When Vitamin C Becomes Toxic

Posted on Categories Discover Magazine

On a warm July morning, Sasmit Roy was easing into his day at Centra Lynchburg General Hospital in Virginia. As a consulting nephrologist, Roy gets called in when patients have kidney issues the general hospital staff need help with. He was reviewing the patients on his caseload when he was alerted to a new patient, admitted the night before, in potential kidney distress.

Jeanne’s face was turned toward the window when Roy walked into her room, but he could immediately tell she was worried: The 74-year-old was undergoing treatment for endometrial cancer, where cancer cells are found in the lining of the uterus. Now, she was up against another medical challenge. Retired and looking forward to her granddaughter’s upcoming wedding, she just wanted to be healthy enough to spend time with her family.

Life seemed to have alternate plans for Jeanne, though. Her oncologist had referred her to the hospital after standard blood tests showed abnormally high creatinine readings. Jeanne’s levels of this compound, which forms as proteins break down in muscles, were higher than normal — much higher. While typical creatinine levels register anywhere from 0.5 to 1.1 milligrams per deciliter of fluid, Jeanne’s creatinine clocked in at 6.8, almost seven times above normal. The compound is usually filtered out of the bloodstream by the kidneys, so high levels of creatinine are an immediate red flag for kidney issues.

(Credit: Kellie Jaeger/Discover)

Running through the checklist

First, Roy needed to rule out the simplest explanation for the creatinine spike: whether or not his patient was simply dehydrated. Dehydration is not uncommon in patients on chemotherapy drugs, like Jeanne, who often don’t feel up to eating or drinking or who might be vomiting. He started her on a saline drip and sent for a standard workup, including an ultrasound to check for obstructions or tumors on the kidneys.

Your kidneys sit just below your rib cage, nestled behind the stomach, liver and pancreas, curved like two commas. Their main role is to filter your blood — about half a cup every minute — removing waste materials and excess fluid to be excreted as urine. Blood runs through structures in the kidney called nephrons, which are divided into two parts, the glomerulus and the tubule. The glomerulus does the filtering, while the tubule sends blood and other crucial material back into the bloodstream.

Conditions like diabetes, lupus, and high blood pressure can damage the kidneys over time, reducing their ability to function. Infections, some kinds of cancer, and some medications can also cause a condition called nephritis, or inflammation of the nephrons, that can quickly lead to kidney failure.

When Jeanne’s ultrasound came back showing nothing visibly wrong with her kidneys, Roy started running through the checklist. He sent out for blood and urine tests to check for nephritis, and sat down with Jeanne to dig deeper into her history.

At Jeanne’s bedside, Roy could tell right away that something had changed since he’d last seen her. She’d grown noticeably pale, and had also become drowsy and nauseous. The visible signs backed up his hunch that something serious was going on. Perhaps she was allergic to the chemotherapy drug, paclitaxel, that she’d been receiving via injection for the past six months.

Meanwhile, Jeanne’s tests came back “absolutely clean,” even as her physical condition argued otherwise. Perhaps more worrying, her creatinine numbers were drifting even higher, a clear signal that something was affecting her kidneys. On top of that, her blood was growing steadily more acidic — another kidney warning sign. Jeanne’s kidneys were failing. Unless dialysis was performed to clean the blood toxins that were already accumulating inside her body, a host of cardiac and neurological complications — and even death — could follow.

“That’s when things started getting really serious,” Roy says. With little else to go on, Roy went back to Jeanne’s bedside. She’s a cancer patient, he thought. Am I missing something, or is she taking anything that she hasn’t told me?

Half an hour into an exhaustive review of Jeanne’s treatment history and cancer journey, a new detail emerged — a “little thing” she’d forgotten to mention until then. For the past few months, Jeanne had been seeing a doctor in Charlottesville who’d been giving her injections to help her feel better and improve her appetite.

The news of mystery injections sent alarm bells clanging in Roy’s mind. A few more questions revealed their contents: vitamin C.

Taking a few extra doses of one of the most common vitamins in the world might seem harmless. But, as the adage goes, the dose makes the poison. Jeanne was getting weekly intravenous doses of 100 grams of vitamin C, or a whopping 50 times the safe upper limit per day. Suddenly, her mysterious kidney issues snapped into focus.

Taking action

Vitamin C, also called ascorbic acid, is a crucial supplement. We need it to make connective tissue, heal wounds, and synthesize neurotransmitters. It plays an important role in the immune system, and also acts as a potent antioxidant. Our bodies don’t make much vitamin C by themselves, so we need to get it from our diets. Vitamin C is found in many fruits and vegetables, like citrus fruits, bell peppers, and tomatoes, and for those who might want more, it’s commonly found in tablet form.

Many commercially available vitamin C supplements are around 500 milligrams of vitamin C. The doses Jeanne was getting clocked in at 100,000 milligrams per week, or the equivalent of downing an entire bottle of vitamin C pills at once. Her treatments had been administered by an alternative medicine physician, based on preliminary evidence that megadoses of the vitamin might play a role in treating cancer. It’s currently being studied for its potential to help with sepsis and severe burns, as well.

But instead, Jeanne’s injections were killing her kidneys. Vitamin C is turned into a compound called oxalate in the kidneys as they process it for removal. Oxalate forms sharp-edged crystals, which, in high enough amounts, can accumulate in kidney tubules and block them.

Normally, your kidneys can clear excess vitamin C from your bloodstream. “But if it exceeds a certain limit, then the kidneys’ capacity to filter it is saturated, so then it tends to build up,” Roy says.

The results of a kidney biopsy confirmed his suspicions: Jeanne’s kidneys had been overwhelmed with vitamin C, and oxalate crystals were clogging her kidney tubules, causing the organ to fail as cells began dying. Roy immediately started Jeanne on dialysis, which took over her kidneys’ role of filtering her bloodstream, hopefully giving them a chance to heal themselves. Jeanne had received a cumulative dose of 600 grams of vitamin C over six weeks. Looking through the scientific literature afterward, Roy found that was higher than any dosage previously reported. Intravenous injections like hers are particularly dangerous, as they hit the bloodstream all at once.

Roy had the delicate task of breaking the news to Jeanne, who’d been placing her trust in an alternative doctor who turned out to have nearly killed her. He proceeded with empathy, gently breaking down what was happening in her kidneys and explaining that her injections were likely to blame. Unsurprisingly, the news was shocking. Jeanne was visibly upset, and went so far as to call the alternative medicine doctor in front of Roy to take the man to task for his actions.

With dialysis, Jeanne’s condition stabilized, and she was eventually discharged from the hospital. Luckily, she was able to attend her granddaughter’s wedding, and has enjoyed spending time with her family again, even as she continues to battle cancer. Unfortunately, the damage to her kidneys proved to be permanent; she still relies on dialysis sessions three times a week to stay healthy.

For Roy, the experience was a case study in being direct and empathetic with patients. “Always talk to the patient and ask them what else they’ve been taking,” he says. “They might be very hesitant, but sit with them; just be reassuring.” Patients seeking alternative treatments can often feel like they’ve exhausted their options, particularly when they’re facing a frightening diagnosis. Alternative therapies aren’t always harmful, but, as Jeanne found, patients don’t always know what they’re getting into.

This story was originally published in our March April 2024 issue. Click here to subscribe to read more stories like this one.

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