DEAR DR. BLONZ: Since the pandemic, I haven't been able to find good old-fashioned bagged barley in any grocery store. This is a product that arguably has been around since the early days of man -- now, not available. This doesn't make sense. My dad said I should ask you. Where did barley go? -- J.R.

DEAR J.R.: You have my support for the use of barley, a healthful cereal grain in the grass family that was one of the first cultivated grains. Barley has many benefits, including about three times the fiber of oats. (Read more on the benefits of barley at b.link/swvzy4ky.) Note that cereal grains -- a category that includes wheat, rye, triticale (a wheat/rye hybrid) and barley -- contain gluten, so those with a gluten disorder should avoid them.

Barley can still be found through online sources, but there has, indeed, been a decrease in its availability. While barley is a hardy crop, it is not invulnerable to climate change. Excessive heat or cold can affect plants at their flowering stage, which impacts grain yield and quality. Current shifts in temperature, erratic rainfalls and unpredictable weather conditions have had an impact in crop yields. U.S. agriculture, led by Idaho, Montana and North Dakota, produces enough for our needs. However, the war in Ukraine has had an impact, as Russia is the largest producer of barley, and Ukraine is the third-largest exporter. There may be a trickle-down effect on worldwide barley production, resulting in a drain on availability from our domestic crop.

Keep looking, and you can find it. And thanks to your father for the referral.

DEAR DR. BLONZ: I read that rhubarb contains large amounts of oxalate, which is a natural toxin. Should I be concerned about rhubarb pie, which is a holiday favorite at our home? -- M.M., Chicago

DEAR M.M.: Oxalate is found in rhubarb, spinach, soy and other plants. Oxalate can form an insoluble mineral salt with mineral elements, such as iron and calcium, making them unavailable for absorption. For this, oxalate it is often referred to as an "anti-nutrient."

Consumption of healthful plant foods that contain oxalate can mean less of these minerals will be absorbed. This is not necessarily an event of clinical significance, as the impact is based on the amount of oxalate present, and cooking and digestion can break it down. (Some individuals are more sensitive to oxalate than others.)

Back to your question. Since the main source of the oxalate in rhubarb is in its leaves, and not the stalks, your family favorite should not pose a problem. (For more on issues relating to oxalates, see b.link/jkbw848.)

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: 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.