Development and validation of an interview-administered FFQ for assessment of vitamin D and calcium intakes in Finnish women.

Increased vitamin D fortification of dairy products has increased the supply of vitamin D-containing products with different vitamin D contents on the market in Finland. The authors developed a ninety-eight-item FFQ with eight food groups and with a question on supplementation to assess dietary and supplemental vitamin D and Ca intakes in Finnish women (60ºN). The FFQ was validated in subgroups with different habitual vitamin D supplement use (0-57·5 µg/d) against the biomarker serum 25-hydroxyvitamin D (S-25(OH)D) and against 3-d food records (FR) (n 29-67). Median total vitamin D intake among participants was 9·4 (range 1·6-30·5) µg/d. Spearman's correlations for vitamin D and Ca ranged from 0·28 (P 0·146, FFQ v. S-25(OH)D, persons not using supplements) to 0·75 (P<0·001, FFQ v. FR, supplement use included). The correlations between the FFQ and S-25(OH)D concentrations improved within increasing supplement intake. The Bland-Altman analysis showed wide limits of agreement between FFQ and FR: for vitamin D between -7·8 and 8·8 µg/d and for Ca between -938 and 934 mg/d, with mean differences being 0·5 µg/d and 2 mg/d, respectively. The triads method was used to calculate the validity coefficients of the FFQ for vitamin D, resulting in a mean of 1·00 (95 % CI 0·59, 1·00) and a range from 0·33 to 1·00. The perceived variation in the estimates could have been avoided with a longer FR period and larger number of participants. The results are comparable with earlier studies, and the FFQ provides a reasonable estimation of vitamin D and Ca intakes.

Calcium intake in health maintenance - a systematic review.

BACKGROUND: Calcium (Ca) is an essential nutrient for the human body. Despite lively research, there is uncertainty about Ca requirements in terms of desirable health outcomes including an upper intake level above which the potential for harm increases. OBJECTIVES: The aim was to conduct a review to update requirements and desirable or harmful health effects of Ca on the current scientific evidence. METHODS: We searched Medline and Swemed from January 2000 to December 2011 and included all systematic reviews that reported Ca supplementation or usual Ca intake on health outcomes. Meta-analyses, randomized clinical trials and cohort studies were included in the second search between May 2009 and March 2011 and an additional search covering studies till the end of 2011. This review concentrated on studies reporting independent effects of Ca, although a few recent trials report sole effects of Ca on health outcomes, most trials use Ca in combination with vitamin D vs. placebo. RESULTS: In total, we reviewed 38 studies addressing the effects of Ca on bone, pregnancy-related outcomes, cancers, cardiovascular outcomes, obesity, and mortality. There was a lot of heterogeneity in the study protocols, which made it difficult to draw any strong conclusions. According to the literature, high Ca intake seems to have a small positive effect on bone mineral content (BMC) or bone mineral density (BMD) in children and postmenopausal women. We did not find any consistent evidence on the effects of Ca on bone health in premenopausal women or men. Also, the evidence that Ca supplementation reduces fracture incidence is scarce and inconsistent. Maternal diet may influence the peak bone mass of offspring but more studies are required. There was no overall effect of Ca intake on cancers. Ca was associated with a decreased risk of breast cancer and a slightly increased risk of prostate cancer in two of the three studies. No associations were found with other cancers. We found no consistent association between cardiovascular outcomes and Ca intake except for blood pressure. A small decrease of 2-4 mmHg in systolic blood pressure was found in pregnant and in hypertensive subjects with Ca supplementation. Reviewed studies did not show consistent evidence relating Ca intake to either mortality or obesity. CONCLUSION: Based on this evidence, there is no need to change the Nordic recommendations for Ca intake. However, due to heterogeneity in the studies it is difficult to interpret the results and provide single summary statement.

Mono- and polyphosphates have similar effects on calcium and phosphorus metabolism in healthy young women.

PURPOSE: Phosphate (Pi) salts, often mono- (MP) or polyphosphates (PP), are commonly used as additives in the food industry. Previous studies have shown that the effects of MP and PP on calcium (Ca) and phosphorus (P) metabolism may differ. The aim of this study was to determine whether the effects of MP and PP salts differ on markers of Ca and P metabolism in young women. METHODS: Fourteen healthy women 19-31 years of age were randomized into three controlled 24-h study sessions, each subject serving as her own control. During each session, the subjects received three doses of MP, PP or a placebo with meals in randomized order. Both Pi salts provided 1,500 mg P/d, and the diet during each session was identical. Markers of Ca and P metabolism were followed six times over 24 h. RESULTS: During both MP and PP sessions, we found an increase in serum phosphate (S-Pi, p = 0.0001), urinary phosphate (U-Pi, p = 0.0001) and serum parathyroid hormone (S-PTH, p = 0.048 MP, p = 0.012 PP) relative to the control session. PP decreased U-Ca more than did MP (p = 0.014). CONCLUSIONS: The results suggest that PP binds Ca in the intestine more than does MP. Based on the S-Pi, U-Pi and S-PTH results, both Pi salts are absorbed with equal efficiency. In the long run, increased S-PTH, caused by either an MP or PP salt, could have negative effects on bone metabolism.

Habitual high phosphorus intakes and foods with phosphate additives negatively affect serum parathyroid hormone concentration: a cross-sectional study on healthy premenopausal women.

OBJECTIVE: Foods can contain natural phosphorus (NP) and phosphate-containing food additives (AP). The main objective of the present study was to investigate whether NP and AP of habitual diets differ in their effects on markers of Ca metabolism. We also investigated the impact of total habitual dietary P intake on markers of Ca metabolism. DESIGN: Cross-sectional study. Fasting blood samples were collected and participants kept a 4 d food record, from which dietary intake of total P and the consumption of NP (milk and cheese, excluding processed cheese) and AP (processed cheese) sources were calculated. Participants were divided into groups according to their NP- and AP-containing food consumption and into quartiles according to their total P intake. SETTING: Southern Finland. SUBJECTS: One hundred and forty-seven healthy premenopausal women aged 31-43 years. RESULTS: Relative to the lowest total dietary P quartile, mean serum parathyroid hormone (S-PTH) concentration was higher (P = 0.048, analysis of covariance (ANCOVA)) and the mean serum ionized Ca concentration lower (P = 0.016, ANCOVA) in the highest P intake quartile. Mean S-PTH concentrations were higher among participants who consumed processed cheese (P = 0.027, ANCOVA) and less milk and other cheese than processed cheese (P = 0.030, ANCOVA). CONCLUSIONS: High total habitual dietary P intake affected S-PTH unfavourably. Furthermore, phosphate additives may have more harmful effects on bone than other P sources, as indicated by higher mean S-PTH concentration among participants who consumed AP-containing foods. Because of the high dietary P intake and current upward trend in consumption of processed foods in Western countries, these findings may have important public health implications.

Increased calcium intake does not completely counteract the effects of increased phosphorus intake on bone: an acute dose-response study in healthy females.

A high dietary P intake is suggested to have negative effects on bone through increased parathyroid hormone secretion, as high serum parathyroid hormone (S-PTH) concentration increases bone resorption. In many countries the P intake is 2- to 3-fold above dietary guidelines, whereas Ca intake is too low. This combination may not be optimal for bone health. In a previous controlled study, we found that dietary P dose-dependently increased S-PTH and bone resorption and decreased bone formation. The aim of the present study was to investigate the dose-response effects of Ca intake on Ca and bone metabolism with a dietary P intake higher than recommended. Each of the twelve healthy female subjects aged 21-40 years attended three 24-h study sessions, which were randomized with regard to a Ca dose of 0 (control day), 600 or 1200 mg, and each subject served as her own control. The meals on each study day provided 1850 mg P and 480 mg Ca. S-PTH concentration decreased (P < 0.001) and serum ionized Ca concentration increased (P < 0.001) with increasing Ca doses. The bone formation marker, serum bone-specific alkaline phosphatase, did not differ significantly (P = 0.4). By contrast, the bone resorption marker, urinary N-terminal telopeptide of collagen type I, decreased significantly with both Ca doses (P = 0.008). When P intake was above current recommendations, increased Ca intake was beneficial for bone, as indicated by decreased S-PTH concentration and bone resorption. However, not even a high Ca intake could affect bone formation when P intake was excessive.

High phosphorus intakes acutely and negatively affect Ca and bone metabolism in a dose-dependent manner in healthy young females.

Ca and P are both essential nutrients for bone and are known to affect one of the most important regulators of bone metabolism, parathyroid hormone (PTH). Too ample a P intake, typical of Western diets, could be deleterious to bone through the increased PTH secretion. Few controlled dose-response studies are available on the effects of high P intake in man. We studied the short-term effects of four P doses on Ca and bone metabolism in fourteen healthy women, 20-28 years of age, who were randomized to four controlled study days; thus each study subject served as her own control. P supplement doses of 0 (placebo), 250, 750 or 1500 mg were taken, divided into three doses during the study day. The meals served were exactly the same during each study day and provided 495 mg P and 250 mg Ca. The P doses affected the serum PTH (S-PTH) in a dose-dependent manner (P=0.0005). There was a decrease in serum ionized Ca concentration only in the highest P dose (P=0.004). The marker of bone formation, bone-specific alkaline phosphatase, decreased (P=0.05) and the bone resorption marker, N-terminal telopeptide of collagen type I, increased in response to the P doses (P=0.05). This controlled dose-response study showed that P has a dose-dependent effect on S-PTH and increases PTH secretion significantly when Ca intake is low. Acutely high P intake adversely affects bone metabolism by decreasing bone formation and increasing bone resorption, as indicated by the bone metabolism markers.

Bread fortified with cholecalciferol increases the serum 25-hydroxyvitamin D concentration in women as effectively as a cholecalciferol supplement.

Fortification of foods is a feasible way of preventing low vitamin D status. Bread could be a suitable vehicle for fortification because it is a common part of diets worldwide. The bioavailability of cholecalciferol from bread is not known. We studied cholecalciferol stability, the concentration of the added cholecalciferol, the dispersion of cholecalciferol in bread, and the bioavailability of cholecalciferol from fortified bread. Three batches of fortified low-fiber wheat and high-fiber rye breads were baked; from each batch, 3 samples of dough and bread were analyzed for their cholecalciferol content. In a single-blind bioavailability study, 41 healthy women, 25-45 y old, with mean serum 25-hydroxyvitamin D concentration 29 nmol/L (range 12-45 nmol/L), were randomly assigned to 4 study groups. Each group consumed fortified wheat bread, fortified rye bread, regular wheat bread (control), or regular wheat bread and a cholecalciferol supplement (vitamin D control) daily for 3 wk. The daily dose of vitamin D was 10 mug in all groups except the control group. The vitamin dispersed evenly in the breads and was stable. Both fortified breads increased serum 25-hydroxyvitamin D concentration as effectively as the cholecalciferol supplement. Supplementation or fortification did not affect serum intact parathyroid hormone concentration or urinary calcium excretion. In conclusion, fortified bread is a safe and feasible way to improve vitamin D nutrition.