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Vitamin C: Sources, benefits & deficiency

various fruits and vegetables high in vitamin c on a wooden board
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Vitamin C, also known as ascorbic acid, is important for many functions in the body. Although it takes pride of place in many immune-boosting supplements, its effect on our health goes far beyond preventing seasonal sniffles. Vitamin C is a complex and powerful nutrient that is essential for our bodies to grow and thrive. 

What’s more, scientists are still uncovering the full potential of vitamin C when it comes to preventing chronic diseases. What may come as a surprise to many is that they are also not entirely sure whether it can cure the common cold. Although it has become a common practice to pop vitamin C supplements to fight off respiratory infections, there is surprisingly little evidence that it actually works. But that doesn’t mean vitamin C isn’t good for our immune system. In fact, quite the opposite.

So what does vitamin C do? How much do you need? And where can you find it? Here, we cut through confusion and discuss everything you need to know about ascorbic acid and its role in our bodies. 

Why do we need vitamin C?

Although many just view it as an immune-booster, ascorbic acid is critical to various aspects of our health and wellbeing. According to the Nutrients (opens in new tab) journal, vitamin C is crucial to the formation of collagen, hormones (particularly adrenaline) and carnitine — a compound that helps turn dietary fat into energy. Vitamin C protects against oxidative damage, helps with iron absorption in the digestive tract, and is involved in numerous metabolic pathways. It is a true multitasker.  

Tissue growth and repair

According to the National Institutes of Health (opens in new tab) (NIH), vitamin C is essential for the proper functioning of your connective tissues, including the skin, tendons, ligaments, and blood vessels. That’s because your body needs this micronutrient to form collagen, a type of protein that gives them structure and firmness. Vitamin C is also crucial to repairing and maintaining cartilage, bones and teeth, as well as healing wounds and forming scar tissue.

It is particularly important for tissue repair. According to a review in the Orthopaedic Journal of Sports Medicine (opens in new tab), vitamin C may be key to a speedy recovery from musculoskeletal injuries. 

Antioxidant

Vitamin C is a powerful antioxidant. Dr. Sherry Ross, a gynaecologist and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California, explains that it helps protect cells from damage caused by free radicals that we are exposed to in the environment such as air pollution, cigarette smoke and ultraviolet light from the sun. Ascorbic acid is also needed to regenerate other antioxidants within the body, including vitamin E.  

At the same time, scientists are still examining whether vitamin C, by limiting the damaging effects of free radicals, might help prevent or delay the development of certain cancers, cardiovascular disease, and other diseases rooted in high levels of oxidative stress. 

Immunity

Vitamin C is often taken to prevent or cure the common cold and respiratory infections. However, the evidence behind this claim is not black and white. 

According to the Nutrients (opens in new tab) journal, there are several mechanisms in which vitamin C strengthens our defences against microbes and harmful environmental factors: it supports the integrity of our connective tissues, enhances the production of immune-boosting white blood cells and reduces the levels of inflammation. At the same time, many studies (opens in new tab) have shown that vitamin C supplementation does not decrease the number of infections in the general population. Two controlled trials have found a reduction in the duration of cold symptoms however, with up to 6-8g/day of vitamin C. However, the exact dose needed is not known.

woman with a cold blowing her nose

(Image credit: Getty images)

Eye health

The evidence is emerging that vitamin C may play a role in eye health. As reported in the Nutrients (opens in new tab) journal, the last decade has seen a lot of progress in understanding how this micronutrient may help prevent cataracts. Cataracts is a condition in which your eye lens gets clouded, progressively restricting your vision. It is the leading cause of blindness in the world. Since cataracts are heavily linked to age and type 2 diabetes, it is a growing public health concern. It has been suggested that antioxidants like vitamin C could delay the onset of this debilitating condition and improve the quality of life of those at risk. 

Brain health

Vitamin C could also play an important role in brain health. As described in the Nutrients (opens in new tab) journal, this micronutrient helps maintain integrity and function of the central nervous system. Vitamin C ensures that our neurons work properly and that the transmission of signals across our body goes without interruption.

image of a brain scan with writing

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Dental Health

Periodontal disease, also referred to as periodontitis or gum disease, is a condition in which the gums and bone that surround the teeth become severely inflamed. According to the International Journal of Environmental Research and Public Health (opens in new tab), individuals who suffer from periodontitis are more likely to be deficient in vitamin C. Ascorbic acid supplementation has also been linked to lower risk of developing gum disease, as well as better treatment outcomes.

How much vitamin C do you need?

The recommended daily allowance (RDA) for vitamin C varies, depending on age, gender and other factors. Typically, the RDA is 75mg for women and 90mg for men, according to the NIH. (opens in new tab) Pregnant and nursing women should take 80mg to 120 mg, depending on age. Individuals who smoke require 35 mg more per day than non-smokers.

Most of the population can take up to 2g of this nutrient without any side effects, since vitamin C is water soluble. This means that it is not stored by the body and is filtered out by the body in urine. 

What are the best sources of vitamin C?

It is a common belief that citrus fruits are the best sources of vitamin C. However, many fruits and vegetables boast similar, if not higher, levels of ascorbic acid. These include: 

  • Guavas: 377mg (419% DV) per cup / 228mg (254% DV) per 100g 
  • Kiwifruit: 167mg (185% DV) per cup / 93mg (103% DV) per 100g 
  • Bell peppers: 152mg (169% DV) per cup / 128mg (142% DV) per 100g 
  • Strawberries: 98mg (108% DV) per cup / 59mg (65% DV) per 100g
  • Oranges: 96mg (106% DV) per cup / 53mg (59% DV) per 100g 
  • Broccoli: 81mg (90% DV) per cup / 89mg (99% DV) per 100g  

Close up of Caucasian woman slicing red bell pepper

(Image credit: Getty Images)

Vitamin C deficiency

Vitamin C deficiency is known as scurvy. Typical symptoms include muscle weakness, swollen and bleeding gums, loss of teeth, poor wound healing, anaemia, skin problems, and weight loss. In severe cases, the scurvy can be fatal. Vitamin C deficiency used to be a relatively frequent phenomenon between the 16th and 18th century, and occurred mostly among sailors who did not have access to fresh produce. However, nowadays extreme cases are rare among Western populations. 

It’s also worth noting that certain individuals may be at an increased risk of vitamin C deficiency. These include smokers and hospital patients recovering from surgery, trauma, sepsis, and burns.

Vitamin C: Are there any risks?

Vitamin C is considered to be relatively safe when taken in high doses. Some studies (opens in new tab) even suggest that, in certain cases, they may have clinical use. However, it is not recommended to take more than 1g of ascorbic acid a day. According to the Nutrients journal, high doses of vitamin C may cause diarrhea, bloating and abdominal pain. Scientists are also concerned that they may increase the risk of kidney stones. Those prone to kidney stones should get clearance from their doctor before taking high doses of vitamin C.

This article is for informational purposes only and is not meant to offer medical advice.

Additional resources

Anna Gora
Health Writer

Anna Gora is a Health Writer for Future Plc, working across Coach, Fit&Well, LiveScience, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a BSc degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.

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