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. 

Vitamin D, Sun, and Cancer

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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Golden blood: The rarest blood in the world

We explore the history of blood types and how they are classified to find out what makes the Rh-null type important to science and dangerous for those who live with it.

What is the rarest blood type?

Abid Katib/Getty Images
Surprising Science
  • Fewer than 50 people worldwide have 'golden blood' — or Rh-null.
  • Blood is considered Rh-null if it lacks all of the 61 possible antigens in the Rh system.
  • It's also very dangerous to live with this blood type, as so few people have it.
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China's "artificial sun" sets new record for fusion power

China has reached a new record for nuclear fusion at 120 million degrees Celsius.

Credit: STR via Getty Images
Technology & Innovation

This article was originally published on our sister site, Freethink.

China wants to build a mini-star on Earth and house it in a reactor. Many teams across the globe have this same bold goal --- which would create unlimited clean energy via nuclear fusion.

But according to Chinese state media, New Atlas reports, the team at the Experimental Advanced Superconducting Tokamak (EAST) has set a new world record: temperatures of 120 million degrees Celsius for 101 seconds.

Yeah, that's hot. So what? Nuclear fusion reactions require an insane amount of heat and pressure --- a temperature environment similar to the sun, which is approximately 150 million degrees C.

If scientists can essentially build a sun on Earth, they can create endless energy by mimicking how the sun does it.

If scientists can essentially build a sun on Earth, they can create endless energy by mimicking how the sun does it. In nuclear fusion, the extreme heat and pressure create a plasma. Then, within that plasma, two or more hydrogen nuclei crash together, merge into a heavier atom, and release a ton of energy in the process.

Nuclear fusion milestones: The team at EAST built a giant metal torus (similar in shape to a giant donut) with a series of magnetic coils. The coils hold hot plasma where the reactions occur. They've reached many milestones along the way.

According to New Atlas, in 2016, the scientists at EAST could heat hydrogen plasma to roughly 50 million degrees C for 102 seconds. Two years later, they reached 100 million degrees for 10 seconds.

The temperatures are impressive, but the short reaction times, and lack of pressure are another obstacle. Fusion is simple for the sun, because stars are massive and gravity provides even pressure all over the surface. The pressure squeezes hydrogen gas in the sun's core so immensely that several nuclei combine to form one atom, releasing energy.

But on Earth, we have to supply all of the pressure to keep the reaction going, and it has to be perfectly even. It's hard to do this for any length of time, and it uses a ton of energy. So the reactions usually fizzle out in minutes or seconds.

Still, the latest record of 120 million degrees and 101 seconds is one more step toward sustaining longer and hotter reactions.

Why does this matter? No one denies that humankind needs a clean, unlimited source of energy.

We all recognize that oil and gas are limited resources. But even wind and solar power --- renewable energies --- are fundamentally limited. They are dependent upon a breezy day or a cloudless sky, which we can't always count on.

Nuclear fusion is clean, safe, and environmentally sustainable --- its fuel is a nearly limitless resource since it is simply hydrogen (which can be easily made from water).

With each new milestone, we are creeping closer and closer to a breakthrough for unlimited, clean energy.

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There never was a male fertility crisis

A new study suggests that reports of the impending infertility of the human male are greatly exaggerated.

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