There's also, I fear, a trap here where we believe we understand nutrition, only to discover there are nuances that we still don't have a great handle on.
As an example, there's the emerging posibility that one's gut flora can have a huge impact on overall health - and that certain types of foods can have a negative or positive impact on that gut flora.
Manipulating basic elements could easily lead to our skipping over critical parts of our health needs, with unintended consequences down the line.
Put another way: our dietary habits and nutritional systems developed over tens-to-hundreds of thousands of years. I'm very leery of any theory that we can easily replace that.
Right, gladly I believe we are some way beyond 'emerging' and into 'researching' , 'This year, the US National Institute of Mental Health spent more than US$1 million on a new research programme aimed at the microbiome–brain connection.' http://www.nature.com/news/gut-brain-link-grabs-neuroscienti...
When I was doing nanotech 10+ years ago, and people asked me when nanorobots were coming, I'd always ask them why they thought nanorobots would be different than, say, bacteria, or viruses? The constraints "at the bottom" (as Feynman would say) are quite high—and we're not really very close to being able to engineer at that scale. Heck, even making a robot the size of a grain of rice is a pretty daunting task, and a nanorobot would be built on a scale that's 10^12 to 10^18 times smaller (the cubic relationship is a real bitch), depending on what you mean by "nanoscale".
Engineering a "thing" to convert basic chemicals and sunlight into food is a pretty significant task. While I would bet that plants are nowhere near close to optimal, they're already solving the problem. Changing & rethinking an existing system is far easier than simply creating one from whole cloth.
If I had to guess, I'd say that "producing food from manipulating basic elements" using a piece of tech entirely designed by human hands, from scratch, is at least a couple of centuries in the future.
If we ever get to tame energy I don't think we'll need to care about water and food. It seems inefficient to tame energy only to then invest more time in food research to give our bodies energy.
As an example, there's the emerging posibility that one's gut flora can have a huge impact on overall health - and that certain types of foods can have a negative or positive impact on that gut flora.
Manipulating basic elements could easily lead to our skipping over critical parts of our health needs, with unintended consequences down the line.
Put another way: our dietary habits and nutritional systems developed over tens-to-hundreds of thousands of years. I'm very leery of any theory that we can easily replace that.