Interesting topic..
Out of health reasons I had to drastically change my diet to avoid all processed foods, and I stopped drinking coffee and I do not drink anything other than water or tea for the most part.
I follow a diet based on the paleolothic diet, you guys can google it if you're interested, but in a nutshell it's eating what our ancestors would have eaten before agriculture. So basically I eat anythign that would not require processing to be eaten. Meat, Vegetables, fruits, and I drink mainly water and herbal or green tea.
A guy called Ray Audette wrote a book called "Neanderthin", in which he adopted this diet to cure some of the diseases he was suffering from, including rheumatoid arthritis and diabetes. He was able to reverse those diseases simply by changing his diet, and I've read articles where he claimed that his hair stopped falling out.
I'm pretty sure I can agree with that, it seems like my hair stopped thinning when I adopted this diet, although I changed my diet for more important reasons. I certianly can vouch for feeling better, and I dropped 40 pounds.
The amount of food additives put into our foods, and artificial foods on the market today is absolutely staggering. Many of these additives are toxic or cause allergic reactions in people, and affect the body's chemistry and hormonal balances. It's not that far fetched to think that some of these might be affecting our hair growth, if they affect other parts of the body.