Calcium, Vitamin D and Bone Health for Ajax Residents

Ask almost anyone what bones need and the answer comes back quickly: calcium. Ask what vitamin D has to do with it and the answers become less certain. Some people picture a vitamin that only matters for children, others assume a daily glass of milk takes care of everything, and many have a bottle of supplements in the cupboard without being quite sure why.

This article looks closely at those two nutrients. It explains what each one actually does, why they depend on each other, where they turn up in everyday food, and what to ask your health-care provider before you start, stop or change a supplement. It also covers one practical detail that matters to patients booking a bone density scan at our clinic in Ajax: why calcium tablets need to wait until after the scan.

If you are looking for a broader overview of exercise, smoking, alcohol and other habits that affect bone, our earlier article on osteoporosis prevention basics covers that ground. Here, the focus stays on the nutrition side.

Calcium is a bank account, not a one-way deposit

Your skeleton holds the vast majority of the calcium in your body. That calcium gives bone its hardness, but bone is also doing a second job that is easy to overlook: it acts as a reserve.

Calcium is needed far beyond the skeleton. Your heart relies on it to beat in rhythm, your muscles need it to contract, your nerves use it to send signals and your blood uses it to clot. Because those jobs cannot be put on hold, the body keeps the level of calcium in the blood within a tight range at all times.

When the calcium you eat is not enough to keep that level steady, the body draws on its reserve and releases calcium from bone. It is a sensible system in the short term. Over months and years, though, if withdrawals keep outpacing deposits, the account slowly runs down. That is one reason calcium intake is discussed so often in conversations about bone health. It is less about building bone overnight and more about not forcing the body to keep borrowing from its own skeleton.

Vitamin D is the gatekeeper

Calcium from food does not automatically reach your bones. It first has to be absorbed through the wall of the intestine and into the bloodstream, and that step depends heavily on vitamin D. Without enough vitamin D, the body absorbs only a portion of the calcium you eat, no matter how good your diet looks on paper.

Vitamin D also plays a role in muscle function, which has its own link to bone health. Muscles that work well help with balance, and good balance helps prevent the falls that lead to many fractures.

Where vitamin D comes from

Vitamin D is unusual among nutrients because the body can make it. When sunlight reaches the skin, a chemical reaction starts the process. The amount produced depends on several things:

• Season and latitude. In southern Ontario, the sun sits lower in the sky for much of the year. Through the late fall and winter months, the skin makes little vitamin D, even on a bright January afternoon along the Ajax waterfront.
• Time outdoors. Many adults spend most daylight hours at work, in the car or at home.
• Skin coverage. Clothing, and sunscreen used to protect against skin cancer, both reduce how much vitamin D the skin makes. Sun protection is still important; this is simply one reason food and other sources matter.
• Skin tone. People with darker skin generally make less vitamin D from the same amount of sun.
• Age. Older skin tends to produce less vitamin D than younger skin.

Food can contribute too, although relatively few foods are naturally rich in it. Fatty fish such as salmon, trout, mackerel and sardines contain vitamin D, as do egg yolks. In Canada, cow’s milk and many plant-based beverages and margarines are fortified with it.

For all of these reasons, vitamin D is a common topic in Canadian health care, and it is a reasonable question to raise at a check-up.

Finding calcium on your plate

Most people think of dairy first, and milk, yogurt and cheese are certainly convenient sources. But the families who live in Ajax, Pickering and Whitby cook from a wide range of traditions, and many of those cuisines include calcium-rich foods that rarely make the standard lists.

Familiar and less familiar sources

• Dairy: milk, yogurt, kefir, cheese and paneer
• Fortified beverages: many soy, almond, oat and other plant-based drinks have added calcium (shake the carton, since the added calcium can settle)
• Fish with soft bones: canned salmon and sardines, where the softened bones are eaten along with the fish
• Soy foods: tofu made with calcium sulphate, which will be listed on the ingredients, and some fortified soy products
• Legumes: white beans, chickpeas and some lentil dishes contribute smaller amounts
• Greens: bok choy, kale, collard greens and gai lan
• Nuts and seeds: almonds, and sesame seeds or tahini
• Fortified foods: some orange juices and breakfast cereals

Not all calcium is absorbed equally

A food’s calcium content and the amount your body actually takes in are not always the same. Spinach is the classic example. It contains a fair amount of calcium, but it also contains compounds called oxalates that bind to calcium and keep much of it from being absorbed. Spinach is still a nutritious vegetable; it just should not be counted on as a main calcium source. Greens such as bok choy and kale tend to give up their calcium more readily.

The body also seems to absorb calcium better when intake is spread across the day rather than packed into one large serving. A yogurt at breakfast, a salmon sandwich at lunch and a tofu stir-fry at dinner may serve you better than the same total in a single sitting.

Reading the label

On the Nutrition Facts table found on most packaged foods in Canada, calcium is listed with a percentage of the Daily Value. As a general guide, 5% or less is considered a little and 15% or more is considered a lot. That quick comparison can help when you are choosing between two brands of yogurt or plant-based beverage. Vitamin D may or may not appear on the table, so check the ingredients list for words such as “vitamin D3” if you want to know whether it has been added.

The supplement question

Many adults take calcium, vitamin D or both. Some were advised to by their doctor, some picked up a bottle after reading an article, and some are taking a multivitamin that already includes them without realizing it. Whether you need a supplement, and how much, depends on your age, your diet, your health conditions, your medications and, sometimes, test results. That is why this article does not give amounts. Your doctor, nurse practitioner, pharmacist or a registered dietitian can look at your situation as a whole.

Osteoporosis Canada publishes general guidance on calcium and vitamin D for adults, and their general message is worth knowing: aim to get calcium mainly from food, and consider a supplement to fill a gap if your provider recommends one. Vitamin D is often discussed differently, since it is hard to get enough from food alone in a Canadian winter. Your provider can tell you how that guidance applies to you.

More is not always better

It can be tempting to assume that if some calcium is good, extra must be better. That is not the case. Very high calcium intake, especially from supplements, may cause problems for some people, and very high doses of vitamin D can also be harmful. Taking several products that each contain the same nutrient is a common way to end up with more than intended.

Questions worth bringing to your appointment

If you are unsure whether your current approach makes sense, these questions can help structure the conversation:

1. Based on what I eat, do I need a calcium supplement at all, or is my diet likely enough?
2. Should I be taking vitamin D, and in what form and amount for my situation?
3. Do any of my medications interact with calcium or vitamin D, and should I space them apart?
4. Is there a reason to check my vitamin D level with a blood test?
5. Does my history of kidney stones, digestive problems or another condition change your advice?

Medication timing

Calcium can affect how well some medications are absorbed. Examples that are often mentioned include some thyroid medications, certain antibiotics and some medications used to treat osteoporosis itself. If you take any regular prescription, ask your pharmacist whether it should be taken at a different time of day from your calcium. Pharmacists are a very accessible source of this kind of advice, and most will happily review a full list of what you take, including over-the-counter products.

People who may want to pay closer attention

Anyone can come up short on calcium or vitamin D, but some groups are more often discussed:

• Older adults, whose skin makes less vitamin D and whose appetite or diet may have changed
• People who avoid dairy because of lactose intolerance, allergy or preference, unless fortified alternatives are part of the routine
• People following a vegan diet, who may rely on fortified beverages and calcium-set tofu
• People with darker skin or who cover most of their skin outdoors
• People who spend little time outside, including those who are housebound or living in long-term care
• People with conditions that affect absorption, such as celiac disease or inflammatory bowel disease, or who have had certain types of stomach or bowel surgery
• People taking medications that affect bone, such as long-term steroids

Being in one of these groups does not mean something is wrong. It simply makes the topic worth raising with your provider.

Why your supplement waits on bone density scan day

If you have been referred for a bone mineral density scan at Rossland Diagnostic Clinic, your preparation instructions will ask you not to take calcium supplements or iron tablets on the day of the exam until after the scan is finished.

The reason is practical. A bone density scan measures mineral in a specific area, most often the lower spine and hip. A calcium or iron tablet that has not yet dissolved can sit in the digestive tract close to the area being measured. Because the tablet is made of dense mineral, it could show up in the measurement and affect the result. Waiting a few hours removes that possibility. You can take your usual supplement once you have left the clinic.

A few related reminders for scan day:

• Wear clothing without zippers or metal fasteners if you can.
• Bring your health card and your requisition.
• Food that naturally contains calcium, such as your usual breakfast, is generally not the concern; the instruction is about supplements and iron tablets. If you are unsure, call the clinic before your appointment.

If you are wondering whether a scan is appropriate for you in the first place, our guide on who should get a bone density test walks through common referral reasons.

Nutrients are one piece of a bigger picture

Calcium and vitamin D matter, but they cannot do the work alone. Bone also responds to weight-bearing movement and muscle strength, and many fractures are really the result of falls. Our article on preventing falls and fractures looks at that side of bone protection in more detail.

Protein, overall diet quality, and avoiding smoking and heavy drinking all play a part as well. And if your doctor has diagnosed osteoporosis, nutrition usually supports, rather than replaces, the other parts of your care plan.

Common questions

Can I get enough vitamin D from the sun in summer and skip it the rest of the year? The body can store some vitamin D, but how long those stores last varies a great deal. Whether you need vitamin D in the colder months is a good question for your provider.

Is calcium from a supplement the same as calcium from food? Both provide calcium, but food also brings protein and other nutrients, and many health organizations suggest food as the first choice. Supplements can help fill a gap when your provider thinks one is needed.

Should I stop my supplement before a bone density scan for several days? The clinic’s instruction is to skip calcium and iron supplements on the day of the scan until afterwards. Do not stop any prescribed medication without speaking to your doctor first.

Does a bone density scan measure my calcium level? No. A bone density scan estimates the mineral content of bone in specific areas. Calcium and vitamin D levels in the blood are checked with blood tests, which your doctor would order separately if needed.

A simple next step

If you are not sure your diet or supplements are serving your bones well, write down what you usually eat and everything you take, and bring that list to your next appointment. It turns a vague worry into a conversation your provider can work with.

When a bone density scan has been recommended and you have a requisition, our team in Ajax is glad to help you book it. Call 905-426-3111 or request an appointment, and we will confirm how to prepare.