DEAR DR. BLONZ: Is it dangerous to eat an entire apple, including the seeds? One of my friends does this all the time, but I know there is cyanide in apple seeds. I have mentioned it and he said he has been doing it his entire life. -- H.N., Piedmont, Calif.

DEAR H.N.: You are correct about the cyanide. Apple seeds -- along with apricot kernels, peach pits, cherry pits and stems, and the leaves and roots of some rose family species -- are natural sources of the cyanide-containing compound known as amygdalin. Cyanide has an ability to quickly and effectively slow down body metabolism, so it can be a very potent poison. But as with most toxic materials, it is the dose that's the key.

The body has a recovery mechanism that can cope with small amounts of cyanide, and the relative amount of amygdalin in the seeds of one apple does not represent a significant health risk. There is little to worry about if you happen to eat the seeds while enjoying your apple.

Consider also that apple seeds have a rather tough seed coat that is difficult to digest. Most seeds pass through the digestive tract intact -- that is, without transferring any amygdalin to the person eating them. (Actually, this is a method of seed dispersal found in nature: An animal in one location eats the entire fruit and eventually expels the seeds in a new location.) Because whole-fruit blenders and juicers crush the seeds, and because multiple apples can be used in one serving, it would be prudent for those using these devices to remove the seeds beforehand.

DEAR DR. BLONZ: Does it become dangerous to drink orange juice once it has become slightly fizzy? How does this differ from carbonation? -- R.L., Berkeley, Calif.

DEAR R.L.: Fizz, when intentional, comes from carbonation, which is the addition of carbon dioxide gas (CO2). Carbon dioxide will not dissolve well into warm water, but it becomes more soluble as the temperature goes down. Pressure helps "hold" the gas in solution. This explains the "pop" and greater release of gas when a soda is uncapped at room temperature. At best, the carbon dioxide is only loosely held in the water, which explains why agitations such as pouring a warm soda over ice, or shaking the bottle, brings forth a gaseous eruption.

When you consume carbonated beverages, some of the swallowed gas can be absorbed and exits the body through exhaled air. The rest exits the body through belching, a process by which the esophagus opens and allows the pent up gas out from the stomach. If it manages to make its way past the stomach, the gas can pass through the GI tract and exit at the other end.

Fizz that develops in orange juice is a sign of spoilage due to microbial fermentation of the sugars in the juice. The fermenting organism gives off carbon dioxide gas that can be detected by your tongue, thus giving a sensation similar to that caused by carbonation. There will also tend to be a loss of sweetness during this type of spoilage since the fermentation organisms feed off the simple sugars for fuel. Because the spoilage organism is unknown and there is a potential health risk, it is best to discard the juice when you sense any type of unplanned fizz.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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: As part of a long-term effort to lose weight, we are making small changes in the foods we eat at our house. One change is to lower -- but not eliminate -- our carbohydrate intake: mainly cutting out sweets, added sugar and extra bread. My question is about the combination of grains and legumes. I've been told that when you eat beans and rice at the same time, the amino acids combine to make a complete protein. I'm confused how the body digests this combination. Does it handle these foods as a protein or as carbohydrates? Do I need to give up my favorite brown rice and black bean recipe? -- K.W., San Francisco

DEAR K.W.: Making gradual changes that can be maintained will usually win over a dietary "radical shift." The reasoning is that once you are done with your radical diet, you go right back to the way of eating that got you in trouble in the first place. Given this, you have my respect for your approach.

Beans and rice both contain complex carbohydrates, a modicum of fat, and protein in the form of amino acids. These nutrients will be digested in the same manner whether they are eaten separately or at the same time. These complex carbohydrates will not be as impactful as sweets on your blood sugar levels. (For more on this, consult glycemicindex.com.) Both beans and rice contain amino acids, but neither has the complement needed to make protein. When eaten together or during the same day, their amino acid profiles complement each other. By this I mean that the essential amino acid missing from beans (legumes) is in plentiful supply in rice (grains), and vice versa. I am uncertain why you might think it necessary to forgo brown rice and black beans. All you need to do is to keep an eye on your total caloric intake and stick to healthful foods such as these, and you will continue to progress.

DEAR DR. BLONZ: We had a wonderful meal at my parents' house, and there was enough for leftovers. They made individual leftover packets for the freezer, but accidentally left them on the counter overnight. When it was discovered the next morning, my mom put the packets in the freezer and insisted that freezing would kill any bacteria that might have grown during the night. She won't believe me that this is dangerous or that anyone who ate the leftovers could get sick. She said she can defrost and cook them in the microwave. Is this a safe practice? Does freezing kill bacteria? -- T.D., Casa Grande, Ariz.

DEAR T.D., Freezing does not make foods fresher than they were before they were frozen. Whenever a food is defrosted, bacterial growth picks up right where it left off. Eating foods that have been left out on the counter in the way you describe would be a dangerous roll of the dice. There would be no guarantee of safety even if you were to pay special attention to cooking the food thoroughly the next day. In my considered opinion, the best course is to toss the stuff.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 was told by my optometrist that the irritation in my eyes is due to a condition known as blepharitis, and that I should be taking flax oil to provide the omega-3 fats that can help this condition. I recall in one of your columns that flax oil might not be the best way to get omega-3s, so I wanted some confirmation. Could you please give me an update of the best sources of omega-3s? -- K.L.F., Dobbs Ferry, N.Y.

DEAR K.L.F.: I am not a medical doctor (or an optometrist), so what I provide here should not be taken as medical advice. That being said, let's go through what's known.

Blepharitis is a condition in which there is swelling or inflammation of the eyelids (more details at tinyurl.com/mla285c). There are a number of possible treatments for this condition, and that's something you need to discuss with your health professional. If a decision is made to increase the body's omega-3 fatty acids, it usually refers to eating in a way to increase the long-chain omega-3s that include EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which are 20 and 22 carbons long, respectively. This might be selected because increasing the level of EPA and DHA in the body can have anti-inflammatory effects. EPA and DHA are found in certain fish such as salmon, but not in plants such as flax, walnuts, canola, and soy. Plants can contain an omega-3 fat, but it is typically an 18-carbon-long omega-3 known as ALA (alpha-linolenic acid).

The body can convert ALA into EPA and DHA, but it's not an efficient process. One paper in the June 2006 supplement of the American Journal of Clinical Nutrition reported that, at most, women can only convert 21 percent of ALA into EPA, and only up to 9 percent of ALA into DHA. For men, the rates are only up to 8 percent conversion for EPA and 4 percent for DHA. Most of the ALA we eat gets burned for energy.

So why the recommendation for flax oil? In looking through the scientific literature I found an important study in the December 2008 issue of the Transactions of the American Ophthalmological Society that reported a beneficial effect from flax seed oil on blepharitis. This might be the source of the recommendation. The authors, however, pointed out that they used flax seed oil not because it was the best source, but rather because fish oil products can have an odor and the study was placebo-controlled. They did not want their subjects to be able to detect whether they were receiving an omega-3 supplement or the placebo (olive oil, in this case). There was also a concern regarding the potential for heavy metal contaminants in fish oil products. The authors correctly pointed out that flax seed oil must first be converted to EPA/DHA before it can act as an anti-inflammatory.

Our bottom line here is that if there is a desire to increase the level of EPA and DHA in the body, you should discuss with your health professional if it might be more effective to eat more fish, or take a fish oil supplement containing EPA and DHA. There are now odorless products and ones that are distilled to eliminate potential contaminants.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.