May 27

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Calcium as a nutrient in your body


Up until now, you may never have appreciated how important the nutrient calcium is to your health. In your body, it's present in 3 main forms. The huge majority (over 99%) of stored calcium is combined with phosphate in your bones.

The remaining 1% is present as free 'ions', or bound to proteins.

Don't let this small percentage fool you though. It's impos­sible to overstate how important calcium is to your metabolism. In particular, the control it has over metabolic path­ways.

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Calcium has a very interesting property. Unlike other metal ions, free calcium can both bind strongly and unbind to proteins extremely rapidly. Consequently, nature uses this property in your body enabling calcium to act as a chemical 'switch'.

Why do we need the nutrient calcium?

Mention calcium and most people immediately think of bones and teeth.

Perhaps its most important function, calcium is needed to switch muscles on and off. That is to say, without calcium, you wouldn't be able to contract any of your muscles.

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Calcium is also vital for transmitting nerve signals. The release of neurotransmitter chemicals such as serotonin, acetylcholine and norepinephrine requires calcium release from the synaptic vesicles.

All cells require intracellular calcium to function. For instance, calcium regulates the transport of other nutrients in and out of cells. For these reasons, calcium can be considered as a lynchpin in controlling metabolism.

Additionally, as if that wasn't enough, calcium is also an important co-factor for blood clotting. More specifically, it's involved in the conversion of fibrinogen to fibrin.

Finally, calcium also activates numerous key enzyme systems around the body.

OK I'm convinced - how much calcium do I need?

Calcium is critical for regulating metabolism. Due to this, our bodies try to maintain a constant blood calcium level. That is to say, between 7-10mg/100ml.

As a result of natural processes, we lose around 400 to 1000mg of calcium every day. Subsequently, if we don't consume enough calcium in our diet, our body releases calcium into our bloodstream from our bones.

However, long-term dietary calcium inadequacy can lead to osteoporosis. As a result, the bone structure becomes weakened.

The UK Reference Nutrient Intake Figures (UK RNI) for dietary calcium are as follows:

Age / Gender

Daily Requirement (mg)

Children

​Up to 12 months

1-3 years

4-6 years

7-10 years

​525

350

450

550

Men

​11-18 years

19 years and older

​1000

700

Women

​11-18 years

19 years and older

Lactating

​800

700

extra 550

To clarify, precise calcium requirements are difficult to determine. Calcium absorption and reten­tion can be affected by other factors. For example stress, heavy exercise, lactation, high-fat, high protein and high phos­phorous diets all increase the need for calcium.

Where can I find calcium as a nutrient in food?

Easily the best sources of calcium are milk and its products such as yoghurt, cheese and other dairy produce.

These foods are also rich in milk sugars, which increase the bioavailability of the calcium to the body. Additionally, other good non-dairy sources of calcium include green vegetables, seeds, canned fish (with bones) and dried peas and beans.

Lastly, 'hard' water contains dissolved calcium and can provide a significant proportion of dietary calcium.

What happens if I don't get enough calcium?

In short, the greatest risk is bone demineralisation, which weakens the bones. As a result, the bones become vulnerable to fractures. Known as osteoporosis, prolonged low calcium intakes are associated with this debilitating condition.

Some evidence also links low calcium intake with an increased risk of colon cancer. Furthermore, low calcium intakes have also been linked with high blood pressure, muscle cramps and tremors and insomnia.

Who should take the most care to maintain calcium intake?

Growing children, adolescents and young adults all need to ensure ade­quate calcium intake to build maximum bone density.

Research also suggests post-menopausal women need extra calcium.

Vegans, dieters and those with dairy allergies also need to take special care with calcium. Even a well-balanced dairy-containing diet struggles to meet daily calcium needs once the calorie intake falls below 1600kcal per day.

​If it's an important nutrient, can I get too much calcium?

Excess dietary calcium is easily excreted. Therefore, calcium is quite non-toxic.

However, very high calcium intakes combined with high vitamin D or low magnesium intakes have been linked to soft tissue calcification. As a result, excess calcium is literally dumped in body tissues.

Am I getting enough calcium?

Use this chart to see how whether your diet is likely to contain enough calcium. Certainly, by far the best sources are milk and milk products.

Food

Calcium content (mg per 100g)

​Cheddar cheese

​720

​Milk (all varieties)

​620

​Canned sardines

​550

​Sesame seeds

​420

​Watercress

​170

​Low-fat yoghurt (fruit)

​150

​Spinach

​136

​Fromage frais (plain)

​89

​Peas (frozen, cooked)

​59

​Wholemeal bread

​54

​Baked beans

​53

​Broccoli

​47

​Oranges

​40

Iceberg lettuce

​20

White rice (boiled)

​18

Lean beef

​15

Avocado

​11

Melon

​6

Potatoes (boiled)

​5

Apples

​4

​Figures supplied by the USDA Nutrient Data Laboratory and the UK Food Standards Agency

​If you liked this, you may enjoy reading about other nutrients...

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Paul Stokes

About the author

Paul Stokes BSc (Hons) is a Certified Personal Trainer, Accredited Sports Nutritionist, qualified Exercise to Music Instructor, Precision Nutrition coach, Massage Therapist and teaches 8 of the Les Mills Group Exercise programs. He currently works in the Oil & Gas industry as a Wellness Coach, imparting his vast knowledge and experience to improve the quality of life of several hundred offshore workers.

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