E300

Ascorbic Acid (Vitamin C)

Last reviewed: 11 May 2026

Antioxidant additive and the essential nutrient vitamin C — the same molecule.

What is E300 (Ascorbic Acid)?

E300, known as Ascorbic Acid or simply Vitamin C, is a water-soluble vitamin and powerful antioxidant used to preserve food and prevent browning.

Why it's used in food:

• Prevents oxidation – stops fruits and vegetables from turning brown
• Antioxidant – protects nutrients, colours, and flavours from degradation
• Preserves freshness – extends shelf life naturally
• Enhances iron absorption – improves bioavailability of iron in foods
• Fortification – adds nutritional value to products
• Blocks nitrosamine formation – prevents carcinogenic compounds forming in cured meats

E300 is essential for human health. Unlike most animals, humans cannot produce vitamin C and must get it from diet. The UK recommended daily intake is 40mg for adults (though many health experts recommend 100-200mg).

Where is E300 Found?

E300 is one of the most widely used food additives, found in thousands of products:

Common Foods Containing E300:

• Fruit juices and drinks – prevents browning and oxidation
• Processed fruits – canned fruits, dried fruits, fruit salads
• Bread and baked goods – improves dough quality and shelf life
• Breakfast cereals – added for fortification (nutritional benefit)
• Processed meats – bacon, ham, sausages (blocks cancer-causing nitrosamines)
• Beer and wine – prevents oxidation and off-flavours
• Soft drinks and cordials – antioxidant and preservative
• Frozen vegetables – maintains colour and nutrients
• Jams and preserves – prevents browning and spoilage
• Baby foods – nutritional fortification
• Vitamin supplements – as the active ingredient
• Crisps and snacks – prevents rancidity in fats

Naturally High in Vitamin C (E300):

These foods contain high levels of natural E300:

• Oranges, lemons, limes, grapefruit (50-80mg per 100g)
• Strawberries, kiwi fruit (60-90mg per 100g)
• Bell peppers (especially red) (120-200mg per 100g)
• Broccoli, Brussels sprouts (80-100mg per 100g)
• Blackcurrants (180mg per 100g – very high)
• Tomatoes (15-25mg per 100g)

Health Benefits of E300

Unlike most E-numbers, E300 is actively beneficial to health:

1. Essential Nutrient

Vitamin C is essential for survival. Without it, you develop scurvy (a potentially fatal disease). Key roles:

• Collagen production – for healthy skin, bones, blood vessels, and connective tissue
• Immune function – supports white blood cells and antibody production
• Wound healing – necessary for tissue repair
• Antioxidant protection – neutralizes free radicals that damage cells

2. Powerful Antioxidant

E300 protects cells from oxidative damage:

• Neutralizes harmful free radicals
• May reduce risk of chronic diseases (heart disease, cancer)
• Protects eye health (may slow age-related macular degeneration)
• Supports brain health and may reduce dementia risk

3. Enhances Iron Absorption

Vitamin C significantly improves iron absorption from plant-based foods:

• Converts iron into a more absorbable form
• Especially important for vegetarians and vegans
• Can double or triple iron absorption when consumed together

4. Blocks Nitrosamine Formation (Cancer Protection)

This is why E300 is added to processed meats like bacon and ham:

• Nitrites (E250) in cured meats can form nitrosamines (carcinogenic compounds)
• Vitamin C blocks this conversion, reducing cancer risk
• Studies show vitamin C-rich foods alongside processed meats lower cancer risk

5. Immune Support

Vitamin C supports immune function:

• Shortens duration and severity of colds (modest effect)
• Supports production of white blood cells
• Helps antibodies function properly

What the science shows

Metabolism and excretion

Ascorbic acid is water-soluble. Excess intake beyond what the body needs is excreted in urine. The body can store roughly 1.5–3g total, and intake above tissue saturation simply passes through. This is the structural reason vitamin C doesn't accumulate to toxic levels.

UK Reference Nutrient Intake (NRV) — 80mg/day

• UK adult NRV: 80mg/day (the label reference value used on UK packaging since EU FIC came into UK law)
• SACN's reference intake to prevent scurvy: 10–40mg/day depending on age
• EU/US tolerable upper intake level: 2,000mg/day in adults

High-dose effects

Typical food-additive levels are 10–100mg per serving — well below any threshold. Documented effects at gram-scale supplement doses include:

• Digestive upset (loose stools, nausea) above ~2,000mg/day
• Increased risk of oxalate kidney stones in people with a history of stone formation, at intakes above ~1,000mg/day

Regulatory status

UK / EU: approved as a food additive (antioxidant) and as a nutrient for fortification. EFSA's 2015 re-evaluation set no numerical ADI for the food-additive use range.

US: FDA classifies ascorbic acid as Generally Recognized As Safe (GRAS).

Labelling: on UK packaging E300 appears as "E300", "ascorbic acid", or "vitamin C".

Natural vs. Synthetic E300

Many people wonder if synthetic E300 is inferior to natural vitamin C. The answer: they're identical.

Chemical Structure

• Natural vitamin C (from oranges): C₆H₈O₆
• Synthetic E300: C₆H₈O₆
• Result: Molecularly identical – your body processes them the same way

How Synthetic E300 is Made

Most commercial vitamin C is made using the Reichstein process:

• Starts with glucose (from corn or wheat)
• Fermented with bacteria to convert to ascorbic acid
• Purified to pharmaceutical-grade vitamin C
• Used in supplements and food additives

Are Natural Sources Better?

Some argue natural sources contain additional beneficial compounds (bioflavonoids, phytonutrients). While true, the vitamin C itself is identical. Benefits of natural sources:

• Contain fibre, bioflavonoids, and other nutrients
• More balanced nutrition overall

Natural-source whole-food vitamin C comes alongside bioflavonoids, fibre and other phytonutrients that synthetic E300 doesn't include. The vitamin C molecule itself is identical; the surrounding food matrix differs.

Why ascorbic acid is added to cured meats

Cured meats — bacon, ham, sausages — are preserved with sodium nitrite (E250) and/or sodium nitrate (E251) for both colour and microbial control (nitrite is the standard botulism control in cured meats). Under high-temperature cooking, residual nitrite can react with secondary amines in the meat to form N-nitrosamines, several of which are IARC-classified carcinogens.

Ascorbic acid (E300) and its sodium salt sodium ascorbate (E301) inhibit nitrosamine formation by competing for the nitrosating intermediates. The published literature reports reductions in nitrosamine formation of 80–90% under typical cured-meat manufacturing conditions. EU and retained UK regulations require or encourage ascorbic-acid addition in nitrite-cured products specifically for this reason.

This doesn't change IARC's Group 1 classification of processed meats (driven by the nitrite/nitrosamine chemistry and by haem-iron interactions). It does reduce one of the formation pathways meaningfully.

Reading a UK label

Look for "E300", "ascorbic acid", or "vitamin C" in the ingredient list — most often in cured meats, soft drinks, fruit prep, breakfast cereals, infant foods and any product where browning needs to be slowed.

Last updated: 11 May 2026