Fish can't save your body's key filtration organ from excess booze… but a new evidence review indicates that their omega-3 fats can help protect liver health.
Fatty liver is defined as having fat make up more than 10 percent of your liver's weight, due to a gradual buildup of excess fat in liver cells
The excess fat leads to inflammation of the liver, which causes liver damage and can ultimately lead to liver failure.
Now, a new analysis suggests that fish-derived omega-3s can help prevent and reverse fatty liver disorder.
And it shows that fish fats can improve insulin sensitivity in people with the increasingly common condition, thereby discouraging diabetes.
What is fatty liver?
Fatty liver occurs most often in seriously overweight people and among those who drink too much alcohol.
Ten to 25 percent of American adults have fatty liver—with the incidence on the rise—and it affects as many as 75 percent of obese persons.
According to the American Liver Foundation, there are no known treatments for fatty liver, which is usually detected when a doctor notices that a patient's liver is slightly enlarged, or sees signs in a blood test.
The Foundation says that the best way to reduce your risk of developing fatty liver is to maintain a healthy weight and blood triglyceride levels while avoiding excess alcohol.
And evidence from a separate study suggests that it's also risky to drink too much sweetened soda or fruit juice.
About half of the sugar in all sweet drinks occurs in the form of fructose, which is processed in the liver and tends to get stored there as fat. (We delve into the details of that phenomenon below; see “Sodas and juices linked to fatty liver”.)
Review affirms omega-3s as a fatty-liver fighter
The new review was conducted by researchers from Scotland's University of Edinburgh, who examined the evidence from prior animal studies and the four extant clinical studies.
As they wrote, “Animal studies demonstrate they [dietary omega-3s] reduce hepatic steatosis [fat buildup in liver cells], improve insulin sensitivity and reduce markers of inflammation” (Masterton GS et al. 2009).
Importantly, the Scottish team found it plausible that omega-3 fatty acids would improve liver health because it's been shown that omega-3s exert helpful influences.
First, omega-3s are proven to help maintain healthy triglyceride levels… a key recommendation for preventing fatty liver.
And dietary omega-3s also alter the “expression” of key genes in ways that discourage conversion of dietary sugars to fat stored in the liver, and stimulate the burning and breakdown of existing liver fat.
The Scots also reported finding evidence that omega-3s improve insulin sensitivity and reduce inflammation, thereby, as they wrote, “…offering several potential therapeutic mechanisms” (Masterton GS et al. 2009).
However, their conclusions were tempered by the fact that none of the four encouraging human studies employed the kind of design needed to provide proof: “Clinical trials in human subjects generally confirm these… [lab and animal]… findings but have significant design inadequacies” (Masterton GS et al. 2009).
In other words, as they concluded, “Omega-3 fatty acids are a promising treatment… which require... [testing]... in randomized placebo-controlled trials” (Masterton GS et al. 2009).
Sodas and juices linked to fatty liver
While omega-3s appear to discourage and reduce fatty liver, sweet drinks seem to promote the problem.
An Israeli study published last summer found that drinking too much sweetened soda or too much fruit juice can cause fatty liver.
A team based at Ziv Medical Center in Haifa reported that people who drink more than one liter (about four cups) of sweetened beverages daily were five times more likely to develop fatty liver.
Scientists led by Dr. Nimer Assy recruited 60 middle-aged patients with fatty liver and 30 gender- and age-matched people without fatty liver.
The doctors collected information on the participants' physical activity and intake of food and soft drinks, and drew blood to test it for indicators of insulin resistance, inflammation, and the balance between pro-oxidants (free radicals) and antioxidants.
After six months, they found that 80 percent (four out of five) of the people in the study who were diagnosed with fatty liver drank more than half a liter (about two cups) of fruit juices or sugar-sweetened sodas every day. [question from me: did the juices have added sweeteners? It might be good to specify “unsweetened” fruit juices if not, since many assume fruit juices without added sugar are okay and might think you're writing about Sunny Delight or Hawaiian punch or some such.]
In contrast, only 17 percent (one out of five) of those without fatty liver drank sweetened liquid to excess.
Overall, the participants diagnosed with fatty liver consumed five times more sugars from soft drinks, compared to the healthy subjects.
Seven percent of the fatty liver patients consumed one soft drink per day, 55 percent consumed two or three sweet drinks per day, and 38 percent averaged more than four soft drinks per day.
The most common sweetened drinks consumed by fatty liver patients were fruit juices (47 percent) and cola (32 percent).
Interestingly, their analysis showed that consumption of sugary beverages was a strong predictor of fatty liver, independent of the increased risk linked to having metabolic syndrome.
Cane sugar and high-fructose corn syrup: Equally risky in excess
All sodas and natural fruit juices are high in sugars, and it doesn't much matter whether those sugars are in the form of sucrose (as in cane sugar or natural fruit juices) or high-fructose corn syrup (as in sweetened sodas or juices with added sweeteners).
This is because sucrose and high-fructose corn syrup alike are half glucose and half fructose.
Unlike glucose, which gets burned off quickly or gets stored in the brain and muscles, fructose is processed through the liver, and excess intake can result in being converted to fat in liver cells.
Thus, with regard to risk of fatty liver, it is not necessarily better to drink fruit juice as opposed to soda… unless, as the Israeli team noted, the juice you drink retains ample amounts of fibrous pulp, which reduces processing of fructose in the liver.
Abid A, Taha O, Nseir W, Farah R, Grosovski M, Assy N. Soft drink consumption is associated with fatty liver disease independent of metabolic syndrome. J Hepatol. 2009 Nov;51(5):918-24. Epub 2009 Aug 21.
Angulo P (2002). Nonalcoholic fatty liver disease. New Engl J Med 346 (16): 1221–31.
Hamaguchi M, Kojima T, Takeda N, Nakagawa T, Taniguchi H, Fujii K, Omatsu T, Nakajima T, Sarui H, Shimazaki M, Kato T, Okuda J, Ida K (2005). The metabolic syndrome as a predictor of nonalcoholic fatty liver disease. Ann Intern Med 143 (10): 722–8.
Masterton GS, Plevris JN, Hayes PC. Review article: omega-3 fatty acids - a promising novel therapy for non-alcoholic fatty liver disease. Aliment Pharmacol Ther. 2009 Dec 30. [Epub ahead of print]