DEAR DR. BLONZ: I would like your help to settle an argument at a recent dinner. There seems to be such a push to restrict salt consumption in general, but the only hazard I am aware of is that salt can raise blood pressure in some people. Is there any other risk associated with salt? -- H.T., via email

DEAR H.T.: The main issue with excess salt intake is, as you mention, its association with high blood pressure (hypertension). But this is nothing to be dismissive about. High blood pressure currently affects roughly half of adults. It's called "the silent killer" because there are no warning signs until problems such as heart disease, stroke or kidney disease have already developed. The only reliable way to determine whether you have hypertension is to check your blood pressure regularly.

Salt and sodium are not automatically antagonistic for everyone, even those with high blood pressure. But there is no health benefit from excessive salt -- only liability. For those at high or uncertain risk about their blood pressure, it is best to keep salt to a minimum. Another point to consider is that one's sensitivity to salt, and ability to consume it safely, can change over time.

Finally, saltiness is one of our basic tastes. Salt helps to bring out the flavors in food. But the point should be to enjoy the natural flavor of foods, rather than that which comes from the salt shaker. Consider it a warning sign if you routinely reach for the shaker before you taste the food. (See b.link/2qkdb4 for more on high blood pressure.)

DEAR DR. BLONZ: I work with second- and third-graders as a student teacher. We would like to know: How do scientists determine the levels of protein and other nutrients in fruits, vegetables, meats or processed foods that contain them all? And where can I take my students to show them scientists analyzing foods? -- T.T., Chicago

DEAR T.T.: To analyze foods, representative samples are put through a series of laboratory tests that measure the amounts of macronutrients -- such as protein, fat and carbohydrate -- and micronutrients in the item. ("Macro" means larger amounts of the nutrient, whereas "micro" means smaller amounts. Read more at b.link/33chvc.) Each nutrient has its own test. Independent laboratories around the country perform these analyses, although food companies often have their own labs, as well.

You should check in your area for food manufacturers with in-house labs that offer tours. Consider creating a list of options and allowing the students to vote for their selection. I grew up in the Chicago area, and a trip like that was one of my most memorable class outings. I predict you will find companies willing to open their doors to your students.

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: 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.