The advantages of eating fish for pregnant women outweigh the disadvantages

There have been anecdotal reports that pregnant women eating foods containing mercury may cause the birth of "freaks", especially marine fish such as sharks, sailfish, Atlantic mackerel and brickhead fish high in the heavy metal mercury (commonly known as mercury), which can damage the nerves
of the fetus.
However, a recent study published in Neurotoxicology confirmed that the benefits outweigh the harms of eating fish in pregnant women, that the increase in mercury levels was not associated with poor outcomes in fish-eating subjects, and that children born to fish-eating mothers showed excellent neurocognitive performance
.

Although numerous studies have shown the benefits of fish intake during pregnancy, there are concerns that contaminants such as mercury in fish may have harmful effects
.
A 2019 study titled "Relationships between seafood consumption during pregnancy and childhood and neurocognitive development: Two systematic reviews" suggests that Methylmercury levels in the mother's hair and cord blood were inversely associated
with cognitive performance at age 7.
Studies have clearly linked methylmercury levels to pilot whale intake, but the subsequent hypothesis is that seafood may still be responsible for the increased mercury levels in the mother's body, which in turn leads to increased mercury levels in the fetus, and that mercury levels in pregnant women should be minimized
.
So while the advice for pregnant women is usually that eating fish is beneficial, the side caveat is to avoid eating fish
high in mercury.

However, seafood contains many nutrients
that are essential for children's growth and development.
Longitudinal studies conducted in Seychelles, where fish is the main diet, demonstrated that increased maternal intake of foods containing mercury did not have harmful effects
on children's cognition.
Is this also the case in the UK where people eat fish less often? The researchers measured the total mercury levels in the whole blood and umbilical cord tissue of
the participants.
Researchers have been tracking the growth and development of the subjects' offspring, particularly their cognitive development, over time, and found no adverse results
.
These beneficial findings are similar to those observed in the Seychelles, where while Seychelles traditionally eat large amounts of fish and fish consumption is high, barracuda needs to be consumed more than 5 times a week to exceed the FAO/WHO provisional weekly tolerable total mercury intake limit, which is not a rate
that the average person can achieve.
Therefore, the advice to warn about eating fish should be revisited and the beneficial value
of eating fish during pregnancy should be called.

With this background, further research is needed to assess the true relationship between maternal fish intake, mercury biomarker levels and offspring outcomes during pregnancy, particularly cognitive measurements
.
The large study tested the blood and umbilical cord tissue of 12,000 pregnant women for mercury
.
Trials of fish intake in antenatal pregnant women found that the relationship between maternal mercury intake and offspring development was established, that children born to fish-eating mothers performed well in neurocognition, and that increased mercury levels were not associated
with adverse outcomes for fish eaters.

The study summarised cohort data from a relatively industrialized region of southwest England and compared outcomes
for babies born to pregnant women who consumed fish and did not eat fish, based on the degree of fetal exposure to mercury in the womb.
As with the cohort in Seychelles where almost all pregnant women ate fish, the researchers found a positive correlation
between mercury levels exposed in utero among children born to mothers who ate fish during pregnancy and their complex understanding and reasoning skills.
The paper does not discuss the results of the genetic association with mercury found in the trial, nor does it discuss the epigenetic association
shown in the Seychelles population.
These are still worth scrutinizing, but whether they interact with fish, mercury and future generations has yet to be confirmed
.

Senior researcher Dr Leda Chatzi said: "Eating fish may be a common pathway thought to ingest certain heavy metal pollutants that can adversely affect
future generations.
However, when pregnant women eat fish more than 3 times a week, the harm of ingesting heavy metal contaminants can offset the benefits
of eating fish.
"So, how can pregnant women avoid excessive intake of heavy metals while ensuring that they get rich nutrition from fish?" Leda Chaz said: "Fish is an important source of nutrition, pregnant women should stick to the recommendation to eat fish 1-3 times a week, but in moderation
.
Because fish can be contaminated with mercury and other heavy metals, excessive intake can lead to excessive levels of heavy metals in the body
.
"Secondly, it is recommended that pregnant women should choose to eat fish with less heavy metal residue, such as small fish
from pure and unpolluted waters and at the bottom of the food chain.
In addition, consuming a fish oil N-3 supplement from a reliable source is also a good option to avoid heavy metals
while supplementing with N-3.
Therefore, the intake of fish rich in n-3 by pregnant women can not only promote fetal brain and visual development, but also benefit the metabolic health
of offspring.

(Source: BioExploration)

China Food News (October 12, 2022, Edition 03)

(Editor: Han Songyan).