Role of Calcium and Vitamin D

What roles do calcium and vitamin D play in the body?

Calcium is an essential nutrient needed by all living creatures, including humans and Vitamin D is a prohormone that helps the body absorb calcium, which is essential for bone health.

Bones and teeth contain 99% of the body’s calcium.

Many different foods contain calcium. Manufacturers may also fortify certain food products with calcium and vitamin D. Getting enough sunlight is the best way to help the body create vitamin D.

Roles of calcium and vitamin D

Calcium is crucial for bone development and growth in children. It is also responsible for the maintenance of strong bones in adults.

As well as its role in bone health, calcium aids in muscle contraction. When a signal arrives at the muscle, calcium is released, helping the muscle to contract. As calcium leaves the muscle, the muscle relaxes.

Calcium also plays a role in effective blood clotting.

Research suggests that vitamin D also plays a vital role in bone health, as it regulates calcium in the blood. Without vitamin D, the kidneys would excrete too much calcium.

There is growing interest in the role of vitamin D in reducing allergic response and protecting against certain cancers, including colorectal and breast cancer.

Vitamin D also plays an important role in:

  • supporting lung function and good cardiovascular health
  • insulin regulation and glucose metabolism
  • brain, immune, and nervous system health

Additional health benefits of calcium and vitamin D

As well as its crucial role in bone health, calcium may also reduce the risks associated with high blood pressure.

A 2019 article in the journal Nutrients suggests that calcium may help lower blood pressure. Another study from 2020, involving 136,249 participants, suggests that calcium has a protective effect against colorectal cancer. However, research on this is still in the early stages.

Appropriate levels of calcium and vitamin D can also support a healthy pregnancy. A recent review shows an association between higher vitamin D levels and a lower risk of preeclampsia and premature birth.

Due to its role in insulin regulation and glucose metabolism, vitamin D can support effective diabetes management.

The effect of too much or too little calcium and vitamin D
  • Too much calcium may cause constipation. High levels of calcium can also interfere with iron and zinc absorption.
  • High calcium levels rarely come from dietary sources. They are most likely due to excessive supplementation.
  • High levels of calcium from supplementation may increase a person’s risk of kidney stones.
  • Some studies show a link between high levels of calcium and increased risk of heart disease, but others found no association.
  • Some studies also show that high levels of calcium may increase prostate cancer risk.

Too little calcium in the body is known as hypocalcemia. Over time, a calcium deficiency may result in the following symptoms:

  • muscle aches, pains, and cramps
  • tingling or numbness in the hands, arms, legs, feet, and around the mouth
  • fatigue
  • insomnia
  • brain fog
  • dry skin, nails, and hair
  • alopecia
  • skin conditions such as eczema and psoriasis
  • severe PMS
  • dental problems
  • depression

Those most at risk from low levels of calcium include:

  • post-menopausal people
  • people of childbearing age with amenorrhea
  • people who do not consume dairy products, such as vegans or ovo-vegetarians
  • people with lactose intolerance who avoid dairy

Long-term deficiency in calcium or vitamin D can result in osteoporosis, where the bones become more fragile and prone to breaking.

Some studies show a link between increased risk of depression and low levels of vitamin D. However, there is no evidence to show vitamin D supplementation prevents depression or reduces its symptoms.

People at higher risk of low levels of vitamin D include:

  • breastfed infants
  • people who rarely expose their skin to the sun
  • people with darker skin tones
  • older adults
  • people with conditions that limit fat absorption, such as Crohn’s disease
  • people with obesity or who have undergone gastric bypass surgery

Too much vitamin D can be harmful. However, a person cannot get too much vitamin D from sunlight, only from excessive supplementation.

High levels of vitamin D may result in:

  • nausea
  • vomiting
  • muscle weakness
  • confusion
  • pain
  • loss of appetite
  • dehydration
  • excessive urination and thirst
  • kidney stones

Extremely high levels of vitamin D can result in kidney failure, irregular heartbeat, and death.

Good dietary sources of calcium and vitamin D

Calcium is present in several foods. Good dietary sources of calcium include:

  • dairy products, such as milk, yogurt, and cheese
  • fortified dairy alternatives, such as soy milk
  • green leafy vegetables, such as kale, Chinese cabbage, and broccoli
  • canned sardines and salmon
  • tofu
  • fortified products, including breakfast cereals and fruit juices
  • nuts and seeds
  • legumes

Most grain-based foods, such as bread and pasta, are not rich in calcium. However, they can add a large amount of dietary calcium if consumed regularly and in large amounts.

There are limited dietary sources of vitamin D.

Most dietary sources of vitamin D come from fortified foods. Most milk producers in the United States fortify milk with vitamin D. Manufacturers often add vitamin D to plant-based milk, such as soy, almond, or oat milk.

Manufacturers may also add vitamin D to breakfast cereals, orange juice, yogurt, and margarine.

The following foods provide a limited natural source of vitamin D:

  • fatty fish, such as trout, salmon, and mackerel
  • beef liver
  • egg yolks
  • cheese
  • mushrooms
Supplementation of calcium and vitamin D

Calcium and vitamin D supplements are available in tablet, chewable, and liquid forms.

Calcium supplements usually contain either calcium carbonate or calcium citrate. People should take calcium carbonate with food.

People can take calcium citrate with or without food. Those with absorption issues or conditions such as inflammatory bowel disease should choose calcium citrate.

Some people may experience gastrointestinal issues with calcium supplementation. Taking a supplement with meals and spreading the dose throughout the day may help with these issues.

Vitamin D supplements contain either vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol). Both forms are effective, though D3 appears to result in higher levels in the blood.

Supplement manufacturers extract D2 from yeast. D3 can come from:

  • lanolin, which comes from wool
  • fish oil
  • algae oil

People following a vegan diet should check the source of supplements containing D3 or choose supplements containing D2. They should consult with a doctor before taking an over-the-counter supplement.

If someone is very low in vitamin D, they may need a clinical-grade prescription.


Calcium and vitamin D plays a crucial role in bone health and have several other health benefits.

High levels of calcium and vitamin D in the body are rare and likely to come from excessive supplementation. Calcium and vitamin D deficiencies are more common and can have a negative effect on health, including causing osteoporosis.

There are many dietary sources of calcium. The primary source of vitamin D is sunlight. People can obtain additional calcium and vitamin D from supplements.

Source & credit:

Written by Rachael Troughton