What Happened to Vitamin G? Uncovering the Truth About the 'Missing' Nutrient

January 5, 2026 •

2 min read

In the 1920s, scientists isolated a factor from the 'water-soluble B' complex that was shown to promote growth in rats, labeling it vitamin G. However, this name has since disappeared from nutritional science, leading many to wonder what became of the 'missing' nutrient. The truth is that as vitamin research progressed, what was once called vitamin G was reclassified as a more familiar compound: riboflavin, or vitamin B2.

Quick Summary

Vitamin G is an obsolete term for riboflavin (vitamin B2), a vital water-soluble nutrient essential for cellular energy production and overall health. Its initial name was abandoned as scientists identified and reclassified the components of the B-vitamin complex, leading to the standardized naming conventions used today.

Key Points

Obsolete Term: The name "vitamin G" is an obsolete term for what is now known as riboflavin, or vitamin B2.
B-Complex Reclassification: What was initially believed to be a single "vitamin B" was later found to be a complex of multiple water-soluble vitamins, necessitating a new naming system.
Essential Nutrient: Riboflavin (B2) is crucial for cellular energy production, metabolism of fats and carbohydrates, and acts as an antioxidant.
Modern Interpretations: In recent times, the term "Vitamin G" has been co-opted metaphorically to refer to the benefits of spending time in "green" spaces or practicing "gratitude".
Dietary Sources: Riboflavin can be found in a variety of foods including dairy products, eggs, lean meats, and green leafy vegetables.
Naming History: The disappearance of vitamin G highlights the fluid nature of early vitamin nomenclature, which was based on discovery order and later refined based on chemical and functional properties.

The Case of the Disappearing Vitamins: A Historical Context

The history of vitamin discovery in the early 20th century involved numerous researchers and a complex process. The initial alphabetical naming system was often inconsistent, leading to confusion and the abandonment of many early designations as nutritional science advanced. Several letters, including F, G, H, I, J, M, and P, were used for potential vitamins that were later reclassified or found not to be essential.

The B-Vitamin Complex and the Demise of Vitamin G

A significant development was the recognition that the original "vitamin B" was a complex of distinct, water-soluble compounds. As individual components were isolated, a numerical classification was adopted.

Initial discovery: A water-soluble factor from yeast and milk whey that promoted growth in rats was initially called vitamin G in the U.S. and part of the B complex in Britain.
Identification: In the 1930s, chemists isolated the fluorescent compound, naming it lactoflavin.
Renaming: After its structure was identified, it was officially named riboflavin.
Standardization: Riboflavin was designated as vitamin B2, integrating it into the numbered B-complex system.

Comparing Riboflavin (Vitamin B2) and Obsolete Vitamin Terminology


Feature	Obsolete Term (Vitamin G)	Modern Term (Riboflavin/B2)
Status	Obsolete early name	Essential water-soluble vitamin
Chemical Identity	Crude extract	Specific chemical compound
Function	Promoted growth in rats	Energy production, metabolism, immune function
Standardization	No longer used	Part of standardized B-complex
Rich Sources	Yeast, milk, eggs	Dairy, meat, eggs, fortified grains, green vegetables

The Function and Importance of Riboflavin (B2)

Riboflavin is essential for two coenzymes, FMN and FAD, which are vital for cellular energy production from carbohydrates, fats, and proteins.

Riboflavin also supports:

Antioxidant Activity: Production of glutathione to protect cells.
Nutrient Metabolism: Helps convert tryptophan to niacin and vitamin B6 to its active form.
Red Blood Cells: Necessary for red blood cell formation.
Migraine Prevention: High-dose supplementation may reduce migraine frequency and severity.

Modern Interpretations of “Vitamin G”

Beyond its scientific history, "Vitamin G" has gained modern, non-scientific meanings:

Vitamin G (for Green): Refers to the health benefits of being in nature, linked to reduced stress and improved mood.
Vitamin G (for Grounding): The concept of physical contact with the Earth for health benefits, though scientific evidence for specific mechanisms is debated.
Vitamin G (for Gratitude): Used metaphorically for the psychological benefits of practicing gratitude.

Conclusion

Vitamin G's story reflects scientific progress. It wasn't lost but reclassified as riboflavin (vitamin B2) as understanding of the B-complex improved. Its journey from a growth factor to an enzyme cofactor highlights the evolution of nutritional science. While not on modern labels, riboflavin is crucial for health. For more information on the history of vitamin discovery, a good resource is the Wikipedia article on vitamins.

Frequently Asked Questions

The term vitamin G was officially replaced by the name riboflavin (vitamin B2) in the 1930s to standardize vitamin nomenclature. All nutritional information for this compound now refers to it as riboflavin.

Riboflavin's primary functions include aiding in cellular energy production, metabolizing carbohydrates, fats, and proteins, and acting as an antioxidant. It also supports healthy vision, skin, and nervous system function.

Yes, a deficiency can cause symptoms such as skin lesions, cracks at the corners of the mouth (angular cheilitis), a swollen tongue, and sore throat. In severe, prolonged cases, it can lead to anemia and cataracts.

Many foods contain riboflavin, including dairy products (milk, cheese, yogurt), eggs, organ meats (liver), lean meats, fortified cereals, and green leafy vegetables like spinach and kale.

Eating a balanced diet that includes a variety of riboflavin-rich foods is the best way to ensure adequate intake. Because it is water-soluble, it must be consumed regularly as the body does not store large amounts.

Yes, several other vitamins were renamed or reclassified. For instance, vitamin F was reclassified as essential fatty acids, and vitamin H was renamed biotin (vitamin B7).

Modern interpretations of the term 'Vitamin G' have arisen in non-scientific fields. They often refer to the benefits of nature (for 'green' spaces), grounding (contact with the earth), or the psychological effects of gratitude.