# Riboflavin 5'-phosphate, Sodium (E101a)

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**Safety rating:** SAFE
**E-number:** E101a
**CAS number:** 130-40-5
**Category:** nutrient
**FDA GRAS:** no
**Adverse events (FDA AERS):** 0
**FDA recalls:** 0
**Last updated:** 2026-04-04

## Summary

Riboflavin 5'-phosphate, sodium (also known as flavin mononucleotide sodium salt) is the sodium salt form of a phosphorylated B vitamin derivative. It functions as a nutrient supplement to fortify food products with bioavailable riboflavin, an essential vitamin critical for energy metabolism and cellular function.

## Regulatory status

| Country | Status |
| --- | --- |
| United States | approved |
| European Union | not_evaluated |
| United Kingdom | approved |
| Canada | approved |
| Australia | approved |
| Japan | approved |
| South Korea | approved |
| Brazil | approved |
| China | approved |
| India | approved |

## Detailed analysis

## What is Riboflavin 5'-phosphate, Sodium?

Riboflavin 5'-phosphate, sodium is a phosphorylated derivative of riboflavin (vitamin B2), one of the B-complex vitamins essential for human health. The compound consists of riboflavin with a phosphate group attached at the 5' position, formulated as the sodium salt to improve stability and solubility in food applications. This form is also commonly referred to as flavin mononucleotide (FMN) sodium or riboflavin 5'-monophosphate sodium.

Riboflavin itself is a naturally occurring compound found in foods such as eggs, almonds, mushrooms, and leafy greens. The phosphorylated form represents a more bioavailable and stable version suitable for food fortification purposes.

## Common Uses

Riboflavin 5'-phosphate, sodium is used as a nutrient supplement in various food and beverage products to enhance their vitamin B2 content. Common applications include:

- Breakfast cereals and grain products
- Nutritional supplements and fortified beverages
- Energy drinks and functional beverages
- Dairy products and plant-based milk alternatives
- Infant formulas and nutritional products for specialized dietary needs

The sodium salt form is preferred in many formulations because it exhibits superior solubility and stability compared to free riboflavin, particularly in liquid applications and under various pH conditions.

## Safety Assessment

Riboflavin 5'-phosphate, sodium has an established safety profile in food applications. The FDA has received zero adverse event reports associated with this additive, and there are no documented FDA recalls linked to its use. The compound is derived from or chemically similar to riboflavin, which is a well-established, essential micronutrient with extensive safety data.

Riboflavin toxicity is considered extremely low because it is a water-soluble vitamin; excess amounts are not stored in the body but are excreted through urine. No upper limit for riboflavin intake has been established by the National Institutes of Health, reflecting the low toxicity profile.

Allergic reactions to riboflavin or its derivatives are exceptionally rare in the general population. The compound does not demonstrate mutagenic, carcinogenic, or reproductive toxicity concerns based on available scientific literature.

## Regulatory Status

While riboflavin 5'-phosphate, sodium is not specifically listed as FDA GRAS (Generally Recognized As Safe), this does not indicate any safety concern. The lack of GRAS status may reflect that regulatory review occurred under different approval mechanisms or timeframes. The additive is permitted for use in food fortification in numerous countries, including European Union member states where it complies with regulations for food additives and nutrient supplements.

In the European Union, riboflavin and its derivatives are approved food additives used in vitamin fortification. The European Food Safety Authority (EFSA) has assessed riboflavin and similar compounds and found them safe for the general population at levels used in food fortification.

The additive complies with international food standards established by the Codex Alimentarius Commission for nutrient fortification.

## Key Studies

Scientific literature on riboflavin and its phosphorylated forms confirms the safety and bioavailability of these compounds. Research demonstrates that riboflavin 5'-phosphate is efficiently absorbed and metabolized in the human body, making it an effective form for nutritional supplementation.

Studies on riboflavin pharmacokinetics show that the phosphorylated form provides good bioavailability, comparable to or exceeding free riboflavin in some applications. The sodium salt formulation maintains stability during food processing and storage without degradation.

No studies have identified safety concerns specific to riboflavin 5'-phosphate, sodium at levels used in food fortification, which typically range from 0.5 to 2 mg per serving depending on the food category.

## Sources

- FDA Substances Added to Food (CFSAN)
- OpenFDA Adverse Event Reporting System (AERS)
- OpenFDA Food Recalls
- EFSA OpenFoodTox
- EU Food Additive Portal

## Citation

Additive Facts. "Riboflavin 5'-phosphate, Sodium (E101a) — Safety, regulation, and evidence." https://additivefacts.com/additives/riboflavin-5-phosphate-sodium. Accessed 2026-05-20.