Felicity on flour in soda bread in the Guardian
Soda bread can be made with white or brown flour, although, as David points out in her English Bread and Yeast Cookery, there is little point using strong bread flour here: the Irish often talk of a "cake" of brown bread, which gives you a fair idea of the texture to aim for. Moist and crumbly, rather than light and airy, is the name of the game. I'll be concentrating on the wholemeal variety – white soda bread is nice enough, but you can't beat the dark, dense, almost absurdly wholesome kind.
Patrick Ryan uses 100% wholemeal flour, "the coarser the better", in the book Bread Revolution, as does David, and Rose Prince in her Pocket Bakery book, with the caveat that it should be "properly grainy". Chef Richard Corrigan uses half wholemeal and half white flour in The Clatter of Forks and Spoons, and Darina Allen uses one part white to just over five parts wholemeal in Forgotten Skills of Cooking.
It can't be denied that a proportion of plain flour gives a lighter result, but that's not what I'm after here. If you'd like a loaf to eat every day, then by all means swap in half the amount of white flour, but I love the nubbly texture and nutty flavour of the wholemeal loaves; they feel ridiculously good for me. Try to get the coarsest ground flour you can; health food shops are often fruitful hunting grounds, or visit the likes of Shipton Mill online.
Prince and Corrigan use rolled oats in their bread, which I'm also a fan of: the more grains the merrier.
“In the midst of winter, I found there was, within me, an invincible summer." Albert Camus