Calcium is one of the most important and abundant minerals in the body. While most people consider calcium to be a nutrient focused solely on bone health, its involvement in bodily functions is much greater than that. In conjunction with keeping bones strong and healthy, calcium aids muscle contractions, allows blood to clot and is one of the key nutrients that allows ALL of our organ systems to function properly. Unfortunately, calcium deficiency continues to be a worldwide public health issue, and can lead to osteoporosis, rickets, and ultimately lead to decreased height/compromised growth in children. On the other hand, excessive calcium does have associated health risks.
In this article, we will focus solely on calcium, explaining its biological functions, dietary sources, how we absorb calcium, how much calcium we need daily, health benefits and risk of deficiency, health risks of excess calcium, and lastly what are the recommendations for calcium balance.
What is calcium?
Calcium is a chemical element represented with the symbol calcium (Ca) and atomic number 20. It is classified as an macromineral in human nutrition meaning it is needed in larger quantities than certain trace minerals like zinc or selenium. Up to 99% of calcium in the body is stored in bones and teeth in order to give structure and strength to those areas of the body.
Calcium’s Purpose for the Body
Calcium serves many functions in the human body. The following are the most important:
1.Health of Bones and Teeth:
Calcium is the primary component of hydroxyapatite crystals that serve the skeleton as a structural framework and is responsible for rigidity, durability, and resistance against fracturing. In youth and adolescence it contributes to growth whereas in adulthood it maintains bone mass.
2.Muscle Contraction:
Calcium ions cause the fibers of muscles to contract by triggering the interplay of actin and myosin proteins that form the muscle units. Muscles can spasm, cramp, and feel weak if calcium levels are low.
3.Blood Clotting:
Calcium initiates the cascade of protein reactions that prevent excessive bleeding of the body after injury, by being a co-factor for the many clotting factors.
4.Nervous System Function:
Calcium ions regulate the release of neurotransmitter chemicals between nerves, which in turn controls the brain and nervous system functioning.
5.Hormonal Secretion:
Calcium is implicated in the release of hormones such as insulin, which is responsible for regulating blood glucose levels. It is also implicated in the activation of enzymes that drive many metabolic functions of the body.
6.Cardiovascular Health:
Calcium contributes to fluid and electrical conduction in the cardiac cells that relates to regulating the rhythm of the heart. Abnormal calcium levels can contribute to arrhythmias or other cardiovascular issues.
Daily Calcium Needs:
The recommended daily allowance for calcium is age, gender, and physiological condition dependent (e.g., pregnancy or lactation). Health authorities recommend (RDA) the following amounts of calcium:
• Infants (0-6 months old): 200 mg/day
• Infants (7-12 months old): 260 mg/day
• Children (1-3 years old): 700 mg/day
• 4-8 years children): 1,000 mg/day
• Adolescents (9-18 years): 1,300 mg/day
• Adults (19-50 years): 1,000 mg/day
• Women (51+ years): 1,200 mg/day
• Male (71+ years old): 1,200 mg/day
• Pregnant and lactating women: 1,000 mg/day through 1,300 mg/day
This information highlights the relative importance of consuming excess calcium when growth is spurting, pregnant or lactating, and at an older age.
Sources of Calcium:
Calcium is found in many types of food, animal and plant-based. Below are the primary sources of dietary calcium.
- Dairy Products
• Milk
• Yogurt
• Cheese
Dairy products are the most bioavailable therapy, and concentrated sources of dietary calcium.
- Plant-Based Sources
• Leafy greens (e.g., kale, bok choy, spinach, and collard greens)
• Broccoli
• Okra
• Almonds and sesame seeds
• Soy beans and tofu (particularly calcium-set tofu) - Fortified Foods
• Plant-based milks (e.g., soy, almond, oat) – calcium-fortified
• Cereals and juice – fortified with calcium - Fish and Seafood
• Sardines (with bones)
• Salmon (with bones)
• Shrimp - Other Sources of Calcium
• Beans and lentils
• Chia seeds
• Sunflower seeds.
Calcium Absorption and Factors That Affect Calcium Absorption:
All calcium ingested is not absorbed in the body. The average amount absorbed from dietary calcium is about 30%, but this varies by several factors.
Factors that enhance calcium absorption
- Vitamin D: necessary to absorb calcium in the intestines.
- Lactose: found in milk and helps enhance calcium absorption.
- Enough stomach acid: helps release calcium from food.
Factors that inhibit calcium absorption
- Oxalates: found in spinach, beet greens, and rhubarb, oxalates bind calcium and inhibit absorption.
- Phytates: found in grains and legumes, phytates can impair calcium absorption.
- Too much sodium and caffeine: increase calcium excretion in the urine.
- Low vitamin D levels: decrease efficiency of absorption.
Calcium deficiency (hypocalcemia):
Calcium not being ingested enough, or not being absorbed enough creates a calcium deficiency that presents with an array of signs and symptoms.
Possible causes of calcium deficiency:
- Name a cause
- Vitamin D deficiency
- Hormonal variance (hypoparathyroidism)
- Chronic kidney disease
- Drinking too much alcohol or caffeine
Signs and symptoms of low calcium (hypocalcemia):
- Muscle cramping and spasming
- Feeling numb or tingling in fingers
- Brittle nails
- Problems with teeth
- Fatigue and irritability
Long-term effects of malabsorption of calcium or inadequate intake of calcium
- Osteoporosis: fragile, weak bones with a risk of fracturing.
- Rickets (in children): weak, soft bones that can lead to skeletal deformities.
- Osteopenia: lower than normal bone density, which can lead to osteoporosis.
Excessive Calcium (Hypercalcemia):
While essential, too much calcium can be detrimental.
Reasons
• Calcium supplement overconsumption
• Hyperparathyroidism
• Certain malignancies
• Renal failure
Indications
• Altered bowel habits with or without abdominal discomfort
• Polyuria
• Nephrolithiasis
• Irregular cardiac rhythm
Therefore, maintaining balance is vital — too little promotes bone resorption, and too much places strain upon the heart and kidneys.
Health benefits of appropriate calcium levels:
- Strong Bones and Injury Prevention
Good calcium intake in youth allows for peak bone mass development which lowers the likelihood of bone fracture later on.
- Reduced Manner of Osteoporosis
Eating enough calcium throughout one’s life can slow the process of age-related bone density loss in older adults, especially in postmenopausal women.
- Dental Health
Calcium helps strengthen tooth enamel and health in your gums which lowers vulnerability to cavities or tooth decay.
- Heart Health
Calcium levels helps maintain a proper rhythm of the heart and healthy blood pressure.
- Weight Control
Some studies have suggested that calcium may help control weight in that it may also aid in fat metabolism, though results have been mixed.
Calcium Supplements:
For individuals who are unable to meet their calcium intake from foods, a supplement could be of assistance. The most typical choices are:
• Calcium carbonate: Absorbs best when taken with food, because it needs stomach acid to absorb properly.
• Calcium citrate: Absorbs well on an empty stomach and is a good choice for individuals with low stomach acid.
Best practice: Do not take more than recommended amounts of a supplement, as excessive amounts of any supplement increases the risk of kidney stones or heart disease.
Calcium and Vitamin D: A Necessary Partnership:
Vitamin D and calcium go hand in hand in supporting the health of your bones. If you do not have enough vitamin D, your intestines will not absorb calcium efficiently no matter how much you are eating. Good sources of vitamin D include:
• Exposure to sunlight
• Fatty fish (salmon, mackerel, tuna)
• Fortified dairy or plant milks
• Supplements
Finding a good balance between the two nutrients is optimal for bone and metabolic health.
Calcium at Different Life Stages:
Infants and Children:
Calcium is critical for growth and development of bone health. A deficiency of calcium could lead to a disorder called rickets or stunted growth.
Adolescents:
This is the most important time for achieving peak bone mass, which establishes a foundation for bone health over a lifetime.
Adults:
Calcium is important for maintaining bone health and metabolic processes in adults. Women specifically need to increase their intake of calcium after menopause.
Elderly:
As a natural process, we lose some bone density as we get older, so calcium (in combination with Vitamin D and exercise) can work to maintain it, therefore decreasing the risk of fracture.
Lifestyle Factors Impacting Calcium Balance:
• Exercise: Weight-bearing exercises, for example, walking, running, or resistance training has been shown to promote bone formation.
• Smoking: Decreases calcium absorption and weakens bones.
• Alcohol: over intake inhibits the metabolism of calcium.
• Balanced diet: A Diet specifically balanced with the right nutrients is important.
Calcium Myths and Misconceptions:
- “Only dairy products contain calcium.” False. There are many other foods, plant-based, and fortified foods that contain calcium.
- “Calcium supplements are safe.” Taking excess calcium can contribute to the development of kidney stones for some, and increased cardiovascular disease risk for others.
- “Calcium, by itself, prevents osteoporosis.” The reality is that, in order for calcium to properly utilize supplementation and dietary consumption, it must be exercised and combined with like vitamin D and other nutrients including magnesium and vitamin K.
Conclusion:
Calcium is more than just a “bone nutrient.” It is a key mineral needed for muscle contractions, nerve signals, blood clotting, and maintaining the health of cells. Sufficient calcium intake throughout a lifetime—from infancy to old age—is necessary to build and maintain strong bones, prevent chronic diseases, and promote health’s overall benefits.
There is a balance. Both too little and too much can present a cancer risk, which is why we must always maintain a variety of foods, supplemental products as needed, and healthy behaviours. When you promote optimal calcium intake through foods rich in the mineral, synergy with vitamin D, and regular physical activity, you will have strong bones and a healthy body throughout life.
