Student Questions: Supermoons and an Apple a Day

Skeptoid answers another round of questions sent in by students from around the world.

by Brian Dunning

Filed under Feedback & Questions

Skeptoid #256
May 3, 2011
Podcast transcript | Listen | Subscribe

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 old wives' tale 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 web sites 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.

Tip Skeptoid $2/mo $5/mo $10/mo One time

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 old wives' tale 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.

Brian Dunning

© 2011 Skeptoid Media Copyright information

References & Further Reading

ACS. "Is Abortion Linked to Breast Cancer?" Learn About Cancer. American Cancer Society, 20 Sep. 2010. Web. 1 May. 2011. <>

Barrett, Stephen. "Antioxidants and Other Phytochemicals: Current Scientific Perspective." Quackwatch. Stephen Barrett, M.D., 3 Jun. 2005. Web. 15 Jan. 2008. <>

Darbre P.D,. "Aluminium, antiperspirants and breast cancer." Journal of Inorganic Biochemistry. 1 Jan. 2005, Volume 99(9): 1912-1919.

Heymsfield, S., Greenberg, A., Fujioka, K., Dixon, R., Kushner, R., Hunt, T., Lubina, J., Patane, J., Self, B., Hunt, P., McCamish, M. "Recombinant leptin for weight loss in obese and lean adults: a randomized, controlled, dose-escalation trial." Journal of the American Medical Association. 1 Oct. 1999, Volume 282, Number 16: 1568.

NCI. "Summary Report: Early Reproductive Events and Breast Cancer Workshop." National Cancer Institute. National Institutes of Health, 4 Mar. 2003. Web. 29 Apr. 2011. <>

Plait, P. "No, the Supermoon Didn’t Cause the Japanese Earthquake." Bad Astronomy. Kalmbach Publishing Company, 11 Mar. 2011. Web. 29 Apr. 2011. <>

Reference this article:
Dunning, B. "Student Questions: Supermoons and an Apple a Day." Skeptoid Podcast. Skeptoid Media, 3 May 2011. Web. 1 Sep 2015. <>


10 most recent comments | Show all 38 comments

I must say, terms like "Old Wive's Tale" don't get to me- but you did hit one of my scientist buttons when discussing the factors of pregnancy that can affect a woman's health.

One that you listed was the "gender" of the baby- that would actually be the "sex" of the baby. Gender is a social role, having to do with sexual identity, that is created by an individual and their own self-image and desires. Sex has to do with the plumbing and is purely physical.

Just a note on something that has bugged me ever since an undergrad bio professor explained to a classmate why she had very little chance of determing the gender of fruit flies, only their sex.

Luke, East Lansing
May 24, 2011 7:20am

@luke that is simply only ONE definition for the word gender. like many words in the english language, there be several!!! HEAVEN FORBID!!!!
a. The condition of being female or male; sex.

justin, port dover
August 19, 2011 3:35am

I agree with Luke and I use the dictionary for non scientific terms.

Henk v, Sin City NSW, Oz
September 8, 2011 6:41pm

Brian, in the answer to Nathan Evans, you seem to have missed the role of fat in satiety. Fat in a meal can produce the feeling of fullness even before reaching the intestines, and is perhaps the best mechanism for preventing overeating.

As for the piece on antiperspirants, you are incorrect in implying that the skin does not absorb what is applied to it. It does. If it didn't, a good part of the cosmetic industry would not exist. There is plenty of evidence that the view of the skin as a nearly impermeable layer of protection is highly inaccurate.

I disagree on the count of aluminum not causing cancer - it has been linked to reproductive cancers, due to its estrogenic properties. And while it may not cause cancers in general, it is a major factor in Alzheimer's disease and can contribute to a variety of psychiatric and reproductive disorders.

I disagree with your comment that "most people's normal diets already deliver more than enough antioxidants than their bodies will make use of." If this was the case, few people would have cancer, or heart disease, or multiple sclerosis, etc. "Most people" consume significant amounts of refined and/or hydrogenated oils, which provide an excessive amount of free radicals to the body, while consuming relatively little fruit and not enough nutrient-dense food like animal organs (which provide the best antioxidants: vitamins).

Jonathan S., Toronto
October 1, 2011 10:53am

Apart from all the flubber website quotes...

for "As for the piece on antiperspirants, you are incorrect in implying that the skin does not absorb what is applied to it. It does. If it didn't, a good part of the cosmetic industry would not exist. There is plenty of evidence that the view of the skin as a nearly impermeable layer of protection is highly inaccurate."

you are right in that the skin soes absorb a few things...HF is a beauty.

And you are right in that " If it didn't, a good part of the cosmetic industry would not exist".

The cosmetic industry is a vehicle to sell garbage along with perfumes and sunscreens.

If cosmetics did what they claim, they would be medicines..

Mud, Sin City, Oz
October 25, 2011 11:15pm

and if you do want to quote trans dermal delivery, that's...medicine.

If you want to quote the incredible advancements in before and after cosmetic use its photography..

If collagen can be transported into skin why not use hydrolysed and extracted collagen fully whetted? A gelatine rub?

Why is a 5 dollar moisturiser just as effective as a 200 dollar moisturiser?

There's the rub..

Muddie continued, sin city
October 26, 2011 4:37am

Very true that much of the modern cosmetic industry is garbage...

At some point about two years ago, my mother got me to try some lotion for my acne - buying it without telling me and then using the guilt-trip to get me to use it. Didn't exactly work, as my acne had other causes and cleared up shortly after I eliminated them. A third of the way through the bottle I noticed it had some aluminum compound in it. Dropped it immediately.

Since then she's been occasionally talking about trying another lotion called ProActiv or something. Bloody expensive and I suspect it would be just as useful (not) as the other one. Thank goodness mother didn't try that tactic again.

Jonathan S., Toronto
October 29, 2011 1:29pm

Proactive is expensive, the same ingredients and quantities as many supermarket preparations.

Jeeps, if you have an Al allergy, I'd see a doctor if I were you. Your head would be killing you.

Pho, Gerringong (near the swamp)
October 29, 2011 5:31pm

I would like to comment on breast cancer and pregnancy. In medical school, I was taught that having children reduced the incidence of breast cancer possibly by decreasing the exposure of the breast tissue to estrogens during pregnancy. Don't know if that theory still holds, but I do believe it is still true that having children does exert of protective effect against breast cancer.

William, Marion, IN
March 3, 2015 8:01pm

Seems like the US has at least as much Acne woo as we have here in Australia. My daughter as a teen and one of her brothers had pretty bad acne; our friendly local Dermatologist prescribed an ethanol solution of Clindamycin (brandname here: "Clindatech Lotion") at Aus$45 a 150 mL bottle. Very effective, and beats OTC and supermarket preparations hollow.

Athro Dai, Kensington Vic Aust
March 4, 2015 4:04am

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