DEAR DR. BLONZ: What is the connection between a very high-protein diet, calcium absorption and bone health? Does it matter whether the excess protein is from animal or plant sources? -- J.F., Boston

DEAR J.F.: Our bones are constantly being broken down and rebuilt, per our genetic programming. Our bones may seem stable, but about 20% of our skeleton "turns over" annually. The human species would not have survived without this ability.

Excess protein can affect calcium levels in the body and its absorption. Interestingly, data suggests that protein from plant sources may have less of a tendency to drain calcium from the body than animal proteins. Why would this be? Proteins get broken down into constituent amino acid parts and become part of the body's pool of amino acids. There are limits to how much of any given amino acid can hang around waiting for its next job; when there is more than the body needs or can handle at a given time, the excess is turned into fat, and stored.

When broken down, animal proteins tend to create more acid substances than proteins from vegetable sources do. Our kidneys handle the increased acid load, but the process can cause calcium loss in the urine. It would be prudent for those concerned with bone loss to avoid excess protein from animal sources and increase the use of plant sources. (For more on dietary protein requirements, see b.link/pa95x45.)

Why would animal proteins be so different from vegetable sources? The animal proteins we consume tend to come from working muscles, whereas plant proteins are involved in structure, enzymes and function. Different functions call for different amino acid compositions; the animal sources involve a greater proportion of the acid-forming ones.

Bones involve more than calcium, so don't forget your other mineral requirements. (For a summary of dietary minerals, see b.link/wqr22zg.)

DEAR DR. BLONZ: Regarding calcium, why only 500 mgs at a time as a supplement? I take a gel capsule, and each is 600 mgs. I have been taking two at bedtime, which I heard was best. Also, I do not want to take it within several hours of my thyroid medication. Could you please comment? -- T.T., Las Vegas

DEAR T.T.: Calcium absorption efficiency decreases when a single dose exceeds 500 mgs. When taking calcium supplements, it is best to follow that advisory and, if needed, distribute it across more than one dose. There are also several medications that a calcium supplement should not accompany -- check with your physician or your pharmacist. (For more on when to take calcium supplements, see b.link/xcnqu77.)

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: My husband and I will be trying to start a family next year. We are both in good health, with no chronic ailments or genetic issues. My diet is fine, but not ideal. I have managed to control my sweet tooth, but I admit I periodically have to rely on fast food at work. Which vitamins and minerals play the biggest role in the baby's development? -- A.P., Atlanta

DEAR A.P.: A developing fetus relies on its mother to have all the needed nutrients in her blood for its use as directed by its unique set of genetic instructions. Each nutrient required to construct and operate its biological systems will be called upon at the proper time.

Here are a few tips on nutritional needs during pregnancy, and a cautionary note.

Following conception, one of the first elements to develop is the nervous system, which communicates vital directions and feedback. This development can occur before a woman even knows she's pregnant. Folic acid plays a key role and must be present at sufficient levels during the first few weeks after conception.

Spina bifida, a congenital disorder in which one or more of the vertebrae of the spinal column fail to develop correctly, is a result of a folate deficiency during the first few weeks of pregnancy. The U.S. Public Health Service therefore recommends that all women of childbearing age should consume at least 400 micrograms of folic acid daily, and increase to 600 mcg during pregnancy.

Iron is needed as the fetal blood supply develops. Sufficient iron stores should be present in the mom-to-be to cover the first months of the baby's life, during which its primary food source is often iron-poor breast milk. The RDA for iron rises to 27 mg during pregnancy.

Calcium and vitamin D are critical for bone development. Calcium absorption doubles during pregnancy, and vitamin D is needed for calcium absorption and utilization. The RDA for calcium is 1,200 milligrams, and the RDA for vitamin D is 10 micrograms.

Another key is water. Recommendations are to drink 8 to 12 glasses of water and other fluids daily during pregnancy. Throughout pregnancy, a woman's blood volume increases by 50 percent. Water is also the base of the amniotic fluid in which the fetus lives and develops.

Your health professional should have informational resources. For more information on eating right during pregnancy, see b.link/7a5l36ef. Food safety for mothers-to-be is also important, so check out this FDA article at b.link/ygb3qlm.

Finally, alcohol consumption is another concern. The developing fetus does not yet have a liver to break down alcohol, and its presence can lead to serious developmental problems. The best advice is that there is no safe time during pregnancy to consume alcohol. (Check out this article from the Centers for Disease Control and Prevention at b.link/u4zdve8.)

Wishing you the best as you move toward the family way.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I am in my middle years, and my hair has become thin and is subject to frequent breakage. Someone suggested that I try some Norwegian kelp, as it was claimed to bolster the thyroid, which, if not functioning properly, will cause hair breakage and loss. Will this nutrient remedy my symptoms and stimulate hair growth? What other natural products would you suggest? -- S., Nashville

DEAR S.: Kelp is a seaweed known primarily for its iodine content, but it also contains small amounts of other minerals and vitamins. Iodine is an essential mineral that plays a role in manufacturing the thyroid hormones, which help regulate body metabolism.

Dry, coarse and breaking hair and hair loss can be symptoms of inadequate thyroid hormone -- hypothyroidism -- so perhaps that was the connection your friend was referencing. That is not the only possible explanation for your dry, thinning hair, and it is unclear whether kelp could be the answer if a lack of iodine is not the issue. Thyroid issues are diagnosed via blood tests.

Hair is among our most actively growing tissues. One's genetic background, certain health conditions, medications and aging can affect how your hair looks, grows and behaves. (For more information on the effects of aging on hair and nails, see b.link/ttn6tetr.)

The quality of your diet is also a factor. Aim for a good mix of fruits, greens and grains, which provide the essential vitamins and minerals. Include a regular intake of seafood, nuts and seeds, which are good sources of minerals and essential fatty acids.

We all need the essential nutrients -- deficiencies can negatively impact most of the body's systems, including the health of our hair -- after all, that's why they are called essential. However, it is unwise to suggest that consuming more than is required will make things better.

Be cautious with dietary supplements specifically promoted for hair health. Look for objective clinical evidence of a supplement's efficacy -- this is key, because you shouldn't rely on evidence only from the company profiting from the sale of the product.

Our hair is greatly influenced by the products and treatments we use on it. Also consider the exposure your hair receives to sunlight, chlorinated pool water, hats, helmets and body lotions. A knowledgeable esthetician or hair stylist can review your current practices and might be able to recommend products suited to your specific issues.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.