DEAR DR. BLONZ: My close friend continues to recover from an emotional blow, after which she was unable to eat for many days. With no real appetite, and at my insistence, she finally started to eat, but it made her nauseous. Her doctors are on this and have found nothing serious, physically; they counsel patience and continued effort.

My concern is that she has lost a lot of weight and doesn't look healthy to me. I hope to better understand what might be happening and what I might do to help her. -- C.F., San Jose, California

DEAR C.F.: Your friend is fortunate to have you for support as she works through this challenging time. I cannot provide medical advice, so it remains essential to keep her health care professionals apprised of developments. I hope that the team includes someone with expertise in emotional support. The passage of time is likely to be the most potent ally.

Without food, the body undergoes a series of coordinated adaptations that pare down any unnecessary energy usage. There will be a tapering of systems not being used; this includes those involved with digestion. The body also slows down its metabolic rate and lowers its temperature as systems shift to a general energy-sparing "budget." This involves less circulation near the skin's surface, helping explain why those deprived of food might have a sallow look.

After being without sustenance for days, any reintroduction of foods must be done slowly and strategically -- beginning with simple foods, such as fruits and fluids -- to limit negative effects. These can range from minor queasiness and nausea to more serious metabolic effects. As there may be additional complexities with her ongoing health conditions and medications, your friend (or you as her proxy) should be in touch with the health team to be sure there are no missteps during the process of reintroducing foods.

Consider glucose, the building block of carbohydrates -- a primary fuel in the body and essential for specific cells. The human body has only a small amount stored for special circumstances. We can survive without a dietary source of carbohydrates (and the glucose it becomes) due to our ability to break down proteins and turn certain amino acids into glucose. This is life-preserving during a prolonged absence of food, but it's not an ideal situation.

The bottom line is that the body will be digesting itself during a fast, in essence -- repurposing its substances for more critical uses. Like other metabolic processes, these create waste; water is the conduit to get these out before they can jam up the works. This explains why we require more water than any other nutrient we ingest. We can survive for weeks without food, but only days without water. Consider encouraging your friend to start with consuming water, or perhaps a drink that provides electrolytes, other minerals and a minor source of carbohydrate calories.

The health team should provide recommendations as the situation evolves. I hope that your friend gets the support she needs during this dark period.

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 am working on many angles to avoid Type 2 diabetes, which runs in my family. I have borderline blood sugar issues, but unlike others in the family, I have improved my diet and now go on daily walks that involve hills or stairs.

My question relates to a lecture in which the physician speaking said that a common additive in bread, calcium propionate, can interfere with how glucose is metabolized and contribute to insulin resistance. A study was cited to support this, but I did not note the author. I am writing because I noticed that the high-fiber, whole-grain bread I now enjoy has this as one of its ingredients. I wanted your take on whether I need to shift to another brand. -- M.M., Phoenix, Arizona

DEAR M.M.: When we hear about a specific substance being suspected of helping or hurting a certain function, it is vital to know the amount of the substance associated with the effect. A closer look at this issue may spare you some concern.

Calcium propionate is a salt of propionic acid, a natural acid found in raisins and other fruits. Propionic acid, or its synthetically made calcium propionate salt, acts as an inhibitor of microbial growth -- most notably of the molds that tend to make themselves at home on breads. At the same time, these substances do not prevent leavening yeasts, which are also microorganisms, from doing their job. This explains why mold inhibitors are used in many breads to prolong shelf life. Some brands, particularly organic ones, use raisin juice as a mold inhibitor -- so propionate may be there even if you don't see "calcium propionate" on the ingredient list. (Read more on calcium propionate at b.link/hxgdw9.)

However, the practical concern about the impact of propionate on glucose metabolism seems a bit exaggerated.

One study reported that calcium propionate did impact glucose metabolism. But when checking the methodology, I noted that the experiment involved giving almost 1,500 mg of calcium propionate (or a placebo) to the subjects on an empty stomach after an overnight fast. That is a hefty amount! As calcium propionate typically makes up about 0.2% of dry flour weight, it would take about six cups of flour to provide that much calcium propionate. That's enough to make over a loaf and a half of bread -- more than anyone should have at one time, especially someone concerned about their blood sugar level.

A subsequent meta-analysis published earlier this year in the American Journal of Clinical Nutrition looked at 13 studies examining the effects of calcium propionate on glucose metabolism. Not surprisingly, that paper, which included the one mentioned above, concluded there was no significant effect on insulin and glucose metabolism.

No need to change bread brands because of this. My congratulations on your diligence; keep up the excellent work.

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: Are oysters a good source of nutrition, and can they help keep me healthy? Which oysters are more nutritious: the big or the small ones? -- J.B., via email

DEAR J.B.: Oysters, a member of the mollusk family that includes clams, mussels, scallops and octopus, are indeed a nutritious treat. They can be prepared in several ways, including grilling and smoking, with various seasonings. They have a unique taste and mouthfeel; there's nothing like it.

They are particularly fresh in my mind -- and palate -- because a few weeks ago, my family traveled to Tomales Bay in Northern California to enjoy lunch outside at the Hog Island Oyster Company. We had a mix of oysters -- including some that were barbecued, a special treat -- all complemented by the excellent weather that day.

In ocean waters, oysters are filter feeders, so eating them raw comes with some risk. (I recommend reading the article on raw oysters at b.link/z2vpqs, then checking out the CDC page on oyster safety at b.link/ccqbx4.) Farm-raising oysters can provide greater levels of control as all aspects, including water quality, can be monitored; I recommend sticking with reliable oyster pros. Of course, cooking oysters will help lessen some of the risk.

Size is not a significant determinant of their nutritional value. Along with protein, oysters are a great source of the essential long-chain omega-3 fatty acids EPA and DHA, along with vitamin B12 and minerals like zinc, copper, iron, magnesium and selenium. All this, in a relatively low-calorie package: A three-ounce serving of oysters provides about 70 calories.

DEAR DR. BLONZ: Following the recommendations on fiber, I began adding oat bran to my daily diet. But now I am hearing that psyllium is much more effective. Which is a better way of adding fiber? -- H.T., Tulsa, Oklahoma

DEAR H.T.: Psyllium comes from the seed of the Plantago plant, a native to India and the Mediterranean. Used as a laxative in India for centuries, psyllium is also the main ingredient of over-the-counter laxatives in this country. On a weight basis, soluble fiber makes up 75% of the psyllium seed. Compare this to oat bran's 8% soluble fiber.

Studies reported that adding psyllium to the diet can help lower blood cholesterol levels. Similar to how things sprouted up on the shelf after the first oat bran studies back in the 1980s, psyllium began to appear in commercial cereals and loaves of bread, followed by commercials promoting it. Unlike oats, though, psyllium has little to offer besides its soluble fiber. Oat bran, by contrast, has some protein, magnesium, iron, zinc, thiamine and phosphorous.

Using supplemental fiber can have its downsides. Take care not to add excessive amounts of concentrated fiber, as it increases the chance of side effects such as bloating, cramps, diarrhea and gas. In addition, fiber can interfere with the absorption of nutrients. Medications may also be affected, so touch base with your health professional, especially before adding more than the recommended amount to your diet.

Oat bran would be my choice between the two, as it brings more to the meal than psyllium. But if you're open to a better way, consider sourcing your dietary fiber from a gradual shift to more plant-based whole foods (fruits, vegetables, legumes and whole grains) rather than supplements. Whole foods come with assets beyond fiber.

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.