So I did the no-grains experiment a couple times, and I generally found that eating no grains made my stomach feel a little better. After taking out all the possible extraneous factors, it was a small positive effect, but not quite statistically significant.

I wondered, am I just feeling better because I’m thinking about my food a little more? So I went for another experiment: vegetarianism. This was not as difficult, as I’ve been used to eating not much meat, but eating no meat altogether made me think a bit. So I went almost a month, eating meat only once. (couldn’t resist the opportunity to try a pig’s foot at a Taiwanese place with my friends Will and Jing. FWIW, it was really good.)

Here are the results. Again, these values are arbitrary 1-5 ratings of how good my stomach felt, recorded whenever I remembered to do so.

Average stomach values when I was vegetarian:
[‘2.33’, ‘3.00’, ‘3.43’, ‘2.00’, ‘3.20’, ‘2.71’, ‘2.32’, ‘2.50’, ‘2.50’, ‘3.00’, ‘3.17’, ‘3.14’, ‘3.00’, ‘2.33’, ‘2.33’, ‘3.00’, ‘3.40’, ‘3.14’, ‘3.33’, ‘3.33’, ‘2.67’, ‘3.17’, ‘2.50’, ‘3.33’, ‘3.17’, ‘3.00’, ‘2.67’]
Mean: 2.87710940708

Average stomach values when I was not vegetarian:
[‘2.88’, ‘3.14’, ‘2.37’, ‘3.21’, ‘2.70’, ‘1.64’, ‘3.14’, ‘2.95’, ‘2.53’, ‘3.43’, ‘3.00’, ‘2.62’, ‘4.00’, ‘3.33’, ‘3.11’, ‘3.00’, ‘3.43’, ‘3.00’, ‘2.68’, ‘2.68’, ‘3.42’, ‘3.29’, ‘3.33’, ‘3.12’, ‘3.50’, ‘2.56’, ‘2.83’, ‘3.70’, ‘2.80’, ‘2.88’, ‘3.00’, ‘3.35’, ‘3.36’, ‘3.00’, ‘2.80’, ‘3.00’, ‘3.36’, ‘3.80’, ‘3.56’, ‘3.00’, ‘2.83’, ‘3.52’, ‘2.66’, ‘2.22’, ‘2.78’, ‘2.78’, ‘4.00’, ‘2.25’, ‘2.50’, ‘3.11’, ‘3.80’, ‘3.25’, ‘2.62’, ‘3.55’, ‘3.20’, ‘3.60’, ‘3.81’, ‘2.83’, ‘3.60’, ‘3.30’, ‘3.51’, ‘2.80’, ‘3.22’, ‘2.92’, ‘3.51’, ‘3.38’, ‘2.83’, ‘3.64’, ‘3.71’, ‘3.74’, ‘3.00’, ‘3.43’, ‘2.70’, ‘3.19’, ‘3.08’, ‘2.69’, ‘3.68’, ‘3.43’, ‘2.86’, ‘3.00’, ‘3.37’, ‘2.44’, ‘2.29’, ‘3.24’, ‘2.29’, ‘3.44’, ‘3.00’, ‘3.12’, ‘3.14’, ‘2.70’, ‘3.00’, ‘3.12’, ‘3.77’, ‘2.25’, ‘2.20’, ‘3.40’, ‘3.27’,‘2.89’, ‘2.00’, ‘3.34’, ‘2.77’, ‘2.93’, ‘2.83’, ‘2.90’, ‘2.47’, ‘3.67’, ‘3.85’, ‘2.60’, ‘3.71’, ‘3.00’, ‘3.33’, ‘3.22’, ‘3.00’, ‘2.99’, ‘3.12’, ‘2.70’, ‘3.71’, ‘2.92’, ‘2.84’, ‘2.65’, ‘3.00’, ‘3.38’, ‘2.60’, ‘3.14’, ‘3.29’, ‘3.16’, ‘3.81’, ‘2.36’, ‘3.27’, ‘3.30’, ‘3.40’, ‘2.62’, ‘2.88’]
Mean: 3.07318849872
t = -2.13426416275, p = 0.0343639577132

Huh! So being vegetarian makes my stomach feel a little worse!

Skippable side note: I did travel during some of the vegetarian time. Rerunning the data omitting those values, it comes out the same.

Average stomach value when I was vegetarian: 2.84902728756

Average stomach value when I was not vegetarian: 3.07318849872

t = -2.18353942908, p = 0.0305296553454

Side note that might be relevant: I’ve been recording fewer data points than I used to.

Number of ratings per day when I was vegetarian: 5.22222222222

Number of ratings per day when I was not vegetarian: 7.92481203008

t = -4.99546061942, p = 0.00000154006168467

Side note that also may be relevant: my mood ratings (which I’ve been tracking similarly) are almost significantly different as well. This could strengthen the “eat meat” conclusion, or it could be that I’ve been a little bit down the last couple weeks.

Average mood value when I was vegetarian: 3.33179694171

Average mood value when I was not vegetarian: 3.49920969731

t = -1.95361169902, p = 0.052513305171

Combined conclusions: if I combine my stomach ratings from the two no-grains experiments, my average rating is 3.26375. So by eating meat and not grains, I could ostensibly go from 2.87 to 3.26, an increase of 0.39. How significant is 0.39?
Well, I’ve been collecting data for 160 days. One day had an average value below 2, two days were above 4. The standard deviation is 0.43. So 0.39 is a pretty good jump; I could go from an average day to a day that is better than 2/3 of days. Hmm. I think I’ll start eating (non-factory-farmed) meat again, and stop eating grains when it’s convenient.