DEAR DR. BLONZ: I was diagnosed with goiter after my recent annual checkup, and am now on low-thyroid medication. I was told to maintain a normal intake of iodine -- there was no recommendation to take supplements. I try to eat healthy vegetables, but am now concerned that they can affect my thyroid. I typically use sea salt when I cook, if that makes a difference, but I would like to know more. -- B.T., Greenville, South Carolina

DEAR B.T.: The hormones thyroxine and triiodothyronine are produced by the thyroid: a butterfly-shaped gland in the front of the throat, above the voice box. These hormones regulate our metabolism, and iodine is an essential mineral in their structure. In essence: no iodine, no thyroid hormones.

When iodine is deficient, another gland, the pituitary, makes more of its thyroid-stimulating hormone (TSH), which can stimulate the thyroid to enlarge -- ostensibly to do a better job of grabbing any available iodine in the body. A persistent iodine deficiency can result in a characteristic swelling in the throat area, which is something to see your health professional about.

Here is a relevant bit of history. Iodine is found in seawater, so crops grown near the coast tend to contain this mineral. Goiter based on iodine deficiency was not common in the United States' early years, as most lived near the coast. As populations moved west (but not as far as the Pacific coast), many settled in the country's midsection, where there was no dependable supply of dietary iodine. These regions were eventually nicknamed the "goiter belt" due to the more frequent incidence of iodine deficiency, with its noticeable bulge in the lower throat. In 1926, the government legislated that iodine be added to table salt as a public health measure, dramatically reducing the incidence of goiter. Iodine was the first nutrient substance purposefully added to foods.

Some vegetables, including cabbage, mustard greens, cauliflower and Brussels sprouts, contain goitrogens: compounds that prevent iodine from being used by the thyroid gland. Goitrogens are not a concern unless the above foods are a significant part of your daily menu. Eating iodized salt or ocean fish are good ways to ensure an adequate intake of iodine.

Your health professional's recommendation to avoid iodine supplements is reasonable because today, regardless of whether they use iodized salt, it's rare for anyone eating a varied diet to suffer from an iodine deficiency. And as you use salt from the sea, it's likely that it already contains some iodine.

The Recommended Dietary Allowance (RDA) for iodine is 150 micrograms daily for adults; it is considered a trace mineral. Iodized salt contains 45 micrograms of iodine per gram of salt, which means that the RDA for iodine can be met with just over one half-teaspoon. For more on diseases of the thyroid, see b.link/dzu2q7.

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 cooking class instructor mentioned that broths or gravies should never be covered with an airtight lid until they are cold, because botulism toxins can form in anything lukewarm and covered tightly. How should one handle hot broth that you want to keep for a day or two? -- F.C., Sacramento, California

DEAR F.C.: Botulism is an often-fatal form of food poisoning. It's caused by eating foods that contain a toxin from the bacteria C. botulinum. These bacteria multiply by giving off spores, which produce the botulism toxin.

C. botulinum differ from other bacteria, such as E. coli, listeria and salmonella, in that they can grow without air (oxygen). In addition, the botulism-producing spores are heat-resistant. Food preservation techniques such as canning must include a heat treatment that lasts long enough to kill C. botulinum, knocking out the ability to produce spores. Ten minutes of boiling will destroy the toxin that causes the disease. Outbreaks of botulism from canned foods are usually traced to inadequate heating times or temperatures.

Placing food in an airtight container does not increase the risk of botulism unless the bacteria are already present. It's doubtful that these particular bacteria would be a problem in cooked foods when good sanitary practices have been followed. In fact, leaving the lid off increases the chances that other airborne bacteria can enter any nutrient-rich food or broth. It also increases the likelihood of picking up errant room or refrigerator odors.

It's a good practice to refrigerate leftovers immediately in a sealed container. By rapidly cooling leftovers to refrigerator temperature (40 degrees F.), you help ensure that the food will remain safe. Consider cooling your broth in a covered container with a large surface area, such as a shallow baking dish. One technique I use is to have several flexible, reusable ice packs at the ready in my freezer. That way, when some food needs to be chilled rapidly, the ice packs can be placed under, around or on top of the container.

Other sensible approaches are never eating or tasting from containers with bulges, or from any that spurt liquid when opened. (Note that this is different from vacuum-packed items, which suck in air when opened for the first time.) Find out more about botulism at b.link/hv67cc. For a general reference on food poisoning, you can download the second edition of the FDA's Bad Bug Book at b.link/yg7nrk.

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: Do you know if there is any special value in drinking those "green powder" supplements, other than supplying antioxidants? The company says the nutrients in their greens are more efficiently absorbed than other supplements because they are in a powder form. After two months of taking the product, I realized there was no effect I could notice.

I want to know if this is the best thing to take if I'm not eating enough vegetables in my daily/weekly diet. -- R.R., Tulsa, Oklahoma

DEAR R.R.: I don't support the use of supplements as a substitute for good eating. Most of those powders are made from dried grasses, although there are many types on the market, and they tend to supply a modicum of nutrients and phytochemicals. If essential nutrients, including dietary fiber, are present in measurable amounts, they must be listed on the Nutrition Facts (or Supplement Facts) label. Check the details on your product's ingredient statement; make sure you know what you are paying for.

Aside from testimonials, there is little clinical evidence to support any special benefits -- such as preventing or treating disease, or being significantly more effective due to quicker absorption -- from powdered supplements. There is likely to be a grassy taste from such products, but they should be safe to consume if made following the extensive good manufacturing practices of the FDA.

However, such supplements do not "fill in the blanks" for one who routinely comes up short on healthful eating. You may want to rethink that "if I'm not eating enough" stance as acceptable for your well-being.

Then there's the fact that supplements are usually costly. You are paying for the manufacturer to use energy to dehydrate and process real food into a powder, perhaps add some vitamins, minerals and herbs, then package, ship and market the finished product. Why not simply eat real, whole foods from your local produce market?

You ask about "the best thing to take," and here is my answer: The best thing is a plant-focused (but not necessarily vegetarian) whole-foods diet, with daily servings of physical activity. Think of what you have to gain from such an approach, then begin gradually and set interim goals. I don't know where you are in life, but isn't this a value you would want to pass on to your next generation? It is all a matter of priorities, and the payoff is one you will have an opportunity to appreciate as you get older.

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.