Is grouper safe to eat? (Health effects)

In this brief guide, we will answer the question “Is grouper safe to eat?”. We also will discuss how mercury concentration can make some fish species should be avoided.

Is grouper safe to eat?

Yes, grouper is safe to eat. Grouper, often referred to as hammour fish, is recognized for its high nutritional value. It boasts protein with a high biological value, encompassing all essential amino acids. Furthermore, grouper fish serves as a rich source of vital minerals, vitamins, and fats, including essential fatty acids crucial for human well-being. (1)

What are grouper health benefits?

Grouper muscle is rich in a diverse range of macronutrients and micronutrients that contribute to overall health. The meat of grouper offers an ideal composition of fatty acids crucial for maintaining optimal well-being. Certain individual fatty acids within these groups possess distinct biological properties with positive impacts on health.

Grouper fish stands as a valuable reservoir of fat-soluble vitamins, including vitamin A (retinol) and vitamin D (calciferol vitamin). Vitamin A is an essential nutrient, vital in small quantities for the human visual system, while vitamin D is necessary for regulating blood calcium and phosphate levels, bone formation, muscle function, nerve conduction, and general cellular processes throughout the body.

Notably, fat-soluble vitamins are more resistant to heat than their water-soluble counterparts, such as vitamin B1 (thiamine) and vitamin B3 (niacin), but exposure to high temperatures and oxygen can degrade them.

Fish serves as an excellent source of high-quality protein and ranks among the top food sources of long-chain omega-3 fatty acids, namely DHA and EPA. These omega-3 fatty acids are dietary necessities and hold significant importance in promoting heart health, as well as supporting brain and eye development. (2, 3)

What are the potential risks of grouper consumption?

Worries surrounding mercury exposure have frequently led to restrictions on grouper consumption. Excessive methylmercury, a specific form of mercury, has the potential to adversely affect neurocognitive development and can be found in various fish species.

Nevertheless, empirical data indicates that it takes consumption of fish in quantities well beyond typical intake for mercury exposure to be a genuine concern. The FDA and EPA have pinpointed seven fish varieties to be avoided during pregnancy due to their elevated mercury content.

These include shark, king mackerel, swordfish, tilefish from the Gulf of Mexico, marlin, orange roughy, and bigeye tuna. These recommendations stem from the well-documented high mercury levels in these fish and the limited neurocognitive benefits they provide. Therefore, grouper is generally considered a safe choice. (4)

What is the amount of mercury in grouper?

On average, grouper typically contains approximately 0.45 parts per million (ppm) of mercury. As a general rule, fish situated higher up in the food chain tend to exhibit higher overall mercury levels.

Fish varieties like barracuda, escolar, marlin, orange roughy, sablefish, sea bass, shark, swordfish, and specific types of tuna have been identified with total mercury levels that average around or surpass 0.5 ppm. In particular, marlin, shark, swordfish, and certain fresh tuna species have been reported to have average total mercury levels exceeding 1.0 ppm. (3)

What are the health hazards of methylmercury?

The primary organs targeted by organic mercury-induced toxicity in humans are the central and peripheral nervous systems, with the developing fetus being particularly sensitive to its effects. Fetal exposure to methylmercury can impact the developing nervous system at concentrations much lower than what affects adults.

In cases of exposure to exceptionally high levels of methylmercury over the short to long term, initial neurological effects typically present as non-specific symptoms like tingling sensations, general discomfort, and blurred vision.

Subsequently, additional symptoms may emerge, including narrowing of the visual field, hearing loss, speech difficulties, and impaired coordination. In cases of extremely high exposure, methylmercury poisoning can progress to coma and, in severe cases, lead to fatality.

When ingested, organic mercury, such as methylmercury, is highly absorbable from the gastrointestinal tract and distributed throughout the body. Methylmercury easily penetrates both the blood-brain barrier and the placenta, thus posing significant risks to neurological and developmental health. (3)

What factors affect mercury accumulation in grouper?

Higher mercury levels are typically found in larger and older fish, particularly among species higher up in the food chain as fish, in general, have limited abilities to metabolize and eliminate mercury once absorbed from their surroundings. 

The formation of methylmercury in coastal sediments is subject to temporal and spatial variations and is influenced by various factors, including bioturbation, sediment hydrodynamics, sediment chemistry, and the interplay of physicochemical, physiological, and ecological factors affecting the transport of mercury from sediments to organisms.

Inorganic mercury enters coastal and marine environments through atmospheric deposition and riverine inflow. The primary source of methylmercury (MeHg) in marine organisms stems from its production in coastal and continental shelf sediments.

The initial step in the introduction and biomagnification of mercury in the marine food web involves the uptake of MeHg from the water column by marine phytoplankton.  (5)

Should grouper be avoided?

Avoiding grouper due to concerns of excessive mercury intake is generally unnecessary. In fish consumption advisories related to mercury (Hg), grouper species within the Serranidae family are often grouped together and simply labeled as “Grouper.” However, it’s important to note that grouper species exhibit significant variations in growth rate, maximum age, and maximum size.

Among the three species of grouper, two (red grouper and scamp) have mean mercury concentrations that fall within the “Good Choices” category, allowing for one meal per week, as recommended by the US EPA and US FDA. Additionally, one species (gag) falls within the “Good Choices” category for two meals per week. (6)

Conclusion

 In this brief guide, we answered the question “Is grouper safe to eat when pregnant?”. We also discussed how mercury concentration can make some fish species should be avoided. In my perspective as a food scientist, grouper is safe and consuming it 1 to 2 times per week, depending on the species, offers no risk.

References