 Many health benefits have been attributed to having higher vitamin D levels in the blood. Examples include reduced risk of musculoskeletal disorders, infectious diseases, autoimmune diseases, cardiovascular disease, diabetes, several types of cancer, neurocognitive dysfunction, adverse pregnancy, and birth outcomes in all cause mortality. But most such attributions are based on observational studies, meaning just drawing correlations between the two. And having high vitamin D levels may just be a marker of good health. After all, vitamin D is the sunshine vitamin who has higher levels of vitamin D in their blood, people who run around outside. So maybe the D is just a marker for exercise, and that's really what's lowering disease risk. And indeed, when vitamin D supplements are actually put to the test and randomized controlled trials, they often fail to support a direct vitamin D benefit. In this video, I'm going to explore the randomized controlled trial data on vitamin D supplementation for COPD, chronic obstructive pulmonary diseases like emphysema, critical illness like whether we should be giving vitamin D to people in the ICU, cardiovascular disease like heart attacks and strokes, preventing depression, treating depression, vitamin D for weight loss, and vitamin D for lung cancer survival, prostate cancer survival, and colorectal cancer survival. What do you think? Do you think vitamin D supplements will help with some of them? All of them? None of them? Let's find out. The efficacy of vitamin D therapy for patients with COPD, a meta-analysis of randomized controlled trials, found that compared to placebo, vitamin D can improve lung function, improve six-minute walk distance, and reduce acute exacerbation, sputum volume, and COPD assessment test scores. In other words, so far so good. Vitamin D supplements are effective for treating COPD. What about vitamin D supplementation for critically ill adult patients? If your loved one ends up in the ICU for whatever reason, should you try to press the doctors to give them a vitamin D boost? Overall, nine randomized controlled trials involving nearly 2,000 patients were included and no significant difference in mortality was observed. Okay, so far, D is one for two. What about cardiovascular disease? widespread fascination with vitamin D as a panacea is responsible for nearly a hundredfold increase in vitamin D testing and supplementation over the last decade. And no wonder, follow people over time and there is an unequivocal association between low vitamin D status and people's risk of getting and dying from our leading killer cardiovascular disease. But is it cause and effect? Maybe low vitamin D levels are a result of cardiovascular disease rather than the cause. If you have chest pain, you're probably not out in the sun running around. That's why there's been more than 20 randomized controlled trials to put vitamin D to the test and no benefit for heart attacks, no benefit for strokes, no benefit for mortality. The good news, of course, is that heart disease is preventable, is reversible, but requires significant cleaning up of your diet. What about vitamin D for preventing depression? Among older adults, five years of vitamin D supplementation had no effect on the occurrence of depression or change in mood scores. These findings do not support the use of D to prevent depression. What about treating depression? Every single one of the trials for patients suffering from major depression found a benefit to vitamin D supplementation over placebo, though more is not necessarily better and it may take a few months for it to kick in. Let's see how we're doing on the scoreboard. Obesity is next. Effects of vitamin D supplementation on general and abdominal obesity results from 20 randomized controlled trials show no significant effect on the measures of obesity, including BMI, Waster Conference, or waist to height ratio. Treating cancer is up next. Vitamin D supplementation and survival of patients with the most common type of lung cancer. In early stage lung cancer, all you can do is try cutting out the primary tumor, but despite adding chemo, tumor relapse rates remain high. Surgeons noted that patients who had surgery during the summer seemed to do better than those in the winter, which was chalked up to higher vitamin D status. So they randomized patients to 1,200 international units of vitamin D a day or placebo, and over the next few years, no significant difference in either relapse-free survival or overall survival was seen with vitamin D compared with the placebo group. But that was in the total study population. What if you just looked at the patients who started out with low vitamin D levels? In that case, there did appear to be a benefit from D supplementation. Among those starting out with D levels under 20 nanograms per milliliter, which is equivalent to 50 nanomoles per liter, depends which units your lab uses, half of those who took the placebo relapse and half died. But those who started out with low levels and were treated with actual vitamin D, 86% remained in remission, and 91% remained alive. What about the effects of vitamin D supplementation on prostate cancer? A systematic review and meta-analysis of clinical trials found that there were no significant differences in total mortality between participants receiving vitamin D supplementation and those receiving placebo. That brings us to here, though again note the lung cancer benefit was only seen in those who started out with low levels. And vitamin D supplementation for colorectal cancer survival? Yes. A systematic review and meta-analysis of randomized controlled trials found that supplementation imparts a 30% reduction in bad outcomes overall, with a 24% reduction in the risk of dying, specifically from your colorectal cancer and a third lower risk of disease progression or death from any cause. The optimal dose for this survival benefit remains unclear since the trials use different doses, but looks like between 2000 and 4000 international units a day is a good place to start.