What are calcium and vitamin D and why do we need them?

Calcium is a mineral essential for building and maintaining strong bones and teeth, something most of us already associate it with. But beyond that, which isn’t as widely known, calcium also supports muscle contraction (including your heart), blood clotting, and nerve function. In other words, it’s working quietly in the background to keep your body moving, your heart pumping, and your brain firing.

Vitamin D, on the other hand, is a fat-soluble vitamin often called the “sunshine vitamin” because our bodies can make it when skin is exposed to sunlight. Its main role is helping us absorb calcium from food. Easily put, think of calcium and vitamin D as two good friends that need to work together to protect our bones, teeth and muscles.

Can we get enough calcium and vitamin D through diet alone?

Technically, yes, but realistically, not always. As a dietitian, lots of people ask me if we just eat well, can we avoid supplements? And the answer is that in an ideal world, you absolutely could. Unfortunately, life doesn’t always make it that simple. Calcium and vitamin D are what we call “tiny but mighty” nutrients (micronutrients). They don’t take up much space in your diet, but getting the right amount every day can be surprisingly hard. With our grey skies, it’s especially hard to hit vitamin D targets in Ireland. Studies show many of us (yes, even people who think they’re eating well) fall short and vitamin D deficiency is one of the most common deficiencies in Ireland. It’s particularly common in:

• People over 65 or post menopausal women

• Breastfed babies, pregnant and breastfeeding women

• Children under 5

• People with darker skin

• Anyone who spends most daylight hours indoors (hello office jobs!)

• People with certain gut or medical conditions that affect absorption

If you read that list and thought “That’s me”, don’t worry, you’re in good company. Deficiency is more common than most people realise, which is why checking in on your calcium and vitamin D is worth doing.

What happens if you’re deficient?

Low calcium levels can weaken bones, making them more prone to fractures, not just in old age, but from falls or accidents at any time. Women can build bone density up until around age 30, and after that we can no longer increase our bone density. That’s why calcium for children, young adults and teenagers is so important. For those over 30, although we can’t increase bone density further, we can do our best to maintain the density that we have.

Calcium also helps our muscles function properly, including our heart. When we don’t get enough, we’re not just risking brittle bones; we’re also interfering with key systems in the body. Of course, weaker teeth are at higher risk too.

Vitamin D deficiency has been linked to bone disorders like osteomalacia or osteoporosis. We’re also learning more about its role in immune health and even mental health and low vitamin D has been associated with increased risk of depression. During the COVID-19 pandemic, many experts encouraged supplementation to support the immune system.

So, should you supplement?

Let’s start with calcium. You should consider supplementing if you’re not regularly getting at least 3 portions of calcium-rich foods a day. A portion could look like:

• A glass of milk with breakfast

• A slice of cheese in your sandwich

• A yogurt pot after dinner

If you don’t eat dairy, are vegan, or have a restricted diet, you might well be falling short and could benefit from a supplement.

For vitamin D: The HSE currently recommends 10 micrograms (400 IU) per day for most people from Halloween (October 31st) to St. Patrick’s Day (March 17th). However, some groups like those listed above are encouraged to supplement all year round.

You don’t need a prescription to take vitamin D or calcium. Many pharmacies sell them separately or combined. Just be careful not to double or triple up as excess vitamin D is stored in the body and can become toxic over time. More is not more! The HSE advises not exceeding 25 micrograms (1,000 IU) per day unless directed by a healthcare professional. Similarly, too much calcium can cause problems, especially for heart health.

Still unsure if you need a supplement?

Ask your GP for a blood test to check your vitamin D levels, and chat about whether your calcium intake is sufficient. If you have a family history of osteoporosis or you’re postmenopausal, you might want to explore getting a DEXA scan to assess bone density and future fracture risk.

In Summary:

• Calcium keeps your bones and muscles strong

• Vitamin D helps your body absorb and use calcium

• Many people in Ireland are at risk of deficiency, especially in the winter months

• Supplementation can be a helpful, safe support, but it should be done thoughtfully. If in doubt, always check with your GP. Your bones (and future self) will thank you!

References & Further Reading

If you’d like to dive deeper into the evidence behind these recommendations, you can check out: Osteoporosis: A Nutrition Fact Sheet for Health Professionals – INDI

Written By: Lorna Ryan, Registered Dietician