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Vitamin D, Sun, and Cancer

Kas Thomas: The evidence is substantial enough that people should start thinking about taking substantial amounts of vitamin D as prophylaxis against cancers of all kinds. 

One of the most striking findings regarding cancer incidence is that for many forms of the disease, cancer incidence is higher the further you live from the equator. Also, studies have found that the most serious cases of cancer are diagnosed in the winter.


This is true, for example, of colorectal cancer.

The accompanying graph comes from a 2005 paper by Mohr et al. that correlates cloud cover and distance from the equator with colorectal cancer (CRC) incidence in 175 countries. It shows quite clearly that colorectal cancer incidence varies with latitude. The countries with the lowest CRC rates are near zero degrees latitude (the equator).

The trend doesn't just apply to colorectal cancer. It also applies to breast cancer. (See graphic below.)

Breast cancer and colorectal cancer are distinctly different cancers, so in order for these graphs to be as similar as they are, there must be a common denominator of extremely broad applicability underlying the latitude trend. And there is. It turns out the common denominator is vitamin D.

More than 2,500 research studies have been published in biomedical journals investigating the inverse association between vitamin D (and its metabolites) and cancer, including almost 300 epidemiological studies. For a good overview, I recommend the review article by Garland et al. (2009). As you review the literature, you might notice (as I did) a certain amount of hesitancy on the part of big-name researchers to come right out and pronounce vitamin D a bonafide cancer-preventive agent, due to the relative dearth of prospective (intervention-based) randomized controlled trials. (One intervention study worth reading is the 2007 trial by Lappe et al. in Am J Clin Nutr.) After the CARET disaster, no one wants to get caught recommending a vitamin regimen based on epidemiological happy-talk, and I can understand that.

Nevertheless, I think the weight of the evidence in favor of vitamin D, at this point, is substantial enough (and any down side negligible enough) that people should start thinking about taking substantial amounts of vitamin D as prophylaxis against cancers of all kinds (not just CRC and breast). If you can get adequate sun exposure, your body will make ample vitamin D on its own. (As a rough guide, 20 minutes of exposure over 40% of your body gives the equivalent of 10,000 IU, although this can vary considerably depending on skin color.) Absorption of supplemental vitamin D varies. Your doctor can suggest guidelines applicable to your body type.

My advice is: Read the literature and decide for yourself whether or not to start a vitamin D regimen. Don't wait for FDA, CDC, the National Cancer Institute, or anyone else to give you the green light on this one. They've got their own agendas to worry about.

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Is the universe a graveyard? This theory suggests humanity may be alone.

Ever since we've had the technology, we've looked to the stars in search of alien life. It's assumed that we're looking because we want to find other life in the universe, but what if we're looking to make sure there isn't any?

According to the Great Filter theory, Earth might be one of the only planets with intelligent life. And that's a good thing (NASA, ESA, and the Hubble Heritage Team [STScI/AURA]).
Surprising Science

Here's an equation, and a rather distressing one at that: N = R* × fP × ne × f1 × fi × fc × L. It's the Drake equation, and it describes the number of alien civilizations in our galaxy with whom we might be able to communicate. Its terms correspond to values such as the fraction of stars with planets, the fraction of planets on which life could emerge, the fraction of planets that can support intelligent life, and so on. Using conservative estimates, the minimum result of this equation is 20. There ought to be 20 intelligent alien civilizations in the Milky Way that we can contact and who can contact us. But there aren't any.

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The key to better quality education? Make students feel valued.

Building a personal connection with students can counteract some negative side effects of remote learning.

Future of Learning
  • Not being able to engage with students in-person due to the pandemic has presented several new challenges for educators, both technical and social. Digital tools have changed the way we all think about learning, but George Couros argues that more needs to be done to make up for what has been lost during "emergency remote teaching."
  • One interesting way he has seen to bridge that gap and strengthen teacher-student and student-student relationships is through an event called Identity Day. Giving students the opportunity to share something they are passionate about makes them feel more connected and gets them involved in their education.
  • "My hope is that we take these skills and these abilities we're developing through this process and we actually become so much better for our kids when we get back to our face-to-face setting," Couros says. He adds that while no one can predict the future, we can all do our part to adapt to it.
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Study details the negative environmental impact of online shopping

Frequent shopping for single items adds to our carbon footprint.

A truck pulls out of a large Walmart regional distribution center on June 6, 2019 in Washington, Utah.

Photo by George Frey/Getty Images
Politics & Current Affairs
  • A new study shows e-commerce sites like Amazon leave larger greenhouse gas footprints than retail stores.
  • Ordering online from retail stores has an even smaller footprint than going to the store yourself.
  • Greening efforts by major e-commerce sites won't curb wasteful consumer habits. Consolidating online orders can make a difference.
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Personal Growth

Childhood sleeping problems may signal mental disorders later in life

Chronic irregular sleep in children was associated with psychotic experiences in adolescence, according to a recent study out of the University of Birmingham's School of Psychology.

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