Fish oil may modestly lower ALT levels, but the evidence is inconsistent. Some clinical trials show meaningful reductions, while others show no effect at all. The most recent and comprehensive meta-analyses paint a mixed picture: one found a statistically significant but small average reduction in ALT with omega-3 supplementation, while another found no significant benefit compared to placebo.
What the Clinical Evidence Shows
Two major meta-analyses have looked at this question and reached somewhat different conclusions. A systematic review published in Cureus, which pooled results from studies on people with fatty liver disease, found that omega-3 supplementation significantly decreased ALT levels, with an average reduction of about 2 units (U/L). That’s a real but modest drop, and the individual studies varied dramatically. One trial saw ALT fall by over 14 units, another by about 8 units, while some showed no change at all, and one actually saw ALT rise slightly.
A separate meta-analysis published in Frontiers in Nutrition told a less encouraging story. Across nine studies comparing fish oil to placebo in people with fatty liver disease, there was no significant difference in ALT levels between the two groups. Interestingly, the same analysis did find that fish oil significantly improved levels of AST, a related liver enzyme, but the benefit didn’t extend to ALT specifically.
The inconsistency across trials likely comes down to differences in dosage, the type of omega-3 used, how long people took it, and how severe their liver condition was to begin with. In people with normal or near-normal ALT levels, fish oil doesn’t appear to move the needle. In people with elevated ALT from fatty liver disease, the results depend heavily on the specifics of supplementation.
How Omega-3s Affect the Liver
ALT is an enzyme concentrated in liver cells. When those cells are inflamed or damaged, ALT leaks into the bloodstream, which is why a blood test showing elevated ALT typically signals some degree of liver stress. The most common cause of mildly elevated ALT in the general population is non-alcoholic fatty liver disease (NAFLD), where excess fat accumulates in the liver and triggers inflammation.
Omega-3 fatty acids from fish oil work on several fronts that could, in theory, reduce that inflammation. They lower levels of pro-inflammatory signaling molecules like IL-6 and TNF-alpha while boosting anti-inflammatory ones like IL-4 and IL-10. They also help reduce the amount of fat stored in liver cells, which is the root driver of inflammation in fatty liver disease. Less fat in the liver means less inflammation, which means less ALT leaking into the blood. The problem is that this mechanism doesn’t always translate into a measurable ALT reduction in clinical trials, especially at typical supplement doses.
DHA Appears More Effective Than EPA
Fish oil contains two main omega-3 fatty acids: EPA and DHA. These are often lumped together, but they don’t have equal effects on the liver. Research comparing the two has found that DHA is more effective than EPA at reducing liver fat, lowering markers of systemic inflammation, and improving signs of liver fibrosis. Some researchers have suggested that trials showing little benefit from fish oil may have used formulations with too much EPA relative to DHA.
This matters when choosing a supplement. Many standard fish oil capsules contain more EPA than DHA, or roughly equal amounts. If your goal is liver health specifically, a DHA-dominant formulation may be more appropriate. Researchers who reviewed the available evidence have recommended high-quality DHA, or at least equal amounts of EPA and DHA, to meaningfully affect fatty liver progression.
Dosage and How Long It Takes
One well-designed randomized controlled trial gave overweight men about 2 grams of fish oil daily (containing roughly 590 mg EPA and 410 mg DHA) for 12 weeks and found no change in liver fat, ALT levels, or any other liver-related blood markers compared to placebo. All participants had ALT levels in the normal range throughout, which is an important detail. If your liver enzymes aren’t elevated to begin with, fish oil won’t push them lower.
Trials that did show ALT reductions generally used higher doses, treated people who already had fatty liver disease with elevated enzymes, and ran for at least 12 weeks or longer. The studies showing the largest drops in ALT (8 to 14 units) tended to involve people with more advanced fatty liver disease and used omega-3 doses in the range of 2 to 4 grams per day. At standard over-the-counter doses of 1 to 2 grams, the effect on ALT is likely too small to be clinically meaningful for most people.
What Guidelines Actually Recommend
The American Association for the Study of Liver Diseases (AASLD), which sets practice guidance for managing fatty liver disease, does not recommend omega-3 fatty acids as a treatment for liver-specific benefits. Their guidance explicitly notes that omega-3 polyunsaturated fatty acids have not been found to have liver-specific benefits in NAFLD. They do, however, recommend omega-3 supplementation for a different purpose in people with fatty liver disease: managing high triglycerides, particularly when levels exceed 500 mg/dL, where omega-3s can help reduce the risk of pancreatitis.
In other words, fish oil has a recognized role in the metabolic profile of people with fatty liver disease, but that role is about triglycerides and cardiovascular risk, not about directly treating liver inflammation or lowering ALT.
Safety at Higher Doses
If you’re considering higher doses of fish oil to target liver enzymes, there are trade-offs to be aware of. A large prospective cohort study published in BMJ Medicine found that regular fish oil use was associated with a 13% higher risk of developing atrial fibrillation (an irregular heart rhythm) in people without pre-existing cardiovascular disease. The STRENGTH trial found that 4 grams per day of marine omega-3s was associated with a 69% higher risk of new-onset atrial fibrillation in people already at high cardiovascular risk. The risk appears to increase with dose, so pushing beyond standard supplementation levels carries real cardiac concerns.
The Bottom Line on ALT
Fish oil is not a reliable way to lower ALT levels. In people with fatty liver disease, high-dose omega-3 supplementation (particularly DHA-rich formulations) can produce modest reductions in some cases, but the effect is inconsistent across studies and not large enough for medical guidelines to endorse it for that purpose. If your ALT is elevated, the interventions with the strongest evidence are weight loss of 7 to 10% of body weight, regular exercise, and addressing metabolic risk factors like insulin resistance and high triglycerides. Fish oil can play a supporting role in that broader metabolic picture, but expecting it to meaningfully lower ALT on its own is not well supported by current evidence.