Vitamin C: what your body actually needs, and how much
Vitamin C is one of the essential vitamins your body cannot make or store — which means it needs to come from your diet regularly. It's genuinely important, and it plays several distinct roles across the body. But how much do you actually need, how easily is it met from food, and when might a supplement actually make a difference? This article walks through the honest picture.
What vitamin C actually does in the body
Vitamin C plays several distinct roles that are well-established in nutrition science:
- Supports collagen synthesis — required for the body to make collagen for skin, blood vessels, bones, cartilage, gums, and teeth
- Supports immune function — involved in various immune cell activities and function
- Acts as an antioxidant — helps protect cells from oxidative damage caused by free radicals
- Supports iron absorption — particularly non-heme iron from plant sources
- Supports normal energy metabolism — involved in metabolic processes that produce energy from food
- Supports the nervous system — involved in neurotransmitter production
These are the well-established roles of vitamin C when you have adequate intake — not treatments for deficiency states, and not health claims specific to a Kollo product.
How much do you actually need?
The US Recommended Dietary Allowances (RDAs) for vitamin C are:
- Adult men: 90mg per day
- Adult women: 75mg per day
- Pregnant women: 85mg per day
- Breastfeeding women: 120mg per day
- Heavy smokers: add approximately 35mg per day to the base RDA
The Upper Tolerable Limit for vitamin C from supplements is 2000mg per day for adults — above this level, gastrointestinal side effects (upset stomach, diarrhea) become more common. Most people meeting their RDA from food don't need to think about this limit.
Dietary sources of vitamin C
Fruit and vegetables are the primary dietary sources. Approximate figures per serving:
- Red bell peppers — around 150mg per raw pepper
- Broccoli — around 90mg per cooked cup
- Kiwi fruit — around 90mg per fruit
- Strawberries — around 85mg per cup
- Oranges — around 70mg per medium fruit
- Kale, Brussels sprouts, cabbage — around 50-80mg per cooked cup
- Grapefruit — around 70mg per half fruit
- Tomatoes — around 15-20mg per medium fruit (lower but adds up)
One orange, one kiwi, or a serving of red peppers or broccoli each already meets or exceeds the daily RDA. This is why clinical deficiency is uncommon in ordinary balanced diets.
When is deficiency actually more likely?
Clinical vitamin C deficiency (scurvy) is rare in modern developed diets — but there are specific groups where the risk is genuinely higher:
- Heavy smokers — increased vitamin C requirements, often combined with lower fruit/vegetable intake
- Severe alcohol dependency — poor nutrition combined with impaired absorption
- Older adults with very restricted diets — particularly those living alone or with limited food access
- Restrictive eating patterns or eating disorders — very limited food variety
- Extreme low-carb or ketogenic diets without vitamin C sources — if fruit and vegetables are heavily restricted without careful planning
- Some medical conditions — including inflammatory bowel disease, cancer, and certain absorption disorders
If you fall into one of these groups and are concerned about your intake, please speak to your doctor or healthcare provider.
Signs of vitamin C deficiency
Because deficiency is uncommon, it's worth being clear that many of the symptoms listed below overlap with a wide range of other conditions. Bruising, fatigue, and skin changes can all have completely different causes. These signs are typically associated with sustained low vitamin C intake over weeks or months:
- Easy bruising — vitamin C is essential for collagen in blood vessel walls; low levels can cause weakened vessels that rupture easily
- Bleeding or spongy gums — a classic later sign of deficiency
- Poor wound healing — collagen synthesis is impaired, slowing tissue repair
- Corkscrew-shaped body hair — a distinctive dermatological sign of significant deficiency, sometimes called "corkscrew hair"
- Follicular hyperkeratosis — small raised bumps around hair follicles (not the same as keratosis pilaris, which is a common and largely genetic condition unrelated to vitamin C)
- Fatigue and low mood — though these have many other causes and should be investigated by a doctor
- Joint or muscle aches — from impaired collagen synthesis in connective tissues
How marine collagen fits
Marine collagen supplementation has strong evidence for supporting skin outcomes (elasticity, hydration, appearance of fine lines) over 8-12 weeks, and emerging evidence for joint comfort at 12+ weeks. Kollo Premium Liquid Marine Collagen is a marine collagen product — not a vitamin C supplement.
However, the Kollo formula does include vitamin C alongside its marine collagen peptides. So while Kollo isn't a treatment for vitamin C deficiency, its formula does contain vitamin C which supports the roles described earlier. If your goal is meeting your daily vitamin C requirement, a balanced diet including fruit and vegetables is the primary answer; a supplement can be additional. If you have a diagnosed vitamin C deficiency, please follow your doctor's guidance on appropriate supplementation.
Featured Product
Premium Liquid Marine Collagen
10,000mg of Naticol® marine collagen daily, alongside vitamin C, B vitamins, and l-lysine. Informed Choice certified. Not suitable for anyone with a fish allergy.
Shop Liquid CollagenFrequently Asked Questions
How much vitamin C do I need daily?
The US RDA (Recommended Dietary Allowance) is 90mg per day for adult men and 75mg per day for adult women. Heavy smokers need approximately 35mg more per day. Pregnant women need 85mg per day; breastfeeding women need 120mg per day. A single orange contains around 70mg — close to or above the RDA on its own. Most people eating a broadly balanced diet including fruit and vegetables meet their daily needs from food.
Do I need a vitamin C supplement?
If you eat fruit and vegetables regularly, almost certainly not — you're likely already meeting your daily needs from food. Vitamin C is water-soluble; excess is generally excreted rather than stored. If you're in a specific at-risk group (heavy smoker, restrictive diet, older adult with limited food access), speaking to your doctor about your intake and any need for supplementation is more useful than assuming you need one. Very high-dose vitamin C supplements (above 2000mg/day) can cause gastrointestinal side effects.
Is Kollo a vitamin C supplement?
No. Kollo Premium Liquid Marine Collagen is a marine collagen supplement — its primary purpose is providing marine collagen peptides for skin, hair, nail and joint support. The formula does include vitamin C alongside B vitamins and l-lysine, but Kollo isn't marketed or positioned as a vitamin C supplement, and it isn't a treatment for diagnosed vitamin C deficiency.
Is vitamin C deficiency common?
Clinical vitamin C deficiency (scurvy) is rare in the US with a typical diet — the daily requirement is small and easily met by ordinary fruit and vegetables. However, subclinical low intake can occur in specific groups: heavy smokers, people with severe alcohol dependency, older adults with restricted diets, those with restrictive eating patterns, and certain medical conditions. If you're in one of these groups and concerned, please speak to your doctor or healthcare provider.
Can vitamin C prevent colds?
The evidence picture is honest: high-dose vitamin C hasn't been shown to prevent colds in the general population. Some research suggests it may modestly reduce cold duration if taken regularly, and there's some evidence for benefit in people under significant physical stress (like extreme athletes). Vitamin C plays a role in supporting normal immune function — but this is about supporting normal immunity when you have adequate intake, not preventing infections.
What's the best form of vitamin C to take?
For most people, getting vitamin C from food is preferable to supplements. If supplementation is appropriate for your circumstances, standard ascorbic acid is well-absorbed. Liposomal, buffered, and other specialty forms are marketed as superior — the evidence for meaningful advantage over standard ascorbic acid is limited. Whatever form you take, the dose matters more than the form for most purposes.
Kollo Health was co-founded by Jenni Falconer — TV presenter, radio host, ten-time London Marathon runner and host of the RunPod podcast. Read her story and why she created Kollo.
