Balancing the Risks and Benefits of Vitamin C Supplements

Mainstream medicine has long had a healthy skepticism of dietary supplements, extending to the present day with commentaries like “Enough is enough.” In an essay entitled “Battling quackery,” however, published in the Archives of Internal Medicine, it’s argued that we may have gone too far in our supplement bashing, as evidenced by our “uncritical acceptance” of supposed toxicities; the surprisingly “angry, scornful tone” found in medical texts using words like “careless,” “useless,” “indefensible,” “wasteful,” and “insidious”; and ignoring evidence of possible benefit.

“To illustrate the uncritical acceptance of bad news” about supplements, the authors discussed the “well-known” concept that high-dose vitamin C can cause kidney stones, as I highlight in my video Do Vitamin C Supplements Prevent Colds but Cause Kidney Stones? Just because something is well-known in medicine, however, doesn’t mean it’s necessarily true. In fact, the authors couldn’t find a single, reported case.

We’ve known that vitamin C is turned into oxalates in the body, and, if the level of oxalates in the urine gets too high, stones can form, but, even at 4,000 mg of vitamin C a day, which is like a couple gallons’ worth of orange juice, urinary oxalates may not get very high, as you can see at 1:10 in my video. Of course, there may be the rare individuals who have an increased capacity for this conversion into oxalates, so a theoretical risk of kidney stones with high-dose vitamin C supplements was raised in a letter printed in a medical journal back in 1973.

When the theoretical risk was discussed in the medical literature, however, the researchers made it sound as if it were an established phenomenon: “Excessive intake of vitamin C may also be associated with the formation of oxalate stones.” Sounds less like a theoretical risk and more like an established phenomenon, right? That statement had seven citations supposedly suggesting an association between excessive vitamin-C intake and the formation of oxalate kidney stones. Let’s look at the cited sources, which you can see from 1:47 in my video. One reference is the letter about the theoretical risk, which is legitimate, but another listed citation, titled “Jaundice following the administration of niacin,” has nothing to do with either vitamin C or kidney stones. What’s more, the other five citations are just references to books. That may be acceptable if the books cited primary research themselves, but, instead, there was a kind of circular logic, where the books just cite other books citing that theoretical risk letter again. So, while it looks as if there’s a lot of evidence, they’re all just expressing this opinion with no new data.

By that time, there actually were studies that followed populations of people taking vitamin C supplements and found no increased kidney stone risk among men, then later, the same was shown in women. So, you can understand the frustration of the authors of “Battling quackery” commentary that vitamin-C supplements appeared to be unfairly villainized.

The irony is that we now know that vitamin-C supplements do indeed appear to increase kidney stone risk. The same population of men referenced above was followed further out, and men taking vitamin-C supplements did in fact end up with higher risk. This has since been confirmed in a second study, though also of men. We don’t yet know if women are similarly at risk, though there has now also been a case reported of a child running into problems.

What does doubling of risk mean exactly in this context? Those taking a thousand milligrams or so of vitamin C a day may have a 1-in-300 chance of getting a kidney stone every year, instead of a 1-in-600 chance. One in 300 “is not an insignificant risk,” as kidney stones can be really painful, so researchers concluded that since there are no benefits and some risk, it’s better to stay away.

But there are benefits. Taking vitamin C just when you get a cold doesn’t seem to help, and although regular supplement users don’t seem to get fewer colds, when they do get sick, they don’t get as sick and get better about 10 percent faster. And, those under extreme physical stress may cut their cold risk in half. So, it’s really up to each individual to balance the potential common cold benefit with the potential kidney stone risk.


What about intravenous vitamin C? I’ve got a whole video series on that, including:

If you’re not taking vitamin C supplements for pharmacological effects and just want to know how many vitamin C-rich fruits and vegetables to eat every day, check out my video What Is the Optimal Vitamin C Intake?.

Is there anything we can put into our mouth that really might help prevent colds? These videos will point you in the right direction:

And, if you’re interested in learning about the most important steps you can take to prevent and treat kidney stones, look no further than my videos How to Prevent Kidney Stones with Diet and How to Treat Kidney Stones with Diet.

What about high-oxalate vegetables such as rhubarb, spinach, beet greens and swiss chard? I’d encourage a moderation in intake. If you’re going to take my advice to ideally eat cups of dark green leafy vegetables a day I’d recommend sticking with other greens such as kale or collards.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Why Did Doctors Keep Prescribing Cancer?

We’ve known about the role of estrogen in breast cancer going back to the 1800s, when surgical removal of the ovaries seemed to help in some cases. Ovaries were said to send out “mysterious” influences to the rest of the body, which were identified as estrogen in 1923. The medical profession jumped on this discovery and started injecting menopausal women by the thousands, and it was said that “[t]he ‘shot’ gives a ‘respectable’ hook on which to hang the visit to the doctor…” Soon, there were pills and patches, and medical journals like the Journal of the American Medical Association regaled doctors with ads I feature in my video How Did Doctors Not Know About the Risks of Hormone Therapy? on how they can “help the women to happiness by simply prescribing estrogen” and, “[w]hen women outlive their ovaries…,” there is Premarin.

As far back as the 1940s, concerns were raised that this practice might cause breast cancer, noting it would have been nice to figure this out before we started dosing women en masse. But breast cancer risk didn’t seem to matter as much, because heart disease was the number-one killer of women, reviews concluded, and because women taking hormones appeared to have lower heart attack rates, which would outweigh any additional breast cancer. However, women taking estrogen tended to be of a higher socioeconomic class, exercised more, and engaged in other healthy lifestyle changes like consuming more dietary fiber and getting their cholesterol checked. So, maybe that’s why women taking estrogen appeared to be protected from heart disease. Perhaps it had nothing to do with the drugs themselves. Despite the medical profession’s “enthusiasm for estrogen replacement therapy,” only a randomized clinical trial could really resolve this question. We would need to divide women into two groups, with half getting the hormones and half getting a placebo, and follow them out for a few years. There was no such study…until the 1990s, when the Women’s Health Initiative study was designed.

Wait a second. Why did it take the bulk of a century to decide to definitively study the safety of something prescribed to millions of women? Perhaps because there had never been a female director of the National Institutes of Health until then. “Just three weeks after being named NIH Director in 1991, [Bernadine Healy] went before Congress to announce, ‘We need a moon walk for women.’ That ‘moon walk’ took the form of the Women’s Health Initiative, the most definitive, far-reaching clinical trial of women’s health ever undertaken in the United States.”

The bombshell landed in summer 2002. There was so much more invasive breast cancer in the hormone users that they were forced to stop the study prematurely. What about heart disease? Wasn’t that supposed to balance things out? The women didn’t just have more breast cancer—they had more heart attacks, more strokes, and more blood clots to their lungs.

The news that women treated with hormone replacement therapy “experienced higher rates of breast cancer, cardiovascular disease, and overall harm has rocked women and physicians across the country.” Estrogen started out as the most prescribed drug in America before the study, but, after, the number of prescriptions dropped immediately and, within a year, so did the incidence of breast cancer in the United States.

The most important question about this story is why were we all so surprised? There had been “decades of repeated warnings” about the risks of cancer. In fact, the reason breast cancer patients had so much trouble suing the pharmaceutical company was that “the drugs have contained warning labels for decades.” And, with that disclosure, surely any reasonable physician would have included it in their risk and benefit discussions with their patients, right? It’s like the warning labels on packs of cigarettes. If you get lung cancer now, you should have known better. And, so, if you were on hormone replacement therapy and got breast cancer, don’t blame the drug company. They warned you about the risks, right there in the fine print.

Why didn’t more doctors warn their patients? Even after the study came out, millions of prescriptions continued to be dispensed. That’s a lot of cancer in our patients we caused, wrote one doctor. “How long will it take us to discard the financial gains, to admit that we are harming many of our patients, and to start changing our prescription habits?”

“Why did this practice continue in the face of mounting evidence of harm?” Well, it is a multibillion-dollar industry. “Despite an overwhelming amount of evidence to the contrary, many physicians still believe that estrogenic hormones have overall health benefits,” a “non-evidence-based perception [that] may be the result of decades of carefully orchestrated corporate influence on medical literature.” Indeed, “[d]ozens of ghostwritten reviews and commentaries published in medical journals and supplements were used to promote unproven benefits and downplay harms of menopausal hormone therapy…” PR companies were paid to write the articles that were then passed off as having been written by some expert.

What now? “Gynecologists must switch allegiance from eminence-based to evidence-based medicine.” In other words, they must consider what the science says and not just what some so-called expert says. It’s been said that the “current culture of gynecology encourages the dissemination of health advice based on advertising rather than science.”

“Women were placed in the way of harm by their physicians, who acted as unsuspecting patsies for the pharmaceutical companies.” If we really wanted to prevent heart attacks in women, simple lifestyle behaviors can eliminate more than 90 percent of heart attack risk. So, instead of being Big Pharma’s pawns, “recommending a healthful diet, increased exercise, and smoking cessation would truly benefit women’s health.”


The whole Premarin debacle speaks to the importance of putting purported therapies to the test (see, for example, Do Vitamin D Supplements Help with Diabetes, Weight Loss, and Blood Pressure?), as well as to the power of Big Pharma (Eliminating Conflicts of Interest in Medical Research), medical community collusion (American Medical Association Complicity with Big Tobacco), and my most series on mammograms.

What about Plant-Based Bioidentical Hormones and Soy Phytoestrogens for Menopause Hot Flashes? Check out the videos to find out.

In general, patients (and doctors) tend to wildly overestimate the efficacy of pills and procedures. See Why Prevention Is Worth a Ton of Cure and The Actual Benefit of Diet vs. Drugs.

Medical care, in general, may be the third leading cause of death in the United States. See How Doctors Responded to Being Named a Leading Killer.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Reversing Massive Obesity With Diet

Dr. Walter Kempner introduced the first comprehensive dietary program to treat chronic kidney disease and, in doing so, also revolutionized the treatment of other disorders, including obesity. Kempner was Professor Emeritus of Medicine at Duke, where he came up with the so-called rice diet, which basically consisted of rice, sugar, fruit, and fruit juices, was extremely low in sodium and fat, and included no animal fat, no cholesterol, and no animal protein. The sugar was added as a source of calories so people wouldn’t lose too much weight. But some people need to lose weight, so he started treating obese patients with a lower calorie version of the diet, which I discuss in my Can Morbid Obesity Be Reversed Through Diet? video.

He published an analysis of 106 patients who each lost at least 100 pounds. Why 106? Kempner simply picked the last 100 people who lost more than 100 pounds, and, by the time he finished reviewing their charts, 6 more had joined the so-called century club. Average weight loss among them was 141 pounds. “This study demonstrates that massively obese persons can achieve marked weight reduction, even normalization of weight, without hospitalization, surgery, or pharmacologic intervention…[O]ne important fact to be gained from this study is that, despite the misconception to the contrary, massive obesity is not an uncorrectable malady. Weight loss can be achieved, massive obesity can be corrected, and it can be done without drastic intervention.”

Well, Kempner’s rice diet is pretty drastic, so definitely don’t try this at home. In fact, the rice diet is dangerous. It’s so restrictive that it may cause serious electrolyte imbalances, unless the patient is carefully medically supervised with frequent blood and urine lab testing. Dangerous? Says who? Said the world’s number-one advocate for the rice diet: Dr. Kempner himself.

The best, safe approximation of the diet, meaning low in sodium and without fat, protein, or cholesterol from animals, would be a vitamin B12-fortified diet centered around whole, unprocessed plant foods. However, even a medically supervised rice diet could be considered un-drastic compared to procedures like getting one’s internal organs stapled or rearranged, wiring someone’s jaws shut, or even undergoing brain surgery.

Attempts have been made to destroy the parts of the brain associated with the sensation of hunger, by irradiation or going in through the skull and burning them out. “It shows how ineffective most simpler forms of treatment are that anyone should think it reasonable to produce irreversible intracranial lesions in very obese patients.” The surgeons defended these procedures, however, explaining that their “justification in attempting the operation is, of course, the very poor results of conventional therapy in gross obesity, and the dark prognosis, mental and physical, of the uncorrected condition.” In reply, a critic countered, “Such strong feelings [about how dark the prognosis is] run the risk of being conveyed to the patient, to the effect of masking the operative dangers and steam-rolling the patient’s approval.” The surgeon replied, “If any ‘steamrolling’ is taking place, it comes rather from obese patients who sometimes threaten suicide unless they are accepted for experimental surgical treatment.”

As of 2013, the American Medical Association officially declared obesity a disease, by identifying the enormous humanitarian impact of obesity as requiring the medical care and attention of other diseases. Yet the way we treat diseases these days involves drugs and surgery. Anti-obesity drugs have been pulled from the market again and again after they started killing people—an unrelenting fall of the pharmacological treatment of obesity.

The same has happened with obesity surgeries. The procedure Kempner wrote about was discontinued because of the complication of causing irreversible cirrhosis of the liver. Current procedures include various reconfigurations of the digestive tract. Complications of surgery appear to occur in about 20 percent of patients, and nearly one in ten of which may be death. In one of the largest studies, 1.9 percent of patients died within a month of the surgery. “Even if surgery proves sustainably effective, the need to rely on the rearrangement of [our] anatomy as an alternative to better use of feet and forks [that is, diet and exercise] seems a societal travesty.”


For more on Kempner and his rice diet, see my videos:

Learn more on the surgical approach in Reversing Diabetes with Surgery and Stomach Stapling Kids.

And, for more on weight, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: