Tuna is Protein Rich, Protects Eyesight, Reduces Heart Disease Risk and Helps to Prevent Arthritis

Tuna was once considered by the samurai unfit to eat, and is now one of the most popular fish in Japan.

It was in 1903 that a sardine shortage led to a cannery filling the cans with albacore, a species of tuna which had no commercial value. The canned tuna soon became popular, and the tuna industry came into being.

Dolphins became a bycatch of tuna, and in 1972 Congress enacted the Marine Mammal Protection Act (MMPA) to protect dolphins from harmful fishing methods. These efforts to protect dolphins have paid off, with dolphin deaths in the eastern tropical Pacific Ocean tuna fishery decreasing by 97%.

Various dolphin safe labels are now being used to verify that dolphins are not being harmed in the tuna fishing process. However, the US Consumers Union has explained that this is no guarantee because there is no third party and independent verification of the dolphin friendly claims.

Health Benefits of Tuna

Nutrients
Tuna is an excellent source of the omega-3 fatty acids EPA and DHA, protein, potassium, selenium, and vitamin B12. It's a very good source of niacin and phosphorus.

Glycemic Index (GI)
In a study to determine the estimated GI of various foods, it was concluded that tuna has a GI of 0.

Protein
Tuna is an excellent source of protein, and while some vitamin and mineral losses occur during canned tuna processing, the protein nutritive values are not dramatically changed.

Cancer Prevention
In a prospective study of 61,433 women it was suggested that consumption of fatty fish such as tuna may reduce the occurrence of renal cell carcinoma (kidney cancer).
Preliminary studies have shown that fatty acids present in fish inhibit the growth of breast cancer, and the Oncology Department at St Thomas' Hospital in London has proposed that premenopausal women over the age of 40 years who are shown to be at increased breast cancer risk supplement their diet with omega-3 fatty acid rich fish.

Alzheimer’s Disease
Data collected in a study on the dietary intake of EPA and DHA fatty acids from fish concluded that moderate fish consumption may postpone cognitive decline in the elderly. Another study demonstrated that a diet high in fish is associated with better cognitive performance in the elderly.
In the Cardiovascular Health Cognition Study, consumption of fatty fish more than twice per week was associated with a reduction in risk of dementia by 28%, and Alzheimer’s Disease by 41% in comparison to those who ate fish less than once per month.

Blood Pressure
An international study of 4680 men and women ages indicated that omega-3 fatty acid intake (largely from fish) may be beneficial in preventing adverse blood pressure levels.

Eyesight Health
The results of a study have demonstrated that omega-3 fatty acid intake and fish consumption is associated with a reduced risk of age-related macular degeneration.
A high dietary intake of Omega-3 fatty acids is also associated with a decrease in dry eye syndrome.

Heart Health
Several studies and clinical trials have provided strong evidence that modest consumption of fish or fish oil (1-2 servings/wk of oily fish, or approximately 250 mg/d of EPA+DHA) substantially reduces the risk of coronary heart disease death.

Arthritis
There is evidence from double blind, placebo-controlled clinical trials that the increase of dietary omega-3 fatty acids supplied as fish oil can have beneficial effects in rheumatoid arthritis.

Nutrient Values of Fresh Yellowfin Tuna per 100g
Calories 139kcal	Energy Value 582kj	Total Fat 1.22g	Carbohydrates 0.00g	Sugars g
Dietary Fiber 0.0g	Protein 29.97g	Sodium 47mg	Zinc 0.67mg	Potassium 569mg
Iron 0.94mg	Magnesium 64mg	Copper 0.082mg	Calcium 21mg	Vitamin C 1.0mg
Vitamin E mg	Vit. B3 (Niacin) 11.936mg	Vitamin B6 1.038mg	Vit. B1 (Thiamin) 0.501mg	Vit. B2 (Riboflavin) 0.057mg

1. Large predatory fish such as tuna have the highest levels of mercury contamination, which is a known developmental neurotoxicant.
2. A guide to mercury levels in tuna and other fish can be downloaded here: Mercury Wallet Card
3. In government food safety tests, canned albacore or white tuna, in addition to fresh or frozen tuna steaks, was found to have significantly more mercury than the canned chunk light tuna.
4. Pregnant women, women of childbearing age, nursing mothers and young children should avoid fish with high levels of mercury.
5. Bluefin tuna, which is prized for its use in Sushi, is facing extinction due to over fishing, and for this reason alone should be avoided.
6. Although most manufacturers display a “dolphin friendly” label on their cans, long line tuna fishing is undiscriminating, and the bycatch includes sharks, turtles and albatrosses.
7. Some canned tuna contains MSG, and is best avoided. References:
1. The Encyclopedia of Healing Foods by Michael Murray, Joseph Pizzorno, and Lara Pizzorno.
2. Benders' Dictionary of Nutrition and Food Technology.
3. USDA National Nutrient Database for Standard Reference.
4. Photo of tuna steak by Chensiyuan.
5. Institute of Food Technologists, Jan/Feb 1983. v. 48.
6. Wolk A, Larsson SC, Johansson JE, Ekman P. Long-term fatty fish consumption and renal cell carcinoma incidence in women. JAMA. 2006 Sep 20;296(11):1371-6. PMID: 16985229.
7. Stoll BA. N-3 fatty acids and lipid peroxidation in breast cancer inhibition. Br J Nutr. 2002 Mar;87(3):193-8. PMID: 12064327.
8. van Gelder BM, Tijhuis M, Kalmijn S, Kromhout D. Fish consumption, n-3 fatty acids, and subsequent 5-y cognitive decline in elderly men: the Zutphen Elderly Study. Am J Clin Nutr. 2007 Apr;85(4):1142-7. PMID: 17413117.
9. Nurk E, Drevon CA, Refsum H, Solvoll K, Vollset SE, Nygård O, Nygaard HA, Engedal K, Tell GS, Smith AD. Cognitive performance among the elderly and dietary fish intake: the Hordaland Health Study. Am J Clin Nutr. 2007 Nov;86(5):1470-8. PMID: 17991661.
10. Ueshima H, Stamler J, Elliott P, Chan Q, Brown IJ, Carnethon MR, Daviglus ML, He K, Moag-Stahlberg A, Rodriguez BL, Steffen LM, Van Horn L, Yarnell J, Zhou B; INTERMAP Research Group. Food omega-3 fatty acid intake of individuals (total, linolenic acid, long-chain) and their blood pressure: INTERMAP study. Hypertension. 2007 Aug;50(2):313-9. Epub 2007 Jun 4. PMID: 17548718.
11. Seddon JM, George S, Rosner B. Cigarette smoking, fish consumption, omega-3 fatty acid intake, and associations with age-related macular degeneration: the US Twin Study of Age-Related Macular Degeneration. Arch Ophthalmol. 2006 Jul;124(7):995-1001. PMID: 16832023.
12. Miljanović B, Trivedi KA, Dana MR, Gilbard JP, Buring JE, Schaumberg DA. Relation between dietary n-3 and n-6 fatty acids and clinically diagnosed dry eye syndrome in women. Am J Clin Nutr. 2005 Oct;82(4):887-93. PMID: 16210721.
13. Mozaffarian D. Fish and n-3 fatty acids for the prevention of fatal coronary heart disease and sudden cardiac death. Am J Clin Nutr. 2008 Jun;87(6):1991S-6S. PMID: 18541600.
14. James MJ, Cleland LG. Dietary n-3 fatty acids and therapy for rheumatoid arthritis. Semin Arthritis Rheum. 1997 Oct;27(2):85-97. PMID: 9355207.
15. PMID: 16275829. Huang TL, Zandi PP, Tucker KL, Fitzpatrick AL, Kuller LH, Fried LP, Burke GL, Carlson MC. Benefits of fatty fish on dementia risk are stronger for those without APOE epsilon4. Neurology. 2005 Nov 8;65(9):1409-14.
16. Costa LG. Contaminants in fish: risk-benefit considerations. Arh Hig Rada Toksikol. 2007 Sep;58(3):367-74. PMID: 17913692.

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