Fish, Blood Types, and Mental Balance: Insights from Scientific Studies

Fish consumption, particularly rich in omega-3 fatty acids like EPA and DHA, has been extensively studied for its role in supporting brain health and mental well-being.

Systematic reviews and randomized controlled trials (RCTs) indicate that omega-3s from fish promote neurodevelopment, reduce inflammation, and enhance cognitive function, especially in young adults and athletes. For instance, a systematic review of RCTs found that omega-3 polyunsaturated fatty acids (PUFAs) inhibit neuronal cell death, lower inflammation, and improve brain functions, with benefits observed in young participants for memory and learning.

Another RCT in young adults showed that EPA-rich supplementation improved cognitive performance and reduced brain activation effort during tasks, suggesting more efficient neural processing.

In athletic populations, the International Society of Sports Nutrition’s position stand, based on critical literature review, supports omega-3 supplementation for exercise recovery, reduced inflammation, and brain health, including lower neurofilament light concentrations—a marker of brain injury—in contact sports athletes.

A meta-analysis confirmed improvements in reaction time, mood, and proinflammatory markers like TNF-α with fish oil intake.

These effects align with benefits for high-energy individuals under 30, where faster recovery and mental resilience are key, as omega-3s modulate neurotransmitters like serotonin to alleviate fatigue and support mood regulation.

Regarding mental health, meta-analyses of RCTs demonstrate omega-3 supplementation’s efficacy in reducing anxiety and depressive symptoms.

A dose-response meta-analysis of RCTs found that each 1 g/day of omega-3 reduced anxiety symptoms, with low certainty but consistent trends across trials.

For depression, a meta-regression of placebo-controlled trials showed significant antidepressant effects, particularly with EPA-dominant formulations. Evidence also suggests benefits for OCD and neurological imbalances, though trials are limited; one crossover RCT of adjunctive EPA in OCD showed potential, but larger studies are needed.

Overall, omega-3s from fish (2–3 servings weekly) support mental equilibrium across populations, independent of specific vulnerabilities like phlegm-related issues, which lack direct links in the literature.

However, claims linking fish intake to blood types A or B—suggesting avoidance for those with low activity, anxiety, or neurological issues—lack empirical support.

The “blood type diet,” which posits ABO-specific food interactions via lectins, has been debunked by systematic reviews finding no ABO-specific agglutination or health outcomes from type-tailored diets. A PLOS One study of 1,455 adults tested cardiometabolic markers and found no interaction between ABO genotype and blood-type diets; benefits, if any, stemmed from general healthy eating patterns, not blood group specificity. No trials connect fish avoidance to reduced OCD or anxiety in A/B types, and ABO links to anxiety risk (e.g., slightly higher in B) do not involve dietary modulation by fish.

On combining fish and eggs, warnings of increased clotting risks are unsubstantiated, particularly by blood type.

While choline in eggs can elevate TMAO—a gut-derived compound linked to platelet hyperresponsiveness and thrombosis risk in supplement studies—no RCTs show synergy with fish causing circulatory issues. A 2021 RCT found egg consumption did not raise TMAO or enhance clotting in healthy adults, unlike isolated choline supplements. Fish’s anti-inflammatory omega-3s may even counter potential TMAO effects from dietary choline.

Finally, pairing fish with dates for “balance” has no direct studies, but dates offer independent benefits.

Rich in fiber, potassium, and antioxidants, dates support gut-brain health and reduce inflammation, potentially aiding metabolic stability post-fish meal. No evidence ties them to phlegm reduction or anxiety relief specifically after fish, but their polyphenols may broadly enhance mental health via antioxidant pathways.

In summary, scientific evidence robustly supports fish’s omega-3s for youth, athletes, and mental health across blood types, without the caveats of type-specific restrictions or combinations.

References

1. Dighriri IM, et al. Effects of Omega-3 Polyunsaturated Fatty Acids on Brain Functions: A Systematic Review. Cureus. 2022;14(10):e30091.
2. Vitale K, Getzin A. International Society of Sports Nutrition Position Stand: Long-Chain Omega-3 Polyunsaturated Fatty Acids. J Int Soc Sports Nutr. 2024;21(1):2441775.
3. Bauer I, et al. Omega-3 supplementation improves cognition and modifies brain activation in young adults. Hum Brain Mapp. 2014;35(4):1271-1286.
4. Heileson JL, et al. Nutritional Optimization for Brain Health in Contact Sports: A Systematic Review and Meta-Analysis on Long-Chain ω-3 Fatty Acids. Nutrients. 2024;16(7):1030.
5. Kris-Etherton PM, et al. Nutrition and behavioral health disorders: depression and anxiety. Nutr Rev. 2021;79(3):247-260.
6. Su KP, et al. Association of Use of Omega-3 Polyunsaturated Fatty Acids With Changes in Severity of Anxiety Symptoms: A Systematic Review and Meta-analysis. JAMA Netw Open. 2018;1(5):e182327.
7. Wang J, et al. ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. PLoS One. 2014;9(1):e84749.
8. Cusack L, et al. Blood type diets lack supporting evidence: a systematic review. Am J Clin Nutr. 2013;98(1):99-104.
9. Zhu J, et al. Dietary Choline Supplements, but Not Eggs, Raise Fasting TMAO Levels in Participants with Normal Renal Function: A Randomized Clinical Trial. Am J Med. 2021;134(6):748-752.
10. Al-Farsi YM, et al. Effect of Dates on Blood Glucose and Lipid Profile in Type 2 Diabetic Patients. Pak J Med Sci. 2014;30(2):292-296.