It's not about control, it's about disclosure...Let me push back a little.A Constitutional right? No.
Doesn't knowing what food the government allows to be sold in the open market fall under them looking out for our general wellfare? Which is a constitutional right if I'm not mistaken.
The federal government has no power over what food is 'allowed' to be sold. General Welfare is perhaps the most abused clause in the document, at least by those that seek to reject the notion of a federal government with limited powers. After all, ANYTHING could be considered controllable by the central planners if it was the fed's job to provide welfare, which was not the original intent. Not even close. In fact, it meant the opposite of what you're implying. General welfare is not giving the government the authority over every area of life, but only those specific powers listed or enumerated in the Constitution.
Let's see what Jame Madison had to say about it:
“With respect to the words general welfare, I have always regarded them as qualified by the detail of powers connected with them. To take them in a literal and unlimited sense would be a metamorphosis of the Constitution into a character which there is a host of proofs was not contemplated by its creator.”
Why so many support the notion of every increasing central control is beyond baffling to me. Are you just naturally inclined to want to be told what to do? I don't get that.