Why Does Vitamin E Smell Fishy?

January 1, 2026 •

4 min read

Pure vitamin E, known chemically as tocopherol, is naturally a slightly viscous oil with a faint nutty or nearly odorless profile. Therefore, a pronounced fishy odor from your vitamin E capsule is a strong indication that the product is no longer in its optimal condition.

Quick Summary

A fishy scent from a vitamin E supplement is not normal and often indicates the product has gone rancid due to oil oxidation or has been contaminated with low-quality fish oil. It is a sign of product degradation.

Key Points

Rancidity: The most common reason for a fishy smell is that the carrier oils within the vitamin E softgel have gone rancid or oxidized.
Carrier Oils: Vitamin E is fat-soluble and is often suspended in vegetable-based carrier oils that can oxidize when exposed to air, light, or heat.
Omega-3 Contamination: Poor quality control can lead to cross-contamination with rancid fish oil, which is also susceptible to oxidation.
Natural vs. Synthetic: Pure tocopherol (vitamin E) is nearly odorless, with natural forms having a faint nutty scent, but not a strong fishy one.
Discard if Smelly: Consuming rancid oil is unhelpful and potentially harmful, as it can increase oxidative stress rather than reduce it.
Proper Storage: Always store vitamin E in a cool, dry, and dark place, and check for the expiration date.

The Surprising Truth Behind the Fishy Odor

Many consumers are surprised to find that their vitamin E supplement has an unpleasant, fishy smell. Since pure, high-quality vitamin E is nearly odorless, this scent is a clear signal that something is amiss. The most common culprit is a process known as rancidity, which affects the oils in the capsule, though other factors like contamination also play a role. Understanding these reasons is crucial for maintaining the quality and effectiveness of your dietary supplements.

Rancidity and Oil Oxidation

Vitamin E is a fat-soluble vitamin, which means it is often suspended in carrier oils within its softgel capsule to aid absorption. These carrier oils are typically sourced from vegetables like soybean or wheat germ. Like any fat, these oils are susceptible to oxidation, a chemical process that occurs when fats are exposed to oxygen, light, or heat. This is the same reason why cooking oil goes bad if left open for too long. Oxidation breaks down the polyunsaturated fats in the oil, and the resulting compounds, known as peroxides, are responsible for the unpleasant fishy or 'off' smell. The vitamin E itself, being an antioxidant, is meant to protect these oils from this very process. However, over time, or with poor storage, the vitamin E's protective capacity can be overwhelmed, leading to spoilage.

Common causes of oxidation include:

Expiration: All vitamins have a shelf life, and their potency and quality decrease after the expiration date.
Improper Storage: Storing supplements in a hot, humid, or brightly lit location (like a bathroom cabinet) can accelerate the oxidation process.
Exposure to Air: A loose cap or a cracked capsule can allow air to get in, compromising the freshness of the product.

Contamination from Fish Oil

Another significant cause of a fishy odor is cross-contamination from other ingredients, most notably fish oil. Many people take fish oil supplements (for omega-3 fatty acids) alongside their vitamin E. If the fish oil is of poor quality or has gone rancid, its strong smell can permeate the entire bottle. Sometimes, a manufacturer may even combine these supplements into a single pill, and if the quality control is poor, the fish oil can be the source of the rancid smell. This is more common with lower-quality brands that may not employ stringent testing for freshness and purity.

Mixed Tocopherols and Natural Variations

It is also worth noting that not all vitamin E is the same. Natural vitamin E (d-alpha-tocopherol) and synthetic vitamin E (dl-alpha-tocopherol) have different properties. Natural, plant-derived vitamin E often contains 'mixed tocopherols,' which can have a faint, nutty scent, but this is distinct from a strong, fishy smell. Synthetic vitamin E, derived from petrochemicals, tends to be more odorless. While a slight smell is characteristic of some natural varieties, a fishy smell is a sign of degradation.

Comparison Table: Fresh vs. Rancid Vitamin E


Aspect	Fresh Vitamin E Capsule	Rancid Vitamin E Capsule
Odor	Nearly odorless or faint nutty scent, especially for natural forms.	Strong, unpleasant fishy smell, sometimes with a sour undertone.
Color	Clear, viscous oil, typically a pale yellow to amber color.	May become darker or cloudy due to oxidation.
Texture	Smooth and consistent inside the softgel.	Oil may feel stickier or have an unusual consistency.
Taste	No distinct taste.	Can leave a strong, unpleasant aftertaste.
Bioavailability	Fully potent and ready for absorption.	Reduced potency, potentially increasing the body's need for antioxidant protection.

What to Do If Your Vitamin E Smells Fishy

If your vitamin E supplement exhibits a fishy odor, the best course of action is to discard it. Consuming rancid oil is counterproductive, as it can increase the body's need for antioxidant protection, which is precisely why people take vitamin E in the first place. Continuing to use a spoiled supplement can diminish its intended benefits and may even be harmful. It is recommended to choose a reputable brand that clearly states its quality control measures, and to store all supplements correctly in a cool, dark, and dry place.

Conclusion

In summary, the next time you ask, "why does vitamin E smell fishy?" you can be certain it is not a natural characteristic of the vitamin itself. The pungent aroma is a warning sign of degradation caused by oxidation of the carrier oils or contamination from rancid fish oil. To ensure you are receiving the full health benefits of your supplement, it is vital to be mindful of its expiration date and storage conditions. If the product smells fishy, it's a clear signal to toss it and invest in a fresh, high-quality replacement. For more information on vitamins and supplements, you can visit the National Institutes of Health (NIH).

Frequently Asked Questions

No, it is not safe. A fishy smell indicates that the oil has gone rancid. While it may not be immediately toxic, consuming rancid oil increases oxidative stress, which is the opposite of what vitamin E is meant to do.

Tocopherol is the chemical name for a group of compounds that make up vitamin E. There are several forms, including alpha-, beta-, gamma-, and delta-tocopherol.

Yes. You can prevent it by storing the bottle in a cool, dark, and dry place, away from direct sunlight and heat. Also, make sure the cap is screwed on tightly after each use and always check the expiration date before purchasing.

Yes, this can apply to any supplement containing oil, including fish oil and multivitamin softgels. Rancidity is a risk for any product with polyunsaturated fats.

Natural vitamin E (d-alpha-tocopherol) may have a faint nutty scent from its vegetable oil source, while synthetic vitamin E (dl-alpha-tocopherol) is typically odorless. A strong fishy odor is not natural for either.

Pure, high-quality vitamin E should be nearly odorless, or have only a very subtle, faint scent depending on the natural oil it is derived from.

In very rare cases, a metabolic disorder called trimethylaminuria can cause a person's sweat, urine, and breath to smell fishy. This is a separate health condition and not related to the supplement itself.