Are milk or dairy products necessary to meet the calcium recommendations?
Sommaire de l'article
The Calcium Recommendations ("ANC") are calculated as the sum of the requirements for maintenance, growth, pregnancy and lactation, modified by a coefficient which takes into account the intestinal calcium absorption, and a margin of safety. However, this approach has led to criticisms pointing out that the values obtained could be too high for many individuals. This can be addressed by introducing the notion of "guide-values" representing 90% of FCaR (ANC) which equal to 800 mg per day in adults and approximately 1 gram in adolescents, post menopausal women (> 55 years), and elderly men and women (see Sci. Aliments, 26, 115-122, 2006). Cow milk, which contains more than 1 g Ca per litre, and dairy products are by far the most important contributory foods for calcium consumption since they account for 70% of the average total calcium intake. Is it possible to fulfil the ANC without using dairy products? A simple calculation of a daily diet combining usual food ingredients according to the recommended energy intakes shows that non-dairy part of the diet provides usually less than 450 mg Ca per day. Using the "guide-values", this indicates that 400 to 600 mg calcium a day (equivalent to 2 to 3 "portions" of dairy products containing 200 mg each) are missing according to age and physiologic status of the person. By choosing the Ca-richest ingredients (avoiding milk and milk products), it is feasible to increase calcium intakes. For example, a diet composed of rich Ca foods such as small fishes with spines (sardines), shellfish, almonds, some specific vegetables, dry fruits and a rich Ca mineral water may reach 1000 mg Ca a day. So, it is possible to answer "yes" to the early question. However, this is not a plain "yes". In fact, almonds, legumes (beans, soy, lentil…), whole-wheat by-products, spinach, watercress which are the Ca-richest vegetables also provide anti-nutritional factors like phytates or oxalates… These decrease Ca bioavailability, thus increase the amounts of calcium to provide. For those vegetables devoid of the inhibiting factors (cabbage, broccoli), their calcium is absorbed similarly to that of dairy product. However, it would be necessary to consume at least one kg of cabbage (or 2.5 kg of oranges) to provide as much calcium as does a litre of milk. Finally, some mineral waters are also interesting sources of non-dairy calcium (up to 500 mg/L). In this paper, acid/base equilibrium relative to urinary calcium loss is also discussed. In conclusion, milk and dairy products are not compulsory to ensure ANC, but the choice of other Ca-rich foods is very limited, the menu to deliver these is more difficult to establish and would be fastidious to eat on a long-term basis. Finally, these other foods may also cause some nutritional problems concerning their calcium bioavailability, which is not so "guaranteed" than that of the milk calcium.