Calcium is the most abundant mineral in the human body. Calcium’s primary role is the construction and maintenance of bones and teeth. Approximately 99% of total body calcium is in the skeleton and teeth and they act as a storage reservoir for this as well as other minerals. The other 1% is in blood and soft tissues. Calcium is found in two different forms in the bones. One form is bound tightly and is not easily removed, while a second form can be easily removed from bone to aid in maintaining normal blood calcium levels.

 Adequate intake of calcium is essential for maximising bone density and reaching peak bone mass. Therefore, an inadequate intake of calcium can adversely influence bone formation and may contribute to osteoporosis. Osteoporosis is a decrease in bone density and strength that results in increased susceptibility to bone fractures. Calcium is also used for numerous other body functions. It helps to transport ions (electrically charged particles) across cell membranes allowing muscle contraction to occur. It assists in regulating heart rhythm, as well as helping to control blood pressure, nerve transmission and the release of neurotransmitters. Calcium is also a vital component in blood-clotting systems and helps in wound healing.

Most of us rely on dairy as our main source of calcium. However, there are many foods that can help (or hinder) your calcium uptake.

The Australian Health Survey released last year revealed that most women and older men in this country don’t have enough calcium in their diets.

As you age, the body’s ability to absorb this important mineral decrease, making bones more fragile and vulnerable to osteoporosis. So one doesn’t want to lose the calcium you’re ingesting. You’ve no doubt heard that vitamin D helps the absorption of calcium, but calcium has more friends (and foes) than that. 

Here are some of the lesser-known nutrients and foods that can impact your calcium levels.

1. Prunes and Raisins

Both of these fruits contain a good amount of calcium, but that’s not only why they’re appearing on this list. They’re also great sources of boron. This mineral helps to prevent the body from losing calcium through urine by maximising the activity of oestrogen and Vitamin D in bones. This means that without enough boron, you’re literally flushing calcium down the toilet. Boron works by stimulating the body to produce more oestrogen, which is good news for those who are going through menopause. Decreased oestrogen levels during this time of life triggers increased activity of osteoclasts – the cells that have been shown to break down bone. 

Other sources of boron: It’s widely found in fruit, vegetables, legumes and nuts, particularly almonds, apples, oranges and cherries. There’s currently no RDI for boron, but if you eat the daily recommended two serves of fruit and five serves of veg, you’ll be covered.

Food sources for vitamin D: Vitamin D does not occur naturally in many foods as it is a fat-soluble vitamin. It is found in some high-fat foods such as butter, margarine and cream. It is also found in oily fish such as salmon and tuna, as well as liver and kidney. Vitamin D can be absorbed by the body during digestion; however, it can also be manufactured by the body when the skin is exposed to sunlight (approximately 10 to 15 minutes of sunlight exposure two to three times per week will assist the body to meet its requirements for vitamin D).

2. Feast on avocado

The flesh of this nutritious fruit is rich in magnesium, which is “the key to the body’s proper assimilation and use of calcium”, according to Dr Carolyn Dean, medical director of the US Nutritional Magnesium Association and Creator of The Completement Now Wellness Programme and Author of The magnesium miracle. She adds: “If we consume too much calcium without sufficient magnesium, the excess calcium isn’t utilised correctly and may actually become toxic, causing calcification of the arteries, leading to heart attack and cardiovascular disease.” 

Other sources of magnesium: Oily fish, leafy greens, oats, wholegrain, almonds and dark chocolate are also rich in this important mineral. The recommended daily intake of magnesium is 320 mg/day for women aged 30-50. Lauren McGuckin, an accredited practising dietitian and Dietitians Association of Australia spokesperson, advises spreading this amount across the day via an oat-based breakfast, a handful of almonds, a salmon and avocado sandwich on multigrain, a banana, and a cup of spinach in a salad.

3. Eat less bran and beans

Both of these fibrous foods are rich in phytic acid and oxalic acid, which bind to calcium and can inhibit its absorption. The acids are also found in spinach, Swiss chard, beets, rhubarb, berries, beans, wheat bran, seeds and grains. The extent to which these acids affect calcium absorption varies from person to person. One way to keep track of your intake is to only eat seasonal fresh veg. This allows nature to rotate different types of greens in and out of your diet, so you’re not overloading on one that’s high in these acids. For the same reason, having a green smoothie with spinach or Swiss chard every day isn’t a good idea. 

4. Cut back on salt

Excess sodium is excreted into your urine, and it takes calcium with it. 

A 2013 Japanese study found that older women who consumed excessive amounts of salt were four times more likely to have bone fractures, regardless of their bone density. The recommended daily sodium intake for adults is 1600 mg – less than one teaspoon. Reduce your consumption by eliminating processed snacks such as potato chips, and use herbs and spices to enhance meals. “Eliminate or cut back processed foods, cheese, takeaway meals and ready-made sauces,” naturopathic nutritionist Jan Purser says. Potassium-rich foods such as banana, sweet potato and rockmelon can help limit calcium loss. 

5. Are alcohol and caffeine bad for your bones?

Alcohol: It’s been proven that too much booze over a long period can affect calcium absorption and interfere with the enzymes in the liver that help vitamin D to be at its most active. What isn’t known is whether moderate alcohol consumption is good or bad for bones, so drink responsibly and in moderation.  

Caffeine: Good news is that the amount of calcium you excrete by drinking tea and coffee is so small that one or two tablespoons of milk could make up for it. Studies that have reported otherwise were likely based on the theory that people consuming a lot of caffeinated drinks weren’t drinking calcium-rich alternatives.

6. Cola: Are you a soda addict?

Drinking seven or more colas per week is associated with a reduction in bone mineral density and an increase in risk of fracture.

The negative effects on bone health seem to be limited to diet and regular cola-type sodas. That’s because colas contain phosphoric acid, a food additive that appears to weaken the intestines and the absorption of calcium. Instead of cola, go for a bubbly alternative better suited to osteoporosis prevention, such as seltzer mixed with fresh fruit juice.

7. Inflammatory Foods

Nightshade vegetables, such as tomatoes, mushrooms, peppers, white potatoes, and eggplant, can cause bone inflammation, which can lead to osteoporosis. However, these vegetables contain other vitamins and minerals good for your health, so, like beans, they shouldn’t be totally avoided. As long as you make sure to get enough calcium — 1,200 milligrams a day, you can eat these foods and still support good bone health.

8. Raw Spinach and Swiss Chard

Rich green raw spinach and Swiss chard contain bone-healthy calcium; however, they also contain substances called oxalates, which can bind up the calcium and make it unavailable to the body.

To enjoy the other health benefits of these vegetables (and help prevent osteoporosis at the same time), “If you eat spinach, the oxalates will prevent you from absorbing the calcium from the spinach, but if you put some cheese on it, you will absorb calcium from the cheese,” says Felicia Cosman, MD, medical spokeswoman for the American National Osteoporosis Foundation’s Generations of Strength campaign. For maximum bone health, Cosman suggests balancing them with foods that contain calcium readily absorbed by the body.

References:

http://www.nutritionalmagnesium.org/

Cambridge VCE Health and Human Development text by Sonia Goodacre / Chrissy Collins / Carolyn Slattery