DEAR DR. BLONZ: I heard a lecturer on TikTok stating that an organic tomato can have nine times the iron of a conventionally grown tomato. Is this correct? -- B.O., Atlanta

DEAR B.O.: Where do they come up with this stuff? An organically grown medium tomato and a conventionally grown tomato will each provide about .3 mg of iron. (See the NIH Fact Sheet at b.link/iron-x23 for more on iron.) I'm posting your question because the more salient issue here is the growing enormity of health nonsense on social media -- sometimes presented in engaging lectures by people who appear to know what they are talking about and to have genuine credentials.

When you come across something that runs contrary to logic, demand objective evidence rather than accepting the word of someone on social media. Don't be swayed by people who call themselves "doctor" or post too many positive comments. Fake degree certifications are on the rise -- and with artificial intelligence, it is likely to get worse; a content creator can generate multiple comments of admiration under different names to make it look like others support what they say. Always verify that concepts are evidence-based and that the proponents have legitimate academic training in the field in which they present themselves as experts.

DEAR DR. BLONZ: I appreciate your article on sea salt, but one of my prime arguments against table salt is the presence of additives. I know they iodize table salt by adding a compound containing iodine, which is not a problem, but why are they adding other compounds, such as calcium silicate and silicon dioxide? I have no problem with blood pressure and use salt on occasion. Would I be better off using a natural or sea salt where these compounds are not present? -- T.S., East Orange, New Jersey

DEAR T.S.: There are a couple of items to consider. First, crystals of sodium chloride, the essential ingredient of table salt, absorb moisture from the air and form clumps over time. Salt affected would have a hard time making it out of a shaker. Restaurants used to put small oyster crackers in salt shakers to prevent clumping, eventually switching to dried rice.

Another method is to add tiny amounts of anti-caking compounds, such as calcium silicate or silicon dioxide, which absorb moisture before it can clump the salt. These anti-caking substances are harmless at the levels used. (Silicon dioxide is the same compound in sand and quartz crystals.) It's up to you -- you can opt for a free-flowing product, or one that needs a bit more of a shake. You will note that sea salt crystals tend to be larger than table salt crystals.

Any discussion of table salt versus sea salt should also consider that salt from seawater will contain small amounts of other minerals and substances from the water, which can include heavy metals or microplastics. While these levels are harmless, the message is to conduct a complete analysis of brands you are considering.

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 best way to handle hot leftovers? I have always thought they should never be put in containers with airtight lids until cooled, for fear that botulism can form when anything warm is covered tightly. I'm also concerned that putting hot items in the refrigerator can cause problems in neighboring foods already cooled. -- R.T., Portland, Oregon

DEAR R.T.: Botulism is a serious food poisoning caused by consuming foods that contain a toxin from the bacteria Clostridium botulinum (C. botulinum). These bacteria multiply by giving off spores, which can produce the toxin that causes botulism, a severe and often deadly illness.

C. botulinum differs from other bacteria, such as salmonella, E. coli or strep, in that it grows in low-acid, oxygen-free environments. The botulism-producing spores are resistant -- but not immune -- to heat. C. botulinum is a problem with improperly processed canned foods, such as vegetables, fish and meat. To be safe, food preservation techniques, including canning, must include a heating component designed to kill the botulism spores. Outbreaks of botulism are usually traced to inadequate heating processes or temperatures.

Placing food in an airtight container is unlikely to increase the risk of botulism unless the bacteria are already present. It's unlikely that these particular bacteria would pose problems in properly cooked foods when good sanitary practices have been followed. For more in-depth information about botulism, see the NIH page at b.link/r42w55tb.

Leaving food containers uncovered increases the chances that other airborne microbes can enter your food. In the refrigerator, the air in the container will contract as it cools and can pick up errant refrigerator odors.

It's best to refrigerate leftovers in sealed containers within two hours of use. By rapidly cooling these foods to refrigerator temperature (40 F), they will remain safe. Consider using resealable containers with a large surface area. I place flexible, reusable ice packs on top and around food containers to facilitate the cooling process.

DEAR DR. BLONZ: I am seeking information on the nutritional value of domestic rabbits. Someone told me that rabbit has more protein than chicken or turkey. Is this true? -- H.H., Las Vegas

DEAR H.H.: Rabbit's vitamin and mineral content is comparable to other meats, but it is leaner than chicken, turkey or beef. Because of its lower percentage of fat, rabbit yields more protein per pound. One four-ounce serving of rabbit provides 37 grams of protein, which is 74% of the adult daily value (DV); it also provides B vitamins, including three times the DV for vitamin B12 and about one-third the DV of iron.

Rabbit's leanness creates challenges with its preparation, as overcooking can result in a tough meat. This is why recipes frequently call for rabbit to be marinated, braised or made into a stew.

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 choose high-fiber breads for sandwiches. I have learned from experience that just because the bread is brown and the label says it's wheat or multigrain, it isn't necessarily made from whole grains. I bought a product labeled "stone-ground wheat" bread, but found it was white bread with unbleached enriched wheat flour at the top of the ingredient list. There were other grains listed, along with "natural" coloring. Is this permitted? -- P.A., San Francisco

DEAR P.A.: Wheat bread is made with wheat flour, which can be white, whole-grain or a combination. A 100% whole-grain wheat bread will show "100% whole wheat" as the first item on the ingredients list, and there should be no other flours listed unless they are also described as "100% whole-grain."

The phrase "stone ground" is not indicative of the whole-grain character of the bread. While a bit misleading to have bread that's not whole-grain made to appear as though it is, such products are legal so long as they do not claim to be 100% whole-grain. Color can be confusing, as there are whole-wheat breads made from an albino whole-wheat grain; these will be lighter in color but provide the fiber and other assets of the whole grain. The lesson here is to always check the ingredients list and Nutrition Facts panel before you buy.

DEAR DR. BLONZ: Weight charts tend to ask for a body-frame size to determine ideal weight. I want to get some "before" measurements before starting an exercise program. What determines body-frame size? -- N.N., Nashville

DEAR N.N.: It's great to get a handle on your starting point before you begin an exercise program. Aside from a dispassionate evaluation in front of a mirror and a frank assessment of how your clothes fit, there are a couple of ways to calculate frame size.

Frame size can be calculated using the ratio of body height to the wrist's circumference measured in inches. The wrist measurement is at the crease -- the area between the wrist bone and the bottom of the hand. For women, a ratio of 11 or above represents a small frame, 10.1 to 10.9 is a medium frame, and 10 or lower is a large frame. For men, 10.4 or above represents a small frame, 9.6 to 10.3 is a medium frame, and 9.5 or lower is a large frame.

A less precise but more convenient method is to try to touch your thumb and index finger around the wrist crease. Assuming you have fingers of average length, if they do not touch, you have a large frame; if they meet, you have a medium frame, and if they overlap, you have a small frame.

When considering body size, body mass index (BMI) may be better -- this measure relies on height and weight. Check the National Institutes of Health page on BMI at b.link/naa5r4. All such measures are based on averages from large populations; they might not work for all body shapes, but they can serve as a baseline measure to track progress as you start your exercise program.

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.