ABSTRACT
OBJECTIVE: This study investigated the effects of caffeine intake associated with inadequate or adequate calcium intake in laparotomized or ovariectomized rats by means of the calcium balance. Forty adults Wistar rats were ovariectomized or laparotomized. METHODS: The animals (n=40) were randomly placed in eight groups receiving the AIN-93 diet with 100% or 50% of the recommended calcium intake with or without added caffeine (6mg/kg/day). The animals were kept in individuals metabolic cages at a temperature of 24°±2ºC, light/dark cycles of 12/12 hours, and deionized water available ad libitum. On the 8th week of the experiment, food consumption was measured and 24-hour urine and 4-day feces were collected to determine calcium balance [Balance=Ca intake-(Urinary Ca+Fecal Ca)]. RESULTS: Animals with adequate calcium intake presented higher balances and rates of calcium absorption and retention (p<0.05) than those with inadequate calcium intake, regardless of caffeine intake (p<0.05). Caffeine intake did not affect urinary calcium excretion but increased balance (p<0.05) in the groups with adequate calcium intake. CONCLUSION: Adequate calcium intake attenuated the negative effects of estrogen deficiency and improved calcium balance even in the presence of caffeine.
OBJETIVO: Investigar a relação entre a ingestão de cafeína e a adequação de cálcio dietético em ratas ovariectomizadas ou inteiras, por meio do balanço de cálcio. Foram utilizadas 40 ratas Wistar adultas submetidas à cirurgia de ovariectomia ou laparotomia. MÉTODOS: Os animais foram alocados em grupos (n=5) e receberam dieta AIN-93M contendo 100 ou 50% da recomendação de cálcio com ou sem adição de cafeína (6mg/kg/dia). As fêmeas foram alojadas em gaiolas metabólicas individuais, à temperatura de 24±2ºC e ciclo de 12 horas claro/escuro e receberam água deionizada ad libitum. Na oitava semana de experimento, quantificou-se a ingestão da dieta e coletaram-se fezes de 4 dias e urina dos animais por 24 horas para determinação do balanço [Balanço=Ca Ingerido - (Ca Fecal+Ca Urinário)]. RESULTADOS: Por meio de interação entre fatores, foi observado que o consumo de 100% de cálcio elevou o balanço e os teores de cálcio absorvido e retido (p<0,05) quando comparados aos grupos 50%. As ratas com adequação no consumo de cálcio aumentaram o balanço (p<0,05), independentemente da suplementação de cafeína. A ingestão de cafeína não afetou a excreção urinária de cálcio e elevou (p<0,05) o balanço nas ratas com 100% de cálcio, mas não nas com 50%. CONCLUSÃO: A adequação no consumo de cálcio atenuou os efeitos deletérios da redução estrogênica e proporcionou maior balanço de cálcio mesmo com ingestão de cafeína.
Subject(s)
Animals , Female , Rats , Caffeine/administration & dosage , Calcium, Dietary/administration & dosage , Estrogens/deficiency , Rats, WistarABSTRACT
O cálcio (Ca) dietético é fundamental para a saúde óssea. Tanto o teor como a biodisponibilidade do elemento nos alimentos devem ser considerados. Este artigo objetiva sumarizar os fatores envolvidos na absorção e destacar os alimentos com melhor disponibilidade do Ca. Este é absorvido principalmente no jejuno e o pH baixo parece favorecer sua absorção, que é maior no crescimento, na gestação/lactação e na carência de Ca ou fósforo (P), e menor no envelhecimento. As maiores fontes, e com melhor absorção, são os laticínios bovinos. Outros alimentos apresentam concentrações elevadas de Ca, mas com biodisponibilidade variável: os ricos em ácidos oxálico e fítico apresentariam uma menor absorção, enquanto que os ricos em carboidratos teriam uma absorção maior. Por apresentarem uma biodisponibilidade do Ca mais próxima da do leite bovino, o leite de outros animais, o de soja enriquecido e alguns vegetais, em quantidades adequadas, poderiam ser usados como alternativas a este.
Dietary calcium (Ca) is fundamental to the bone's health. Both the purport and the element bioavailability in the food need to be considered. The purpose of this work was to summarize the factors involved in Ca absorption and point out the sources with higher bioavailability. Ca is mostly absorbed in the jejunum and low pH seems to favor its absorption, which is higher during growth, gestation/lactation and Ca and phosphorus (P) deficiency, and lower with aging. The richest and best-absorbed Ca source is cow's milk and its derivatives. Other foods show high Ca concentrations but variable bioavailability: foods rich in phytates and oxalates show a smaller absorption and carbohydrate-rich foods show higher absorption. Since Ca bioavailability in other animal's milk, soymilk and some vegetables is closer to that in cow's milk, adequate amounts of these foods could be used as an alternative.
Subject(s)
Humans , Animals , Male , Female , Bone Density Conservation Agents/pharmacokinetics , Bone Resorption/metabolism , Calcium, Dietary/pharmacokinetics , Diet , Intestinal Absorption/physiology , Nutritional Requirements , Biological Availability , Bone Density/physiology , Calcium Carbonate/metabolism , Calcium/deficiency , Lactation/metabolism , Lactose Intolerance/metabolism , Lactose/metabolism , Milk/metabolism , Osteoporosis/diet therapy , Osteoporosis/prevention & control , Soy Milk/pharmacokinetics , Vegetables/metabolismABSTRACT
This study examined the effect of excess calcium (Ca) on the iron (Fe) bioavailability and bone growth of marginally Fe deficient animals. Two groups of weanling female SD rats were fed either normal Fe (35 ppm) or Fe deficient diet (8 ppm) for 3 weeks. Then each group of animals were assigned randomly to one of three groups and were fed one of six experimental diets additionally for 4 weeks, containing normal (35 ppm) or low (15 ppm) Fe and one of three levels of Ca as normal (0.5%), high (1.0%), or excess (1.5%). Feces and urine were collected during the last 3 days of treatment. After sacrifice blood, organs, and femur bone were collected for analysis. Final body weight and average food intake were not affected by either the levels of dietary Ca or Fe. Low Fe diet significantly reduced the level of serum ferritin, however, for Hb, Hct, and TIBC no difference was shown than those in the normal Fe group. TIBC increased slightly by high and excess Ca intake in low Fe groups. For both normal and low Fe groups, high and excess Ca intakes reduced the apparent absorption of Fe and Fe contents of liver significantly (p < 0.05). Calcium contents in kidney and Femur of rats that were fed high and excess levels of Ca were significantly greater than those of normal Ca groups. However, weight, length, and breaking force of the bone were not affected by increased Ca intakes. Both in control and low Fe groups, high and excess intakes of Ca decreased the apparent absorption of Ca. These results indicate that the excess intakes of calcium than the normal needs would be undesirable for Fe bioavailability and that the adverse effects be more serious in marginally iron deficient growing animals. In addition bone growth and strength would not be favorably affected by high Ca intakes, though, the long term effect of increased Ca contents in bone requires further examination.
Subject(s)
Animals , Female , Humans , Rats , Absorption , Biological Availability , Body Weight , Bone Development , Calcium , Diet , Eating , Feces , Femur , Ferritins , Iron , Kidney , LiverABSTRACT
This study has investigated the bioavailability of calcium in eggshell powder (ESP) for the purpose of reutilizing eggshells as the calcium source. The experiment was designed 2 X 2 factorial method with two sources, CaCO3 and ESP, and two levels, 0.2% and 0.4% calcium. Weanling SD rats were assigned randomly to one of 4 groups and provided by one of the isocaloric, 20% casein based 4 different experimental diets for 4weeks. Deionized water was given and environment was kept from any contamination of minerals. The body weight, diet intake, feed efficiency ratio (FER), bone growth, Ca contents of bones, and apparent absorption were measured. FER (0.38 - 0.40) and kidney weight were not different among groups and the weight and length, Ca content, strength of two bones Tibia and Femur were not affected by Ca sources except Femur Ca content. Ca content of Femur was greater in ESP groups than that of CaCO3 groups. The body weight gain, bone growth, the Ca contents and strength of bones were significantly greater in 0.4% calcium groups suggesting 0.2% calcium is not sufficient for the optimum growth in the growing rats. These results indicate that ESP be a proper Ca source comparable or superior to CaCO3. However the apparent absorption rate of final 3 days of feeding did not support the observed results showing lower rate in ESP than CaCO3 groups. Further study be needed in the absorption aspect.