This graph shows my brain test reaction times over roughly one year. Each point is a different test; I usually do two tests per day back to back. I assume faster = better. In February 2013 I returned to Berkeley from Beijing. In August 2013 I went back to Beijing. When I returned to Berkeley, my scores got worse (slower). I was shocked. Surely Berkeley is healthier than Beijing. At first I thought it was jet lag, but the scores stayed worse long after that made sense. Then I thought it might be some difference in diet, even though I eat similar food in the two places. I tried to make my Berkeley diet closer to my Beijing diet. This might have helped. I noticed accidentally that chocolate improved my score and started eating chocolate frequently. This artificially reduced the difference since in Beijing I had not been eating chocolate. In Berkeley I started doing two things I hadn’t done in Beijing: alternate-day fasting and whole-body vibration. I don’t know if they made a difference. When I returned to Beijing in September, my scores got better, even though I was not eating chocolate. Eventually I improved my sleep in Beijing but that seemed to make little difference. The comparison is far from perfect — many things varied — but by and large my scores got worse when I went from Beijing to Berkeley and improved when I went from Berkeley to Beijing.
What might have caused this? There are a hundred possibilities but one stands out. In both places, I brew and drink several cups of tea every day. In Beijing, everyone, including me, drinks water from big plastic bottles that are delivered to your house. You can choose pure water or “mineral” water, which has added magnesium and potassium. In Berkeley I use tap water (Brita filtered). I don’t think potassium affects brain function — for example, eating bananas makes no difference — but there is plenty of evidence that magnesium improves brain function. In Beijing I had tested a magnesium supplement and found no effect, consistent with the idea that I was already getting enough. Magnesium is also believed to improve sleep. In Beijing I seemed to sleep better than in Berkeley. Again, this is consistent with a difference in magnesium levels (more in Beijing). If ordinary magnesium-enriched water improves brain function, it would be significant because it is so easy, in contrast to other ways of increasing magnesium levels.