Dr Hannah Theobald, British Nutrition Foundation, 52–54 High Holborn, London WC1V 6RQ, UK. E-mail: h.theobald

Corresponding Author

British Nutrition Foundation, London, UK

Dr Hannah Theobald, British Nutrition Foundation, 52–54 High Holborn, London WC1V 6RQ, UK. E-mail: h.theobald
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SUMMARY

1

INTRODUCTION

2

SKELETAL FUNCTIONS OF CALCIUM

2.1

Bone

2.2

Bone growth

2.3

Body calcium changes

2.3.1

Fetal growth

2.3.2

Pre-term infants

2.3.3

Infancy

2.3.4

Childhood and adolescence

2.4

Attainment of top bone mass

2.5

Skeletal calcium changes in later life

2.6

Calcium and also dental health

3

REGULATORY ROLE OF CALCIUM

3.1

Introduction

3.2

Intracellular calcium

3.3

Role in blood clotting

3.4

Role in digestion

3.5

Role in neurological and also muscular function

4

CALCIUM HOMEOSTASIS AND METABOLISM

4.1

Plasma calcium homeostasis

4.2

Absorption

4.3

Markers of calcium absorption and status

4.4

Excretion

4.4.1

Factors that affect urinary calcium excretion

5

DIETARY REFERENCE VALUES

5.1

Dietary recommendation values

5.2

Guidance on high intakes

6

SOURCES OF CALCIUM IN THE DIET

6.1

Milk and also dairy products

6.2

Ceactual products

6.3

Plant foods

6.4

More sources of calcium

7

CALCIUM INTAKE IN THE UK

7.1

Key dietary sources

7.2

Current intakes in the UK

7.3

Trends in intake

8

BIOAVAILABILITY OF CALCIUM FROM FOODS

8.1

Dietary factors affecting calcium absorption

8.1.1

Vitamin D

8.1.2

Fat

8.1.3

Protein

8.1.4

Other dietary factors

8.2

Bioavailcapability from different dietary sources

8.2.1

Milk and also milk products

8.2.2

Calcium from plants

8.2.3

Other food sources

9

BONE CALCIUM LOSS

9.1

Bone calcium loss

9.1.1

Pregnancy and also lactation

9.2

Factors affecting age-connected bone loss

9.3

Osteoporosis

9.3.1

Definition

9.3.2

Public health and wellness implications

9.3.3

Primary and also additional osteoporosis

9.4

Dietary calcium, bone mass and also age-connected loss of bones

9.4.1

Bone loss and calcium supplementation in early-post-menopausal women

9.4.2

Bone loss and calcium supplementation in late-post-menopausal women

9.4.3

Fracture risk

10

CALCIUM IN HEALTH AND DISEASE

10.1

Calcium and also cancer

10.2

Calcium and also cardiovascular disease

10.3

Calcium and weight management

10.4

Hypercalcaemia

10.5

Calcium stone formation

11

CONCLUSIONS

ACKNOWLEDGEMENTS

REFERENCES

Summary Calcium is an important nutrient as all living cells require calcium to reprimary viable; calcium is also required for a variety of specific functions in the body. The majority (∼99%) of calcium present in the body is found in bone, through a smaller amount uncovered in teeth. The remainder (10(PO4)6(OH)2>, which provides rigidity. Calcium is crucial for bone development as it is compelled for the mineralisation (impregnation of the bone matrix with minerals) of bone; the price of calcium deplace in bone is proportional to rate of development. An sufficient intake of calcium is one of a number of factors which are vital for getting bone mass and attaining height bone mass (PBM). Diets containing inadequate amounts of calcium may cause a low bone mineral thickness, which might have implications for bone wellness, notably danger of osteoporosis, in later life.

As well as having actually a skeletal feature, calcium plays a regulatory duty in a number of specialised functions in the body. Calcium plays a duty in muscle (consisting of cardiac muscle) contraction, neurotransmitter secretion, digestion and blood coagulation (clotting). Calcium also plays a structural duty external of the skeleton, for instance in organelles and membranes. Disturbances in the structural and regulatory functions of calcium can have actually effects for wellness and condition. For this reason, calcium homeostasis is tightly regulated to encertain that plasma concentrations of calcium ions are maintained within a set range (i.e. 1.1–1.3 mmol/L). Homeostasis is regulated at 3 main sites: the kidneys, bone and the gastrointestinal tract. Control is mediated with the calciotropic hormones: parathyroid hormone (PTH), calcitriol and calcitonin. In response to changes in plasma calcium concentrations, absorption of calcium from the gastrointestinal tract deserve to be altered, along with urinary excretion and calcium resorption from bone.

The UK reference nutrient intake (RNI) for calcium for adults aged over 19 years is 700 mg/day; requirements are better throughout childhood, adolescence and also throughout lactation. No guidance has been issued on high intakes, although exceeding an intake of 1500 mg calcium/day in the create of supplements is discouraged as this can reason stomach pain and also diarrhoea. Calcium intake shows up to have enhanced over the last 30 years or so. On average, British men consume 1007 mg calcium/day, whilst the average British woguy consumes 777 mg/day (Henderboy et al.), but intakes of calcium are a concern amongst certain teams of the population. For example, a high propercent of teenage boys and also girls and women aged 19–24 years fail to satisfy the lower reference nutrient intake (LRNI) for calcium, i.e. their intakes are likely to be insufficient.

A wide number of foods contain calcium, however the amount of calcium, offered per 100 g or per serving, and also its bioavailability differ considerably. The significant resource of calcium in British diets is milk and milk assets (giving more than 40% of calcium intake among adults), followed by cereals and also cereal products (providing 30% of intake). The contribution from cereals is high because although they are not a affluent source, they are consumed in relatively large amounts and likewise some grain products are fortified via calcium. For instance, it is a mandatory necessity that white and also brown wwarmth flours contain specified amounts of calcium, which is completed with fortification. Further sources of calcium include plant foodstuffs, consisting of soya beans, some pet products (e.g. eggs) and water. The bioavailcapacity of calcium from a food is influenced by the existence of a number of various other compounds within a food. Dietary determinants that affect absorption of calcium incorporate fat (reduces absorption), protein and phosphorus (both rise absorption). The bioavailcapacity of calcium from milk and also milk commodities is in the region of 30% compared to 5% from spinach. Spinach, although containing a fairly huge amount of calcium, is not taken into consideration a bioavailable resource, as it contains a high concentration of oxalic acid which inhibits the absorption of calcium. Phytic acid and also uronic acid, additionally discovered in plant foodstuffs, have a comparable result. However before, the bioavailability of calcium from other plant foods items is great, e.g. broccoli (check out Bioavailability of calcium from foods). Soya beans are likewise a notable exemption, in that they contain high amounts of both oxalic and phytic acids, yet are a bioavailable source of calcium (bioavailcapability is in the area of 30– 40%). The bioavailcapability of calcium from soya commodities will certainly vary depending on the product.

A low intake of calcium throughout growth has actually ramifications for bone mass, as the amount of calcium consumed in the diet influences the amount of calcium that have the right to be preserved by the skeleton during periods of development. An poor intake of calcium combined via adequate power and also protein intakes may result in a low calcium content of bone, which might have implications for bone health and wellness later in life. The attainment of a high PBM in early on adulthood is important as bone mineral (consisting of calcium) content starts to decrease after that. PBM has been reported to be reached as beforehand as the late teenage years or as late as the mid-thirties; this relies on the site in the skeleton . A number of factors affect bone mineral losses, e.g. physical task (immobility speeds up loss), hormonal standing and sex. In womales, loss of bone mineral is increased roughly the time of the menopausage, as a result of a fall in circulating oestrogen concentrations. An excessive loss of bone connected with ageing have the right to lead to osteoporosis, which is characterised by micro-architectural changes in bone tproblem, loss of bone mineral and also reduced strength of bone which eventually increases the threat of bone fracture. Osteoporosis is associated via morbidity and also raised mortality and also is a major concern in the UK and also across the occurred civilization. As the population eras, the incidence of osteoporosis will increase and lug through it added expenses to the health and wellness mechanism and the economic situation.

There is some proof that increased intakes of calcium later in life might assist sluggish the rate of bone loss connected with ageing. The proof is strongest among older postmenopausal women, rather than in the time of the early on stages (initially 5–10 years) of the menopause. It appears that most advantage is obtained from consuming additional calcium in the irreversible. Further study is required to investigate optimal dietary calcium intakes in relation to minimising bone mineral losses and reducing the danger of osteoporosis.

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Calcium might have a function in the aetiology of chronic disease, with proof saying that raised calcium intakes may help in the prevention of colorectal cancers. There is weaker proof to imply that calcium may offer some protection versus breastern cancer and also even more study needs to be performed to confirm or refute an result. Calcium has actually lengthy been argued to play a role in the aetiology of cardiovascular disease; early ecological studies said that consumption of hard (calcium-containing) water was associated through a reduced hazard. Calcium exerts modest blood pressure and also lipid-lowering results, which might be of relevance in reducing risk of cardiovascular condition. In addition, there is preliminary evidence suggesting that calcium may play a role in weight management. Data from epidemiological studies imply an inverse association in between calcium intake and also bodyweight. Human being trials in this location are still in their infancy; at present findings must be construed via caution. A variety of mechanisms that might underlie this result of calcium on bodyweight are presently being investigated and also even more human trials are underway.