Osteoporosis is a condition resulting in the thinning of bone tissue and loss of bone mass over time. It is caused by excessive loss of calcium from bones. As a result, bones become fragile and break easily. During childhood, calcium is actively deposited in the bones to support growth and development. The bone stops growing in length and density at approximately age 20 for men and 16 for women. This is the point we achieve peak bone mass.
The greater the peak bone mass, the lower the risk of Osteoporosis. Women are generally at higher risk of Osteoporosis as they achieve peak bone mass at an earlier age. Pregnancy and menopause also increases calcium losses from the bone.
Calcium and bone health
Osteoporosis can be prevented through proper bone nutrition especially ensuring adequate calcium consumption. The best time to increase intake of calcium is during the developing years of a child when the bone is still actively growing and has yet to achieve peak bone mass. However, adults can also benefit greatly from increasing their calcium intake to maintain adequate calcium supply preventing the body from dipping into the calcium reserves which is the skeleton.
The recommended daily amount (RDA) of calcium is as follows:
| Age group | Male | Female | Pregnant & Lactating |
| 0-6 months | 200mg | 200mg | |
| 7-12 months | 260mg | 260mg | |
| 1-3 years | 700mg | 700mg | |
| 4-8 years | 1000mg | 1000mg | |
| 9-18 years | 1300mg | 1300mg | 1300mg |
| 19-50 | 1000mg | 1000mg | 1000mg |
| 51-70 | 1000mg | 1200mg | |
| 71 and above | 1200mg | 1200mg |
The main dietary sources of calcium include milk and milk products e.g. cheese and yoghurt. Calcium can also be found in soy products, sardines, nuts, dark leafy green vegetables and calcium fortified foods. As part of a healthy diet, it recommended to consume 2-4 servings of calcium-rich foods daily. Choose low-fat/reduced-fat dairy as much as possible as dairy products are naturally high in saturated fat. As a guide, refer to the calcium content of the following calcium-rich foods:
| Food | Amount | Calcium content |
| Dairy & Soy | ||
| Milk (skim, low-fat, whole) | 1 cup | 300mg |
| Buttermilk | 1 cup | 300mg |
| Nonfat milk powder | 5 tbsp | 300mg |
| Low-fat yoghurt | 1 cup | 450mg |
| Soy milk, calcium fortified | 1 cup | 200-400mg |
| Hard cheese (cheddar, jack) | 1 oz | 200 mg |
| Mozzarella cheese | 1 oz | 200mg |
| Parmesan cheese | 1 Tbsp | 70mg |
| Soft tofu | 4 oz | 200mg |
| Firm tofu, calcium set | 4 oz | 300mg |
| Vegetables | ||
| Broccoli | 1 cup | 180mg |
| Kale, raw | 1 cup | 55mg |
| Spinach, cooked | 1 cup | 240mg |
| Swiss chard, cooked | 1 cup | 100mg |
| Fish | ||
| Sardines, canned with bones | 3 oz | 370mg |
| Mackerel | 3 oz | 250mg |
| Nuts & grains | ||
| Almonds | 1 oz | 80mg |
| Sesame seeds | 1 oz | 280mg |
| Brown rice, raw | 1 cup | 50mg |
| Cereals, calcium fortified | ½ cup | 200-300mg |
Tips to incorporate more calcium into your diet
ü Use bones (e.g. chicken, beef, fish) for homemade soup stock
ü Add shredded reduced-fat cheese into pastas, salads & sandwiches
ü Add minced dark greens such as kale and spinach to casseroles, soups and stews
ü Use calcium fortified soy milk, non-fat dairy milk or buttermilk in your recipes instead of water in recipes such as pudding, oatmeal and mashed potatoes
ü Add a hearty dose of legumes such as pinto beans or soybeans into your pastas and salads
ü Enjoy sesame or almond spread on toast instead of your usual peanut butter and jelly
ü Toss some fresh fruit into low-fat yoghurt as breakfast or even dessert
Calcium supplements
One can also consider calcium supplementation if there is difficulty in meeting the calcium requirement through food exclusively. Calcium in the form of calcium citrate has a much higher absorption that calcium carbonate. However, they are generally pricier as well.
A more effective way of consuming calcium supplement is in spilt dosages. It is advisable not to exceed 500mg of calcium per dose as anything above 500mg cannot be effectively absorbed by the body. Bear in mind that supplements as the name suggest are meant to supplement the diet and not intended as the only calcium source. It is very important to incorporate calcium-rich foods into your diet to protect your bones.
Vitamin D & bone health
Vitamin D is essential for bone health as the body requires vitamin D for calcium absorption in the intestines. It also maintains the balance of calcium levels in the blood to prevent calcium depletion from bones. The general recommendation for vitamin D is 400-600IU daily for adults under 50 and 800-1000IU for adults over 50.
Vitamin D is present in very few foods. Foods rich in vitamin D include: Cod liver oil, animal liver, oily fishes and vitamin D fortified foods e.g. vitamin D fortified milk. Most of our vitamin D is produced by our own skin when exposed to UV rays in sunlight. In general, 10–15 minutes exposure of hands, arms and face 3–4 times per week under moderately strong sunlight if climate permits is recommended for optimal vitamin D production.
Individuals who live in climates with low sun exposure or those who wear covered clothing are at risk of vitamin D deficiency. They may consider taking a vitamin D supplement to achieve their daily recommended intake. Most calcium supplements and multivitamins do contain vitamin D. Alternatively, there are also pure vitamin D supplements available.
Dietary risk factors for increased calcium losses
(i) High phosphoric acid intake
Found mainly in carbonated drinks, phosphoric acid increases urinary calcium excretion. In addition, due to the acidity of phosphoric acid, the body uses calcium to neutralize the acid in order to maintain the blood pH. On a side note, carbonated soft drinks are loaded with sugar, so it is probably a sound choice to limit the intake of these beverages.
(ii) High protein intake
Protein is essential for health. Be aware of how much protein you require and consume enough but not excessive. The metabolism of protein generates acids which again require calcium to neutralize. If the calcium supply is inadequate, the body will tap on the bone for calcium leading to bone depletion.
(iii) High caffeine intake
For coffee addicts, it may not be good news to know that caffeine increases the excretion of calcium from the body. An intake of >300mg of caffeine per day has been shown to significantly increase calcium loss. To minimize the effects of caffeine on bone loss, it is advisable to limit yourself to not more than 2 cups of caffeine-containing beverages per day.
(iv) High sodium intake
Like caffeine, high salt intake increases excretion of calcium in the urine even though the specific biological mechanism is different. Studies show that every extra gram of salt consumed per day will produce a 1% increase in bone loss yearly. Sodium has a large potential to influence bone depletion. High salt intake is also associated with increased blood pressure. For both the bone and cardiovascular health, a low-sodium diet is highly recommended.
A nutritionally balanced diet is essential for the maintenance of healthy bone mass. However, diet is only one part of the equation. Exercise also plays an important role in supporting bone health. Weight-bearing exercises help to increase the strength of bone and support calcium deposition in the skeleton. There are many simple weight-bearing exercises that one can do in the comfort of your own home. One does not have to be a nutrition expert or a fitness instructor to build strong and healthy bones. All it takes some discipline and commitment.
About the author
Kelly Kims is a certified dietitian and nutritionist who has practiced as a clinical dietitian in major tertiary hospitals. Her clinical interest includes nutritional therapy for weight management, diabetes, cardiovascular disease and cancer. She is also an accredited sports dietitian who has experience in counseling athletes and fitness fanatics about sports nutrition. She is also co-owner and writes about nutrition and diets at quickeasydietsthatwork.com