 Let's say you really need to find reliable information about the best diet for high blood pressure, or heart disease, or diabetes. Where do you go? Do you go to a website sponsored by Big Pharma that wants to sell you pills to fix your problem? Or do you want to treat the cause? Welcome to the Nutrition Facts podcast with the latest peer-reviewed research on the best ways to eat healthy and live longer. Today we take a close look at the mighty power of vitamin C, and we start with the risks and benefits of using vitamin C for depression and anxiety. Emerging evidence suggests that higher daily intake of fiber-rich fruits and vegetables is associated with lower incidences of anxiety in adults, and at the same time greater happiness, higher life satisfaction, and greater emotional well-being. So persuading people to consume more fruits and vegetables may not only benefit their physical health in the long run, but also their mental well-being in the short run. Fruit consumption, for example, has protective association with leaving killers, like heart disease, stroke, diabetes, and cancer, as well as depression. The question is, why? Several different mechanisms have been proposed. For example, it may be the antioxidants and anti-inflammatory properties of produce, like averaging the free radicals that are involved in some of the inflammation associated with depression. If that's the case, what about just taking vitamin C supplements? The brain has some of the highest levels of vitamin C in the body, so the thought is, if we take extra vitamin C, it may have some sort of therapeutic role in brain diseases, especially given it's not just an antioxidant, but also has other critical functions in the brain, such as helping to build neurotransmitters like dopamine, so you don't know whether it actually helps until you put it to the test. One study found a beneficial effect, adding vitamin C as an adjunct treatment to an anti-depressant, while another study found no benefit from vitamin C supplementation. So there are mixed results for vitamin C and depression. Here's another study that found no benefit when it came to depression, but those randomized to vitamin C instead of placebo pills did show a significant decrease in anxiety level. And this wasn't only seen in this study. The effects of oral vitamin C supplementation on anxiety in students, double-blind, randomized, placebo-controlled trial. High school students were given 500 milligrams a day, or placebo. 500 milligrams of vitamin C is about what you find in five oranges for yellow kiwi fruit or guavas, or one and a half yellow bell peppers. Within just two weeks, the vitamin C reduced anxiety compared to placebo, along with providing a significant drop in heart rate. Given these data showing vitamin C may have anxiety-reducing effects, researchers sought to find out if only a single dose could acutely affect emotional states. And indeed, within only two hours of taking some C, subjects experienced a significant drop in anxiety compared to placebo, though only among those who started out the most anxious in the first place. As a bonus, vitamin C supplementation may lower your blood pressure for a few points, but whole fruits and vegetables can do the same thing and may even do it better for those who need it the most. As I've shown previously, even just adding two servings of fruits and vegetables a day can have psychological well-being benefits within only two weeks, and you won't be put at risk of kidney stones like you would with vitamin C supplements, though that appears to be only a problem in men. Here's a fun fact. There are now experiments that can show how much vitamin C our body absorbs and excretes. Here's the story. For many years, the RDA, the recommended daily allowance for vitamins, was just based on preventing deficiency with a margin of safety. But the minuscule amount of vitamin C, for example, needed to avoid scurvy, not necessarily the ideal intake for optimal health. So what might be the optimal intake of vitamin C? Let's ask the body. How might we do that? By seeing how much the body absorbs and excretes. If you swallow 15 milligrams of vitamin C, which is what you get eating about a quarter of an orange, your body sucks up nearly 90% of it. But if you take a supplement containing 1250 milligrams, your body seems to realize that's too much, and so clamps down on absorption at the intestinal lining level, and you end up absorbing less than half. So by doing experiments where you slowly ratchet up the intake, you can see when the body starts to say, OK, that's enough. And that magic level of intake appears to be about 200 milligrams a day. When you take up to 200 a day, your body sucks it all up. But above that, your body tries to block further absorption, suggesting our intestinal vitamin C transport mechanisms have evolved to fully absorb up to about 200 milligrams of vitamin C a day. In addition, vitamin C is reabsorbed in our kidneys back into our bloodstream to maintain our vitamin C blood levels up at around 70 or 80 micromoles per liter, which is what you reach at a vitamin C intake of about 200 milligrams a day. So even if you take 10 times as much vitamin C supplements, you know, 2,000 milligrams a day, your body will just pee and poop it out to keep your blood levels in that narrow range. So based on these kind of data, one might propose that 200 milligrams is the optimal daily intake of vitamin C. You can confirm using disease data at what daily intake of vitamin C is there the lowest stroke risk, for example, apparently at about 200 milligrams a day. While dietary vitamin C intake was associated with a lower stroke risk, vitamin C supplements were not, which is consistent with the overall body of evidence showing that antioxidant supplements in general don't seem to protect against heart attacks or strokes. But wait, can you get all the way up to an intake of 200 milligrams a day without taking supplements? No problem. Single servings of fruits and vegetables may have about 50 milligrams each, so a measly 5 servings of fruits and veggies a day could get you to ideal blood levels. Finally today, what can we conclude about the role of IV vitamin C after 33 years of trials involving more than 1,500 patients? Studies in the 70s showed an extraordinary survival gain in terminal cancer patients with vitamin C is simple, relatively non-toxic therapy, and so no wonder it got a lot of attention, especially when reported by a world-renowned scientist Linus Pauling. But studies like this in the 1980s found no such benefit, and so last they were left with the inevitable conclusion that the apparent positive results in the original study were the product of bias rather than treatment effectiveness. In the 1990s though, an alternative explanation arose. The disappointing 80s research only used oral vitamin C, whereas the apparently successful 70s experiments also gave vitamin C intravenously, and we didn't realize until the 90s that the same dose given IV can lead to dramatically higher levels in the bloodstream than if taken orally. So maybe high-dose vitamin C does help in terminal cancer, but maybe only when given intravenously. Encouraging case reports continued to be published. Here there was a regression, remission, and cured, documented, and individual cases of advanced kidney cancer, bladder cancer, and lymphoma. But that's three success stories out of how many. I mean, if it was 3 out of 100 or even 3 out of 1,000, well, okay, if the treatment is sufficiently non-toxic. But there's evidence that IV vitamin C is widely used in the alternative medicine world, as in 86% of practitioners serve it. Just those 172 practitioners alone treated about 10,000 patients a year, and you ask the manufacturers, and they're selling hundreds of thousands of vials of the stuff in the US. Now it's not all being used for cancer, but presumably at least thousands of cancer patients are being treated every year with IV vitamin C. Making the publication of three remarkable case reports seemed less impressive. So no matter how amazing these cases seemed, it's possible the cancer's just spontaneously regressed all on their own and was just a coincidence that happened after they were given vitamin C. To know for sure you have to put it to the test. To date, there's been some small pilot studies, and the results so far have been disappointing. The good news is that even insane doses of IV vitamin C seem remarkably safe, but failed in this study of two dozen patients to demonstrate anti-cancer activity. Similar small studies have been published all the way through to the present, with tantalizing but inconclusive results. What we do know is that the present state of cancer treatment is unsatisfactory. People have this perception that chemotherapy will significantly enhance their chances for a cure, but put all our cancer killing chemo together, and the overall contribution to five-year survival is on the order of two percent. All those side effects for 2.1 percent, at a cost of maybe $100,000 per patient per year. So it may be worth looking deeper into therapies like IV vitamin C. However, the lack of financial reward, since vitamin C can't be patented and sold for $100,000, and bias against alternative medicine could dissuade conventional investigators and funding agencies from seriously considering this approach. So decades later, what can we conclude? After trials which have included at least 1,600 patients over 33 years, we have to conclude that we still don't know whether vitamin C is any clinically significant anti-tumor activity. Although there is currently no definitive evidence of benefit, the Mayo Clinic randomized controlled trials did not negate the potential benefit based on what we now know about the oral versus IV routes of administration. So we're kind of back to square one. Does it work or not? There are highly polarized views on both sides, but everyone's working off the same incomplete data. What we need are carefully controlled clinical trials. The question is, what do we do until then? If it was completely non-toxic, then one would argue, well, buddy, you've got to lose. But it's not. It's only relatively non-toxic. For example, there have been rare but serious cases of kidney injury reported. After all, if it's so safe, why did our bodies evolve to so tightly control against excess absorption? It can also be expensive and time consuming. Each infusion costs $1 to $200 out of pocket since insurance doesn't pay for them, which can be quite a boon for alternative medicine practitioners. About 90% of the millions of doses of vitamin C being dispensed are in for-profit arrangements. So there's financial pressures pushing in both directions for and against this treatment. Now, given the relative safety and expense, though, if controlled studies even find a small benefit, it would be worthwhile. And if they don't, okay, fine. The vitamin C question can be put to rest once and for all. But in cancer treatment, we don't have the luxury of jettisoning possibly effective, relatively non-toxic treatments. We should revisit promising avenues without prejudice and with open minds. 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