Vitamin C
Vitamin C (ascorbic acid) is a water-soluble vitamin the body uses for collagen synthesis, immune function, antioxidant protection of cells, and to help absorb iron from plant foods. UK NHS reference intake is 40 mg/day for adults. Most UK adults meeting the eat-five-a-day pattern cover this from food; supplementation is sensible for those who do not, and during specific situations like recovery or pregnancy.
Camden Medicals editorial · Last reviewed 12 June 2026 · Next review June 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Vitamin
- NHS daily RNI
- 40 mg
- Typical supplemental
- 40-500 mg/day in supplemental form
- Top use evidence
- Strong
On this page
What it is
Vitamin C is the simplest of the vitamins by chemistry — L-ascorbic acid, a six-carbon sugar acid. Humans cannot make it (we lost the enzyme L-gulonolactone oxidase in evolution) and so must obtain it from food. Most other mammals make their own.
UK food sources are abundant and varied: peppers (red and green), citrus fruit, blackcurrants, kiwi, strawberries, broccoli, Brussels sprouts, potatoes (in all forms), and tomatoes. Cooking and prolonged storage reduce vitamin C content; raw and lightly-cooked sources retain more.
In supplements, vitamin C appears as ascorbic acid, sodium ascorbate, calcium ascorbate, or as plant-derived sources such as acerola powder standardised to a stated vitamin C percentage. The body uses each form similarly at nutritional doses.
At a glance
- UK NHS reference intake: 40 mg/day for adults (slightly higher in pregnancy and breastfeeding).
- Required for collagen formation — connective tissue, blood-vessel walls, gums, skin, bone matrix.
- Megadosing (multiple grams per day) is not supported by UK guidance and increases the risk of GI upset and oxalate-related kidney concerns.
- Cochrane evidence: regular ≥200 mg/day does not reduce the chance of catching a cold in the general population, but modestly shortens cold duration when supplemented daily.
What people use it for
UK adults whose diet does not reliably include daily fruit and vegetables
For people whose diet does not reliably supply vitamin C, a supplement helps meet the 40 mg/day NHS reference intake. Vitamin C carries authorised UK food-supplement claims — it contributes to the normal function of the immune system, to normal collagen formation, to the protection of cells from oxidative stress, and to the reduction of tiredness and fatigue. Most adults who eat fruit and vegetables daily already meet the reference intake from food. [1]
StrongPeople taking iron supplements for low iron or iron deficiency
Vitamin C taken with non-haem iron (for example ferrous fumarate, or iron from plant foods) increases iron absorption from that dose. "Vitamin C increases iron absorption" is an authorised UK function claim, and NICE describes the same effect in its iron-deficiency anaemia guidance. The boost is not wanted in iron-overload conditions such as haemochromatosis. [1,6]
StrongSmokers
Smoking accelerates vitamin C turnover, so smokers reach an adequate blood level less easily. International reference bodies commonly suggest an extra 35 mg/day for smokers; UK NHS guidance does not set a separate smoker reference intake but recommends a healthy, varied diet. The simplest reading is to make sure intake is comfortably at or above the 40 mg/day reference intake. [7]
Some evidenceModeratePregnancy and breastfeeding
The NHS adult reference intake rises to 50 mg/day in pregnancy and 70 mg/day during breastfeeding — easily met from a diet that includes fruit and vegetables. The same authorised vitamin C function claims apply. Gram-level (megadose) supplementation is a separate question; talk to your pharmacist, GP, or midwife before taking high-dose supplements in pregnancy. [1]
StrongAdults with very limited fruit and vegetable intake (risk of low vitamin C)
Persistently very-low intake leads to deficiency (scurvy). Meeting the 40 mg/day reference intake maintains normal vitamin C status and avoids this; the NHS describes adequacy as readily achievable from food. If you cannot achieve it from food, talk to your pharmacist or GP about a supplement. [1]
StrongPeople who take vitamin C to avoid catching colds
Vitamin C is widely taken in the hope of avoiding colds; the current evidence does not support this use. The Cochrane review of more than 25 randomised trials found that regular supplementation does not reduce the chance of catching a cold in the general population. Taken daily it modestly shortens how long a cold lasts, but starting it once a cold has already begun does not. [3]
Popular, not provenInsufficientAdults taking high-dose vitamin C for heart-disease or cancer prevention
High-dose vitamin C is sometimes promoted for preventing heart disease or cancer; the available evidence does not support this. Large randomised trials in non-deficient adults found no reduction in major cardiovascular events, and there is no UK-authorised claim for these uses. Sustained very-high intake also raises the risk of stomach upset and, in susceptible people, calcium-oxalate kidney stones. [8]
Not supportedInsufficient
How it works
Vitamin C is an electron-donor (reducing agent) — that is the chemistry behind every role it plays. It is a co-factor for the prolyl- and lysyl-hydroxylase enzymes that crosslink collagen, an antioxidant that quenches reactive oxygen species in plasma and cells, and a co-factor in catecholamine and carnitine biosynthesis. It also reduces dietary non-haem iron from Fe³⁺ to Fe²⁺ in the gut, increasing iron absorption from plant sources.
Common myths
Myth"Megadose Vitamin C prevents colds"
RealityCochrane meta-analyses across 25+ trials find that regular vitamin C supplementation does not reduce the chance of catching a cold in the general population. Daily ≥200 mg supplementation modestly shortens cold duration in adults, but starting it once a cold has already begun does not. Megadosing past gram-quantities does not improve this and increases the risk of GI upset and, with very long-term high doses, oxalate accumulation. [3]
Myth"Vitamin C boosts immunity"
RealityThe authorised UK health claim is that vitamin C "contributes to the normal function of the immune system". That is a claim about adequacy supporting normal function, not about supplementation producing an above-normal effect. The two are commonly conflated by marketing. Vitamin C is required for normal immune function; people who are deficient benefit from correction. Above adequacy, immune-function gains are not established. [2]
Myth"Liposomal vitamin C is dramatically more bioavailable"
RealitySome pharmacokinetic data shows modestly higher peak plasma levels for liposomal formulations versus standard ascorbic acid. At nutritional doses (≥100 mg) standard ascorbic acid already achieves close to saturation absorption from the gut. The practical difference at adequacy doses is small. [9]
Myth"Natural-source vitamin C (e.g. acerola) is fundamentally different from synthetic ascorbic acid"
RealityThe vitamin-C molecule itself is identical regardless of source. Whole-food sources also carry plant compounds (flavonoids, polyphenols) at modest absolute amounts, and the food matrix may slightly slow absorption — sometimes desirable for tolerance. At adequacy doses, both forms support nutritional adequacy.
Common online questions
Synthesised from the questions UK shoppers most often ask online about Vitamin C. Each answer is editorial and links to its evidence in the Sources list below.
Does vitamin C prevent colds?
No, not in the general population. The Cochrane review (Hemilä & Chalker, CD000980) pooled 29 trials and ~11,300 participants and found that routine vitamin C supplementation does not reduce the risk of catching a cold. The same review did find a small reduction in cold duration (~8% in adults, ~14% in children) at supplementation of 200 mg/day taken regularly — not started once a cold has already begun. [3]
Is liposomal vitamin C worth the extra cost?
Some pharmacokinetic studies (Davis et al. 2016) show modestly higher peak plasma vitamin C levels with liposomal formulations compared to standard ascorbic acid. At nutritional doses (≥100 mg) standard ascorbic acid already achieves close to saturation absorption from the gut, so the practical difference at adequacy doses is small. There are no clinical-outcome comparison studies to date. [9]
How much vitamin C is too much?
The NHS notes that taking less than 1,000 mg per day from supplements is unlikely to cause harm. Above this, stomach upset, loose stools, and bloating become common (and reversible). EFSA has not formally set a Tolerable Upper Intake Level. Long-term very-high doses can raise the risk of calcium-oxalate kidney stones in susceptible individuals. [1]
Should I take vitamin C with my iron supplement?
Vitamin C increases iron absorption from non-haem iron sources — that is one of the GB-authorised health claims. If your GP has prescribed iron, taking it with a glass of orange juice or with a vitamin C supplement is the standard recommendation to improve absorption. The exception is if you have an iron-overload condition such as haemochromatosis, where the absorption boost is not desirable. [2,7]
Is rosehip vitamin C better than ascorbic acid?
The vitamin C molecule itself (L-ascorbic acid) is identical regardless of whether it comes from rosehip, acerola, or synthetic manufacture. Rosehip and acerola also carry small amounts of plant polyphenols. At nutritional doses both natural-source and synthetic forms support adequacy equivalently in steady-state human studies (Carr & Vissers 2013). If you prefer a fruit-derived source for personal reasons, that is a reasonable preference; do not pay a large premium for a bioavailability claim that is not supported by the evidence.
Can vitamin C cause kidney stones?
Sustained very-high vitamin C intake (well above 1,000 mg/day, for years) is associated with increased calcium-oxalate kidney-stone risk in susceptible individuals — vitamin C is partially metabolised to oxalate. Population epidemiology is mixed. If you have ever had a calcium-oxalate kidney stone, keep your vitamin C intake near the RNI (40 mg/day) and discuss higher doses with your GP. [7]
⚖️ The official position
What may lawfully be claimed about Vitamin C in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“Vitamin C contributes to the normal function of the immune system”
“Vitamin C contributes to the protection of cells from oxidative stress”
“Vitamin C contributes to the reduction of tiredness and fatigue”
“Vitamin C contributes to normal collagen formation for the normal function of blood vessels”
“Vitamin C contributes to normal collagen formation for the normal function of bones”
“Vitamin C contributes to normal collagen formation for the normal function of cartilage”
“Vitamin C contributes to normal collagen formation for the normal function of gums”
“Vitamin C contributes to normal collagen formation for the normal function of skin”
“Vitamin C contributes to normal collagen formation for the normal function of teeth”
“Vitamin C contributes to normal functioning of the nervous system”
“Vitamin C contributes to normal psychological function”
“Vitamin C contributes to normal energy-yielding metabolism”
“Vitamin C increases iron absorption”
“Vitamin C contributes to the regeneration of the reduced form of vitamin E”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
14 authorised claims — show / hide
- "Vitamin C contributes to the normal function of the immune system"
- "Vitamin C contributes to the protection of cells from oxidative stress"
- "Vitamin C contributes to the reduction of tiredness and fatigue"
- "Vitamin C contributes to normal collagen formation for the normal function of blood vessels"
- "Vitamin C contributes to normal collagen formation for the normal function of bones"
- "Vitamin C contributes to normal collagen formation for the normal function of cartilage"
- "Vitamin C contributes to normal collagen formation for the normal function of gums"
- "Vitamin C contributes to normal collagen formation for the normal function of skin"
- "Vitamin C contributes to normal collagen formation for the normal function of teeth"
- "Vitamin C contributes to normal functioning of the nervous system"
- "Vitamin C contributes to normal psychological function"
- "Vitamin C contributes to normal energy-yielding metabolism"
- "Vitamin C increases iron absorption"
- "Vitamin C contributes to the regeneration of the reduced form of vitamin E"
Camden guides citing Vitamin C
Editorial pieces from the Camden blog that reference Vitamin C. Each guide cites the evidence it draws on.
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Common cold — incidence in the general population
InsufficientEvidenceinsufficientUK guidance leads: the NHS does not recommend vitamin C supplements to prevent colds, and there is no UK-authorised claim for cold prevention. Beneath that, the research Camden reviewed: the Cochrane review across more than 25 randomised controlled trials found that regular vitamin C supplementation does not reduce the risk of catching a cold in the general population. The evidence does not support taking it for this purpose. [3]
Common cold — duration in adults already taking it daily
ModerateEvidencemoderateUK guidance leads: the NHS frames vitamin C as a nutrient met from a varied diet, not as a cold treatment, and no UK-authorised claim covers cold duration. Beneath that, the research Camden reviewed: the Cochrane review found a small reduction in how long colds last (about 8% in adults and 14% in children) when vitamin C is taken regularly at 200 mg/day or more — an effect seen with ongoing daily intake, not when started after a cold has already begun. [3]
Iron-deficiency anaemia (alongside iron supplementation)
ModerateEvidencemoderateUK guidance leads: the NHS states that vitamin C increases iron absorption, NICE Clinical Knowledge Summaries note the same effect for non-haem iron in their iron-deficiency anaemia guidance, and "Vitamin C increases iron absorption" is an authorised UK function claim. Beneath that, the research Camden reviewed: vitamin C taken with a non-haem iron source increases iron absorption from that meal or dose; the effect is well established for plant-source and supplemental iron, though some trials adding vitamin C to oral iron found little extra clinical benefit over iron alone. [1,6]
Cardiovascular disease prevention (general population)
InsufficientEvidenceinsufficientUK guidance leads: NICE does not list vitamin C supplementation as a pathway for cardiovascular risk reduction, and no UK-authorised claim links vitamin C to cardiovascular outcomes. Beneath that, the research Camden reviewed: large randomised trials of vitamin C in non-deficient adults (for example the Physicians' Health Study II, 2008) found no reduction in major cardiovascular events. Using vitamin C for this purpose is not supported. [8]
Wound healing in deficient adults
LimitedEvidencelimitedUK guidance leads: the NHS describes vitamin C as needed for healthy skin, blood vessels, and connective tissue and for wound healing, which is the basis of its authorised collagen-formation claims. Beneath that, the research Camden reviewed: adequate vitamin C is required for normal collagen synthesis and therefore for normal wound healing, but supplementation above adequacy in people who are not deficient has not been shown to speed healing further. [1]
Safety
Vitamin C is generally well tolerated at intakes near the UK Reference Nutrient Intake (40 mg/day) and at typical supplement doses up to ~1,000 mg/day. Side effects from higher doses are uncomfortable but reversible.
Talk to your pharmacist or GP first if you:
- You have haemochromatosis or another iron-overload condition (vitamin C boosts iron absorption from the gut).
- You take iron supplements (vitamin C boosts absorption — usually intended, but worth knowing if iron levels are already adequate).
- You take warfarin or another anticoagulant.
- You have ever had calcium-oxalate kidney stones.
- You have G6PD (glucose-6-phosphate dehydrogenase) deficiency — very-high-dose vitamin C has been linked to red-blood-cell breakdown in this group.
- You are pregnant or breastfeeding — food-dose vitamin C is fine; gram-level supplements are a separate question.
- You are about to have a urine glucose, faecal occult-blood, or some other lab tests — vitamin C can interfere; flag your supplement use.
Common side effects: At supplemental doses above ~1,000 mg/day: stomach upset, loose stools, and bloating. Reverses when you reduce or stop the dose.
Pregnancy and breastfeeding
The NHS adult vitamin C RNI rises slightly in pregnancy (50 mg/day) and breastfeeding (70 mg/day). Easily achievable from a diet that includes fruit and vegetables. Routine supplementation at the RNI level is generally regarded as safe in pregnancy. Avoid megadose (gram-level) supplementation during pregnancy. As with any supplement, talk to your pharmacist, GP, or midwife before starting.
NHS RNI rises to 70 mg/day during breastfeeding.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- History of calcium-oxalate kidney stones — discuss long-term high-dose vitamin C with your pharmacist or GP.
- Haemochromatosis or iron-overload conditions — vitamin C increases iron absorption; clinical advice is needed.
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency — high-dose vitamin C has been associated with haemolysis in this group.
Drug interactions
- Iron supplements — vitamin C increases iron absorption; this is usually intended (recommended) but worth knowing if iron levels are already adequate.
- Some anticoagulants (warfarin) — interaction reports are mixed and modest; tell your prescriber and pharmacist about all supplements.
- Long-term high-dose vitamin C may interfere with some laboratory tests (e.g. urinary glucose, occult-blood) — flag your supplement use before testing.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Stomach upset, diarrhoea, and flatulence at supplemental doses above ~1,000 mg/day.
Rare side effects
- Long-term very-high doses have been linked to kidney-stone risk in susceptible adults (oxalate metabolism).
How to take it
- UK Reference Nutrient Intake
- 40 mg/day
- Typical supplemental range
- 40-500 mg/day in supplemental form
- UK upper limit (supplemental)
- 1000 mg/dayEFSA does not set a numerical Tolerable Upper Intake Level for vitamin C; the UK NHS guidance suggests that supplementing more than 1,000 mg/day may cause stomach pain, diarrhoea, and flatulence, and that effects reverse on stopping.
- Timing
- Anytime — vitamin C is water-soluble and not stored long-term.
How to spot quality
Look for
- Vitamin C content per serving stated explicitly (mg + % NRV).
- Form named: ascorbic acid, sodium ascorbate, calcium ascorbate, or a standardised plant source (e.g. acerola at a stated vitamin C percentage).
- GMP-certified manufacture; ideally third-party potency testing.
- No added sugar in chewables marketed to children.
Red flags
- Megadose marketing without specific clinical context (e.g. "5,000 mg daily" framed as routine).
- "Boosts immunity" wording — the authorised UK claim is "contributes to normal function".
- Vague "complex" formulations with no per-form mg breakdown.
- Comparative claims that "natural" vitamin C is dramatically more bioavailable than synthetic — overstated in supplement marketing.
Where Camden lands · meets the bar
Camden's catalogue currently delivers vitamin C as a co-ingredient via acerola. NB-502 (Mushroom Complex) provides 25.5 mg / 32% NRV per 2-capsule serving from acerola fruit powder, and NB-503 (Lion's Mane with Acerola) provides 12.75 mg / 16% NRV per capsule. Vitamin C content is declared in mg + % NRV in both, meeting the encyclopaedia look-for bar. A standalone Camden vitamin C SKU is not yet in the catalogue. For routine adequacy at 40 mg/day, a standalone ascorbic-acid or sodium-ascorbate supplement at that dose level is the simplest path. We are evaluating a standalone NB- vitamin C product.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Iron
Strong evidenceVitamin C reduces ferric iron to the absorbable ferrous form — a classic enhancer of plant iron uptake.
Non-haem iron (in plants, beans, fortified cereals, eggs) enters enterocytes as the ferrous (Fe²⁺) form via DMT1, but is mostly present in food as ferric (Fe³⁺). Vitamin C reduces ferric to ferrous iron in the stomach and forms a soluble chelate that survives the higher duodenal pH where absorption occurs. The effect is well-established for non-haem iron from plant sources and from oral iron supplements (ferrous sulfate, ferrous fumarate). Haem iron from meat is absorbed by a different pathway and is less affected by ascorbic-acid co-administration. Recent guidance (Stoffel 2017) suggests alternate-day single morning doses are absorbed more efficiently than the older twice-daily-with-vitamin-C pattern, partly because morning hepcidin rise blocks the evening dose.
Evidence: Hallberg & Hulthén 2000 (Am J Clin Nutr) modelled the dose-response. Li 2020 (JAMA Netw Open) RCT in iron-deficient adults showed no benefit of adding vitamin C to oral iron versus iron alone — the food-iron evidence is stronger than the supplemental-iron evidence. [10,11,12]
Doses studied: 100 mg vitamin C with 18–65 mg iron at the same meal (food-iron context); alternate-day morning dosing for supplements per Stoffel 2017
Found in Camden: Iron & Vitamin C Gummies 7mg 150 Gummies
Collagen
Moderate evidenceVitamin C is the required cofactor for the enzymes that build the collagen triple helix.
Collagen synthesis in fibroblasts depends on prolyl-hydroxylase and lysyl-hydroxylase enzymes, which use vitamin C (ascorbic acid) as an obligate cofactor to hydroxylate proline and lysine residues in nascent procollagen chains. Hydroxyproline and hydroxylysine are required for triple-helix stability and cross-linking. Without vitamin C, collagen synthesis fails (the underlying lesion in scurvy). Co-supplementation is studied for skin elasticity, tendon repair (DePhillipo 2018), and post-surgical wound healing.
Evidence: Pullar 2017 (Nutrients) reviews vitamin C in skin biology. DePhillipo 2018 (Orthop J Sports Med) systematic review on vitamin-C-enriched gelatin for tendon repair. Mechanistic case strong; clinical-outcome trials remain limited. [13,14,15]
Doses studied: 500 mg vitamin C with 5–15 g hydrolysed collagen taken 30–60 min before exercise (DePhillipo 2018 protocol)
Zinc
Moderate evidenceImmune-cluster classic pairing — UK Article 13.1 immune claims for both. Cochrane support for cold-symptom duration with high-dose zinc lozenges.
Vitamin C is required for normal immune-cell function (neutrophil chemotaxis, lymphocyte proliferation, oxidative-burst capacity) and carries the UK Article 13.1 authorised claim "Vitamin C contributes to the normal function of the immune system." Zinc provides separate immune-cell function support and direct anti-rhinoviral activity (zinc binding to rhinovirus 3C-protease). Both nutrients hold UK Article 13.1 immune claims; the combination is the textbook UK winter-immune formulation.
Evidence: Cochrane reviews of zinc lozenges show modest reduction in cold duration at higher zinc doses. UK Article 13.1 claims authorised for both vitamin C and zinc on immune function. [2,2]
Doses studied: 10–25 mg zinc with 80–1000 mg vitamin C daily
Vitamin E (alpha-tocopherol)
Moderate evidenceAntioxidant pair — vitamin C regenerates oxidised α-tocopherol via redox cycling.
α-tocopherol scavenges lipid peroxyl radicals in cell membranes and becomes a tocopheroxyl radical. Ascorbic acid donates an electron at the membrane interface to regenerate active α-tocopherol, completing the antioxidant cycle. UK Article 13.1 vitamin E "contributes to the protection of cells from oxidative stress" + UK vitamin C oxidative-stress claim.
Evidence: Vitamin C / vitamin E redox cycle is textbook biochemistry. UK Article 13.1 claims authorised for both nutrients on cell protection from oxidative stress. [2,2]
Doses studied: 12 mg vitamin E with 80–1000 mg vitamin C daily
Acerola
Moderate evidenceVitamin C source cluster — acerola is a natural high-vitamin-C fruit; UK Article 13.1 vitamin C claim cluster.
Acerola (Malpighia glabra / emarginata) contains 1500–4500 mg vitamin C per 100 g fresh fruit, plus naturally co-occurring bioflavonoids (rutin, quercetin) and anthocyanins. UK Article 13.1 vitamin C claims attach to the vitamin C content; acerola-derived vitamin C is bioequivalent to synthetic ascorbic acid for the authorised-claim threshold purposes. Camden's NB-553 (Vit C Acerola) is built around this pairing.
Evidence: UK Article 13.1 claims authorised for vitamin C content irrespective of source. Acerola fruit provides a naturally occurring vitamin C plus phytonutrient matrix. [2]
Doses studied: Acerola extract delivering 80–1000 mg vitamin C daily
Found in Camden: Purifera™ Vitamin C Acerola Immune Complex 120 Capsules
N-Acetyl Cysteine (NAC)
Limited evidenceGlutathione-cycle pairing — NAC substrate + vitamin C reduction-cycling support.
NAC delivers cysteine — the rate-limiting substrate — for hepatic glutathione synthesis. Vitamin C reduces oxidised glutathione (GSSG) back to the active reduced form (GSH), keeping the antioxidant pool functional. The pair is mechanism-complementary on the glutathione-cycle axis. UK Article 13.1 vitamin C oxidative-stress claim authorised; NAC has no UK authorised claim.
Evidence: Glutathione redox cycle is textbook biochemistry. Combination not directly trialled; mechanism well established. [2]
Doses studied: 600–1200 mg NAC with 80–1000 mg vitamin C daily
Alpha Lipoic Acid (ALA / thioctic acid)
Limited evidenceAntioxidant trio with vitamin E — ALA recycles oxidised vitamin C and vitamin E.
α-lipoic acid is a universal antioxidant: ALA reduces oxidised glutathione; reduced glutathione reduces oxidised vitamin C (dehydroascorbate → ascorbate); reduced vitamin C in turn reduces oxidised vitamin E. The cascade keeps multiple antioxidant pools regenerated. UK Article 13.1 vitamin C oxidative-stress claim authorised; ALA has no UK authorised claim.
Evidence: Antioxidant-cycle biochemistry well established. Combination not directly trialled at scale. [2]
Doses studied: 300–600 mg ALA with 80–1000 mg vitamin C daily
Elderberry (Sambucus nigra, Black Elder)
Limited evidenceThe classic UK immune-cluster pairing — vitamin C provides the UK Article 13.1 authorised immune claim; elderberry provides the traditional cold/flu adjunct framing.
Vitamin C is required for normal immune-cell function and carries the UK Article 13.1 authorised claim "Vitamin C contributes to the normal function of the immune system" at intakes above the 12 mg NRV trigger. Elderberry (Sambucus nigra) provides anthocyanin and flavonoid content with traditional cold/flu adjunct framing; no UK authorised claim. The pairing carries the vitamin-C immune claim while the elderberry contributes the traditional-use narrative.
Evidence: UK Article 13.1 vitamin C immune-function claim authorised. Elderberry has limited cold-duration evidence (Tiralongo 2016). Combination is commercial-formulary common, not directly trialled. [2]
Doses studied: Elderberry extract 300–1000 mg with vitamin C 80–1000 mg, daily for 5–10 day acute course
Echinacea (Echinacea purpurea / E. angustifolia / E. pallida)
Limited evidenceAuthorised-claim anchor for an echinacea cold product — vitamin C provides the UK Article 13.1 authorised immune claim that echinacea cannot.
Vitamin C is required for normal immune-cell function (neutrophil chemotaxis, lymphocyte proliferation) and carries the UK Article 13.1 authorised claim. Echinacea provides the THR-registered traditional immune-adjunct framing but no UK authorised claim under Article 13.1 (botanicals are on hold). The pair allows a cold-formulation product to carry the vitamin-C immune claim lawfully while the echinacea contributes traditional-use depth.
Evidence: UK Article 13.1 vitamin C immune-function claim authorised. Cochrane echinacea cold-prevention reviews mixed (Karsch-Völk 2014). Combination not directly trialled. [2]
Doses studied: Echinacea purpurea extract 200–500 mg + vitamin C 80–1000 mg per dose, daily for 7–10 day acute-cold course
Beta-Glucan (β-glucan)
Limited evidenceCommon-cold-symptom-cluster pairing — yeast or mushroom β-(1-3,1-6) glucan and vitamin C are routinely co-formulated in winter immune supplements.
Vitamin C carries the UK Article 13.1 immune claim. Yeast or mushroom β-(1-3,1-6) glucan engages innate-immunity Dectin-1 receptors; oat / barley β-(1-3,1-4) glucan does NOT (different receptor profile — see beta-glucan for the distinction). Combination is commercial-formulary common in winter immune products; vitamin C provides the lawful authorised claim.
Evidence: UK Article 13.1 vitamin C immune claim authorised. Yeast / mushroom β-glucan immune-modulation evidence is mechanistic + small-trial; not directly trialled with vitamin C. [2]
Doses studied: 80–1000 mg/day vitamin C plus 100–500 mg/day standardised mushroom or yeast β-(1-3,1-6) glucan
L-Glutamine
Limited evidenceGut-mucosa cluster — glutamine intestinal-cell substrate + vitamin C antioxidant.
L-glutamine is the principal energy substrate for intestinal mucosal cells (enterocytes preferentially oxidise glutamine over glucose). Vitamin C provides antioxidant + collagen cofactor function on the same axis. Mechanism-complementary on gut-mucosa maintenance. UK Article 13.1 vitamin C oxidative-stress claim authorised; L-glutamine has no UK authorised claim.
Evidence: Glutamine-as-enterocyte-fuel mechanism well established. UK Article 13.1 vitamin C oxidative-stress claim authorised. Combination not directly trialled. [2]
Doses studied: 5–10 g/day L-glutamine with 80–1000 mg vitamin C daily
Shiitake (Lentinula edodes)
Limited evidenceUK-authorised immune claim from vitamin C complements shiitake's no-authorised-claim immune narrative.
Vitamin C carries the UK Article 13.1 immune claim shiitake cannot lawfully make. Shiitake (Lentinula edodes) provides lentinan β-(1-6, 1-3)-glucan and a traditional polysaccharide- immune adjunct framing. Pair allows a shiitake-bearing immune formulation to carry the vitamin-C authorised claim lawfully.
Evidence: UK Article 13.1 vitamin C immune-function claim authorised. Shiitake immune-modulation evidence limited; mostly in-vitro and Asian clinical literature. [2]
Doses studied: 300–1000 mg shiitake extract with 80–1000 mg vitamin C daily
Found in Camden: Mycofera™ Mushroom Complex 120 Capsules