Journal of Osteoporosis In the rat, indigestible carbohydrates of plants, such as fructo-oligo-saccarides, have been shown to increase intesti- nal calcium absorption, calcium balance, and bone mineral density [15, 16]. Among mechanisms of action are increased absorption area of the large bowel produced by a high ﬁbre content and formation of short-chain fatty acids which could promote calcium absorption in the colon. Also ﬁbre compo- nents of fruits and vegetables might have these eﬀects. Green vegetables may also promote retaining of calcium through their vitamin K content [17] and possibly imply that frequent use of vegetables may increase BMD. Like coﬀee, also colas contain caﬀeine, and this methyl xanthine may be a risk factor for osteoporotic fractures [18]. It has, however, been questioned whether caﬀeine intake has any harmful eﬀect on bone health in subjects ingesting adequate levels of calcium [19]. With reference to literature, many of the diet items of the Dietary Index could, in theory, inﬂuence the acid load. In general, a food may be classiﬁed as either acidic or alkaline by its inﬂuence on the urine pH. We emphasize that many of the index components provide acid when ﬁrst entering the gastro intestinal system, such as colas and other types of soft drinks, fruits, and berries. Thus, a local acid eﬀect, for example, on the teeth is expected, irrespective of type of the acid. However, their ﬁnal eﬀect on the acid load of the body could diﬀer appreciably, depending on the metabolic fate of the ingested acids. Vegetables and fruits have been shown to produce more alkaline urine [20]. Thus, contrary to what might be expected, even fruits with a sour taste give a re- duced acid load due to their high content of salts of organic acids [21]. A high intake of fruits and vegetables should accordingly lower the acid load and reduce the urinary loss of calcium. In keeping with these considerations, we previously reported an association between hip fractures and a low intake of vegetables and fruits [22]. In the present study, we observed a positive association between BMD and intake of raw vegetables, but only with borderline signiﬁcance. It is tempting to suggest that the present results could be of some interest when considering prevention and treatment of osteoporosis, but more research is needed. A high intake of sugar sweetened soft drinks may give an increased acid load partly because of the presence of carbonic acid, citric acid, and, in colas also, phosphoric acid [23, 24]. Additionally, also the fructose component of sucrose seems to have the ability to increase the acid load due to uric acid formed during catabolism of fructose in the liver [25]. As discussed by Barzel and Jowsey [26], intake of colas may increase the acid load and have a negative eﬀect on the skeleton. Although the phosphorus content in colas is higher than in most other beverages, others have suggested that it is not high enough to yield a relevant amount of dietary acidity [27]. However, in this context it is crucial to examine the acid potential of dietary phosphate, that is, whether phosphate is monobasic, dibasic, or tribasic [3]. Several studies indicate that ingestion of low doses of acids can increase urinary calcium excretion in man and increase the risk of osteoporosis and bone fractures, whereas intake of alkali buﬀers such as bicarbonate may reduce bone loss [28–33]. However, one study found a weak association 5 between decreased bone health and acid load only in women [34], and a few studies did not ﬁnd any association at all [11, 35]. In a meta-analysis, Fenton et al. [36] concluded that there is no evidence that higher phosphate intakes are detrimental to bone health, and the same author reported in a more recent study that urine pH and urine acid excretion did not predict osteoporosis risk [37]. As discussed by Heanay and Layman [38], intake of pro- tein may have both negative and positive eﬀects on bone health depending on a variety of factors, but the impact of protein on acid production seems to be minor compared with the alkalinizing eﬀects of fruits and vegetables. Thus, currently the literature seems to provide ambiguous infor- mation on the signiﬁcance of protein intake on bone health. Although basic physiology and even early experimental studies suggest a dietary acid load might increase the risk of osteoporosis [26, 39], it is not clariﬁed whether the modern Western diet might give an acid load of a magnitude which could aﬀect the bone mineral density in man. In a Canadian prospective population-based study, the researchers found two underlying dietary patterns in the participants; one was composed of intake of fruits, vegetables, and whole grains (named “nutrient dense”), the other consisted of intake of soft drinks, fast food, certain meats, and sugar-containing desserts (named “energy dense”) [40]. In subgroups of the participants, the nutrient dense factor was associated with increased BMD when adjusted for body mass index, whereas the energy dense factor was associated with decreased BMD. They concluded that some factors related to the energy dense dietary pattern, which in their study resulted in increased BMI, may partially oﬀset the advantages of higher body mass index with regard to bone health [40]. Possibly, one explanation of their results could be that the negative ef- fect of the probably more acidic energy dense diet would counterbalance the positive eﬀect of increased BMI, an inter- pretation which would seem in support of the present results. In Norway, the annual turnover of carbonated beverages increased ﬁfteen times between 1950 and 2002, but then levelled oﬀ [41], which means that there was a high con- sumption in the years before collection of the present data in 2000. It has been suggested that negative eﬀects of cola bever- ages could be attributed to the content of phosphoric acid, and two studies in rats have found that cola consumption induces reduction in bone mineral density [42, 43]. The last one suggests that the decrease in BMD might be related to the renal damage caused by cola drinks in addition to other related factors [43]. Recently, cola intake was shown to acutely increase the calcium excretion in women [44]. However, a meta-analysis concluded that there is no evidence that higher phosphate intakes, regardless of protonation of phosphate, are detrimental to bone health [36]. Although there has been a decrease in the consumption of sugar-sweetened soft drinks among children and adoles- cents during the last years in Norway, the consumption is still among the highest in the world. Almost 50% of the total consumption of sugar in Norwegian youth comes from sugar-sweetened soft drinks and lemonade [45]. The negative