Introduction
- Fish and other seafood contain important and unique
nutrients, including n-3 fatty acids. In addition, fish is low in saturated fat
and high in protein.
- The Dietary Guidelines of Americans suggest consuming 6-8 oz (~2 servings; 1 oz ≈
28.3 g) per week.
- Examples of fatty fish include salmon, herring, mackerel,
anchovies or sardines.
- About 1 in 5 Americans met the suggested weekly intake of
fish and seafood.
Fish consumption and
Cardiac Disease
- The clearest health benefit from fish consumption is
cardiac disease prevention, including a decreased risk of heart attack, stroke,
arrhythmias, and sudden cardiac death.
- One large trial found that a moderate consumption of
seafood (1–2 servings per week) decreased the risk of dying of coronary artery disease
by 36%.
- The n-3 fatty acids within fish and seafood have been
shown to protect against cardiac arrhythmias, lower blood pressure and heart
rate elevations, improve arterial compliance, and lower triglycerides at higher
doses of g/d.
- n-3 fatty acids decrease the risk of cardiac arrhythmias
by stabilizing the myocardium directly, lowering the resting heart rate, and
increasing left ventricular filling capacity.
- Consumption of tuna or other broiled/baked fish was
inversely associated with fatal ischemic heart disease. However, consumption of
fried fish or fish sandwiches did not have this same cardiac protection
Fish Consumption and
Prostate Cancer
- A recent meta-analysis of 37 studies concluded that the
consumption of fish or fish oil does not demonstrate consistency in reducing
prostate cancer incidence.
- This may be due to the heterogeneity of the studies
without reporting fish type, cooking method (fried vs baked), or consistent
measurement of weekly fish intake
Fish Consumption and
Other Chronic Diseases
- Consumption of fish and supplementation with ω-3-fatty acids
have been well studied for ameliorating chronic disease as they downregulate a
number of proinflammatory mediators and transcription factors
- There is evidence showing that ω-3 fatty acids can decrease
inflammation and be useful in the treatment of rheumatoid arthritis, IBD and
psoriasis.
- Several studies have shown a benefit of fish oil in depression
and Alzheimer disease.
- The most recent study showed that “moderate seafood
consumption was correlated with lesser Alzheimer disease neuropathology.
Although seafood consumption was also correlated with higher brain levels of
mercury, these levels were not correlated with brain neuropathology” (Morris etal. JAMA. 2016;315(5):489-497. doi:10.1001/jama.2015.19451)
Mercury and Toxins
- The fish types with the highest concentration of mercury include shark, swordfish, king mackerel, and tilefish (also known as golden
bass or golden snapper).
- The seafood with the lowest
levels of mercury includes anchovies,
sardines, catfish, Pollock, salmon, clams, oysters, and shrimp.
- Aside from mercury, the most common contaminants of concern
in seafood include polychlorinated biphenyls (PCBs) and dioxins.
- The amount of PCBs and dioxins found in fish is low and
equivalent to the levels found in other commonly consumed foods such as meats,
dairy products, and eggs.
- The Environmental Protection Agency, the Food and Drug Administration,
and the Institutes of Medicine report conclude that the evidence is insufficient to recommend limitations on fish
intake in adults given the proven health benefits, especially on cardiac
disease.
Fish Consumption in Pregnancy and Children
- Children of women who consumed <340 g/wk of seafood
during pregnancy and breastfeeding have evidence of delayed brain development, including
decreased intelligence levels and worse social and behavior scores.
- The 4 fish types with the highest concentration of mercury
mentioned above should be avoided during pregnancy and breastfeeding and in
young children.
- Outside of these 4 less commonly consumed fish, pregnant and breastfeeding mothers should
be encouraged to consume 2 servings of fish per week for their own health
as well as the neurocognitive development of the baby
- Most studies have
proven that the benefits of fish intake exceed the possible unconfirmed risks
Farm-Raised vs Wild-Caught Fish
- Farm-raised fish are typically grown in large pens
submerged in a pond, lake, or salt water, whereas wild-caught fish are caught
in their natural environment by fisherman
- Farm-raised fish are fed an unnatural diet typically
containing more fat, with some evidence that farm-raised fish may have lower
levels of ω-3 fatty acids. In addition, farm-raised fish may be treated with antibiotics
and pesticides
- However, wild-caught fish are also exposed to toxins in
their natural food sources.
- Many species may be overfished in their natural
environments and therefore farm-raising these fish may be more sustainable
Can Fish Oil Supplements Replace Fish in the Diet?
- Multiple studies have now been performed that have not
shown a benefit of fish oil/ω-3 supplements on cardiac disease or stroke risk
- In fact, 1 well-performed systematic review of 794,000
participants concluded that fish consumption was significantly associated with
a reduced risk of cerebrovascular disease, but ω-3 supplements were not.
- Therefore, the beneficial
effects of fish may come from the wide variety of nutrients contained in them
such as vitamin D, B-complex vitamins, essential amino acids, and trace
elements.
- On the other hand, higher
intake of fish and seafood could be associated with decreased consumption of
red meat, which is detrimental to cerebrovascular and cardiac health.
- In addition, higher seafood consumption may be a marker
for an overall healthier diet pattern and higher socioeconomic status, which
are associated with improved health outcomes.
Conclusion
- Moderation and variety are the key to safe and healthy
fish consumption.
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