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Does Too Much Vitamin C Cause Side Effects?

Health + Wellness
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By Brianna Elliott, RD

Vitamin C is a very important nutrient that's abundant in many fruits and vegetables.


Getting enough of this vitamin is especially important for maintaining a healthy immune system. It also plays an important role in wound healing, keeping your bones strong, and enhancing brain function.

Interestingly, some claim that vitamin C supplements provide benefits beyond those that can be obtained from the vitamin C found in food.

One of the most common reasons people take vitamin C supplements is the idea that they help prevent the common cold.

However, many supplements contain extremely high amounts of the vitamin, which can cause undesirable side effects in some cases.

This article explores the overall safety of vitamin C, whether it's possible to consume too much, and the potential adverse effects of taking large doses.

Vitamin C is Water-Soluble and Not Stored in Your Body

Vitamin C is a water-soluble vitamin, which means it dissolves in water.

In contrast to fat-soluble vitamins, water-soluble vitamins do not get stored within the body.

Instead, the vitamin C that you consume gets transported to your tissues via body fluids, and any extra gets excreted in urine (1Trusted Source).

Since your body does not store vitamin C or produce it on its own, it's important to consume foods that are rich in vitamin C daily (1Trusted Source).

However, supplementing with high amounts of vitamin C can lead to adverse effects, such as digestive distress and kidney stones.

That's because if you overload your body with larger-than-normal doses of this vitamin, it will start to accumulate, potentially leading to overdose symptoms (3Trusted Source).

It's important to note that it's unnecessary for most people to take vitamin C supplements, as you can easily get enough by eating fresh foods, especially fruits and vegetables (1Trusted Source).

Summary

Vitamin C is water-soluble, so it's not stored within your body. If you consume more than your body needs, it's excreted in your urine.

Too Much Vitamin C May Cause Digestive Symptoms

The most common side effect of high vitamin C intake is digestive distress.

In general, these side effects do not occur from eating foods that contain vitamin C, but rather from taking the vitamin in supplement form.

You're most likely to experience digestive symptoms if you consume more than 2,000 mg at once. Thus, a tolerable upper limit (TUL) of 2,000 mg per day has been established.

The most common digestive symptoms of excessive vitamin C intake are diarrhea and nausea.

Excessive intake has also been reported to lead to acid reflux, although this is not supported by evidence.

If you're experiencing digestive problems as a result of taking too much vitamin C, simply cut back your supplement dose or avoid vitamin C supplements altogether.

Summary

Ingesting more than 2,000 mg of vitamin C per day may lead to gastrointestinal upset, including symptoms like diarrhea and nausea.

Vitamin C May Cause Iron Overload

Vitamin C is known to enhance iron absorption.

It can bind to non-heme iron, which is found in plant foods. Non-heme iron is not absorbed by your body as efficiently as heme iron, the type of iron found in animal products.

Vitamin C binds with non-heme iron, making it much easier for your body to absorb. This is an important function, especially for individuals who get most of their iron from plant-based foods.

One study in adults found that iron absorption increased by 67% when they took 100 mg of vitamin C with a meal.

However, individuals with conditions that increase the risk of iron accumulation in the body, such as hemochromatosis, should be cautious with vitamin C supplements.

Under these circumstances, taking vitamin C in excess may lead to iron overload, which can cause serious damage to your heart, liver, pancreas, thyroid, and central nervous system.

That said, iron overload is highly unlikely if you don't have a condition that increases iron absorption. Additionally, iron overload is more likely to occur when excess iron is consumed in supplement form.

Summary

Since vitamin C increases iron absorption, consuming too much of it is a concern for individuals with conditions that lead to iron accumulation in the body.

Taking Supplements in High Doses May Lead to Kidney Stones

xcess vitamin C is excreted from the body as oxalate, a bodily waste product.

Oxalate typically exits the body via urine. However, under some circumstances, oxalate may bind to minerals and form crystals that can lead to the formation of kidney stones.

Consuming too much vitamin C has the potential to increase the amount of oxalate in your urine, thus increasing the risk of developing kidney stones.

In one study that had adults take a 1,000-mg vitamin C supplement twice daily for 6 days, the amount of oxalate they excreted increased by 20%.

High vitamin C intake is not only associated with greater amounts of urinary oxalate but also linked to the development of kidney stones, especially if you consume amounts greater than 2,000 mg.

Reports of kidney failure have also been reported in people who have taken more than 2,000 mg in a day. However, this is extremely rare, especially in healthy people.

Summary

Consuming too much vitamin C may increase the amount of oxalate in your kidneys, which has the potential to lead to kidney stones.

How Much Vitamin C is Too Much?

Since vitamin C is water-soluble and your body excretes excess amounts of it within a few hours after you consume it, it's quite difficult to consume too much.

In fact, it is nearly impossible for you to get too much vitamin C from your diet alone. In healthy people, any extra vitamin C consumed above the recommended daily amount simply gets flushed out of the body.

To put it in perspective, you would need to consume 29 oranges or 13 bell peppers before your intake reached the tolerable upper limit.

However, the risks of vitamin C overdose are higher when people take supplements, and it is possible to consume too much of the vitamin in some circumstances.

For example, those with conditions that increase the risk of iron overload or are prone to kidney stones should be cautious with their vitamin C intake.

All the adverse effects of vitamin C, including digestive distress and kidney stones, appear to occur when people take it in mega doses greater than 2,000 mg.

If you choose to take a vitamin C supplement, it is best to choose one that contains no more than 100% of your daily needs. That's 90 mg per day for men and 75 mg per day for women.

Summary

It's nearly impossible to consume too much vitamin C from food. However, if you're supplementing with this vitamin, you can minimize your risk of getting too much by taking no more than 90 mg per day if you're a man, or 75 mg per day if you're a woman.

The Bottom Line

Vitamin C is generally safe for most people.

This is especially true if you get it from foods, rather than supplements.

Individuals who take vitamin C in supplement form are at greater risk of consuming too much of it and experiencing side effects, the most common of which are digestive symptoms.

However, more serious consequences, such as iron overload and kidney stones, may also result from taking extreme amounts of vitamin C.

Fortunately, it's easy to prevent these potential side effects — simply avoid vitamin C supplements.

Unless you have a vitamin C deficiency, which rarely occurs in healthy people, it is probably unnecessary for you to take large doses of this vitamin.

Reposted with permission from Healthline. For detailed source information, please view the original article on Healthline.

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Guillain-Barre syndrome occurs when the body's own immune system attacks and injures the nerves outside of the spinal cord or brain – the peripheral nervous system. Niq Steele / Getty Images

By Sherry H-Y. Chou, Aarti Sarwal and Neha S. Dangayach

The patient in the case report (let's call him Tom) was 54 and in good health. For two days in May, he felt unwell and was too weak to get out of bed. When his family finally brought him to the hospital, doctors found that he had a fever and signs of a severe infection, or sepsis. He tested positive for SARS-CoV-2, the virus that causes COVID-19 infection. In addition to symptoms of COVID-19, he was also too weak to move his legs.

When a neurologist examined him, Tom was diagnosed with Guillain-Barre Syndrome, an autoimmune disease that causes abnormal sensation and weakness due to delays in sending signals through the nerves. Usually reversible, in severe cases it can cause prolonged paralysis involving breathing muscles, require ventilator support and sometimes leave permanent neurological deficits. Early recognition by expert neurologists is key to proper treatment.

We are neurologists specializing in intensive care and leading studies related to neurological complications from COVID-19. Given the occurrence of Guillain-Barre Syndrome in prior pandemics with other corona viruses like SARS and MERS, we are investigating a possible link between Guillain-Barre Syndrome and COVID-19 and tracking published reports to see if there is any link between Guillain-Barre Syndrome and COVID-19.

Some patients may not seek timely medical care for neurological symptoms like prolonged headache, vision loss and new muscle weakness due to fear of getting exposed to virus in the emergency setting. People need to know that medical facilities have taken full precautions to protect patients. Seeking timely medical evaluation for neurological symptoms can help treat many of these diseases.

What Is Guillain-Barre Syndrome?

Guillain-Barre syndrome occurs when the body's own immune system attacks and injures the nerves outside of the spinal cord or brain – the peripheral nervous system. Most commonly, the injury involves the protective sheath, or myelin, that wraps nerves and is essential to nerve function.

Without the myelin sheath, signals that go through a nerve are slowed or lost, which causes the nerve to malfunction.

To diagnose Guillain-Barre Syndrome, neurologists perform a detailed neurological exam. Due to the nerve injury, patients often may have loss of reflexes on examination. Doctors often need to perform a lumbar puncture, otherwise known as spinal tap, to sample spinal fluid and look for signs of inflammation and abnormal antibodies.

Studies have shown that giving patients an infusion of antibodies derived from donated blood or plasma exchange – a process that cleans patients' blood of harmful antibodies - can speed up recovery. A very small subset of patients may need these therapies long-term.

The majority of Guillain-Barre Syndrome patients improve within a few weeks and eventually can make a full recovery. However, some patients with Guillain-Barre Syndrome have lingering symptoms including weakness and abnormal sensations in arms and/or legs; rarely patients may be bedridden or disabled long-term.

Guillain-Barre Syndrome and Pandemics

As the COVID-19 pandemic sweeps across the globe, many neurologic specialists have been on the lookout for potentially serious nervous system complications such as Guillain-Barre Syndrome.

Though Guillain-Barre Syndrome is rare, it is well known to emerge following bacterial infections, such as Campylobacter jejuni, a common cause of food poisoning, and a multitude of viral infections including the flu virus, Zika virus and other coronaviruses.

Studies showed an increase in Guillain-Barre Syndrome cases following the 2009 H1N1 flu pandemic, suggesting a possible connection. The presumed cause for this link is that the body's own immune response to fight the infection turns on itself and attacks the peripheral nerves. This is called an "autoimmune" condition. When a pandemic affects as many people as our current COVID-19 crisis, even a rare complication can become a significant public health problem. That is especially true for one that causes neurological dysfunction where the recovery takes a long time and may be incomplete.

The first reports of Guillain-Barre Syndrome in COVID-19 pandemic originated from Italy, Spain and China, where the pandemic surged before the U.S. crisis.

Though there is clear clinical suspicion that COVID-19 can lead to Guillain-Barre Syndrome, many important questions remain. What are the chances that someone gets Guillain-Barre Syndrome during or following a COVID-19 infection? Does Guillain-Barre Syndrome happen more often in those who have been infected with COVID-19 compared to other types of infections, such as the flu?

The only way to get answers is through a prospective study where doctors perform systematic surveillance and collect data on a large group of patients. There are ongoing large research consortia hard at work to figure out answers to these questions.

Understanding the Association Between COVID-19 and Guillain-Barre Syndrome

While large research studies are underway, overall it appears that Guillain-Barre Syndrome is a rare but serious phenomenon possibly linked to COVID-19. Given that more than 10.7 million cases have been reported for COVID-19, there have been 10 reported cases of COVID-19 patients with Guillain-Barre Syndrome so far – only two reported cases in the U.S., five in Italy, two cases in Iran and one from Wuhan, China.

It is certainly possible that there are other cases that have not been reported. The Global Consortium Study of Neurological Dysfunctions in COVID-19 is actively underway to find out how often neurological problems like Guillain-Barre Syndrome is seen in hospitalized COVID-19 patients. Also, just because Guillain-Barre Syndrome occurs in a patient diagnosed with COVID-19, that does not imply that it was caused by the virus; this still may be a coincident occurrence. More research is needed to understand how the two events are related.

Due to the pandemic and infection-containment considerations, diagnostic tests, such as a nerve conduction study that used to be routine for patients with suspected Guillain-Barre Syndrome, are more difficult to do. In both U.S. cases, the initial diagnosis and treatment were all based on clinical examination by a neurological experts rather than any tests. Both patients survived but with significant residual weakness at the time these case reports came out, but that is not uncommon for Guillain-Barre Syndrome patients. The road to recovery may sometimes be long, but many patients can make a full recovery with time.

Though the reported cases of Guillain-Barre Syndrome so far all have severe symptoms, this is not uncommon in a pandemic situation where the less sick patients may stay home and not present for medical care for fear of being exposed to the virus. This, plus the limited COVID-19 testing capability across the U.S., may skew our current detection of Guillain-Barre Syndrome cases toward the sicker patients who have to go to a hospital. In general, the majority of Guillain-Barre Syndrome patients do recover, given enough time. We do not yet know whether this is true for COVID-19-related cases at this stage of the pandemic. We and colleagues around the world are working around the clock to find answers to these critical questions.

Sherry H-Y. Chou is an Associate Professor of Critical Care Medicine, Neurology, and Neurosurgery, University of Pittsburgh.

Aarti Sarwal is an Associate Professor, Neurology, Wake Forest University.

Neha S. Dangayach is an Assistant Professor of Neurology and Neurosurgery, Icahn School of Medicine at Mount Sinai.

Disclosure statement: Sherry H-Y. Chou receives funding from The University of Pittsburgh Clinical Translational Science Institute (CTSI), the National Institute of Health, and the University of Pittsburgh School of Medicine Dean's Faculty Advancement Award. Sherry H-Y. Chou is a member of Board of Directors for the Neurocritical Care Society. Neha S. Dangayach receives funding from the Bee Foundation, the Friedman Brain Institute, the Neurocritical Care Society, InCHIP-UConn Center for mHealth and Social Media Seed Grant. She is faculty for emcrit.org and for AiSinai. Aarti Sarwal does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Reposted with permission from The Conversation.