Fruit is Bad for You (at Least it is for me)

Those of you who know me are aware of my love for data, and the fact that I collect all kinds of health indicators in a search for patterns.  Over the last year, I was shocked by the rise in my A1C levels, which is an indicator of pre-diabetes.  I was also aware of an occasional blood glucose level above 100 mg/dL, which is also associated with the onset of diabetes.  But, my blood glucose levels were not high enough to warrant A1C levels of about 5.7.  So I did what anyone of you would do, and that is to measure my daily blood glucose levels, giving better statistics than a weekly reading.

Indeed, I saw multiple weekly readings above 100 mg/dL with a high of 110 mg/dL.  Then I noticed in a particular week that not one reading was over 100 mg/dL.  The advantage of my highly structured diet is that it was simple to identify the change, and that was that my wife could not find fresh blueberries that week.  We kept a fresh bowel on the kitchen counter, and I would grab a fistful after a meal or as I was lured to them as I passed buy.  Being my favorite fruit, this my sole source of fructose, aside from a special low-sucrose and high-fat/protein chocolate that I make.  (Not to mention the occasional chocolate chip cookie that I have with my grandson when we visit Starbucks and the exquisite pretzels my sister-in-law ships in creative gift boxes every Christmas.)  Blueberries were the only source of regular fructose that I had been eating for the last couple years.

So, I remained off of blueberries for two months to get a decent amount of statistics, and was blown away by the results, shown in the plot.  First, this plot shows the importance of averaging.  There are large fluctuations in the test and in blood glucose levels that depend on all sorts of factors.  The blue open circles show the results while I was eating blueberries and the red solid circles during the time I stopped eating them.  The lines show a least squares fit to the data in the two regions.  The conclusion is that my blood glucose is a full 10 mg/dL lower when I'm not eating blueberries.  The beauty of averaging lots of data points is that the uncertainty can be determined from the scatter, and corresponds to about 1 mg/dL.  So one can argue whether the difference with and without blueberries is 10 mg/dL or 9 mg/dL, but the difference is both large and statistically significant.

I plan on continuing the zero fructose diet for another month or so, followed by another A1C test, which provides a blood glucose value averaged over three months.  This will allow the averages of both tests to be compared.

I will write more on this topic later when I have more time, but the conclusions are:

1. There is no such thing as a universally healthy diet.

2. There is no such thing as a healthy diet that is customized for a particular person.

Rather, our health is a struggle against internal and external forces, which adapts to evolutionary forces imperfectly.  The best we can do is chose a balance that makes each of us relatively healthy, and then we must accept the negative consequences.  In my case, a super-low-carb diet keeps me fit and trim, provides lots of energy and stamina, and has eliminated pesky annoyances such as heartburn and regular migraine headaches.  On the downside, my diet makes me prone to kidney stones.  These can be mitigated with simple meds, which are benign compared to treatments for diabetes and migraine headaches.  And physical stamina is more important to me than pleasing my sugar-craving reward center.

May your New Year be a happy one, optimized for adequate health and pleasures within reasonable constraints. 

I always feel Stupid and Confused

I often get emails asking me about physicist questions.  Sometimes I can't resist answering, especially if it's a simple problem on a fundamental principle.  Try answering the question without looking at my solution, and then check my work to see if I got it right.

EMAIL TO ME:

Hello Professor -

My name is **** and I’m a WSU alum.  My daughter is taking honors science and we are a bit stumped on a question and I was wondering if you could help me.   

Scenario:

A 5 kg ball rolls at 4m/s and hits a fire hydrant.  The ball bounces off at 2 m/s. 

Question:

Which object has the greatest momentum.  The ball, hydrant, or is it the same? 

Answer?

Ball - I chose ball because of the definition of momentum.  The fire hydrant is not moving – the ball is.    And the question is not about force and gives no other information about the hydrant.

If you have a second I’d love to know if I’m correct, or if there is a different answer and explain it to me. 

Thanks,
MY ANSWER:

Hi ****,

I'm assuming that the question is asking for the momentum of the two objects just after the collision.  This problem is testing the concept of momentum conservation.  Momentum conservation ALWAYS holds even when mechanical energy is not conserved.  This is the principle to understand and apply.

Here is how I would solve the problem.  The initial moment of the ball is + 20 kg m/s and it's momentum just after the collision is - 10 kg m/s (assuming it bounced backwards).  Thus, the change of momentum is - 30 kg m/s.  But since momentum must be conserved, and it was initially 20 kg m/s, the ball must have imparted 30 kg m/s to the hydrant.  Now, momentum is conserved: 20 kg m/s (ball before collision) =  30 kg m/s (hydrant) - 10 kg m/s (ball after collision).  It seems strange because you can't see the hydrant moving but that is because it has so much mass.  So even though its velocity is near zero, the mass is so huge that the momentum is substantial.

The reason that I stipulate "just after the collision" is because the hydrant is attached to the earth, so while it might initially start to move one way, it will end up vibrating back and forth.  Probably more detail than you wanted to here, but just in case you were curious.  Another brain teaser: if the hydrant is oscillating after the collision, the momentum is oscillating too, so momentum seems not to be conserved.  The answer is that the hydrant is attached to the earth, so the earth and the hydrant will move in such a way that momentum is conserved.  It always needs to be conserved.

Don't let your daughter feel frustrated.  Applying physics concepts to problems is very difficult.  You only learn after making lots of mistakes, so have her learn from them.  When teaching any physics class, I give lots of problems of this sort, and some students get angry, accusing me of trying to trick them.  In attempting to do problems and then seeing the right way after struggling somehow results in it sinking in in a way that cannot be replicated by just giving the learner answers.

I don't want to undermine the teacher, who is probably giving the class a bunch of problems of this kind to train them to think, so I don't feel comfortable answering such questions in the future, because the struggle is an important part of learning and the teacher is, I hope, directing the struggles in a positive way.  Your daughter should attack problems by arguing with classmates, you, or whoever is up for a good fight.  My colleagues and I continue to do this even now as we learn new things.  Being able to thrive on being constantly confused in the quest to understand is the ticket for success.

I wish your daughter the best in her studies and tell her from a guy who is constantly confused and feeling stupid, this is the way it should be.  And don't give up!

(Pardon the typos, since I didn't have time to proof my email.)

Best,

Mark G. Kuzyk
Regents Professor of Physics
Meyer Distinguished Professor of Sciences
Washington State University
Pullman, WA 99164-2814

Phone: 509-335-4672
Fax: 509-335-7816

Web Page: www.NLOsource.com