From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Wed Jun 06 2001 - 23:07:46 MDT
This is the 40'th update of my fly longevity experiments. In addition
to my latest fly results, I've also included in this update the results of
a series of experiments testing the satiating abilities of various foods.
In fly Run #40 I take a look again at the effects of fruit juices, and
compare this with varying the amount of citric acid. Control and juice
bottles all had 1/4 tsp citric acid added. Doubling the amount of citric
acid yielded results that could not be distinguished from that of the
control. This correspondance is so close, I wonder whether the acid was
indeed doubled. In any case further increasing citric acid to 1 tsp was
clearly beneficial.
The addition of any fruit juice increased maximum lifespan beyond that
obtained with either 1/4 or 1/2 tsp citric acid. Only 1 tsp citric acid
yielded results comparible to that obtained with the juices. I doubt the
juices increase longevity by their acidity. Instead they may provide a
factor which reduces the toxicity of citric acid. One hypothesis I will be
testing is that citric acid may induce a potassium deficiency, which in
turn may harm longevity. A very small amount of additional potassium has
been found to increase fly longevity in a published
experiment. (Mechanisms of Ageing and Development 16: 221-231 1981)
Run #40 Percent Survival on Day
supplement 32 38 44 50 57 63 69 75 79 85 91 96 101 106
____________________________________________________________________
control 66 57 57 43 37 23 9 0 - - - - - -
apple juice 60% 90 85 75 70 60 45 40 40 35 30 15 10 0 -
apple juice 100% 67 64 61 58 50 22 25 25 19 8 3 0 - -
apple juice, Okanagan 75 75 75 71 71 50 25 18 14 7 0 - - -
citric acid 1/2 tsp 59 50 55 45 41 23 5 5 0 - - - - -
citric acid 1 tsp 84 78 72 59 53 34 28 22 9 6 3 0 - -
grape juice 93 90 88 85 80 71 61 20 7 0 - - - -
grapefruit juice, pink 82 79 74 68 56 44 21 15 15 6 3 0 - -
grapefruit juice, white 66 59 50 41 28 22 13 9 6 0 - - - -
orange juice 82 79 68 61 43 32 21 14 14 7 4 4 4 0
pineapple juice 70 63 63 60 50 27 13 7 7 3 0 - - -
Testing the satiating ability of various foods, or food combinations,
using only a single subject (myself) is rather problematic. Statistically
meaningful results would not be obtained during a single meal, since
calorie intake varies too much from meal to meal. If only a single food
was consumed over a week I imagine the results would be meaningful. I
decided to compromise and eat only one food or combination, for one day
and measure calories consumed on a per day basis.
The first food tested was whole grain rye bread, with no
toppings. Intake over one day was calculated at 1388 calories. I found the
"staff of life" to be tasteless, but filling.
Second food was Gala apples. Unlike the bread, eating apples proved to
be a chore. They had very poor short term satiating ability. I'd "fill
up" on apples, but still remain hungry for a short period of time. This
undesirable side effect might be due to an induced protein deficiency. I
vowed not to test any more food combinations that had no protein in
them. At the end of the day I was hungry again, but the idea of trying to
go to sleep on a stomach filled with apples held little appeal. To
compensate for going to bed humgry, I added a 150 calorie fudge factor to
bring up daily intake to ab libitum levels. With this correction,
estimated ad libitum intake was 1413 calories, which is remarkably close
to that for rye bread.
Third food was Astro no fat lactose reduced yogurt. Unlike the other
foods, this involved some variety, as both strawberry, blueberry, and
peach yogurt was consumed. Daily intake was 1483 calories, which is not
significantly different from the other foods. Palatibility was much higher
than the other foods.
Fourth food was boiled whole potatoes. I was rather surprised to find
I consumed 2179 calories of these. However the next day I spontaneously
skipped lunch, due to lack of hunger. I suspect a longer term test lasting
several days would have yielded results not significantly different from
the other foods.
Fifth food was Ryvita high fiber whole rye crispbread. This was much
drier that regular bread, but intake was only slightly higher at 1564
calories.
Sixth was a combination, alternating one container of Astro no fat
yogurt with one Gala apple, all day long. Some experiments with rodents
find that dietary variety stimulates intake. My own experience is that
eating some yogurt with an apple is more satisfying than either alone. I
guessed calorie intake with this combination would be reduced. The
scientists say it should go up. Total intake of both yogurt and apples was
1976 calories. Looks like the scientists win this one.
Seventh food was mixed vegetables, including carrots, cauliflower, and
broccoli. To provide protein I also ate one 500 gm container of no-fat
cottage cheese (336 calories) with the vegetables. Total intake including
both vegetables and cottage cheese was 1768 calories. Some Doctors
recommend vegetables as healthy diet foods. Healthy they may be, but
vegetables certainly are not good diet foods for this spare tire!
Further satiation experiments will be reported with the next fly
longevity update.
FOOD DAILY CALORIE INTAKE
______________________________________
apple, Gala 1413
potato 2179 (skipped lunch next day)
rye bread 1388
rye crispbread 1564
vegetables/cottage cheese 1768
yogurt, no fat 1483
yogurt & apple 1976
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