What B Vitamin Is Destroyed By Light? (And How to Protect It)

November 13, 2025 •

4 min read

Riboflavin (vitamin B2) is highly susceptible to degradation when exposed to light, especially ultraviolet (UV) light. This is a crucial factor in food storage and processing, as manufacturers must take measures to prevent nutrient loss in light-exposed products like milk and fortified cereals. Understanding which B vitamin is destroyed by light is key to maintaining a nutritious diet.

Quick Summary

Riboflavin, or vitamin B2, is the B vitamin that is most easily destroyed by light, a process known as photodegradation. Proper storage in opaque containers is essential to protect this nutrient's potency and prevent deficiency.

Key Points

Riboflavin (B2) is highly light-sensitive: Exposure to light, particularly UV, causes the vitamin to degrade through a process called photodegradation.
Packaging matters for protection: Opaque containers like paper cartons and dark plastic jugs protect riboflavin in milk from light degradation.
Proper storage is crucial: Always store riboflavin-rich foods and supplements in a cool, dark place away from direct sunlight and bright artificial lights.
Deficiency leads to specific symptoms: Ariboflavinosis can cause oral lesions, skin rashes, eye problems, and fatigue, although it is uncommon in most developed countries.
Dietary sources include dairy, eggs, and fortified grains: While riboflavin is found in many foods, fortified products and animal-based sources are often the most reliable dietary contributors.

Understanding Riboflavin's Sensitivity to Light

Riboflavin, also known as vitamin B2, is a water-soluble vitamin that plays a critical role in energy production, cellular growth, and the metabolism of fats, drugs, and steroids. However, one of its most significant characteristics is its high sensitivity to light, particularly ultraviolet and visible light. This vulnerability means that prolonged exposure to light can cause the vitamin to break down rapidly, leading to a significant loss of nutritional value in foods and supplements.

The mechanism of riboflavin's photodegradation involves it acting as a photosensitizer. When exposed to light, riboflavin absorbs energy and produces reactive oxygen species, such as singlet oxygen and superoxide anions. These highly reactive molecules then initiate reactions that lead to the decomposition of the riboflavin molecule and can also damage other nutrients and food components, like proteins and lipids. This process is why food science and manufacturing heavily emphasize light protection for products containing this vital nutrient.

Practical Strategies for Preserving Riboflavin

Protecting riboflavin from light is a straightforward process once you understand the risks. For consumers, this involves conscious choices when purchasing and storing food. The packaging of food products, especially dairy, has evolved specifically to counteract riboflavin's light sensitivity.

Choose Opaque Packaging: This is the most effective method for protecting light-sensitive nutrients. Milk, for instance, is now sold predominantly in paper cartons or opaque plastic jugs rather than the clear glass bottles of the past. This blocks light and preserves the riboflavin content. When buying supplements, opt for those in dark-colored, light-blocking bottles.
Store in a Dark Place: Always keep foods and supplements rich in riboflavin in a cupboard or pantry away from direct sunlight or bright artificial light. This simple action can dramatically extend the shelf life and potency of the vitamin.
Limit Light Exposure During Preparation: While cooking doesn't significantly destroy riboflavin with heat, minimizing the time it spends under bright kitchen lights or by a window is a good practice. Remember that riboflavin is also water-soluble, so boiling can cause some loss into the cooking water. Steaming or microwaving can help retain more of the vitamin.

Symptoms and Causes of Riboflavin Deficiency

While riboflavin deficiency is rare in developed countries like the United States due to food fortification, it can occur in individuals with inadequate intake or certain health conditions. Known as ariboflavinosis, the deficiency can manifest through a variety of symptoms, many of which affect the mouth and skin.

Oral Manifestations: Ariboflavinosis often causes lesions at the corners of the mouth (angular cheilitis), swollen and cracked lips (cheilosis), and a sore, inflamed tongue that may turn a magenta color (glossitis).
Dermatological Issues: Skin rashes, particularly seborrheic dermatitis, can appear on the face, ears, and genital areas, presenting as red, greasy, and scaly patches.
Ocular Problems: Riboflavin deficiency can lead to eye issues like red, itchy eyes (conjunctivitis), sensitivity to light (photophobia), and in severe cases, neovascularization of the cornea.
Neurological and Other Concerns: Fatigue, hair loss, reproductive problems, and anemia are also associated with riboflavin deficiency. Severe, prolonged deficiency can lead to cataracts.

Some populations are at a higher risk of deficiency, including people with alcoholism, malabsorption disorders, or those who follow restrictive diets, such as some vegans, without adequate planning.

Foods Rich in Riboflavin

To ensure adequate intake, include these riboflavin-rich foods in your diet, and remember to store them properly to maintain their nutritional integrity.

Beef liver
Fortified breakfast cereals and bread
Dairy milk and yogurt
Eggs
Lean beef and pork
Salmon
Almonds
Spinach and other green leafy vegetables
Mushrooms

Comparison of B Vitamin Stability


B Vitamin	Name	Sensitivity to Light	Stability to Heat	Notes
B1	Thiamine	Moderate (destroyed by UV)	Less stable, can be destroyed by prolonged cooking	Also sensitive to alkali and oxidation.
B2	Riboflavin	High (especially UV)	Relatively heat-stable, but can be lost in cooking water	Highly vulnerable to photodegradation; requires opaque packaging.
B3	Niacin	Low	High stability	Highly stable to heat, light, air, and acid.
B5	Pantothenic Acid	Low	Less stable to heating	Relatively stable but can be lost during processing.
B6	Pyridoxine	Moderate (especially UV)	Less stable to heat; can be lost in cooking water	Can be lost during processing and heating.
B7	Biotin	Low	High stability	Very stable and not significantly affected by light or heat.
B9	Folate	High (sensitive to UV and visible light)	Easily destroyed by heat	Important to protect from light and heat during cooking and storage.
B12	Cobalamin	Moderate	Can be destroyed by prolonged heat	Sensitive to light, especially in solution.

Conclusion: Prioritizing Nutrient Preservation

In summary, the B vitamin most effectively destroyed by light is riboflavin, or vitamin B2. Its sensitivity to ultraviolet and visible light necessitates specific storage and handling techniques to prevent nutritional loss. For consumers, this means looking for opaque packaging for milk and other dairy products, storing supplements and riboflavin-rich foods in a cool, dark place, and being mindful during food preparation. While a riboflavin deficiency is rare in many parts of the world due to widespread food fortification, understanding its causes, symptoms, and prevention remains important for ensuring optimal health. By making informed choices, it is easy to protect the integrity of this crucial nutrient in your diet. To explore more about the B vitamins and their functions, consult resources like the National Institutes of Health Office of Dietary Supplements.

Frequently Asked Questions

No, while some B vitamins like riboflavin (B2) and folate (B9) are sensitive to light, others like niacin (B3) are very stable. Riboflavin is particularly vulnerable to photodegradation.

Milk is packaged in paper or opaque plastic cartons specifically to protect its riboflavin content from being destroyed by light, which helps preserve the nutritional quality of the milk.

Riboflavin is relatively stable when heated, but because it is water-soluble, a significant amount can be lost when foods are boiled and the water is discarded. Steaming or microwaving are better methods for retention.

Symptoms of riboflavin deficiency, or ariboflavinosis, include sore throat, cracked lips, lesions at the corners of the mouth, skin rashes, red and itchy eyes, and fatigue.

Yes, vitamin B12 is also moderately sensitive to light, especially in aqueous solutions. Similar to riboflavin, B12 supplements are often packaged in dark bottles to protect their potency.

In its dry form, riboflavin is heat-stable. However, its stability decreases in moist heat conditions. Most nutrient loss during cooking occurs because it is water-soluble and leaches into the cooking water, rather than being destroyed by the heat itself.

Store foods rich in riboflavin, such as dairy products, meats, and enriched grains, in a cool, dark place. Always keep light-sensitive supplements in their original opaque containers.