DEAR DR. BLONZ: My regular enjoyment of cashews was put at risk when I heard someone say at a party that they never ate them since they learned cashews contain a toxin and must be avoided. I was skeptical, as I could not imagine their wide acceptance if this were the case, but it did give me pause. I was hoping that you could respond. -- S.N., Los Angeles, California

DEAR S.N.: As someone who enjoys cashews and other nuts and seeds daily, I share your skepticism of those comments. To provide some clarity, cashews belong to the same family that includes the itch-provoking three: poison oak, ivy and sumac. The poison readily shared by those three is the compound named urushiol. (For more on this irritant, see b.link/b2xb6d6.)

The confusion likely stems from the fact that cashews grow with protective shells (see b.link/rf45kfvv), and it's those shells -- not the nuts we enjoy -- that can contain some urushiol. There is careful separation, followed by roasting or steaming, that eliminates the urushiol risk.

It's not only cashews. The outer hull of pistachios -- again, not the shells or kernels inside -- can also contain trace amounts of urushiol; that protective cover also being removed before the shell is roasted and the kernel lands in our hands. Finally, there is a relatively small amount of urushiol in mangos, but it is in the skin, sap and leaves, not the flesh we eat. However, those who have become hypersensitive to urushiol should be aware when handling mangos.

Consider urushiol a particularly annoying example in nature's vast array of protectants designed to keep poachers away so that the plant's seeds have time to mature and develop into plants of their own.

DEAR DR. BLONZ: I've recently become more aware of the nutrition content of food products, and I am concerned about potassium, having learned that too much is as bad as too little. Why isn't potassium listed on most food labels? -- G.B., via email

DEAR G.B.: Potassium, with the chemical symbol K, is a key electrolyte in the body, along with sodium, chloride, calcium, magnesium and bicarbonate. Among potassium's key actions is the regulation of water balance inside our cells. (Contrast this with sodium, which regulates water balance outside the cells.) Potassium is also involved in maintaining our body's acid-base balance and in the transmission of nerve signals, which makes it key to such activities as keeping our hearts beating.

You want to avoid having too much potassium, and supplementation is not usually needed unless there is a specific health problem or a medication in use that might deplete the body of this mineral. If the kidneys are working normally, excess potassium will be excreted in the urine. The adult daily value for potassium is 4,700 milligrams per day. Potassium per serving can be listed on a food label, but it is not required. Good food sources for potassium include fresh, whole foods such as apricots, lentils, acorn squash, potatoes, bananas, legumes, citrus fruit and avocados.

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 know that if you are predisposed to kidney stones, consuming foods high in oxalates is not a good idea. But I also read that oxalates will accumulate in the body. And they are described as tiny, sharp and glasslike. Doesn't sound like something I want in my body. So, even for people who are not prone to kidney stones, is it a good idea to avoid foods high in oxalates like spinach, beets, almonds, etc.? -- B.S., Albany, California

DEAR B.S.: Kidney stones, also referred to as calculi, are painful and nothing to be trifled with, a sentiment that anyone who's had firsthand experience would echo. Family (genetic) history, lifestyle and environmental factors play a role. Adjustments can be made to diet and lifestyle to prevent situations where stones are likely to form and grow large enough to cause misery. But before becoming unduly concerned, the primary goal is to learn whether you are at risk. Asking your family practitioner is key, and a visit to a nephrologist (kidney doctor) may also be warranted. Pathology tests, including urinalysis, can help determine your level of risk.

It is appropriate that you raised the issue of oxalates. Stones form for several reasons, including infection, but about 70% of kidney stones are composed of insoluble calcium salts, usually calcium oxalate. People most likely to suffer from this type are those who have above-normal levels of oxalates in their urine (again, a reason to get those tests).

Does it make sense to limit your intake of the compounds that make up the stones? Several foods are high in oxalates, including spinach, cabbage, chard, beet and rhubarb leaves, cocoa, tea and bamboo shoots. Reducing dietary oxalates is a reasonable strategy, but it won't always solve the problem, and you could be unnecessarily giving up many healthy foods if it turns out that kidney stones are not a huge issue for you. Most of the oxalate inside our body doesn't come from foods; it comes as a result of many metabolic processes.

Research has also found that restricting calcium can increase the risk of developing stones. When you take in adequate amounts of calcium, the calcium can bind with oxalates in food to form calcium oxalate stones in your intestines, which pass from your body. Recent studies have shown that foods high in calcium, including dairy, can help prevent calcium stones. When calcium intake is restricted, almost all the oxalate is absorbed into your bloodstream and passes out through your urine, which could increase the risk of stone formation.

An important lifestyle change to prevent stones is to drink more liquids, with water being the best choice. Even mild chronic dehydration can increase the likelihood of kidney stone formation. Stones are also more common in hot climates and during the summer months, ostensibly because we tend to perspire more and pass more concentrated urine.

Depending on the type of stones that form, dietary adjustments and increased hydration can limit their formation. Some medications can help; another reason to keep your health professional involved.

For a more in-depth consideration, see b.link/3nn8k6, and for kidney stone self-care, see b.link/vstfudp.

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: In a recent column about digestion and gas, I felt you should have mentioned probiotics. I have friends who swear a daily probiotic has changed their lives. I take one also and have had good results. I enjoy your column very much. Thank you. -- S.R., Contra Costa, California

DEAR S.R.: Thank you for your comment, which raises an important topic. Most have heard of the term "microbiome," which refers to the community of microbes that live in our large intestine; it is also referred to as the intestinal flora. Despite their reputation for contributing to ill health, not all bugs are bad. Microbes, which for our discussion will include bacteria, viruses, fungi and archaea, play an important role in helping maintain the ecology in the digestive system. Clinical studies reflect their impacts on our overall health.

However, there are also ones that are not so friendly. Think of the microbiome like the Wild West without a sheriff, where survival is the name of the game. All the players seek to multiply, but it is in the interest of good health that we eat and behave in a way that keeps our microbial allies ahead of the game.

Probiotics are the friendly bacteria; a probiotic food or supplement contains these bacteria. Several probiotic strains can survive in your intestines. A related term, "prebiotic," which is addressed in greater detail below, refers to a food that facilitates the growth and survival of probiotics by providing the nourishment they require.

In the early 1900s, Elie Metchnikoff, a Russian biologist working at the Pasteur Institute in Paris, proposed that health and longevity were linked to the type of bacteria living in the intestines. In his 1908 book "The Prolongation of Life," Metchnikoff attributed the health and long lives of Balkan tribes to the bacteria used to make the yogurt that was a staple of their diet. Milk products have proven to be popular probiotic foods because they are easily cultured to grow these bacteria. The common culturing strains are s. thermophilus and l. bulgaricus.

In addition to yogurt, milk products such as kefir, low-fat acidophilus milk and buttermilk contain these bacteria and can also have added l. acidophilus or bifidus (bifidobacteria) -- friendly bacteria equipped to establish themselves as long-term residents in the large intestines. Always check the label to see what is in products you are considering. Other foods containing friendly bacteria include sauerkraut (fermented cabbage), kimchee, miso soup, tempeh and natto. The friendly bacteria are also available as a dietary supplement. For more on probiotic foods, see b.link/breafb7. For a probiotic pro and con, see b.link/ph7772f.

Prebiotics, an associated topic, are foods with elements that can bypass normal digestion. When arriving in the large intestine, they can serve as nourishment for the microbiome. Foods such as legumes, peanuts, garlic, onions, leeks, Jerusalem artichokes, wheat, barley, asparagus, rye, chicory and berries contain constituent substances that feed the intestinal flora. There are also substances known as fructooligosaccharides (FOS) and inulin, which have a special ability to reach the large intestine intact. (You may see these as ingredients in supplements.) Be sure to discuss any intestinal health issues with your physician and express your interest in opting for a probiotic with the best organisms in the best dosage for issues you face.

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.