Calcium: Bones, Muscles and Nerves Explained
Calcium: Bones, Muscles and Nerves Explained
Ever brushed off a sore back or night-time cramps as just ageing and carried on? Think of your bones as a savings account, with calcium as the deposit. Here is how calcium works, and how to keep topping up with everyday food in the UK.
What Is Calcium?
Calcium is a mineral, which means it is a basic building material your body cannot make on its own. It is the most plentiful mineral in your body, and almost all of it is stored in your bones and teeth, where it gives them structure and hardness. The small remainder circulates in your blood, muscles and nerves.
That small remainder matters. Your body guards the calcium level in your blood very tightly. When it dips, hormones tell your bones to release some, and your kidneys hold on to more instead of passing it out in urine. Think of your skeleton as a calcium bank that your body quietly withdraws from whenever your daily food falls short.
This is a real concern in Singapore. HealthHub Singapore notes that many Singaporeans do not get enough calcium. Osteoporosis is a condition where bones become thin, weak and easier to break.
Why Do People Take It?
Bones and teeth
Bone is living tissue that is constantly broken down and rebuilt. Up to around age 30, building usually wins over breakdown if you get enough calcium and regular movement. After that, breakdown tends to edge ahead, so the bone you bank early is what you draw on later.
Osteoporosis gives few early warnings. Many of us simply put up with aches and carry on, until a small fall causes a fracture. Women often lose bone faster after menopause, because the hormones that help protect bone drop.
Smooth muscle and nerve function
Every time you squeeze a muscle, from lifting a bag of groceries to your heart beating, calcium is part of the signal. It also helps nerves carry messages between your brain and the rest of your body. When blood calcium stays steady, all this runs quietly in the background.
Muscles and nerves cannot wait, so your body protects blood calcium first. If intake stays low for years, your bones are the ones that pay.
Blood clotting and hormone release
When you nick your finger while chopping vegetables, calcium helps your blood clot to seal the cut. It also helps blood vessels move blood around, helps release hormones, and helps control enzymes, the tiny workers that speed up chemical reactions in your cells. Calcium is far more than a bone nutrient. Nearly every cell uses it.
Pregnancy and other research areas
Researchers have studied calcium supplements in pregnancy in relation to preeclampsia, a serious late-pregnancy complication marked by high blood pressure and protein in the urine. The NIH notes that many of these studies involved high-risk women and had weaknesses. Pregnant women should talk to their doctor first.
Evidence is less settled elsewhere. Some long-term studies have looked at calcium intake and colorectal cancer, but supplement trials are mixed. Research has also not clearly shown that calcium helps with weight loss. Be cautious about bold claims in these areas.
Bioavailability & Absorption
Eating calcium is only half the story, because your body absorbs just a portion of it. Babies and young children absorb a lot, since they are building bone fast. Adults absorb far less, and absorption keeps falling with age.
Vitamin D is the key helper, because your gut cannot absorb calcium efficiently without it. Many of us spend most of the day indoors in offices, shops and on trains. HealthHub suggests getting sun on your arms and legs a couple of times a week, or taking a short outdoor walk.
Your plate matters too. Spinach looks high in calcium on paper, but its oxalates, natural compounds that lock onto calcium, mean your body can use very little of it. Bok choy has lower oxalate levels, and kai lan and chye sim are in the same leafy family, so they are a better bet. Steaming or quickly stir-frying greens keeps more calcium than long boiling.
For supplements, calcium carbonate is absorbed best with a meal. Calcium citrate works with or without food and suits people with low stomach acid, which is more common in older adults. The body also absorbs calcium better in smaller amounts, so larger daily totals are usually split across the day. The Linus Pauling Institute adds that calcium can compete with iron and magnesium, so ask your pharmacist about timing if you take several mineral supplements.
Safety Basics
Calcium from food is generally safe. Supplements need more care. Gas, bloating and constipation are the most common side effects, and they sometimes ease if you spread the dose out, take it with meals or switch forms.
Taking more than you need for years is linked to a higher risk of kidney stones. Some studies suggest calcium supplements may raise heart risk, while others find no effect, and experts overall do not think calcium within recommended amounts changes heart disease risk. High calcium from dairy has also been linked to prostate cancer in some studies, but the picture is not settled.
Too much calcium in the blood can cause weakness, confusion, tiredness, loss of appetite, frequent urination, vomiting, constipation and bone pain. See a doctor if you notice these, especially if you take supplements.
Be extra careful if you have kidney disease or a history of kidney stones, or if you are pregnant or breastfeeding. Calcium can interfere with some medicines, including certain antibiotics, thyroid medicine and an HIV drug called dolutegravir, so timing matters. Many antacids are calcium carbonate too, so they count toward your total. If you are stacking a multivitamin, a calcium tablet and antacids, check with a pharmacist first.
Natural Food Sources
Food is the best first stop, and everyday favourites go a long way.
- Milk, yoghurt and cheese: the richest sources. Removing the fat does not lower the calcium, so low-fat versions work just as well. Cheese on toast, or a Welsh rarebit, is a simple way in.
- Ikan bilis and sardines: fish eaten with their soft bones are calcium-rich. Crunchy dried ikan bilis count, as do tinned sardines on toast.
- Calcium-set tofu and soya products: firm tofu (tau kwa), silken tofu and calcium-fortified soya milk help, though tofu made with other setting agents gives little calcium. Check labels.
- Leafy greens: kai lan, chye sim and bok choy are far better calcium sources than spinach. A quick stir-fry of greens with supper helps.
- Fortified foods: some breads, biscuits and orange juices have added calcium. Check the label to see how much calcium has been added.
- Nuts, beans and dried figs: almonds, white beans, dhal, edamame and dried figs add smaller amounts that build up through the day.
- A note on drinks: sweetened hot chocolate and milky tea contain some milk, but plenty of sugar, so do not count on them as your calcium plan.
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Final Thoughts
Calcium is quiet work: it contributes to the maintenance of normal bones. Most healthy adults can get what they need from variety, such as dairy or soya, ikan bilis, tofu and greens, plus a bit of sunshine for vitamin D. Because bone loss rarely hurts until it is advanced, do not just put up with it and wait. If you are over 50, a woman past menopause, avoid dairy, or have a family history of osteoporosis, ask your doctor whether a bone density test or supplement makes sense for you.
This article is for general informational purposes and is not a substitute for professional medical advice. Please consult a qualified healthcare professional before making any changes to your diet or supplement routine.
References
- NIH Office of Dietary Supplements
https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/ - Harvard T.H. Chan School of Public Health
https://nutritionsource.hsph.harvard.edu/calcium/ - MedlinePlus (NIH)
https://medlineplus.gov/calcium.html - Linus Pauling Institute (Oregon State University)
https://lpi.oregonstate.edu/mic/minerals/calcium - Mayo Clinic
https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/calcium-supplements/art-20047097 - HealthHub Singapore 🇸🇬 SG
https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/calcium-for-greater-bone-strength - HealthHub Singapore 🇸🇬 SG
https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/catch-up-on-calcium