Vitamin C, also known as ascorbic acid, is a water-soluble vitamin crucial for various bodily functions, including collagen production, immune support, and iron absorption. It is one of the most widely consumed vitamins globally, often supplemented through tablets, capsules, and powders. While it plays a vital role in overall health, overconsumption of Vitamin C can cause several unwanted side effects. In the UK, the recommended Vitamin C dosage for adults is 40mg, yet many people consume much more through supplements.[1] While it is generally safe, exceeding recommended doses can cause adverse health effects.
This blog explores the side effects of Vitamin C, particularly when consumed in excess, and provides guidance on how to use this essential nutrient safely.
Key Takeaways
• Vitamin C is essential, but taking too much can cause side effects.
• Common side effects include digestive issues, heartburn, and an increased risk of kidney stones.
• Serious risks include iron overload in susceptible individuals and potential kidney damage.
• Stick to the recommended daily Vitamin C intake of 40mg and prioritise getting your Vitamin C from food.
Why Do We Need Vitamin C?
The benefits of Vitamin C are indispensable for a variety of physiological functions that help maintain overall health. Some of its primary roles include:
• Collagen synthesis: Vitamin C is necessary for producing collagen, a protein that maintains skin, joints, bones, and blood vessels strong and resilient.[8]
• Immune system support: It helps stimulate the production of white blood cells, which play a vital role in fighting off infections.[9]
• Iron absorption: Vitamin C increases the body’s ability to absorb non-heme iron, which is available in plant-based foods. This is particularly important for people who follow a vegan diet or vegetarian, as it can help prevent iron deficiency.
• Antioxidant properties: Vitamin C acts as a powerful antioxidant, helping to protect cells from oxidative stress caused by free radicals.[10] These unstable molecules can lead to cellular damage and contribute to chronic illnesses such as heart disease and cancer.
Though Vitamin C is vital for these functions, it is important to understand that more is not always better. Consuming excessive amounts of this vitamin can result in undesirable side effects.
Common Side Effects of Too Much Vitamin C
While most of the Vitamin C we consume is excreted through urine due to its water-soluble nature, high doses—particularly above 1,000mg per day—can lead to side effects.[2] These are some of the most common issues that people experience when they take too much Vitamin C:
1. Digestive Issues
Digestive discomfort is one of the most frequently reported side effects of excessive Vitamin C consumption. The body can only absorb a limited amount of Vitamin C at a time, and any excess remains in the digestive tract, where it can cause irritation. Typical symptoms include:
• Diarrhoea: Large doses of Vitamin C draw water into the intestines, which can lead to loose stools or diarrhoea.[11]
• Nausea: Excessive Vitamin C can cause nausea, especially when taken on an empty stomach or in large quantities at once.[11]
• Abdominal cramps: High amounts of Vitamin C can irritate the gastrointestinal tract, leading to stomach pain and cramping.[12]
For most people, these symptoms subside once they reduce their intake of Vitamin C, but for some, the discomfort can be significant.
2. Heartburn
Due to its mildly acidic nature, Vitamin C can cause heartburn or exacerbate existing acid reflux conditions. Those with pre-existing gastrointestinal conditions, such as gastroesophageal reflux disease (GERD), may be more prone to experiencing heartburn when taking Vitamin C supplements in high doses.[3]
• Acid reflux: Vitamin C supplements, particularly in the form of ascorbic acid, can relax the oesophageal sphincter, allowing stomach acid to move back into the oesophagus, causing a burning sensation in the chest or throat.[13]
3. Kidney Stones
One of the more concerning side effects of excessive Vitamin C intake is an increased risk of developing kidney stones. This occurs because the body metabolises Vitamin C into oxalate, a waste product that can combine with calcium to form calcium oxalate stones.[14] Kidney stones are small, hard deposits that form inside the kidneys and can cause severe pain and complications if not treated properly.[4]
• Risk factors: People who are prone to kidney stones or have a family history of this condition should be cautious about consuming high doses of Vitamin C, particularly through supplements.
Serious Risks and Complications
In addition to the more common side effects, excessive Vitamin C consumption can also lead to more serious health risks, especially when taken in megadoses over extended periods. These complications may not affect everyone, but certain individuals, particularly those with pre-existing health conditions, should be extra cautious.
1. Iron Overload
Vitamin C helps the body absorb iron more effectively, which is typically beneficial. However, in individuals with conditions like haemochromatosis—a genetic disorder in which the body absorbs too much iron—Vitamin C supplementation can exacerbate the problem. Too much iron in the body can damage organs such as the liver, heart, and pancreas, leading to severe health complications like cirrhosis, heart disease, and diabetes.[5]
• Who is at risk: People with haemochromatosis or those who are prone to iron overload should avoid taking large doses of Vitamin C, especially alongside iron supplements.[15]
2. Impact on Kidney Health
Beyond increasing the risk of kidney stones, overconsumption of Vitamin C can negatively impact kidney function. High doses of Vitamin C cause a buildup of oxalate, which the kidneys may struggle to filter out efficiently, especially in individuals with pre-existing kidney conditions. Over time, this may impair kidney function and increase the risk of more serious renal issues.
3. Interaction with Medications
Vitamin C is generally safe for most people, but it can interfere with certain medications. For example, high doses of Vitamin C can reduce the effectiveness of:
• Statins: Used to lower cholesterol, statins may be less effective when taken alongside high doses of Vitamin C.[6]
• Chemotherapy drugs: Some studies suggest that high levels of antioxidants, including Vitamin C, may interfere with the effectiveness of chemotherapy drugs.[6] It is always best to consult a healthcare professional before combining high doses of Vitamin C with any medication to avoid negative interactions.
Vitamin C During Pregnancy
During pregnancy, Vitamin C is important for both the mother and the developing baby, contributing to healthy tissue growth and repair. While moderate food and prenatal vitamin intake is safe and recommended, pregnant women should avoid high doses of Vitamin C supplements.
• Potential risks: Excessive Vitamin C intake during pregnancy may cause digestive issues, like diarrhoea or nausea, and increase the risk of kidney stones. High doses may also cause imbalances in the body’s metabolism of other nutrients.[7]
Pregnant women should always consult their healthcare experts before taking Vitamin C supplements, especially in high doses.
How to Avoid Vitamin C Side Effects
To avoid the unwanted side effects associated with Vitamin C, follow these guidelines:
1. Stick to the Recommended Daily Intake
In the UK, adults should aim for 40mg of Vitamin C per day, which can be easily met through a balanced diet that includes fruits and vegetables. Supplements should be used with caution, particularly in doses over 1,000mg.[7]
2. Choose Natural Sources
Foods with good sources of vitamin C are oranges, kiwi, strawberries, peppers, and broccoli. Unlike supplements, food sources rarely cause side effects, even when consumed in large quantities.
3. Avoid Excessive Supplementation
While supplements are a convenient way to boost Vitamin C intake, they should not be taken in excess. Always adhere to the dosage guidelines on the product label, and consult a healthcare expert if you are considering megadoses for specific health issues.
Conclusion
Vitamin C is a nutrient that provides numerous health benefits, including immune support, improved skin health, and enhanced iron absorption. However, like any nutrient, too much Vitamin C can cause negative side effects, especially when taken in high doses through supplements. Digestive issues, kidney stones, and interactions with medications are among the most common and serious risks associated with excessive Vitamin C intake.
To avoid these complications, it’s important to follow the recommended daily intake, choose natural food sources when possible, and consult a healthcare provider before taking high-dose supplements. By managing your Vitamin C intake responsibly, you can enjoy its benefits without the threat of adverse effects.
If you are not getting enough Vitamin C from your diet, supplements can help cover the gap. At Nature’s Fix, we offer a variety of Vitamin C supplements from trusted brands to support your health and wellness needs.
FAQs
1. Can you overdose on Vitamin C?
Yes, an overdose of Vitamin C can lead to symptoms such as diarrhoea, nausea, and kidney stones, particularly when taking more than 1,000mg per day.[2]
2. What are the side effects of Vitamin C tablets?
Vitamin C tablets can cause digestive upset, heartburn, and in extreme cases, increase the risk of kidney stones when taken in excess.
3. Can too much Vitamin C cause kidney stones?
Yes, excessive Vitamin C increases the production of oxalate, which can lead to the formation of kidney stones, especially in individuals who are predisposed to this condition.[4]
4. Is it safe to take Vitamin C during pregnancy?
Yes, but pregnant women should avoid taking high doses of Vitamin C supplements as they can cause digestive issues and increase the risk of kidney stones.[7]
5. Can Vitamin C interact with medications?
Yes, Vitamin C can interfere with certain medications, such as statins and chemotherapy drugs.[6] Always consult your doctor before taking Vitamin C supplements if you are on medication.
6. Does Vitamin C support hormonal balance in women?
While Vitamin C for women doesn’t directly affect hormonal balance, its antioxidant properties help reduce oxidative stress, which can indirectly support hormonal health, particularly during times of hormonal changes like menstruation or menopause.[16]
7. How much Vitamin C is too much?
Consuming more than 1,000mg per day is considered excessive and may lead to side effects like diarrhoea and kidney stones.[7]
References
1 – https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/
2 – https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/
3 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8055252/
4 – https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/kidney-stones
5 – https://www.ncbi.nlm.nih.gov/books/NBK430862/
6 – https://ods.od.nih.gov/factsheets/VitaminC-Consumer/
7 – https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/
8 – https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
9 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707683/
10 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7285147/
11 – https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-c/faq-20058030/
12 – https://www.medicalnewstoday.com/articles/326249/
13 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5746510/
14- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9959749/
15 – https://pubmed.ncbi.nlm.nih.gov/10218143/
16 – https://www.onlymyhealth.com/essential-vitamins-for-women-hormonal-health-1708079901
