The news is full of stories about what’s bad for you. Plastic, food coloring, trans fats, sun exposure, lack of sun exposure, caffeine, sleeplessness, carbs. It’s nearly impossible to avoid all those things, so wouldn’t it be better just to not know about them? When the media inform us of these dangers, there’s an unstated promise lurking in there that if we can figure out how to live right and avoid them, we will be healthy and live long and prosper. Is that why it’s worth knowing? If we eat our greens and do our yoga, will that save us from all harm?

In a word, no. Life is full of uncontrollable risks. Scientists tend to find new ones wherever they look. Even if we can’t avoid those risks, knowing what they are and how they work will always be a good idea in my book.

A couple recent articles conclude that the risks we live with are closer than we thought, concerning both the common cold and cancer. I think this is actually good news. Our bodies are pretty good at dealing with the dangers we face on a daily basis. The fact that bad things are close to us should not shock us – the world is a dangerous place. But we can live well in it, and our bodies have something to teach us about fighting the good fight.

The first article was a victory for all those mothers out there bundling their kids against the cold, with the argument that getting cold makes you catch cold. They now have scientific proof that they’re right. It turns out that we’re carrying around the common cold much of the time. At any given time, a majority of American adults are carrying around the rhinovirus that causes most common colds in their noses (up to 70% of adults– I can only assume that the number for kids is near 100%, but I have no numbers on that). So chances are, you already have the cold virus, even if you feel perfectly fine.

So why aren’t most of us sick all the time? Because we have immune systems. The cells in your nose are constantly fending off this virus. If you want to avoid getting sick, it’s partly about washing your hands and avoiding sick people, but it’s mostly about keeping your immune system strong. And one thing that weakens those cells in your nose is letting them get cold. When their temperature drops to a few degrees below body temperature, their response to the virus is weakened, the virus multiplies, and you’ll probably catch cold. So keeping your nose warm is as important as washing your hands. Make sure you wrap that scarf nice and tight. (I’ll put in a word here for sugar and stress to be immune system weakeners, but that doesn’t make as cute a headline for this study.)

Much more surprising was the result published in the magazine Science in May. We’ve spent a lot of time looking at mutations in tumor cells in cancer patients to characterize cancer so that we can catch it and treat it sooner. But these scientists decided to look at some healthy cells in healthy people. And they found many more mutations that could lead to cancer than anyone expected.

The tissue they looked at was eyelid tissue from four people over 55 years of age. I know, that’s not a big sample study, so it’s not completely conclusive, but it certainly qualifies as super interesting. These four people were undergoing a procedure to have part of their eyelids removed because the sagging that comes with age was actually interfering with their vision. This way the study scientists didn’t have to ask for volunteers to have bits of skin removed.

Representation of cells with mutations in an average square centimeter of a normal eyelid (not cancerous!). The different colors represent mutations in different genes (so there is a diversity of mutations). The density, size, and nesting of the cells are based on the DNA sequencing in the study.

The scientists sequenced the DNA of the skin cells in the samples. They found lots of mutations, some of which lead to driver cells which may eventually lead to tumors. They were looking specifically for mutations in the NOTCH genes, which have been identified in many skin tumors. They found, on average, 83 cell clones carrying driver mutations per square centimeter of skin in their samples. That works out to about 350 cells with mutations in the size of a postage stamp. An average human adult has about 18,000 square centimeters of skin, but not all of it has UV exposure like the eyelids, so let’s be super optimistic and say we only have about 1000 square centimeters of skin with UV exposure. So that’s 83,000 of these dangerous cell clones we’re carrying around with us, even though we’re perfectly healthy. Cancer feels not so far away, suddenly. Wait a minute while I slather some more sun block on. And stay in indoors.

But wait a minute.  These mutations seldom lead to tumors, statistically speaking. This skin came from healthy adults who had some normal sun exposure, but nearly a quarter of their cells had mutations that might lead to cancer. The finding is surprising and baffling.

Evidently our bodies are pretty good at keeping these mutations in check – they happen pretty often, but they’re not allowed to grow and gather and make tumors. So we have something to learn from our bodies – if we can amplify and support this natural tendency, we might be able to prevent or treat tumor growth. Yes, sometimes things go wrong and people do get tumors, but studies of healthy cells like this can help us pinpoint what goes wrong and what we can do about it. This finding also informs how we treat cancer: suppose we made a drug to target and kill cells with these mutations. It would get rid of the cancer, but it would also take out a significant fraction of perfectly good skin cells. An unpleasant possibility, to say the least.

Caroon of a particle track through a DNA molecule, showing how cosmic rays may cause interactions and changes in DNA.

The facts that cancer-causing mutations are happening in healthy people all the time and most of us are carrying around the cold virus inform my discussion of cosmic rays as an astrophysicist. I end up telling people about these charged particles raining down on us all the time from outer space as part of my research. Sometimes that freaks people out, but we’ve been living with them for a long time. Sometimes they cause DNA changes that may lead to cancer. A study last year  conducted with astronauts in mind (any astronaut going to Mars would get a big dose of cosmic rays) shows that particles like cosmic rays can cause Alzheimer’s in mice. How awful! These things cause cancer and Alzheimer’s and who knows what other neurological problems! Let’s all live deep underground to avoid them! That would work, you know. But then we’d have all sorts of psychological problems, lack of vitamin D, and increased radiation from the natural Uranium in rock, which increases the deeper you go. So… what to do?

We should live courageously with risk. We should study what’s going on around us, the early indicators of disease and chemicals that are bad for us. And we should do what we can to avoid unnecessary risks, and live healthy to the extent we know how to boost our natural defenses. But we should also realize that there’s only so much we can do, and choose to be happy despite ever-present dangers of life.

Most cancer cases are just random, completely out of the power of their hosts. But that doesn’t mean that we should all take up smoking and survive on french fries and beer. It does mean that we should never blame cancer patients for their suffering and should see them as an “us” rather than a “them”, no matter what we think our cancer risk is.
This may be one of those cases in which people would claim that ignorance is bliss, but I would say that knowing is always better than not knowing. Not because with knowing we can avoid all risk. Figuring out how things work is my passion. But it also tends to help us to do good science and live better lives, even if the facts we uncover are scary.

Article on the common cold:

Foxman EF, Storer JA, Fitzgerald ME, Wasik BR, Hou L, Zhao H, Turner PE, Pyle AM, & Iwasaki A (2015). Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. Proceedings of the National Academy of Sciences of the United States of America, 112 (3), 827-32 PMID: 25561542

Article on cancer cells in eyelids:

Martincorena I, Roshan A, Gerstung M, Ellis P, Van Loo P, McLaren S, Wedge DC, Fullam A, Alexandrov LB, Tubio JM, Stebbings L, Menzies A, Widaa S, Stratton MR, Jones PH, & Campbell PJ (2015). Tumor evolution. High burden and pervasive positive selection of somatic mutations in normal human skin. Science (New York, N.Y.), 348 (6237), 880-6 PMID: 25999502

Article on cosmic rays and Alzheimer’s

Cherry, J., Liu, B., Frost, J., Lemere, C., Williams, J., Olschowka, J., & O’Banion, M. (2012). Galactic Cosmic Radiation Leads to Cognitive Impairment and Increased Aβ Plaque Accumulation in a Mouse Model of Alzheimer’s Disease PLoS ONE, 7 (12) DOI: 10.1371/journal.pone.0053275