Practicing self-control can make you smarter
From the book, 'Thinking Fast, and Slow', by Daniel Kahneman. "Based on the famous marshmallow experiment by Walter Mischel, a link was found between cognitive control and intelligence. Those children who did not eat the marshmallow were found to be less likely to take drugs and had substantially higher scores on tests of intelligence as young adults. Researchers from the University of Oregon explored the link between cognitive control and intelligence in several ways, including an attempt to raise intelligence by improving the control of attention. The testers found that training attention not only improved executive control; scores on nonverbal tests of intelligence also improved, and the improvement was maintained for several months."
This makes me think that in addition to diet, emotional support, and physical exercise, parents can implement mental exercise programs at an early age to improve cognitive control and future intelligence.