Table of Contents

Vitamin C Toxicity: Side Effects of High Ascorbic Acid

Takeaways

  • Vitamin C toxicity occurs from excessive intake, usually through supplements
  • Common symptoms include digestive issues and kidney stone formation
  • The body regulates vitamin C levels, making toxicity rare from food sources
  • High-dose supplements can interact with medications and other nutrients
  • Most people can avoid toxicity by staying within recommended daily limits
  • Consult a doctor before starting high-dose vitamin C supplementation

What is Vitamin C?

Vitamin C, also called ascorbic acid, is a nutrient that dissolves in water. It’s necessary for many bodily functions. Vitamin C acts as an antioxidant and also helps the body create collagen, a protein that supports skin, bone and blood vessel health.[1]

Our bodies cannot produce vitamin C, so we must obtain it from external sources like food or supplements. Fruits and vegetables are the best natural sources of vitamin C.[2] Many individuals choose to use supplements to ensure they get sufficient amounts.

Vitamin C is important for a healthy immune system. It also assists the body in absorbing iron from plant-based foods, supports wound healing and contributes to maintaining healthy gums.[3]

Recommended Daily Intake

The daily amount of vitamin C needed varies based on age and life stage. The Recommended Dietary Allowance (RDA) provides guidelines on the appropriate intake for most people each day.[4]

Here is a summary of the Recommended Dietary Allowance (RDA) of Vitamin C for different groups:

Age Group RDA (mg/day)
Infants 0-6 months 40
Infants 7-12 months 50
Children 1-3 years 15
Children 4-8 years 25
Children 9-13 years 45
Teens 14-18 years (boys) 75
Teens 14-18 years (girls) 65
Adults 19+ years (men) 90
Adults 19+ years (women) 75
Pregnant teens 80
Pregnant women 85
Breastfeeding teens 115
Breastfeeding women 120

Some individuals might require more vitamin C than others. For example, smokers should add 35 mg to their daily intake because smoking reduces vitamin C levels in the body.[5]

Specific health conditions, such as some digestive issues and certain cancers, may also increase the need for vitamin C. It’s important to consult with a doctor to understand your particular requirements.[6]

Sources of Vitamin C

Food Sources

Many foods contain vitamin C, with fruits and vegetables being the best natural sources. Some common foods rich in vitamin C include:

  • Citrus fruits (oranges, grapefruits, lemons)
  • Berries (strawberries, blueberries, raspberries)
  • Tropical fruits (kiwi, papaya, mango)
  • Bell peppers
  • Broccoli
  • Brussels sprouts
  • Potatoes
  • Tomatoes

Cooking and storage methods can affect the vitamin C content of foods. Heat and light can break down this nutrient. To maximize your vitamin C intake, consider these tips:

  1. Eat fruits and vegetables raw when possible
  2. Steam or microwave vegetables instead of boiling
  3. Store produce in the refrigerator
  4. Cut fruits and vegetables just before eating

Supplements

Vitamin C supplements are available in various forms, the most common being ascorbic acid. This is the same form of vitamin C found naturally in foods. Other forms include:

  • Sodium ascorbate
  • Calcium ascorbate
  • Ascorbyl palmitate

These alternative forms of vitamin C might be easier to digest for some people, though they often cost more than standard ascorbic acid supplements.

Vitamin C supplements can deliver high doses quickly, which may be beneficial for those with a deficiency. However, it is also easier to consume excessive amounts through supplements.[7]

Most people do not need to take vitamin C supplements. Usually, a balanced diet provides sufficient amounts. It is best to discuss supplement use with a doctor before starting any new regimen.[8]

Understanding Vitamin C Toxicity

Vitamin C toxicity, or an overdose, can occur from consuming too much vitamin C. It is uncommon, as the body generally manages extra vitamin C well. It gets rid of unneeded amounts through urine.[9]

Vitamin C toxicity almost always comes from supplements, not from food. It is very difficult to get too much from diet alone. Even large amounts of vitamin C-rich foods are unlikely to cause problems.[10]

The body regulates how much vitamin C it absorbs. When intake increases, absorption decreases. This mechanism helps prevent toxicity from standard doses. However, very high doses can overwhelm this system.[11]

Vitamin C is a water-soluble vitamin, so excess amounts usually leave the body through urine. However, taking very large doses can lead to a build-up, which is when toxicity can occur.[12]

Symptoms of Vitamin C Toxicity

Excessive vitamin C intake can cause several symptoms, often starting in the digestive system, though other parts of the body can be affected as well.[13]

The main symptoms of vitamin C toxicity include:

  1. Nausea and vomiting
  2. Diarrhea
  3. Stomach cramps
  4. Headache
  5. Heartburn
  6. Skin flushing

These symptoms usually appear when someone takes more than 2,000 mg of vitamin C per day. The severity varies from person to person, and some people may feel sick with lower doses.[14]

Most symptoms usually resolve after stopping high doses of vitamin C. However, long-term overuse might lead to more serious issues such as kidney problems or iron overload.[15]

Gastrointestinal Effects

The digestive system often shows the first signs of vitamin C overload because it is the initial point of contact for supplements. High doses can irritate the stomach and intestinal linings.[16]

Nausea and diarrhea are common symptoms of vitamin C toxicity. These occur when the body is unable to absorb all of the vitamin C, and the extra amount draws water into the intestines leading to loose stools.[17]

Stomach cramps and bloating can also happen with too much vitamin C. These symptoms are typically uncomfortable but not dangerous and usually stop after reducing vitamin C intake.[18]

Some people are more sensitive to these effects and might experience discomfort at lower doses. This does not necessarily indicate toxicity, but it signals a need to reduce intake or consult a doctor.[19]

Kidney Concerns

Excessive vitamin C can affect how the kidneys function. The kidneys filter out excess vitamin C from the blood, while also reabsorbing some to maintain proper balance in the body.[20]

One major concern is the potential for kidney stone formation. Vitamin C breaks down into oxalate, a common component of kidney stones. High vitamin C intake may increase oxalate levels.[21]

Individuals with a history of kidney stones should be cautious and may need to limit vitamin C supplements. This is especially important for those who have oxalate-based stones.[22]

Vitamin C can also affect how the kidneys process other substances. It can alter uric acid levels or change drug clearance rates, which could be problematic for people with kidney disease or who take certain medications.[23]

Interactions with Other Nutrients

High amounts of vitamin C can affect how the body uses other nutrients, potentially altering the absorption or metabolism of certain vitamins and minerals.[24]

Here is information on how vitamin C can interact with other nutrients:

Nutrient Interaction
Iron Enhances absorption, might lead to iron overload
Copper May reduce absorption
Vitamin B12 High doses might reduce B12 levels
Selenium May increase excretion

Vitamin C enhances the absorption of iron from plant sources. While this is generally beneficial, it can be an issue for people with iron overload disorders.[25]

High vitamin C intake may reduce copper absorption. Over time, this could lead to copper deficiency, although this is uncommon with long-term high doses.[26]

Some studies suggest that very high doses of vitamin C might lower vitamin B12 levels. This requires further research, but it is worth considering for vegetarians or older adults.[27]

Maintaining a balance in nutrient intake is important. Taking too much of one vitamin can affect others. This is one reason why a varied diet is often better than relying on supplements.[28]

At-Risk Groups

Certain individuals are at a higher risk of developing vitamin C toxicity. They may be more sensitive to high doses, or have conditions that increase the likelihood of toxicity.[29]

Groups that should take extra care with vitamin C intake include:

  • People with kidney disorders
  • Those with a history of kidney stones
  • Individuals with hemochromatosis (iron overload disorder)
  • People taking certain medications (like blood thinners)
  • Those with G6PD deficiency

People with kidney problems may not clear excess vitamin C efficiently, which could lead to a build-up and toxicity even at lower doses.[30]

Those with a tendency to develop kidney stones should monitor their vitamin C intake. High doses might increase their risk of stone formation.[31]

People with hemochromatosis, a condition where the body absorbs too much iron, need to be careful as vitamin C enhances iron absorption, potentially worsening iron overload.[32]

Certain medications can interact with high-dose vitamin C, like blood thinners such as warfarin. Always consult a doctor about potential supplement interactions.[33]

Individuals with G6PD deficiency, a genetic condition, might experience red blood cell breakdown from very high doses of vitamin C.[34]

Upper Tolerable Intake Level

The Upper Tolerable Intake Level (UL) is the highest amount of daily vitamin C considered safe. Health authorities set this level to prevent toxicity, and it varies by age.[35]

The following table shows the UL of vitamin C for different age groups:

Age Group UL (mg/day)
1-3 years 400
4-8 years 650
9-13 years 1,200
14-18 years 1,800
19+ years 2,000

These levels are specific to supplements and fortified foods. They do not include vitamin C that is naturally found in food, which makes it very difficult to reach these levels from diet alone.[36]

The UL is not a target to aim for. It is a maximum limit to stay below. Most individuals do not need to take doses close to the UL, as the RDA is usually sufficient for good health.[37]

Pregnant and breastfeeding women have the same UL as other adults, but they should consult a doctor about their specific requirements.[38]

Myths and Misconceptions

Several myths surround vitamin C intake and toxicity. Let’s address some common misconceptions:

Myth 1: You can’t get too much vitamin C.[39] Truth: While rare, vitamin C toxicity is possible from high-dose supplements.

Myth 2: More vitamin C always means better health.[40] Truth: The body only needs a certain amount. Extra doesn’t provide more benefits.

Myth 3: High-dose vitamin C cures colds.[41] Truth: Research doesn’t support this. It might slightly reduce cold duration, but doesn’t prevent or cure them.

Myth 4: Vitamin C supplements are always safe.[42] Truth: They can interact with medications and cause side effects in high doses.

Myth 5: Natural vitamins can’t cause toxicity.[43] Truth: Even natural supplements can cause problems in very high doses.

These myths often lead to unnecessary megadosing, where people take very high doses of vitamins. This practice is not proven to be helpful and may even be harmful.

It is crucial to have evidence-based information. Many claims about vitamin C are not supported by scientific studies. Always verify health information with reliable sources.

Prevention and Safe Supplementation

Preventing vitamin C toxicity is generally straightforward. Following these guidelines can help:

  1. Stick to the RDA unless directed by a doctor
  2. Get vitamin C from food sources when possible
  3. Don’t exceed the UL for supplements
  4. Be aware of vitamin C in all your supplements
  5. Talk to a doctor before starting high doses

If you choose to take supplements, start with a low dose and gradually increase only if needed, while closely monitoring for any unusual symptoms.

Carefully read supplement labels. Many multivitamins and other products contain vitamin C. Make sure you are not getting too much from multiple sources.

Remember that more is not always better. The body can only use a certain amount of vitamin C, and excess amounts do not provide additional benefits.

For most individuals, a balanced diet offers sufficient vitamin C. Focus on eating a variety of fruits and vegetables. This approach is safe and provides other essential nutrients.

When to Seek Medical Help

Sometimes, vitamin C toxicity requires medical attention. Be aware of when to seek help from a doctor:

  • Severe or persistent digestive symptoms
  • Signs of an allergic reaction (rare but possible)
  • Symptoms of kidney stones
  • Unusual bruising or bleeding
  • Fatigue or weakness that doesn’t go away

If you are taking high doses of vitamin C and experience these symptoms, stop taking the supplements and contact your doctor.

Consult with a healthcare provider before starting any high-dose vitamin C regimen. They can assess your individual needs and potential risks. This is especially important if you have health conditions or take medications.

During your medical evaluation, be transparent about your supplement use. Inform your doctor how much vitamin C you are taking, including all sources like multivitamins and fortified foods.

Your doctor might order blood or urine tests. These can check your vitamin C levels and overall health, as well as look for signs of toxicity or nutrient imbalances.

FAQ

Can you overdose on vitamin C from food sources?
It’s very unlikely. The body regulates absorption from food well. Toxicity almost always comes from high-dose supplements.

How much vitamin C is too much?
For most adults, doses above 2,000 mg per day might cause side effects. The upper limit is set at this level to prevent toxicity.

What are the long-term effects of vitamin C toxicity?
Long-term high doses might lead to kidney stones or digestive issues. It could also affect the absorption of other nutrients.

Does vitamin C toxicity cause permanent damage?
Most effects of vitamin C toxicity are reversible. Stopping high doses usually resolves symptoms. But long-term overuse might have lasting effects.

Can vitamin C supplements interact with medications?
Yes, vitamin C can interact with several medications. These include blood thinners, chemotherapy drugs, and some antidepressants. Always check with a doctor.

Is it safe to take high doses of vitamin C during pregnancy?
Pregnant women should stick to the recommended amounts unless advised by a doctor. High doses during pregnancy haven’t been well studied for safety.

Vitamin C is vital for good health, supporting our immune system and bodily functions. While it is important to consume enough vitamin C, taking too much can lead to health problems.

Most people can obtain all the necessary vitamin C from their diet. Fruits and vegetables are excellent sources, providing vitamin C along with other helpful nutrients. This natural approach is usually the safest and most effective.

Supplements can be helpful in certain situations. They might benefit those who cannot obtain enough vitamin C from their diet. However, it is crucial to use them carefully and always follow recommended dosages, unless a doctor advises differently.

If you are considering taking high doses of vitamin C, consult a healthcare provider first. They can help you weigh the potential benefits and risks while taking your overall health and current medications into account.

Remember that vitamin C is only one component of a healthy lifestyle. A balanced diet, regular exercise, and good sleep habits all contribute to overall well-being. Focus on these basics before considering high-dose supplements.

In summary, vitamin C is an essential nutrient with numerous benefits, but like many things, too much can cause problems. By understanding vitamin C toxicity, you can make informed choices about your intake. Stay within the recommended limits, listen to your body, and consult with healthcare providers when needed to receive the benefits of vitamin C while avoiding potential issues.

Fact Check
Claim: Vitamin C, also called ascorbic acid, is a nutrient that dissolves in water. It’s necessary for many bodily functions. Vitamin C acts as an antioxidant and also helps the body create collagen, a protein that supports skin, bone and blood vessel health.
Fact check: True. Vitamin C is water-soluble, acts as an antioxidant, and is vital for collagen synthesis.

This is a generally accepted definition and function of vitamin C.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Our bodies cannot produce vitamin C, so we must obtain it from external sources like food or supplements. Fruits and vegetables are the best natural sources of vitamin C.
Fact check: True. Humans cannot synthesize vitamin C and must obtain it from dietary sources, particularly fruits and vegetables.

This is a fundamental characteristic of vitamin C in human physiology. Lack of the enzyme L-gulonolactone oxidase prevents the synthesis of vitamin c in the body.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C is important for a healthy immune system. It also assists the body in absorbing iron from plant-based foods, supports wound healing and contributes to maintaining healthy gums.
Fact check: True. Vitamin C plays a crucial role in immune function, iron absorption, wound healing, and gum health.

These are all well-established roles of vitamin C. It’s essential for various physiological processes.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: The daily amount of vitamin C needed varies based on age and life stage. The Recommended Dietary Allowance (RDA) provides guidelines on the appropriate intake for most people each day.
Fact check: True. Vitamin C requirements vary, and RDAs provide guidance.

RDAs are indeed set based on age, sex, and life stages. The NIH is one reliable source to confirm this.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Some individuals might require more vitamin C than others. For example, smokers should add 35 mg to their daily intake because smoking reduces vitamin C levels in the body.
Fact check: True. Smokers need more vitamin C due to increased oxidative stress from smoking.

Smoking depletes vitamin C levels, so additional intake is recommended. The CDC and other health organizations recommend this.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Specific health conditions, such as some digestive issues and certain cancers, may also increase the need for vitamin C. It’s important to consult with a doctor to understand your particular requirements.
Fact check: True. Certain health conditions can impact vitamin C needs.

Various health conditions can alter the absorption, utilization, or excretion of vitamin C, making individual needs vary. A doctor’s consultation is needed in these circumstances.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C supplements can deliver high doses quickly, which may be beneficial for those with a deficiency. However, it is also easier to consume excessive amounts through supplements.
Fact check: True. Supplements provide higher doses of vitamin C than food sources.

The bioavailability and higher concentrations of supplements can lead to quicker and easier absorption, and the potential for easier overdose.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Most people do not need to take vitamin C supplements. Usually, a balanced diet provides sufficient amounts. It is best to discuss supplement use with a doctor before starting any new regimen.
Fact check: True. A balanced diet is usually sufficient for most individuals.

Food sources, specifically fruits and vegetables provide an abundance of nutrients that provide for most individuals’ dietary requirements without the need for supplementation. Supplementation is best discussed with a healthcare professional.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C toxicity, or an overdose, can occur from consuming too much vitamin C. It is uncommon, as the body generally manages extra vitamin C well. It gets rid of unneeded amounts through urine.
Fact check: True. Vitamin C toxicity is possible but rare due to its water-soluble nature.

The body does typically excrete excess vitamin C through urine.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C toxicity almost always comes from supplements, not from food. It is very difficult to get too much from diet alone. Even large amounts of vitamin C-rich foods are unlikely to cause problems.
Fact check: True. Toxicity from food sources is rare.

The body generally handles vitamin C from food very well. Supplements present a higher potential for toxicity due to concentrated doses.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: The body regulates how much vitamin C it absorbs. When intake increases, absorption decreases. This mechanism helps prevent toxicity from standard doses. However, very high doses can overwhelm this system.
Fact check: True. The body has mechanisms to regulate vitamin C absorption.

The gastrointestinal tract decreases absorption when the dose is high. But, extremely high doses can saturate these pathways.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C is a water-soluble vitamin, so excess amounts usually leave the body through urine. However, taking very large doses can lead to a build-up, which is when toxicity can occur.
Fact check: True. Water-soluble vitamins are typically excreted but can cause problems in very high doses.

Excretion via the urine is the primary route but excessive intake can overwhelm the body’s ability to process it.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Excessive vitamin C intake can cause several symptoms, often starting in the digestive system, though other parts of the body can be affected as well.
Fact check: True. High doses of vitamin C can cause digestive and other symptoms.

The digestive system is often the first to be impacted, but other systems can also be affected.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: These symptoms usually appear when someone takes more than 2,000 mg of vitamin C per day. The severity varies from person to person, and some people may feel sick with lower doses.
Fact check: True. The tolerable upper limit (UL) for vitamin C is 2000mg and symptoms can occur at or above this dose.

This is the general threshold that health organizations set, but individual tolerance can vary. The NIH states 2,000mg is the UL.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Most symptoms usually resolve after stopping high doses of vitamin C. However, long-term overuse might lead to more serious issues such as kidney problems or iron overload.
Fact check: True. Symptoms are often reversible but can become serious with chronic overuse.

Stopping supplementation generally resolves the acute symptoms, but long-term issues can arise. This is generally accepted by medical professionals.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: The digestive system often shows the first signs of vitamin C overload because it is the initial point of contact for supplements. High doses can irritate the stomach and intestinal linings.
Fact check: True. The digestive tract is often the first area affected.

The initial site of processing is the digestive system, where high concentrations of vitamin C can cause irritation, leading to common side effects.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Nausea and diarrhea are common symptoms of vitamin C toxicity. These occur when the body is unable to absorb all of the vitamin C, and the extra amount draws water into the intestines leading to loose stools.
Fact check: True. Nausea and diarrhea are common symptoms.

Unabsorbed vitamin C can draw water into the intestines, causing loose stools and related discomfort.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Stomach cramps and bloating can also happen with too much vitamin C. These symptoms are typically uncomfortable but not dangerous and usually stop after reducing vitamin C intake.
Fact check: True. Stomach cramps and bloating are potential side effects.

These gastrointestinal issues are usually temporary, resolving when the vitamin C intake is lowered.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Some people are more sensitive to these effects and might experience discomfort at lower doses. This does not necessarily indicate toxicity, but it signals a need to reduce intake or consult a doctor.
Fact check: True. Individual tolerance varies.

Some people may be more susceptible to digestive symptoms with vitamin C intake, requiring careful intake adjustments and a doctor’s consultation in some cases.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Excessive vitamin C can affect how the kidneys function. The kidneys filter out excess vitamin C from the blood, while also reabsorbing some to maintain proper balance in the body.
Fact check: True. The kidneys are involved in regulating vitamin C levels.

The kidneys filter and reabsorb vitamin C, but high doses can burden them, which can cause other issues such as kidney stones. This mechanism is well established.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: One major concern is the potential for kidney stone formation. Vitamin C breaks down into oxalate, a common component of kidney stones. High vitamin C intake may increase oxalate levels.
Fact check: True. High vitamin C intake can increase risk of kidney stones.

The breakdown of vitamin C into oxalate is a known pathway. High levels of oxalate is known to increase the risk for kidney stones, particularly in predisposed individuals.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Individuals with a history of kidney stones should be cautious and may need to limit vitamin C supplements. This is especially important for those who have oxalate-based stones.
Fact check: True. Individuals with kidney stones should take caution with vitamin C supplementation.

Due to the increase in oxalate from high vitamin C intake, individuals with a history of kidney stones should use caution.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C can also affect how the kidneys process other substances. It can alter uric acid levels or change drug clearance rates, which could be problematic for people with kidney disease or who take certain medications.
Fact check: True. Vitamin C can affect kidney function and drug metabolism.

High doses of vitamin C can impact renal function and drug metabolism, particularly in those with pre-existing conditions or taking medications. This is an important thing to consider.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: High amounts of vitamin C can affect how the body uses other nutrients, potentially altering the absorption or metabolism of certain vitamins and minerals.
Fact check: True. High vitamin C intake can interact with other nutrients.

Vitamin C can influence the absorption and/or metabolism of other nutrients. This is a point to consider when considering supplementation.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Vitamin C enhances the absorption of iron from plant sources. While this is generally beneficial, it can be an issue for people with iron overload disorders.
Fact check: True. Vitamin C increases iron absorption.

This interaction can cause issues for those with iron overload disorders such as hemochromatosis. The interaction itself is factual.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: High vitamin C intake may reduce copper absorption. Over time, this could lead to copper deficiency, although this is uncommon with long-term high doses.
Fact check: True. High vitamin C intake can potentially reduce copper absorption.

High doses over time have the possibility of reducing copper absorption, though it is not as common as iron absorption.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Some studies suggest that very high doses of vitamin C might lower vitamin B12 levels. This requires further research, but it is worth considering for vegetarians or older adults.
Fact check: Potentially True, more research is needed.

Some studies hint at this interaction, but the exact relationship requires further studies. It is something to consider though, as this has not yet been ruled out.

Claim: Maintaining a balance in nutrient intake is important. Taking too much of one vitamin can affect others. This is one reason why a varied diet is often better than relying on supplements.
Fact check: True. Nutrient balance is important.

Focusing on varied diets over supplementation of vitamins is the ideal approach to health, due to interactions between vitamins and minerals.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Certain individuals are at a higher risk of developing vitamin C toxicity. They may be more sensitive to high doses, or have conditions that increase the likelihood of toxicity.
Fact check: True. Some individuals are at greater risk of vitamin C toxicity.

Specific conditions or traits make some individuals more susceptible to toxicity.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: People with kidney problems may not clear excess vitamin C efficiently, which could lead to a build-up and toxicity even at lower doses.
Fact check: True. Kidney problems increase the risk of toxicity.

Kidney dysfunction impairs vitamin C excretion, increasing the risk for toxicity even at lower levels.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Those with a tendency to develop kidney stones should monitor their vitamin C intake. High doses might increase their risk of stone formation.
Fact check: True. History of kidney stones requires caution with vitamin C.

High doses can increase risk due to increased oxalate production and a tendency to form stones.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: People with hemochromatosis, a condition where the body absorbs too much iron, need to be careful as vitamin C enhances iron absorption, potentially worsening iron overload.
Fact check: True. Hemochromatosis and high vitamin C is not a good mix.

Vitamin C enhancing iron absorption is a risk for people with hemochromatosis.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Certain medications can interact with high-dose vitamin C, like blood thinners such as warfarin. Always consult a doctor about potential supplement interactions.
Fact check: True. Vitamin C can interact with medications.

Interactions can occur, especially with blood thinners such as warfarin, as mentioned. Always consult with your doctor.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Individuals with G6PD deficiency, a genetic condition, might experience red blood cell breakdown from very high doses of vitamin C.
Fact check: True. G6PD deficiency is a risk factor.

High doses of vitamin C can potentially cause red blood cell breakdown in those with G6PD deficiency.

Claim: The Upper Tolerable Intake Level (UL) is the highest amount of daily vitamin C considered safe. Health authorities set this level to prevent toxicity, and it varies by age.
Fact check: True. There is a defined UL for Vitamin C.

The UL is intended to guide safe consumption, with age being a key consideration.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: These levels are specific to supplements and fortified foods. They do not include vitamin C that is naturally found in food, which makes it very difficult to reach these levels from diet alone.
Fact check: True. UL’s apply to supplements and fortified foods.

It is extremely difficult to reach the upper limit using food sources alone, and therefore supplements and fortified foods are the target.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: The UL is not a target to aim for. It is a maximum limit to stay below. Most individuals do not need to take doses close to the UL, as the RDA is usually sufficient for good health.
Fact check: True. The UL is a limit, not a goal.

The recommended daily allowances are sufficient for most individuals, and the UL is a maximum limit to stay under.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Pregnant and breastfeeding women have the same UL as other adults, but they should consult a doctor about their specific requirements.
Fact check: True. Pregnant and breastfeeding women have the same UL but should seek doctor advice.

While the UL is consistent, specific needs may vary. Consulting a doctor is recommended to determine individual requirements for this population.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Myth 1: You can’t get too much vitamin C.
Fact check: True. Toxicity is possible through high dose supplementation.

This is a common myth, but high doses of vitamin C can indeed lead to health issues as discussed in the text. It is always important to be wary of what you take into your body.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Myth 2: More vitamin C always means better health.
Fact check: True. More is not always better.

Once your needs are met, additional vitamin c will not improve your health. It will be eliminated through the urine.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Myth 3: High-dose vitamin C cures colds.
Fact check: True. Vitamin C does not cure colds.

Research does not support this claim, and in best-case scenarios it might slightly reduce the duration of a cold but does not cure or prevent one.

Claim: Myth 4: Vitamin C supplements are always safe.
Fact check: True. Supplements are not always safe.

Supplements can lead to interactions with other medicines, and high doses can cause side effects as described in the text.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

Claim: Myth 5: Natural vitamins can’t cause toxicity.
Fact check: True. Natural vitamins can still cause problems.

Even supplements advertised as ‘natural’ can cause problems if taken in high doses. The mechanism is the same regardless of its ‘natural’ or synthetic status.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/


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Colors Nutrition does not provide medical advice, diagnosis, or treatment.