Saturday, April 23, 2005

Passover came after Easter this year.

I will be going to a Seder tonight. Passover is late this year, and it is a rare year in that Passover comes after Easter. At the 1999 Drosophila Conference in Seattle the "fly board" first considered when to hold the 2005 Drosophila Conference. I thought I knew that Passover always follows Easter, so when someone (Elaine Strauss of the GSA) found that Easter was on March 26, I thought that we could avoid Passover by choosing later dates. I think that I even said so, so when someone else (Thom Kaufman) came up with a later date for Passover (April 24), I was surprised.

Theologically, it makes sense to celebrate Easter after Passover, because the Last Supper was a Passover Seder. Accordingly, early Christians did indeed celebrate Easter in "relationship with the full moon that falls during the Jewish month of Nisan" (from "Calendar," by David Duncan). However, the Christian world does not wish to tie their calendar to the Jewish calendar. Instead, Easter is usually celebrated on the first Sunday after the first full moon after the vernal equinox. Since Passover is almost always the first full moon after the vernal equinox, that amounts to the same thing. In fact, the Catholic church found it necessary to develop a lunar calendar for the purpose of dating Easter; a very useful discussion of this and other calendars can be found in the Catholic Encyclopedia. Another good book on this topic is "The Sun in the Church: Cathedrals as Solar Observatories" by J.L. Heilbron. In this century, Passover occurs no earlier than March 26 and no later than April 24, so this year is as late as it gets (the Naval Observatory provides a nice table of actual dates). I see that Adar II occurs in 2000, 2003, 2005, 2008, 2011, 2014, 2016, 2019, 2022, etc. (according to the 19 year Metonic cycle), with the latest dates for Passover occurring whenever this leap month occurs after two rather than three years. Passover falls after Easter in 2008, 2016 and 2024, three times in each 19 year cycle. There is a lot more to say about this, and I haven't even started on the Chinese calendar (more on that later).


Tuesday, April 05, 2005

Intermittent Fasting

It has been known for a long time that caloric restriction (a significant reduction in food intake – to 60-70% of normal levels) prolongs life,and improves health in many species (even including yeast!). Many people are interested in caloric restriction (for example, a caloric restriction support group on Yahoo! has 1,687 members) but relatively few people are willing to actually follow such an extreme diet. However, evidence that the benefits of caloric restriction result from the activation of a genetic program (involving insulin signaling and the gene SIRT1) rather than reduced metabolic activity per se has opened up the possibility that benefits can be achieved by other means. The current issue of Cell (February 25, 2005) is devoted to reviews on aging and includes an article by Lenny Guarente (PubMed) that makes this point in particular. One hope is finding a drug or dietary supplement that will do the job (perhaps resveratrol). I have paid more attention to the possibility that the same genetic program may be induced by intermittent fasting.

At the beginning of May last year (2004) I started a diet that involves not eating on Mondays, Wednesdays and Fridays. My diet was inspired in particular by a study (Anson et al., 2003) that reported beneficial effects on glucose metabolism and neuronal resistance to injury without an overall reduction in calorie intake. In this study, mice were assigned to four groups (ad libitum, intermittent fasting, caloric restriction and pair fed; this last group was given as much food as the intermittent fasting group ate, but on a daily basis). The intermittent fasting group did as well as the caloric restriction group on a variety of tests but enjoyed almost as much food as the ad libitum group (by making up the difference on days when food was available). A very recent paper by Hsieh et al. 2005 (Effects of Caloric Restriction on Cell Proliferation in Several Tissues in Mice: Role of Intermittent Feeding: PubMed; Am J Physiol Endocrinol Metab) reaches similar conclusions studying cell proliferation.

I fast between dinner of one day and dinner the next day, but eat dinner every day. The fast consists of no calories at all (I allow myself water, tea and coffee), and the precise duration depends on when we have dinner, according to the details of each day's schedule. While I normally fast three times each week, I am flexible. For example, I might allow myself to schedule lunch on a Friday after having fasted on Monday and Wednesday. In fact, I've done this only a few times since starting the diet. One week I postponed Friday's fast so that I fasted on Monday, Wednesday and Saturday that week.

The health benefits of intermittent fasting in humans are certainly not established, and I'm not recommending this diet for anyone else. I find it likely that caloric restriction works in humans because it works in so many other species. However, it is possible that the genetic program is already constitutive in humans. It is also possible that the particular diet I have selected fails to induce the pathway. Perhaps longer but less frequent fasts would be more effective, or many fewer fasts would be sufficient. I don't know, but I am encouraged by the growing evidence that the induction of extreme longevity can be uncoupled from caloric restriction per se.

I don't find this diet to be terribly difficult. In fact, skipping meals can be convenient (I'm busy, after all). For about three weeks after starting the diet I would experience mild hypoglycemic symptoms on the fast days (I was nervous but tired, just a little irritable and not terribly productive) and became sleepy when I ate again. These symptoms have passed. I now feel pretty much the same on fast days and other days. This diet is not about losing weight. I lost about 10 pounds over the first six weeks and then stabilized (and I am starting to gain some of this back). There are side effects. In particular, I don't think that it's a good thing to routinely drink strong coffee on an empty stomach (which is what I'm doing three days each week). I am aware that this diet is the opposite of the standard "healthy eating" advice that advocates a big breakfast and regular meals, and I must confess that I have passed up opportunities to discuss it with my doctor (although I have mentioned it to friends who are doctors). On the other hand, fasts of various kinds are a part of almost all religious traditions. I suspect that a study with direct tests of the relevant biomarkers (reduced serum glucose and insulin levels, or even elevated expression of SIRT) is possible, and will eventually be carried out, but I've decided not to wait for it. In the meantime, I can only quote the endorsement of my friend Peter Roemer, who was responding to an article in "The Economist", (March 31, 2005: "Even a slight decrease in calories may lead to longer lifespans") about the Hsieh et al. article cited above:

"OK, I'm giving it a try. Of course, this is exactly what Steve has been doing for a while. And look, he's still living!!!"

This also appears on as Posting 2.


Monday, April 04, 2005

Rainy days and pleasant company

Janet and I drove to New England for the weekend, to recognize her Aunt Diane's 90th birthday. Diane is healthy and energetic, and she was joined by a large group of loving family and friends. We drove up Friday evening, and stayed at the Heritage Inn in New Milford Friday night. Saturday was a wonderful day spent with wonderful company. I'm truly blessed to have married into such a great family. It was a delight seeing Adam in the New York Times this morning. I'm proud to have married into this family not because of their accomplishments but because of the enthusiasm and intelligence that they all seem to share, which is no doubt responsible for the accomplishments.

We spent a lot of time driving along stone fences and roiling brooks. It was a very wet weekend, featuring overcast skies, intermittent heavy rain and a power outage in New Milford that lasted several hours. Sunday morning we drove along Rt. 7 for a quick visit with Janet's cousin on her father's side, Joey Chernila, his wife Alana, Saidy (who is almost two) and Rose (who was born last month) and saw exciting view of the Housatonic at flood stage: water just inches below the roadway and lots of white water, including a standing wave of three or four feet at one place. I dropped Janet off at the Hartford airport (she's now at the Applied Anthropology meetings) and drove back alone.

On the way, crossing the Delaware River on I-84 at about six, I saw a memorable sight. The river was well up over its banks -- with great expanses of inundated trees -- and the first exit on the Pennsylvania side (Matamoros) was closed. Eastbound traffic was stopped. As I passed over I could see that the intersection below was completely flooded, with the tops of traffic signs just sticking up out of the water, which must have been about six feet deep!