Osteoporosis, Calcium, and Diet

The body cannot produce calcium on its own. In 2002, calcium supplements were the number one selling mineral supplement and the 3rd highest selling supplement overall in the U.S. nutrition industry, totaling approximately $877 million in sales. Source: Nutrition Business Journal, 2002

What is osteoporosis?

Osteoporosis is a “silent” disease characterized by loss of bone mass. It mainly affects women age 60 and older. The leading cause of osteoporosis is a decrease in certain hormones coincident with the aging process, particularly estrogen in women and androgen in men. Due to weakened bones, fractures become commonplace, which leads to serious health risks such as the inability to walk. According to the National Institutes of Health, 10 million Americans have the disease, and another 18 million have osteopenia, its precursor. Fortunately, osteoporosis is preventable for most people.

Proper diet and weight-bearing exercise are the two essentials of a health program for osteoporosis. Staying physically fit through strength training and some form of aerobic exercise lessens the likelihood of falls and fractures, as bones grow stronger and balance improves. Like muscles, bones will lose mass and deteriorate if not used regularly. Walking, jogging, dancing, stair climbing, step aerobics, racquet sports, and weight training are all beneficial activities for preventing or halting the development of osteoporosis. It is advisable to check with your doctor before beginning an exercise program.


Most important dietary considerations for osteoporosis

The treatment plan for osteoporosis always includes ensuring that there are sufficient amounts of calcium and Vitamin D in the diet. Calcium is the major component of bones, and is therefore crucial to maintain bone density. Vitamin D allows calcium to leave the intestine for absorption, and works in the kidneys to reabsorb the calcium that would otherwise be excreted. The two necessarily work well together.

Foods high in calcium and vitamin D

Foods rich in calcium include milk, yogurt, cheese, tofu, sardines, salmon, turnips, and some green and leafy vegetables, such as spinach, broccoli and kale. The main food sources of vitamin D are cold saltwater fish (e.g., salmon, halibut, herring, tuna), fortified milk, egg yolks, liver, and especially fish oils.

The Food and Drug Administration established the Percent Daily Value (%DV) to show consumers how much of a particular vitamin, mineral, or nutrient is contained in a serving size of food. The Daily Value is not a quantity recommendation, but a reference point for the consumer. The DV for calcium has been set at 1,000 milligrams, and for vitamin D at 400 international units (IU). For example, a 1/2 cup serving of broccoli with cheese has a 20% calcium DV. Since the reference for calcium is 1,000 mg, that means you would get 200 milligrams of calcium in that serving.

The following list from the University of Nebraska’s online journal Food Reflections contains the %DV of calcium found in some common foods:

Vegetable Group

* Broccoli with cheese: 1/2 cup = 20% DV
* Collards: 1/2 cup = 20% DV
* Turnip greens: 2/3 cup = 15% DV
* Kale: 2/3 cup = 10% DV
* Bok choy: 1/2 cup = 10% DV
* Broccoli: 1 stalk = 6% DV

Fruit Group

* Orange juice, calcium-fortified: 1 cup = 30% DV

Milk Group

* Yogurt: 8 oz = 35% DV
* Milk (whole, 2%, 1%, skim, chocolate): 1 cup = 30% DV
* Cheese: 1 oz = 20% DV
* Milk pudding: 1/2 cup = 10% DV
* Frozen yogurt: 1/2 cup = 10% DV
* Ice cream: 1/2 cup = 6% DV
* Soy milk, calcium-fortified: 1 cup = 30% DV

Meat & Bean Group

* Tofu prepared with calcium sulfate: 3 oz = 60% DV
* Baked beans with sauce: 1/2 cup = 8% DV
* Pork & beans with sauce: 1/2 cup = 6% DV

Some foods interfere with calcium availability. Excessive protein, sodium, and caffeine can increase the urinary excretion of calcium, while excessive fiber can interfere with its absorption. Foods high in oxalic acid (oxylates), such as spinach, rhubarb, beet greens, chard, and almonds, bind the calcium and make it unavailable. Legumes such as pinto beans, navy beans, and peas are high in phytates, another substance that interferes with calcium uptake. These can be soaked for several hours in water, rinsed, and cooked in new water to neutralize the effect. The National Osteoporosis Foundation recommends eating foods with oxalic acid and phytates one hour before or two hours after the calcium-rich foods.
The National Institutes of Health provides meal planning tips for meeting calcium requirements:

* Use low fat or fat free milk instead of water in recipes such as pancakes, mashed potatoes, pudding and instant, hot breakfast cereals.
* Blend a fruit smoothie made with low fat or fat free yogurt for a great breakfast.
* Sprinkle grated low fat or fat free cheese on salad, soup or pasta.
* Choose low fat or fat free milk instead of carbonated soft drinks.
* Serve raw fruits and vegetables with a low fat or fat free yogurt based dip.
* Create a vegetable stir-fry and toss in diced calcium-set tofu.
* Enjoy a parfait with fruit and low fat or fat free yogurt.
* Complement your diet with calcium-fortified foods such as certain cereals, orange juice and soy beverages.


Calcium and vitamin D supplements

Food is the preferred source, but if you can’t meet your daily requirement from food alone, supplements are often advised. Calcium supplements derived from bone meal, dolomite, or unrefined oyster shells may contain lead or other toxic metals, so it is best to avoid them. Calcium citrate is preferable to calcium carbonate, as it does not require stomach acid for assimilation. Since the “calcium load” at any given time is 500 mg, beyond which the body cannot optimally absorb any more, it is recommended that it be taken in increments throughout the day. For optimal absorption, it has been suggested that it is best to take calcium citrate before bed, and calcium carbonate at dinner time.

The Harvard Health Services website reports that an estimated 30-40% of adults over 50 have a vitamin D deficiency, which accelerates bone loss and increases the risk of fractures. If your vitamin D consumption from food is too low, you might consider getting a calcium supplement that contains Vitamin D, or taking vitamin D alone in supplement form. Vitamin D supplements typically come in strengths from 200–400 IU.
Is it possible to take too much calcium or vitamin D?

Yes. Toxicity resulting from too much calcium or vitamin D in the diet most surely comes from excessive supplementation, rather than from too much of a food source. Tolerable Upper Intake Levels (UL) have been defined by the Food and Nutrition Board of the IOM as “the maximum daily intake unlikely to result in adverse effects.” The UL for calcium for the entire population one year and older is 2500 mg/day, including pregnant and lactating women. It is unlikely that anything higher than 1500 mg a day would have a beneficial effect. Calcium intake in the range of 2000–2500 mg a day (from any combination of food and supplements) can adversely affect the absorption of zinc, iron, and magnesium. In rare cases, high calcium intake can lead to hypercalcemia, or elevated levels of calcium in the blood.

Vitamin D toxicity occurs at amounts exceeding ULs of 1,000 IU for infants up to 12 months of age, and 2,000 IU for all other age groups, including pregnant and lactating women. According to the IOM, high levels of vitamin D can cause nausea, vomiting, poor appetite, constipation, weakness, and weight loss. It can bring on a confused mental state and heart rhythm abnormalities. Calcinosis, which occurs when calcium and phosphate deposits settle in the soft tissues of the body, can also result from vitamin D toxicity.