prior 30 days.
After adjusting three models using different covariables, multivariate logistic regression showed between 12% and 16% of women were ANA-positive, with more than 94% of whom showed speckled pattern of nuclear pattern of nuclear staining. Mercury geometric means were 0.22 ppm in hair, 0.92 µg/L in blood and 0.62 µg/L in urine.
Hair and blood, but not urinary, mercury were associated with ANA positivity, adjusting for confounding factors, hair odds ratio (OR) was 4.10 and blood OR was 2.32 by comparing highest vs. lowest quantiles. The greatest magnitude of association for high-titer (>1:1280) ANA was OR = 11.41 in hair and OR = 5.93 in blood. PCBs were not associated with positive ANA, according to the researchers.
Mercury found in urine samples were inorganic, but methylmercury was the predominant form of mercury present in blood and hair samples, which is accumulated in the body tissue of fish, according to study author, Emily C. Somers, PhD, ScM. Somers told Healio.com/Rheumatology that coal-fired power plants are the largest source of mercury deposition in waterways.
“It gets into the atmosphere, then when it gets deposited into waterways, then the fish consume it and turn it into methylmercury,” Somers said in an interview. “Various types of fish have various amounts of mercury. In general, larger fish that have more mercury, not because of their age, per se, but because those species of fish tend to eat greater numbers of smaller fish.”
The smaller fish also have bioaccumulated mercury during their lifespan, Somers said.
Rheumatologists should advise their patients with rheumatic diseases associated with positive ANA titer such as systemic lupus erythematosus, scleroderma and Sjögren’s syndrome to limit consumption of fish according to EPA and FDA guidelines, particularly women of childbearing age, according to Somers.
According to the FDA, nearly all fish and shellfish contain some mercury. Fish high in mercury which the FDA advises against consuming include swordfish, shark, king mackerel and tilefish. Fish with lower levels of mercury include canned light tuna, catfish, pollock, salmon and shrimp. No more than 12 ounces per week should be consumed, and in the case of white albacore tuna or tuna steak, the amount should be limited to six ounces.
“Albacore isn’t among the highest, but it is among the most commonly consumed, so it’s worth noting,” Somers said.
Not all patients with a positive ANA result have developed a rheumatic or other disease, but consumption of fish should be part of the discussion between the patient and physician, according to Somers.
“A lot of times, a rheumatologist is going to get a referral in the case of positive ANA that is unexplained,” Somers said. “So I would say to anyone who sees patients who have a positive ANA, whether in primary care or a rheumatologist, that it’s something to be aware of, and that it’s a safe recommendation to support what the FDA recommends and to be mindful of the type of fish one is consuming.”
Mercury levels are rising globally, Somers said, but some steps are being taken to reduce atmospheric and waterway mercury pollution.
“The good news is that there is something called the Minamata Convention, named after a Japanese city where a mercury poisoning incident occurred a few years ago,” Somers said. “The international agreement has been designed to reduce mercury emissions in the environment and to eliminate products containing mercury, so that is a very positive development and the U.S. has signed on.” – by Shirley Pulawski
Disclosures: The authors report no relevant financial disclosures.
Click Here to Manage Email Alerts