Calcium absorption from commonly consumed vegetables in healthy Thai women

An Algorithm to Assess Calcium Bioavailability from Foods

BACKGROUND

The recommended calcium intakes to meet calcium requirements at various ages are based on average population absorption values. Absorption is altered by physiology, the calcium load, and type of food. The calcium intake necessary, therefore, to meet requirements depends upon diet composition, through bioavailability.

OBJECTIVE

The objectives of this study was to improve predictions of calcium bioavailability on the basis of the food matrix.

METHODS

We modeled calcium absorption data from individual foods, beverages, and fortified foods that were determined with calcium isotopic tracers and compared with milk as a referent to adjust for physiologic differences of the host.

RESULTS

Data from 496 observations were modeled to develop a predictive algorithm for calcium bioavailability in adults on the basis of calcium load and oxalate and phytate loads, which represent the 2 main inhibitors of calcium absorption.

CONCLUSIONS

This algorithm will be helpful in assessing calcium availability from the food supply, for developing diets for individuals and research cohorts, and for designing policies and interventions to address inadequate calcium intake for populations.

Calcium Absorption from Food Products: Food Matrix Effects

This article reviews physicochemical aspects of calcium absorption from foods. Notable differences are observed between different food products in relation to calcium absorption, which range from <10% to >50% of calcium in the foods. These differences can be related to the interactions of calcium with other food components in the food matrix, which are affected by various factors, including fermentation, and how these are affected by the conditions encountered in the gastrointestinal tract. Calcium absorption in the intestine requires calcium to be in an ionized form. The low pH in the stomach is critical for solubilization and ionization of calcium salts present in foods, although calcium oxalate complexes remain insoluble and thus poorly absorbable. In addition, the rate of gastric transit can strongly affect fractional absorption of calcium and a phased release of calcium into the intestine, resulting in higher absorption levels. Dairy products are the main natural sources of dietary calcium in many diets worldwide, which is attributable to their ability to provide high levels of absorbable calcium in a single serving. For calcium from other food products, lower levels of absorbable calcium can limit contributions to bodily calcium requirements.

Perspective: Striking a Balance between Planetary and Human Health: Is There a Path Forward?

The global adoption of predominantly plant-based sustainable healthy diets will help reduce the risk of obesity- and malnutrition-related non-communicable diseases while protecting the future health of our planet. This review examines the benefits and limitations of different types of plant-based diets in terms of health and nutrition, affordability and accessibility, cultural (ethical and religious) acceptability, and the environment (i.e., the four pillars underlying sustainable healthy diets). Results suggest that, without professional supervision, traditional plant-based diets (vegan, vegetarian and pescatarian diets) can increase the risk of nutritional deficiencies among infants, children/adolescents, adult females, pregnant/lactating women and the elderly. In contrast, flexitarian diets and territorial diversified diets (TDDs, e.g., Mediterranean and New Nordic diets) that include large quantities of plant-sourced foods, low levels of red meat and moderate amounts of poultry, fish, eggs and dairy can meet the energy and nutrition needs of different populations without the need for dietary education or supplementation. Compared to vegan, vegetarian and pescatarian diets, more diverse flexitarian diets and TDDs are associated with reduced volumes of food waste and may be more acceptable and easier to maintain for people who previously followed western diets. Although flexitarian diets and TDDs have a greater impact on the environment than vegan, vegetarian and pescatarian diets, the negative effects are considerably reduced compared to western diets, especially if diets include locally-sourced seasonal foods. Further studies are required to define more precisely optimal sustainable healthy diets for different populations and to ensure that diets are affordable and accessible to people in all countries.

Lactose intolerance in patients with inflammatory bowel diseases and dietary management in prevention of osteoporosis

Lactose intolerance affects 33% to 75% of the world population and may be associated with various genetic factors. Lactose in the diet can be found in milk and dairy products, which simultaneously constitute the primary sources of calcium. Gut microbiota also influences lactose tolerance. Patients with lactose intolerance often stop consuming milk and dairy products, which may lead to calcium and vitamin deficiency and osteoporosis. Insufficient production of lactase also occurs in patients with diseases of the gastrointestinal tract, such as inflammatory bowel diseases. Moreover, Crohn's disease and ulcerative colitis are risk factors for osteoporosis, and the intake of the proper amount of calcium is an essential element in preventing the decrease of bone mineral density. Diet may prevent the development of osteoporosis, thus, educating patients regarding proper diet should constitute a part of the treatment and prevention process. Patients should consume low-lactose, or lactose-free milk and bacterially fermented dairy products. Additionally, plant milk supplemented by calcium and vitamin D, mineral water with calcium, and certain vegetables also may be good sources of calcium.

Bioavailability of Micronutrients From Nutrient-Dense Whole Foods: Zooming in on Dairy, Vegetables, and Fruits

In order to fully exploit the nutrient density concept, thorough understanding of the biological activity of single nutrients in their interaction with other nutrients and food components from whole foods is important. This review provides a narrative overview of recent insights into nutrient bioavailability from complex foods in humans, highlighting synergistic and antagonistic processes among food components for two different food groups, i.e., dairy, and vegetables and fruits. For dairy, bioavailability of vitamins A, B2, B12 and K, calcium, phosphorous, magnesium, zinc and iodine are discussed, whereas bioavailability of pro-vitamin A, folate, vitamin C and K, potassium, calcium, magnesium and iron are discussed for vegetables and fruits. Although the bioavailability of some nutrients is fairly well-understood, for other nutrients the scientific understanding of uptake, absorption, and bioavailability in humans is still at a nascent stage. Understanding the absorption and bioavailability of nutrients from whole foods in interaction with food components that influence these processes will help to come to individual diet scores that better reflect absorbable nutrient intake in epidemiologic studies that relate dietary intake to health outcomes. Moreover, such knowledge may help in the design of foods, meals, and diets that aid in the supply of bioavailable nutrients to specific target groups.

Using stable isotope tracers to study bone metabolism in children

Skeletal mineralization is initiated in utero and continues throughout childhood and adolescence. During these key periods of the life cycle, calcium retention must increase significantly to provide sufficient mineral for bone deposition and skeletal growth. Stable calcium isotopes have served as a fundamental tool to non-invasively characterize the dynamic changes in calcium physiology that occur from infancy through adolescence. These approaches have helped define the dynamics of calcium absorption and utilization in healthy children and in children with chronic diseases. As data in this area have accumulated, new areas of emphasis are beginning to characterize the determinants of variability in mineral retention, the genetic determinants of bone turnover and calcium flux and the impact of the gut microbiome on whole body and niche specific calcium dynamics. Advances in these areas will help define calcium utilization in paediatric populations and provide information that may be useful in maximizing bone acquisition across this critical phase of the life cycle.

Association of Habitually Low Intake of Dietary Calcium with Blood Pressure and Hypertension in a Population with Predominantly Plant-Based Diets

This study aimed to assess the association of habitually low dietary calcium intake with blood pressure or hypertensive risk using data from the China Health and Nutrition Survey (CHNS) in 2009. We included 6298 participants (2890 men and 3408 women) aged 18 years or older in this analysis. Food intakes were measured by 3-day 24-h individual recalls combined with a weighing and measuring of household food inventory. The participants were divided into normotensive, pre-hypertensive and hypertensive groups according to their mean blood pressure of three repeated measurements. Six intake levels were decided by percentiles of gender-specific dietary calcium intakes (P0⁻10, P10⁻30, P30⁻50, P50⁻70, P70⁻90, and P90⁻100). Average dietary calcium intakes were 405 mg/day for men and 370 mg/day for women, 80% and 84% of which were derived from plant-based food in men and women, respectively. Multiple linear regression analyses showed that dietary calcium intakes were not related with blood pressure in both genders (all P > 0.05). Logistic regression analyses showed a lower risk of pre-hypertension with higher dietary calcium intakes in women (all Pfor trend < 0.001), but not in men; no association between dietary calcium intake and hypertensive risk was found in both genders (all Pfor trend > 0.05). This study suggests that there are no conclusive associations of habitually low dietary calcium intake with blood pressure or hypertensive risk in Chinese individuals consuming predominantly plant-based diets.

Vitamin D Status Is Positively Associated with Calcium Absorption among Postmenopausal Thai Women with Low Calcium Intakes

BACKGROUND

Few data exist on the ability of postmenopausal women to absorb calcium from diets habitually low in calcium.

OBJECTIVE

The objective of this study was to evaluate fractional calcium absorption from a green leafy vegetable vs. milk in relation to vitamin D status.

METHODS

We measured fractional calcium absorption from both a dairy- and plant-based source in 19 postmenopausal Thai women (aged 52-63 y) with low calcium consumption (350 ± 207 mg/d) in relation to serum parathyroid hormone (PTH) and serum 25-hydroxyvitamin D [25(OH)D]. Fractional calcium absorption was measured using a triple stable calcium isotope method based on isotope recovery in a 28-h urine collection. Two extrinsically labeled test meals were ingested in random order: a green leafy vegetable (cassia) ingested along with ⁴³Ca or a glass of milk containing ⁴⁴Ca. Women received intravenous ⁴²Ca with the first test meal.

RESULTS

In 19 postmenopausal women studied (mean age, 56.9 ± 3.4 y), ~95% were 25(OH)D sufficient (≥20 μg/L). Serum 25(OH)D status was positively correlated with fractional absorption from both cassia (P = 0.05, R² = 0.21) and milk (P = 0.03, R² = 0.26). Fractional calcium absorption from cassia was significantly lower than that measured from milk (42.6% ± 12.3% vs. 47.8% ± 12.8%, P = 0.03), but true calcium absorption did not significantly differ (120 ± 35 mg/d vs. 135 ± 36 mg/d). Serum PTH was significantly inversely associated with serum 25(OH)D (P = 0.006, R² = 0.37) even though PTH was not elevated (>65 pg/mL).

CONCLUSIONS

These findings suggest that vitamin D status is an important determinant of calcium absorption among Thai women with low calcium intakes, and cassia may be a readily available source of calcium in this population. Furthermore, these data indicate that serum 25(OH)D concentrations may affect PTH elevation in postmenopausal women with low calcium intakes.

Inadequate calcium intake is highly prevalent in Korean children and adolescents: the Korea National Health and Nutrition Examination Survey (KNHANES) 2007-2010

OBJECTIVE

The present study aimed to assess the adequacy of Ca intake and major food sources of Ca in Korean children and adolescents.

DESIGN

A cross-sectional study.

SETTING

Data from the Korean National Health and Nutrition Examination Survey (KNHANES) 2007-2010. We analysed the daily Ca intake, major food sources of Ca and the prevalence of inadequate Ca intake in the study population. Ca intake was categorized as inadequate when the participant's daily Ca intake was less than the Estimated Average Requirement. Subject The study population consisted of 7233 children and adolescents (3973 boys, 3260 girls; aged 1-18 years).

RESULTS

Mean Ca intake was 510·2 mg/d in boys and 431·7 mg/d in girls. Overall, 75·0 % of adolescents (boys 71·6 %, girls 79·1 %) had inadequate Ca intake. The prevalence of inadequate Ca intake increased significantly from toddlers (45-55 %) to adolescents (78-86 %) in both genders. The highest ranked food sources for Ca were dairy products (35·0 %), followed by vegetables (17·3 %), grains (11·3 %) and seafood (9·9 %). Ca intake from dairy products decreased significantly from 57 % in toddlers to 30 % in adolescents, while Ca intakes from other foods increased with age.

CONCLUSIONS

Inadequate Ca intake is highly prevalent and increased with age in Korean children and adolescents. It should be emphasized to encourage children and adolescents to eat more Ca-rich products to meet their Ca needs.

The search for a new paradigm to study micronutrient and phytochemical bioavailability: from reductionism to holism

The study of micronutrient and phytochemical (MaP, i.e., non-energy nutrients) bioavailability has been mainly studied through a reductionist and pharmacological approach. This has led to associate one health effect to one MaP. However, human interventional studies have given conflicting and disappointing results about MaP supplementation. This is because the health effect is the result of the synergetic action of numerous MaPs supplied by foods and/or diets at nutritional doses. A food is not a drug. Therefore, there is a need for more holistic approach to study MaP bioavailability, then their health effect to achieve general recommendations. This paper aims to hypothesize for such a paradigm shift in this topic and to lay new foundations for research in MaP bioavailability.

The role of diet in osteoporosis prevention and management

Diet, a modifiable osteoporosis risk factor, plays an important role in the acquisition and maintenance of bone mass. The influence of diet on bone begins in childhood; even maternal diet can influence bone mass in the offspring. A good general nutritional status and adequate dietary protein, calcium, vitamin D, fruits, and vegetables have a positive influence on bone health, while a high caloric diet and heavy alcohol consumption have been associated with lower bone mass and higher rates of fracture. The evidence for a role of other minerals and vitamins in skeletal health is not as strong, but recent evidence suggests that vitamins C and K might also have an effect on bone.

Malic enzyme gene polymorphism is associated with responsiveness in circulating parathyroid hormone after long-term calcium supplementation

OBJECTIVE

To identify genetic variations associated with parathyroid hormone (PTH) suppression after long-term calcium supplementation.

DESIGN AND PARTICIPANTS

For high throughput SNP screening, subjects consisted of 171 postmenopausal women without osteoporosis at the lumbar spine. A separate group of 19 premenpausal women were recruited for calcium absorption study. Postmenopausal women in the screening group were given 500 mg/day calcium supplementation.

SETTING

Bangkok, Thailand.

MEASUREMENTS

Parathyroid hormone (PTH) and bone mineral density (BMD) were measured at baseline and 2 years after calcium supplementation. High throughput single-nucleotide polymorphism (SNP) screening was performed by comparing estimated allele frequencies derived from hybridization signal intensities of pooled DNA samples on Affymetrix's 10K SNP genotyping microarrays based responsiveness in PTH after calcium supplementation. Genotyping of SNP rs1112482 in malic enzyme gene (ME1) gene, a SNP among those with highest odds ratio of being related to PTH suppression after calcium, was performed in all postmenopausal subjects in the screening group and premenopausal women in the calcium absorption study group in which fractional calcium absorption was assessed by stable isotope dilution. Data were expressed as mean +/- SEM.

RESULTS

PTH significantly decreased after 2 years of calcium supplementation (4.7 ± 1.9 vs. 4.4 ± 1.6 pmol/L, P < 0.01). There was a significant increase in lumbar spine BMD (1.03 ± 0.01 vs. 1.01 ± 0.01 g/cm2, P < 0.001) but not femoral neck BMD. In 108 subjects whose PTH levels decreased after calcium, the suppression of PTH was higher in those with at least one C allele in rs1112482 of ME1 gene (-26.3 ± 2.1 vs. -16.9 ± 1.4%, P < 0.001). Fractional calcium absorption also tends to the higher in subjects in the calcium absorption study group with at least one C allele (n = 6) compared to those without the C allele (n = 13) (58.0 ± 4.9 vs. 49.3 ± 2.8%, P = 0.054).

CONCLUSION

Cytosolic malic enzyme 1 gene polymorphism is associated with the degree of suppression of parathyroid hormone after long-term calcium supplementation. The effect is probably mediated through an increase in intestinal calcium absorption.

Calcium storage in plants and the implications for calcium biofortification

Calcium (Ca) is an essential nutrient for plants and animals, with key structural and signalling roles, and its deficiency in plants can result in poor biotic and abiotic stress tolerance, reduced crop quality and yield. Likewise, low Ca intake in humans has been linked to various diseases (e.g. rickets, osteoporosis, hypertension and colorectal cancer) which can threaten quality of life and have major economic costs. Biofortification of various food crops with Ca has been suggested as a good method to enhance human intake of Ca and is advocated as an economically and environmentally advantageous strategy. Efforts to enhance Ca content of crops via transgenic means have had promising results. Overall Ca content of transgenic plants has been increased but in some cases adverse affects on plant function have been observed. This suggests that a better understanding of how Ca ions (Ca(2+)) are stored and transported through plants is required to maximise the effectiveness of future approaches.