Monday, April 26, 2010

Skeleton in deposit

Although osteoporosis appears later in life, the process begins during childhood. If there is not enough calcium and vitamin D in the diet or, in the case of vitamin D, insufficient sunlight exposure, then not enough skeletal bone is created during our schooldays. Our bones reach peak mass by the age of 30 years and thereafter decline. The rate of the decline is greatly dampened if adequate calcium is consumed, you remain active, don’t smoke and get all your vitamin D needs through diet or sunshine.

Calcium & vitamin D

Your recommended calcium and vitamin D needs increase as you get older to help forestall the brittle bones of osteoporosis. A greater calcium intake slows down the rate of bone loss in the later decades, while the kidneys become less able to activate vitamin D so more D is needed. High calcium foods usually have their calcium levels mentioned on the label. You need about 1000 mg of calcium a day when you are youthful, increasing to 1300mg a day when you head to the retirement village.

Calcium, where art thou?

You know about milk, yogurt and cheese. There is next to no calcium in butter despite it being a dairy food. Calcium is found in the ‘watery’ part of milk, not the fatty part we call butter. Some canned fish can provide calcium providing you eat the soft bones; think of sardines, pilchards, tuna and salmon. Don’t assume other ‘milks’, like soy and rice milk, have calcium unless they specifically state on the label that they are calcium fortified.

The list below shows you how many serves of selected foods you need to eat to get the same amount of calcium found in a serve of milk or yogurt.

Milk, yogurt, 200g [1.0 serve]

Cheddar cheese, 40g [1.0]

Broccoli, ½ cup [5.5]

Brussel sprouts, ½ cup [8.3]

Cauliflower ½ cup [8.6]

Canned sardines, 100g [1.1]

Sesame seeds, 30g [13.0]

Soy milk (unfortified), 250 mL [31.0]

Soy milk (calcium fortified), 250 mL [1.4]


You may recall that Annyca asked about the calcium in almonds. Although I knew their calcium content (about 70mg in a 30g handful) I wasn’t sure how much was likely to be absorbed. That took a little tracking down. Thankfully super-dietitian Helen Mair was able to help. She says you would need to eat about 170g of almonds to get the same amount of calcium as found in a 200 mL glass of milk. That’s about a cup of almonds.

What does it all mean?

Like so many aspects of health, it is what you do throughout life that minimises the risk of brittle bones. Waiting until the first hint of osteoporosis means leaving it too late. Women are more likely to get thin bones because they lose the protection of the hormone estrogen after menopause. In men, testosterone is the hormone that protects bone. Levels of testosterone tend to drop more slowly than does estrogen in women, where women can lose 20% of their bone mass in the decade after menopause. Think about your bones today.

Reference: Whitney & Rolfes. Understanding Nutrition. 10th edition 2005

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