4 ms·

It seems like its easy to identify the harms of extremes. Too little of X causes Y and too much of W causes Z. But with so many variables affecting the human bo

by goda90 6y ago

It seems like its easy to identify the harms of extremes. Too little of X causes Y and too much of W causes Z. But with so many variables affecting the human body(nutritional, genetic, environmental, microbial, mental, etc) how can we even approach being certain about optimal levels in the middle? I don't see how we could control for enough variables for long enough to know how much vitamin D is best for the body, and exactly how it interacts with other variables in regards to various diseases.

Nursie 6y ago
But we can see how supplementation affects outcomes, and it turns out that so far the results on that are pretty 'meh', unless you're supplementing specifically for severe vit D deficiency.
- goda90 6y ago
  I guess my point is, if outcomes are affected by a couple dozen variables, unless we can control for all those variables, then we might not see any affect from this one variable. And there is a limit to how many variables we can reasonably control for.
  - zwaps 6y ago
    Controling for variables is important to establish causality in observational studies. Many fields in social sciences are developing increasingly sophisticated methods to tease out causal relationships (see Pearl, Angrist&Pischke etc.). However, many of these methods try to obtain the conditions similar to the gold standard: Randomized Control Trials. In an RCT, if you assign treatment randomly to balanced subgroups of a population you care about (or one that is even representative), then you do not require to controls. To see that, imagine the treatment being independent of the confounding factors and the distributions across group being the same. It then follows that you can estimate the average treatment effect without bias.
  - davinic 6y ago
    And also the effects of those couple dozen are nonlinear and the degree of nonlinearity probably varies from subject to subject.

by goda90 6y ago

Nursie 6y ago

But we can see how supplementation affects outcomes, and it turns out that so far the results on that are pretty 'meh', unless you're supplementing specifically for severe vit D deficiency.

goda90 6y ago
I guess my point is, if outcomes are affected by a couple dozen variables, unless we can control for all those variables, then we might not see any affect from this one variable. And there is a limit to how many variables we can reasonably control for.
- zwaps 6y ago
  Controling for variables is important to establish causality in observational studies. Many fields in social sciences are developing increasingly sophisticated methods to tease out causal relationships (see Pearl, Angrist&Pischke etc.). However, many of these methods try to obtain the conditions similar to the gold standard: Randomized Control Trials. In an RCT, if you assign treatment randomly to balanced subgroups of a population you care about (or one that is even representative), then you do not require to controls. To see that, imagine the treatment being independent of the confounding factors and the distributions across group being the same. It then follows that you can estimate the average treatment effect without bias.
- davinic 6y ago
  And also the effects of those couple dozen are nonlinear and the degree of nonlinearity probably varies from subject to subject.