Calcium: Its role and cautions

Calcium is another king mineral. We have spoken about magnesium in a previous article, and its interactions with the other three king minerals, potassium, calcium and sodium. Here we will explore the role of calcium.

What is calcium?

Calcium is an essential macro mineral with many vital interactions for healthy bodily functions, including building and maintaining strong bones, contributing to muscle contractions, nerve stimulation, including the heart and facilitating blood clotting.  

Calcium is the most abundant inorganic mineral in the body, with 99% existing in bone and teeth and the remaining 1% in soft tissue and extracellular fluid.

How is calcium regulated in the body?

In other words, how are levels maintained? This occurs through hormonal and physiological processes:

• The parathyroid glands and thyroid glands are the main endocrine glands involved in calcium regulation. When blood calcium levels are too low, parathyroid hormone is created by the parathyroid glands, which stimulates bone resorption and calcium reabsorption in the kidneys, in turn raising calcium levels in the blood. 
• Blood Ca Low = PTH produced = signals bone breakdown (resorption), so serum levels rise.
• The reverse of this process is when calcium blood levels are elevated, resulting in the release of a different hormone called calcitonin from the thyroid glands. This reduces bone resorption and calcium reabsorption in the kidneys, resulting in blood calcium levels lowering.
• Blood Ca High = Calcitonin produced = signals Ca reabsorption, so serum levels drop.
• Therefore, the parathyroid glands and thyroid glands play an important role in ensuring calcium levels remain in the correct range, allowing homeostasis.

Key roles of calcium in the body

• Strengthening teeth and bones.
• Muscle function and contraction - Ionic calcium facilitates muscle contraction through nerve impulses reaching muscle fibres. Calcium is released from storage sites within the muscle cells. The free calcium ions bind to proteins in the muscle cells called troponin and tropomyosin. This binding mechanism facilitates Myosin Heads to fix to actin filaments, leading to muscle contraction. Therefore, without sufficient calcium levels, muscles may not be able to contract efficiently, resulting in weakness and cramps.
• Nervous system – Calcium facilitates neurotransmitter release from synaptic vesicles into the synaptic cleft. This process allows effective nervous system communication.
• Cognitive function – Some research has suggested that calcium levels may play a role in cognitive function and memory. It is believed that low calcium intake could be connected to cognitive decline as we age. Research is ongoing, and it will be interesting to see how this evolves.
• Heart health – The heart is a muscle, so where calcium plays a role in muscle function, it goes without saying that it impacts the heart. The electrical impulses and contractions with each heartbeat are all mediated by calcium levels. Calcium ions work within the heart cells, stimulating contractions. Therefore, abnormalities in blood calcium levels could lead to erratic heartbeats - speak to your GP if you have symptoms or concerns.
• Blood clotting – Calcium ions are part of the process leading to blood clot formation. Low calcium levels could lead to excessive bleeding or, the reverse, too high to excessive clotting.

Interactions with other minerals and effects

• Magnesium - Where magnesium assists in the conversion of vitamin D, this process helps calcium absorption.
• Phosphorus - Calcium and phosphorus work together to form strong bones and teeth. The phosphorus level must be just right, as if it's too high, it can block calcium absorption.
• Vitamin D - improves calcium absorption in the intestine.
• Vitamin C - benefits from taking calcium by assisting in its absorption of iron.

Forms of calcium supplements 

Calcium carbonate 

This form has the highest elemental calcium concentration at 40% by weight. This means fewer supplements would be needed to meet the RDA. This should not be taken on an empty stomach or where low stomach acid is known. It can cause bloating or Constipation, nausea, vomiting, gas, increased urination, fatigue, and bone pain.

Calcium citrate 

This is the second-highest elemental calcium concentration at approximately 21% by weight. This means tablets are often larger and more are required to meet the RDA. Can be taken on an empty stomach and is suitable for people on anti-acids. It is better suited for people with digestive problems. Side effects to watch out for are nausea, vomiting, gas, headache, increased urination, poor appetite, tiredness, and low blood pressure.

Learn more about supplements and how they can support health.

How medications can affect calcium absorption

Biphosphonates 

Where these medications reduce calcium loss in bones, there is a corresponding reduction of calcium in the bloodstream. So a calcium supplement is recommended so that other physiological functions do not suffer.

Prolia or denosumab

These have the same effect as biphosphonates.

Sensipar

This is prescribed for individuals with chronic kidney disease to reduce parathyroid hormone levels. This hormone controls the release of calcium into the bloodstream, so its reduction will lead to low calcium serum levels.

Phenytoin

This medication is used to prevent seizures, but a side effect is its lowering of vitamin D levels, which in turn can affect calcium absorption.

Cisplatin

This and other chemotherapy medications can lower calcium.

Diuretics

Also known as water pills, such as furosemide, diuretics can lead to loss of calcium through urination.

Proton pump inhibitors (used to treat acid reflux)

Medications such as Omeprazole and Nexium can lead to low blood calcium levels.

Antibiotics

These can affect the way the kidneys deal with calcium, leading to low calcium levels.

Note: If you are concerned about calcium levels and any medication you are on, be sure to consult with your GP to learn more before making changes.

Foods that contain calcium

Here is a list of foods high in calcium to consider within your diet:

• vanilla yoghurt (low-fat) - 8 ounces/388 mg
• milk 1% fat - 1 cup/310 mg
• ricotta cheese, whole milk - 1/2 cup/289 mg
• Greek yoghurt, plain (low-fat) - 8 ounces/261 mg
• cottage cheese 2% fat - 1 cup/227 mg
• cheddar cheese - 1 ounce/200 mg
• orange juice, calcium-fortified - 1 cup/349 mg
• collard greens, cooked - 1 cup/268 mg
• spinach, cooked - 1 cup/245 mg
• bok choy, cooked - 1 cup/158 mg
• kale, cooked - 1 cup/177 mg
• broccoli, cooked - 1 cup/62 mg
• tofu, prepared with calcium sulfate - 1/2 cup/434 mg
• sardines, canned, with bones - 3 ounces/324 mg
• soy milk, fortified - 1 cup/299 mg
• black beans, canned  - 1 cup/239 mg
• salmon, canned, with bones - 3 ounces/181 mg
• almond milk, unsweetened - 1 cup/482 mg
• almonds - 1/4 cup/92 mg
• sesame seeds - 1 tablespoon/88 mg
• chia seeds - 1 tablespoon/78 mg
• tahini (sesame butter or paste) - 1 tablespoon/64 mg

Finding the right balance

Nature provides a balance of vitamins and minerals, so a varied and whole food diet can give you the best opportunity of ensuring your calcium levels are optimum. 

Where medications and or symptoms and lifestyle prevent this, a consultation with a nutritionist can guide you to making the right choices to ensure you are on track.

References:

• Calcium Carbonate vs. Calcium Citrate
• Medications That Can Cause High or Low Calcium Symptoms - GoodRx
• Understanding the Synergy Between Calcium and Other Minerals
• Calcium • The Nutrition Source
• Physiology, Calcium - StatPearls - NCBI Bookshelf