236 is a massieve sample size and it is more than sufficient for showing an effect here. The p-values are below 0.001, and while p-values aren't everything, it's a strong indicator that the result is statistically significant.
To infer causality in an epidemiological study such as this you need very large cohorts with very specific results.
Even with huge cohorts you still have relatively indefensible results. The 7 country study is a good example: https://en.wikipedia.org/wiki/Seven_Countries_Study