Q. I know that calcium is related to bone health, but what should I eat, which supplements should I take, and how much do I need? And is vitamin D also important for healthy bones?

A. Calcium is essential for maintaining and building your bones. It's a good idea to get as much calcium in your diet as you can and then take supplements if you need additional calcium.

Dairy products can be a significant part of your bone-building diet — but not if you're allergic to dairy or have lactose intolerance. Not only are they loaded with calcium, but researchers have discovered that they contain specific proteins, especially concentrated in whey, that can enhance bone density.

In addition, a sugar found in dairy products, lactulose, enhances calcium absorption. If you don't tolerate dairy products, there are other food sources rich in calcium.

According to the National Institutes of Health, the recommended daily amounts of calcium ingestion by age group are: 210 milligrams at under 6 months; 270 milligrams at 7 to 12 months; 500 milligrams at 1 to 3 years; 800 milligrams at 4 to 8 years; 1,300 milligrams at 9 to 18 years; 1,000 milligrams at 19 to 50 years; and 1,200 milligrams at over 51 years. Those with osteoporosis should take at least 1,500 milligrams a day.

If you take calcium supplements, use calcium citrate for maximum absorption. (Note: some people experience diarrhea if they ingest too much calcium citrate.)

Calcium needs vitamin D in order to be absorbed in your intestinal tract, so it's important to look at your vitamin D intake as well. You get one type of vitamin D, known as D3 (cholecalciferol), from exposure to sunlight and from eating fish oils and eggs; another type, D2 (ergocalciferol), is made in plants and used to fortify dairy products.

According to a study published in the Journal of Clinical Endocrinology & Metabolism in 2004, vitamin D2 is less effective than vitamin D3; the researchers found that D2 has less than one third the potency. Another study, published in the American Journal of Clinical Nutrition in 2006, reported that "vitamin D2 should not be regarded as a nutrient suitable for supplementation or fortification."

Be sure you're ingesting vitamin D3 for maximum effectiveness. To know if you have enough D3, ask your doctor to run a blood test. The recommended daily intake is 200 international units for people from birth to 50 years old, 400 for those aged 51 to 70, and 600 for those 71 or older. Most bone-building formulas contain 200 to 800 units of vitamin D.

Laurie Steelsmith is a naturopathic physician and licensed acupuncturist in Honolulu, as well as author of "Natural Choices for Women's Health" (Random House). Reach her and read columns at www.drsteelsmith.com. This column is for information only. Consult your health provider for medical advice.