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Calcium is the most abundant mineral in the body, it is vital to build and maintain strong bones and teeth, and functioning of your nerves and muscles. How much calcium you need to eat to meet your body’s needs depends on how well you absorb the calcium that you do eat. You can find calcium in leafy greens, legumes, seaweed, dairy products, some fish and dietary supplements but beware of eating too little or too much calcium as both can lead to health problems.

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What it is

Calcium is an essential mineral for all living creatures including you, with more calcium in your body that any other mineral.  Over 99 percent of that calcium is stored in your teeth and bones while a constant level of the rest of the calcium is in your nerve cells, blood, muscles, body tissues and other body fluids.

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What it does

Calcium is one of the most important of the minerals for the growth and maintenance of your body. You need enough to build and keep your bones and teeth strong. This is for your whole life as your bones are always being remodelled with a continuing cycle of resorption (bone breakdown) and depositing of calcium in new bone.

This breakdown and rebuilding of the bones in your body is continuous from before you are born until the day that you die. What changes is the balance between the two changes as you age. When you are a child there is a lot of bone building and little breakdown, then in midlife the breakdown and building of your bones happen at a similar rate. In your later years of life (this is particularly the case for postmenopausal women) your bones breakdown a lot more than new bones are formed which increases the risk of osteoporosis (a condition with porous weak bones).

The rest of the calcium helps you muscles contract and relax, needed by your nerves to send messages to and from your brain, used by your blood to clot and helps to secrete hormones and activate enzymes as well as maintaining healthy blood pressure.

A good amount of calcium in your diet,
• Throughout your life can help prevent osteoporosis.
• Can lower the risk of colon cancer
• Can reduce blood pressure

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Where you get it

Vegetal Sources

• Tofu
• Fortified soymilk
• Baked beans
• seaweeds
• Leafy green  
• Fortified cereals

Animal Sources
• Yogurt
• Milk, 
• Cheese
• Sardines
• Salmon

Most calcium supplements range between 500mg and 1000mg. Calcium is often combined with vitamin A and vitamin D for maximum benefit through increased absorption. The addition of magnesium in the supplement can also increase absorption.

The two main forms of calcium found in supplements are carbonate and citrate. Calcium carbonate is the most common because it is inexpensive and convenient. The absorption of calcium citrate is similar to calcium carbonate.

Taking more than 600mg of calcium at one time is not seen as beneficial as the absorption of calcium decreases and the amount that you take increase.

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Things to watch out for

Those most at risk
Those people most at risk of a calcium deficiency are: 
• Postmenopausal women
• Infants, young children and teenagers
• Vegans (vegetarians who eat no animal products)

Vitamin and Mineral Interactions
Vitamin D is needed to help the body absorb calcium. 

A lot of research seems to suggest that without adequate magnesium, no calcium can enter the bones. 

Excess calcium can interfere with the absorption of other minerals, iron, zinc, magnesium, and phosphorus

Not Enough
Too little calcium can:
• Lead to osteoporosis 
• Hypertension
• Insomnia

Too Much
A high calcium intake with low calcium absorption can lead to calcium excess. Excess calcium can:
• Lead to diseases of the heart and arteries as all the extra 
• Encourage coronary artery calcification
• Increase the risk of kidney stones
• Increases the risk of some cancers, particularly
o Prostate cancer 
o Ovarian cancer. 

Dairy products are high in saturated fat as well as retinol (vitamin A), which at high levels can actually weaken bones.

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How much you need

Calcium absorption

Infants and young children can absorb up to 60% if the calcium that they eat. Adults absorb roughly 15-30% of calcium ingested, and older people may absorb even less. This  Calcium Absorption variation is broad, depending of diet and other factors. For a person with good calcium Absorption (associated with a good diet) it is not clear that we need as much calcium as is generally recommend.

Vitamin D    
Vitamin D increased calcium absorption. Get sun exposure so that your body can make its own vitamin D or eat foods rich in vitamin D.

A lot of research seems to suggest that without adequate magnesium, no calcium can enter the bones. This fact becomes very clear when we look at a person eating a traditional Chinese diet, with its nuts, seeds and legumes, all rich sources of magnesium. . Their intake of calcium is only a fraction of that of the average person eating a modern western diet high in processed foods, yet, in general, they have stronger bones. They also have few signs of diseases of the heart and arteries. 

Plant interactions
Phytic acid and oxalic acid, which are found in some plants, can bind to calcium and prevent it from being absorbed well by your body. These substances affect the absorption of calcium from the plant itself not the calcium found in other calcium-containing foods eaten at the same time. Examples of foods high in oxalic acid are spinach, collard greens, sweet potatoes, rhubarb, and beans. Foods high in phytic acid include whole grain bread, beans, seeds, nuts, grains, and soy isolates. Although soybeans are high in phytic acid, the calcium present in soybeans is still partially absorbed.

Current calcium recommendations for non-pregnant women are also sufficient for pregnant women because intestinal calcium absorption increases during pregnancy [2]. For this reason, the calcium recommendations established for pregnant women are not different than the recommendations for women who are not pregnant.

Dietary Reference intake (RDI)

The Dietary Reference intake (RDI)** is the set of reference levels of the intake of nutrients considered adequate to meet the known nutrient needs of practically all healthy people. These values include the Recommended Dietary Allowance (RDA) and the Adequate Intake (AI). The RDA is the average daily intake that meets the nutrient requirements of nearly all (97 to 98%) healthy individuals. The AI is established when there is insufficient research to establish an RDA; it is generally set at a level that healthy people typically consume.

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy and general health). 

Adequate Intake (AI) of Calcium

• 0-6 months: 210 milligrams per day (mg/day)
• 7-12 months: 270 mg/day

• 1-3 years: 500 mg/day
• 4-8 years: 800 mg/day
• 9-13 years: 1300 mg/day

Teenagers and Adults
• Males 14-18 years: 1300 mg/day
• Females 14-18 years: 1300 mg/day
• Males age 19-50: 1000 mg/day
• Males age 50+: 1200 mg/day
• Females age 19-50: 1000 mg/day
• Females age 50+: 1200 mg/day

The RDA for pregnant women 
• Females 14-18 years: 1300 mg/day
• Females age 19+: 1000 mg/day

The RDA for lactating women
• Females 14-18 years: 1300 mg/day
• Females age 19+: 1000 mg/day

Upper Limit (UL) 

• 7-12 months: Undetermined

• 1-13 years: 2500 mg/day

Teenagers and Adults
• Males and females14+ years: 1300 mg/day

By far the best way to get your daily requirements of nutrients is to eat a balances diet that contains a wide variety of whole foods from all the food groups.  Note that processed foods are depleted of most of their nutrients.

**Many countries have equivalent recommendations although the RDI’s are accepted throughout the world as a valid source of information. These recommendations are based in scientific knowledge and are presented by the US National Academy of Sciences, US Institute of Medicine and the US Food and Nutrition Board.

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