() is a very common form of rye bread from Denmark.  usually resembles a long brown extruded rectangle, no more than 12 cm high, and 30–35 cm wide, depending on the bread pan in which it is baked. The basic ingredient is rye flour which will produce a plain or "old-fashioned" bread of uniform, somewhat heavy structure, but the most popular versions today contain whole grains (cracked or chopped rye kernels) and often other seeds such as sunflower seeds, linseeds or pumpkin seeds. Most Danes eat rugbrød every day.

The dough may be made exclusively with rye flour or contain up to one third whole rye grains. A small amount of wheat flour, sugar or molasses is often added to adjust the taste or because wheat flour is cheaper than rye (contrary to in former times).

 was the major staple of most of the population until potatoes became widespread during the late 19th century, and even up to the 1950s, Danes ate much larger amounts of  than today. It has been discussed why this bread type prevailed better in Denmark than other Northern European countries.  is implied in the colloquial Danish term for serving prison time,  ('on water and bread'). Until 1933, prisoners could in some circumstances be punished with an allowance of only water, a fixed amount of , salt and possibly lard.

 is regarded somewhat difficult for home baking. Apart from the sourdough preparation, the loaves must not be leavened for too long, or else the taste can become excessively sour, with the relatively pungent acetic acid taking the lead over milder-tasting lactic acid, and enzymes can cause the gluten (protein structure) and starches to degrade and collapse, creating cavities or dense lumps inside the bread or even causing it to shrink during or after baking. Rarely, recipes replace some of the water with ale or beer, but this is not necessary to create the characteristic sourdough taste.

Sourdough is almost always used for the base dough, as commercial yeasts are unsuitable. The naturally fermented dough will develop a Lactobacillus culture in symbiotic combination with naturally present yeasts. It is essential in baking rye-based breads because the chemistry of rye flour produces an environment that is acidic. The most commonly present yeast species in the production of naturally leavened dough is Saccharomyces exiguus, which is more acid-tolerant than commercially produced S. cerevisiae, although the latter and other strains may also be present. Research has shown that when creating a naturally fermented starter, any naturally present S. cerevisiae will have died off after a few days. Sourdough is thus a stable culture of lactic acid bacteria and yeast in a mixture of flour and water. The yeast produces carbon dioxide which leavens the dough, and the bacteria produces lactic acid which contributes flavor. The bacteria metabolizes sugars that the yeast cannot, and the yeast metabolizes byproducts of bacterial fermentation. Commercially produced yeast will not accomplish these processes in rye flour. 

 contains little or no added oils and is low in fat. Additional flavourings, other than salt, can include barley malt syrup or sugar. The bread is rich in protein and dietary fiber and not very sweet, unlike Swedish and German rye bread.

Buttered  is essentially the base for Danish open sandwich .

Further reading
 Boyhus, Else-Marie. "Rugbrød Og Danmarkshistorie. [Rye Bread and Danish History]." Denmark: Schulstad’s Newsletter (2005).
 Hansen, Kirsten Skovmand, Erling Saxholt, and Pia Knuthsen. "Næringsstoffer i rugbrød og hvedebrød: Cerealier del 1–Rugbrød og hvedebrød-Kortlægning af næringsstofindhold. Analytisk undersøgelse." (2012).

See also

 Danish cuisine
 Pumpernickel
 Rúgbrauð
 Ruisleipä
 Schwarzbrot
 Øllebrød

References

External links
Danish Sourdough Rye Bread (Rugbrød) Louise Hurst
Danish Rugbrød recipe Breadtopia
Danish sourdough rye bread recipe
  Mixed grain sourdough & yeast loaf recipe 

Danish cuisine
Rye breads
Sourdough breads