When choosing a fish oil product, many people usually focus only on:

• How much Omega-3 it contains

• How much EPA it provides

• How much DHA it provides

• Where the fish oil comes from

However, there is another important value that health-conscious consumers should know about:

TOTOX (Total Oxidation Value)

Because fish oil contains high levels of unsaturated fatty acids, which provide many health benefits, but they are also highly sensitive to oxidation.

Simply put, oxidation means:

The deterioration and rancidity of oil.

Therefore, fish oil quality is not only about “having a high amount of Omega-3,” but also about whether “the oil is fresh and properly controlled through quality processes.”

What Is TOTOX? 

TOTOX stands for Total Oxidation Value.

It is a value used to evaluate the overall level of oxidation in oils.

It is calculated from two main measurements:

1. Peroxide Value (PV) 

This measures compounds formed during the early stage of oxidation.

These are called:

Primary Oxidation Products

Such as Hydroperoxides.

A higher value may indicate that the oil has started to deteriorate.

2. Anisidine Value (AV)

This measures compounds formed during the later stage of oxidation.

These are called:

Secondary Oxidation Products

Such as Aldehydes, which are associated with the rancid smell of oil.

Therefore, TOTOX reflects both:

• Early-stage oxidation

• Later-stage oxidation

The calculation formula is:

TOTOX = (2 × Peroxide Value) + Anisidine Value

Why Is TOTOX Important for Fish Oil? 

Because Omega-3, especially:

• EPA

• DHA

are Polyunsaturated Fatty Acids (PUFAs).

They contain multiple double bonds, making them more vulnerable to oxidation compared with some other types of fats.

Factors that accelerate oxidation include:

• Oxygen

• Light

• Heat

• Storage time

When oxidation increases, it may affect:

• Oil quality

• Smell and taste

• Product freshness

Therefore, TOTOX is one of the indicators used to evaluate fish oil quality.

What TOTOX Value Is Considered Good? 

Organizations related to marine oil quality, such as GOED (Global Organization for EPA and DHA Omega-3s), provide guidelines regarding Omega-3 quality standards.

Generally, high-quality fish oils aim to control oxidation levels such as:

• Peroxide Value (PV) ≤ 5 meq/kg

• Anisidine Value (AV) ≤ 20

• TOTOX ≤ 26

These values are reference standards commonly used in the Omega-3 industry to control oil quality and freshness.

However, TOTOX is not the only factor to consider when choosing a product. Other important factors include:

• Actual EPA + DHA content

• Source of fish oil

• Manufacturing process

• Storage conditions

• Quality testing standards

Does a Fish Oil With a Fishy Smell Always Mean Poor Quality? 

Many people believe:

“Good fish oil should have no smell at all.”

However, the reality is that many factors can affect smell.

A fishy smell may come from:

• Raw materials

• Manufacturing process

• Capsule coating

• Oxidation

If fish oil has high oxidation levels, it may develop a stronger rancid or unpleasant smell.

Therefore, checking oxidation values is a more scientific approach than judging quality only by smell.

What Else Should You Look for When Buying Fish Oil? 

1. Check EPA and DHA Amounts 

Do not look only at the phrase:

“Fish Oil 1,000 mg”

Because 1,000 mg of fish oil does not always contain the same amount of actual Omega-3.

Check how much it provides:

• EPA (mg)

• DHA (mg)

Because these are the key components that have been widely studied.

2. Check the Form of Omega-3

Common forms include:

Triglyceride (TG)

A naturally occurring form found in fish.

Ethyl Ester (EE)

A form processed to concentrate Omega-3.

Both forms can be used depending on the manufacturing process and overall product quality.

3. Check Testing Standards

A high-quality Omega-3 product should include testing for:

• Heavy metals

• Purity

• Oxidation levels

Who Should Pay Extra Attention to Fish Oil Quality? 

Groups that regularly consume Omega-3, such as:

• People who want to support heart health

• People who eat little fish

• Older adults

• People interested in Brain Health

• Athletes and people who exercise regularly

Because when taking Omega-3 continuously over the long term, choosing a high-quality product becomes especially important.

Summary 

The TOTOX value is a measurement used to evaluate the overall oxidation level of fish oil.

Simply put:

It is one indicator that helps show how fresh the fish oil is and how well its quality has been controlled.

When buying fish oil, do not look only at:

“Does it contain a high amount of Omega-3?”

You should also consider:

✅ Appropriate EPA + DHA levels
✅ Controlled oxidation levels
✅ Quality testing standards
✅ Proper storage conditions

Because good Omega-3 is not only about having a “high amount,” but also about being a high-quality fish oil that preserves the value of its important nutrients.

References

• GOED Voluntary Monograph for Omega-3 EPA and DHA Ingredients, Global Organization for EPA and DHA Omega-3s

• International Fish Oil Standards (IFOS). Quality Criteria for Omega-3 Fish Oils

• Shahidi F, Zhong Y. “Lipid oxidation and improving the oxidative stability.” Chemical Society Reviews, 2010

• Jakobsen J, et al. “Oxidation of fish oils and omega-3 fatty acids.” Food Chemistry, 2013

• Albert BB, et al. “Oxidation of marine omega-3 supplements and its impact on quality.” Scientific Reports, 2015