Thankfully, I just learned about a rather inexpensive medicine that randomized, double-blinded, placebo-controlled studies have shown to be effective in bringing bronchitis to a halt -- Umckaloabo, an extract of Pelargonium sidoides, sold in the US as Umcka. I got a 120 ml bottle of syrup for $15 at Whole Foods. Tastes fine. It takes days for it to end bronchitis, but even after the first day of taking it, I notice that my symptoms aren't as bad as they've been.
Read more about it and its possible effect on the common cold at Michael Eades' blog, an excellent resource for low-carb and general health / nutrition information. Search PubMed for "bronchitis pelargonium" to leaf through the literature. Probably the most important is this recent Cochrane Review paper:
P. sidoides may be effective in alleviating symptoms of acute rhinosinusitis and the common cold in adults, but doubt exists. It may be effective in relieving symptoms in acute bronchitis in adults and children, and sinusitis in adults. Reliable data on treatment for other [acute respiratory infections] were not identified.
How did I manage to get sick on a low-carb diet, while taking 2400 IU of vitamin D in addition to whatever I'm getting from dead animals and sunlight? Simple: after watching Adventureland, the wistful chord it struck made me want to indulge in something sweet. So I had a pint of coconut milk ice cream that same night, another pint the next day, and two pieces of bread and a large fries from Burger King the day after that. I'd been completely unaffected by the various rounds of bugs going around this year, even though I go out to crowded night clubs at least twice a week, which are pathogen breeding grounds. Then within a day or so of binging on sugar or starch (probably between 50 - 60 g per day), I got slammed with fucking bronchitis once more.
This just goes to show how harmful it is to focus on weight as the main signal of health -- being a lardass is probably not healthy (although some fat people are pretty fit), but there are plenty of freaks like me who can funnel a ton of garbage down their gullet and not put on a single pound. Of course, all of the other effects of high blood sugar and high insulin continue on course. Yet when all we tally up is weight, we can't take account of all those other ills.
At any rate, stick to your low-carb diet, get plenty of vitamin D, and have a bottle of Umcka ready just in case.