Student Questions: Supermoons and an Apple a Day

by Brian Dunning
May 3, 2011

Today we're tackling another round of questions sent in by students. Got a question? Send it in, and I'll do my best to give you the best information we know so far on the subject. This time students have been curious about a lot of health questions; including how long it takes your brain to feel full after a meal, whether deodorant is going to kill you with all its evil toxic chemicals, whether getting an abortion actually increases your risk of cancer as some anti-abortion activists tell us, and whether the urban legend of an apple a day keeping the doctor away might not be such a bad idea after all. And as a bonus, we're also going to look at the terrifying Supermoon! so prominently discussed in recent headlines. Let's get started:

Hello, my name is Nathan Evans from Ohio, and I was wondering if it really takes your brain twenty minutes from the time you've eaten to realize that you've taken in food?

It does take some time, but it varies widely depending on what you eat, how much you eat, how hungry you were before, how tolerant you are to fat intake, and other factors. Twenty minutes might be a fair average for some people, but by no means is this as simple as taking x number of minutes for your brain to feel full.

The usual mechanism discussed is what we call an adiposity signal, which tells your brain that enough energy has been taken in, and the appetite becomes satiated. There are two molecules that are known to act as adiposity signals: leptin and insulin. There are receptors in the brain's hypothalamus to which these molecules bind when there are enough of them in your bloodstream, and that's what turns off the appetite. So when you start eating, it does take time for enough food to be digested to trigger the production of these compounds.

Researchers have long looked at leptin as a way to control obesity. It seems reasonable that if you simply give people leptin, they'll always feel full, and will be satisfied not to eat anything. Unfortunately this has not proven to be the case. Leptin doesn't last very long, its solubility is relatively poor, and it's actually not very potent; so what ended up happening is that they had to give a lot, more frequently than was practical, and only the most obese subjects receiving the highest doses received any benefit.

As we discussed in the episode about high-fructose corn syrup, opponents like to charge that all that free fructose interferes with the production of leptin, compared to sugar which has the same amount of fructose chemically bound to glucose. And as we found by surveying the research, there's no truth to this at all.

Hi, I'm Allison from California. I know some people who won't use deodorant because they say the aluminum in it causes kidney cancer and it contains other harmful chemicals. I asked a friend what she uses instead, and she said she uses a "natural" deodorant. Needless to say, it wasn't working very well.  I've heard of these natural deodorants and body crystal deodorants and I'm curious to know more about them, and if deodorant containing aluminum is actually a health hazard.

Well, first of all, your friend is poorly informed on a very significant point: aluminum is used in antiperspirants, which interfere with the function of sweat glands; it's not used in deodorants, which mask body odor with perfumes and/or attack odor causing bacteria. So if she wants to use an aluminum free deodorant product that works a little better than her feel-good all-natural alternative, you can point her to pretty much any commonly available non-antiperspirant deodorant.

In a previous Student Questions episode, we examined the question of whether the aluminum in antiperspirants causes cancer, and the research is very clear with a resounding no. Both the American Cancer Society and the National Cancer Institute have been fighting these untrue chain email claims for years, and both have published position statements on their websites stating that so far, no credible research has shown any link between cancer and any cosmetic products, including both antiperspirants and deodorants. The rumors probably got started because aluminum is a known neurotoxin, but it has get into your body systemically in sufficient doses to have any harmful effect. Antiperspirants are not designed to be eaten, they're intended to be applied to the outside of your skin where they safely shut down sweat glands. That's all. There's simply no mechanism by which they would introduce aluminum into your system, so long as you don't eat them.

This is Kevin from Baldwinsville. I've heard that there is a link between getting an abortion and some forms of cancer. Is this true?

That abortions increase the risk of breast cancer is a claim that's often repeated by some religious and anti-abortion groups, but it's not purely an unfounded scare tactic. There are plausible reasons to take a very serious look at this, and it has to do with hormones. Pregnancies and terminated pregnancies both radically affect a woman's hormones, and it is known that the hormonal changes that occur throughout a woman's life produce changes in the breasts that do influence the chances of breast cancer.

The National Cancer Institute tracks this very closely. In 2003 they held a special workshop to review all the research and determine exactly what kind of cancer risks were associated with reproductive events, including various types of abortions. The good news is that there is no link between abortion and cancer risk, however that's not the only interesting thing that was learned. It turns out that a normal, full-term pregnancy actually increases the risk of breast cancer for a short period of time after the birth. Another unexpected and surprising finding was that hypertension caused by pregnancy is associated with a slightly decreased risk of breast cancer.

The findings also identified many areas where there's a gap in our knowledge. For example, we don't have clear data about whether post-pregnancy changes in the immune system affect breast cancer risk, or whether the birth weight and gender of the baby influence breast cancer risk. There are a lot of interesting questions and intriguing fields of research, but one thing that you do not have to worry about, at least according to the best state of our current knowledge, is getting breast cancer from having an abortion.

Hey Brian, I'm Marie Lars, a freshman at the University of Texas at Austin, and I was wondering what your thoughts were on the "Supermoon" debate. Thanks a lot.

To start with, I don't believe that any serious "debate" exists, but first let's define exactly what "supermoon" means. It's not really an astronomy term; it's more of a sensational media term. Technically we'd refer to a supermoon as a perigee-syzygy event. The moon orbits the Earth in an ellipse, and its closest point is called the perigee. Syzygy is more of a generic term that refers to an alignment of various types, and in this case it means the Earth, moon, and sun are in a line, as they are every time the moon is either full or new. Perigee-syzygy is when these two phases coincide; the moon is at its monthly perigee, and it's also either full or new. Both of these happen about once every month, so there's really nothing remotely astronomically interesting about it.

But on slow news days, something like "Supermoon!!" looks good in headlines. There was a full moon perigee-syzygy in March of 2011. This one was a little bit unusual in that the perigee was at its maximally closest, fractionally closer than most perigees. But don't get too excited; the difference was about equal to taking one step from the endline of a football field. Looking at the supermoon, you wouldn't be able to notice any difference in size from any other monthly perigee. The moon at perigee is about 6% bigger across than average; enough to measure with simple equipment, but not enough to detect by looking without measuring. (A larger number you may have heard broadcast, 12 or 14 percent, is talking about the area; I'm talking about the diameter.)

There are always a few fringe researchers who try to correlate such events with earthquakes or storms or other Earthly events. Serious research has never found any such correlation, nor has any plausible hypothesis been suggested to explain why we might expect one. From a gravitational perspective, a supermoon is almost exactly the same as every other monthly perigee; so unless we have catastrophic disasters every month, we shouldn't have any reason to expect one on a perigee-syzygy either.

Hi Brian, my name's Dylan from Syracuse, New York, and I'd like to know, does an apple a day really keep the doctor away?

This is an urban legend that presumes that a single apple contains whatever it is your body needs to keep from getting sick. As convenient as this might be, there is no such magical ingredient. Disease can come from a huge number of causes, and only a very few of these are deficiencies that a single daily apple would address.

Scurvy is often offered as a good example, but it's not, because apples actually contain very little vitamin C. An orange a day, however, would prevent scurvy. What do apples contain? Basically, antioxidants and fiber. The fiber you'd get from an apple a day would probably keep you regular, alleviating most trips to the doctor for constipation. The benefits you'd get from the antioxidants in a daily apple are a bit harder to quantify. As we've discussed before on Skeptoid, antioxidants do play a role in moderating the oxidation in your body, but it's far from simple. Oxidation is a necessary part of many bodily functions, as well as a natural chemical process that needs to be balanced. Most people's normal diets already deliver more than enough antioxidants than their bodies will make use of, so getting them from daily apples would probably only be significantly beneficial under both of two conditions: First, that your normal diet is terrible; and second, that you consume the daily apple for decades, enough for the benefits to have any measurable cumulative effect.

By Brian Dunning
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