Preventing Osteoporosis: Calcium and Vitamin D


Osteoporosis is a debilitating disease. It is a thinning of the bone tissue and a loss of bone strength over time that ultimately results in fracture. Osteoporosis has been referred to as a pediatric disease with geriatric consequences because failure to optimize peak bone mass in childhood and adolescence affects lifelong bone health and may ultimately result in fractures and disability in the senior years. Although there is no cure for osteoporosis, prevention is possible and nutrition plays an important role. Calcium and vitamin D are well known key nutrients for bone health. Let’s take a closer look at these two bone-building nutrients.

Calcium

The human body contains more calcium than any other mineral.

  • About 99% is found in bones and teeth.
  • The other 1% circulates in the blood where it supports life-sustaining functions, such as maintaining normal heart beat, nerve transmission, blood clotting and muscle contraction.

Just about every cell in the body counts on calcium to function properly. The level of calcium in the blood must stay fairly constant. If the calcium level gets low, calcium is taken from your bones to maintain a normal blood calcium level. Calcium must be consumed every day since it cannot be made by the body. That’s why a diet rich in calcium is so important, particularly when bones are growing and developing.

Daily Requirements

Your calcium requirements vary throughout life. The body’s demand for calcium increases when you – and your bones – are growing, and then later in life to help maintain bone health. As well, women have higher needs after menopause. Table 1 shows your daily calcium needs for various stages of life.

Table 1: Daily Dietary Reference Intakes for Calcium

Age (yearsRecommended Daily Allowance (mg per day) AIM FORRecommended Dietary Allowance (mg per day) STAY BELOW
1 – 37002500
4 – 810002500
9 – 1813003000
19 – 5010002500
51 – 70 men10002000
51 – 70 women12002000
71+12002000

Food sources

Consuming as much calcium as possible each day from food sources is important. Besides supplying calcium, food sources also provide other key bone-building nutrients. Foods that promote bone strength include dairy products (milk, yogurt and cheese), leafy green vegetables, pulses (various beans, such as kidney beans, chick peas, etc.), nuts (almonds) and seeds.

Bioavailability

Bioavailability is the degree to which our body absorbs calcium. This varies depending on the type of food being consumed. Milk and milk products contain calcium that has a higher bioavailability than other foods with calcium. Generally speaking, plant foods, such as spinach, contain compounds that bind to calcium and inhibit its absorption. Although these foods are nutrient rich, they only contribute a small amount of total calcium to the diet. This chart illustrates the number of servings of various foods you would have to eat to get the same amount of calcium found in one cup of milk. For example, you would have to eat about 2¼ cups of broccoli to get the same amount of calcium as you would in one cup of milk.

Supplements

Consuming calcium-rich foods is the best way to meet your daily calcium needs. However, calcium supplements may be recommended for individuals who can’t meet their calcium needs from food alone. But be aware. Overuse of calcium supplements may lead to an increase of kidney stones and heart attack. Therefore, it is best to discuss calcium supplementation with your physician.

Vitamin D

Vitamin D is critical for helping the body use calcium. It stimulates calcium absorption and helps regulate whether calcium is deposited into, or withdrawn from, bone. Recent research suggests that vitamin D may be associated with many other health benefits, including the prevention of certain cancers.

Daily requirements

Many Canadians may not be getting enough vitamin D. What about you? Table 2 indicates the daily recommendations for vitamin D for adults.

Table 2. Daily Dietary Reference Intakes for Vitamin D

Age (years)Vitamin D Requirements International Units (IU) per day AIM FORVitamin D Upper Limit International Units (IU) per day STAY BELOW
9 – 706004000
70 +8004000

Sources

Sunlight

Vitamin D, sometimes called the sunshine vitamin, is made in your body when you expose your skin to sunlight. However, wearing clothing that covers the body or using sunscreen to prevent sun exposure, and having dark skin limits how much vitamin D is made. Also, during the winter months in Canada (October to March), when the sun is the lowest in the sky, we do not get enough sunlight to produce vitamin D. Research has shown that Canadians are especially at risk for low vitamin D levels in the winter.

Following safe sun practices in order to prevent skin cancer is important. The new recommendations are based on the assumption that you have limited sun exposure and that all vitamin D is coming from food and supplements.

Food

Vitamin D is found naturally in very few foods. Fatty fish, egg yolks and liver are some natural sources. To help ensure that you consume an adequate amount, all fluid milk in Canada is fortified with vitamin D. This is one reason why including milk in your day contributes to a balanced diet.

Supplements

Some Canadians cannot get enough vitamin D from food and sunlight, thus they need to take a daily supplement. Health Canada recommends that anyone over the age of 50 take a supplement of 400 IU each day. This is because as the skin ages, it becomes less efficient at making vitamin D.

More is not better. Vitamin D is a fat-soluble vitamin which means your body can store it. Having too much vitamin D can lead to thin bones and high levels of calcium in your body, which may lead to kidney stones or heart problems in severe cases. Health Canada recommends an upper limit of 4000 IU of vitamin D from all sources. If you take supplements containing vitamin D, check with your doctor or a registered dietitian to ensure you are not getting too much. Overdosing is not likely to happen if you get vitamin D only from food sources or sunlight.

November is Osteoporosis Awareness Month. Take the opportunity this month to make sure you are doing what you can to prevent this disease. Following a well-balanced diet that emphasizes nutrient-rich foods that are good sources of calcium and vitamin D is one step towards maximizing your bone health.

AFLCA Members

Are you looking for practical nutrition tools for your clients? Log in to the AFLCA Members section of the website and order free resources today!

Article posted on November 15, 2011; Article revised August 2017

Colinda Hunter

Registered Dietitian

Colinda (BPE, BSc HEc (Nutrition), RD) is a registered dietitian who shares her knowledge of food and the science of nutrition to promote optimal health and wellness. As a nutrition educator with Alberta Milk she develops nutrition education resources and programs for health educators.

Article posted on November 8, 2011


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