Tuna is a widely eaten species of fish. However, canned tuna is often the most common source of mercury in the diet.
The term tuna encompasses several species of fish, including skipjack, albacore, yellowfin, and bigeye. Skipjack is the most commonly consumed species.
Mercury is a chemical
When released into the environment, mercury can become a public health issue when it settles into our oceans and waterways.
Natural bacteria absorb mercury and convert it into methylmercury, introducing it into the food chain. Small fish consume or absorb the methylmercury and are eaten by larger fish. Instead of breaking down or dissolving, however, mercury builds up at every level of the food chain.
Large fish, such as tuna, can have mercury concentrations in their bodies that are
However, tuna is still safe to eat in certain amounts. This article explains how much to eat without affecting health and clarifies the risks of consuming too much.
Mercury is odorless and invisible to humans. Once in the body, however, it can act as a neurotoxin and interfere with the brain and nervous system.
Exposure to mercury
While the brain of a child develops, it rapidly absorbs nutrients. Mercury can affect that absorption, causing learning disabilities and developmental delays. In infants and fetuses, high doses can lead to cognitive difficulties, cerebral palsy, deafness, and blindness.
In adults, mercury poisoning can affect fertility and blood pressure regulation.
Mercury poisoning can also cause the following symptoms:
- memory loss
- vision loss
- numbness of extremities
Recommendations for how often a person should eat canned tuna can vary depending on several factors, including the specific type of tuna, their age, and whether or not they belong to a group that may be more sensitive to the effects of mercury.
According to the
For adults, 4 oz is considered 1 serving. For children, 1 serving is:
- 1 oz for children 1–3 years
- 2 oz for children 4–7 years
- 3 oz for children 8–10 years
- 4 oz for children 11 years and older
Canned light tuna is low in mercury and is considered one of the best choices for individuals that need to limit their exposure to mercury. People who are pregnant or breastfeeding can consume 2–3 servings of canned light tuna per week and children can consume 2 servings per week.
Canned, fresh, or frozen white albacore tuna and yellowfin tuna contain slightly more mercury but are also good choices. Though these varieties of tuna are not recommended for children, those who are pregnant or breastfeeding can consume up to 1 serving per week.
Bigeye tuna, which is often used in sashimi and sushi, is high in mercury and is not recommended for these groups.
Federal, state, and local advisories may also be issued when certain types of fish are considered unsafe to eat.
According to the Environmental Protection Agency, these advisories may apply to specific waterbodies or types of water and can be issued to the general public or specific populations, such as people who are pregnant or breastfeeding.
Certain types of tuna are high in mercury, which can have harmful effects on health in high amounts or in certain populations.
For most healthy adults, it’s recommended to consume at least 2 servings of fish per week, which can include tuna.
However, raw fish and varieties of fish that are high in mercury, such as bigeye tuna, should be avoided in some groups, including small children and people who are pregnant, trying to become pregnant, or breastfeeding.
These groups should select varieties of fish that are low in mercury, including canned light tuna, and limit their intake based on the recommendations set by the FDA.
- Advice about eating fish. (2021).
- Dietary Guidelines for Americans, 2020-2025. (2020).
- Fish and shellfish advisories and safe eating guidelines. (2023). https://www.epa.gov/choose-fish-and-shellfish-wisely/fish-and-shellfish-advisories-and-safe-eating-guidelines
- Health effects of exposure to mercury. (2022). https://www.epa.gov/mercury/health-effects-exposures-mercury
- Mercury levels in commercial fish and shellfish (1990-2012). (2022).
- Posin SL, et al. Mercury toxicity. (2022).
- Questions & answers from the FDA/EPA advice about eating fish for those who might become or are pregnant or breastfeeding and children ages 1 to 11 years. (2022).