DEAR DR. BLONZ: I have started using a hemp milk product with my cereal, and the carton states that it is rich in omega-3 fats -- even more so than fish. I also eat fish, but was wondering if this was true, and if hemp or flax oil can be an effective source of omega-3s. -- F.S., Eureka, California

DEAR F.S.: First, some background on fats. The human body requires both omega-6 and omega-3 fats (or fatty acids), but cannot make them on its own, so they are considered "essential fatty acids" that need to be in our diets. Omega-6 fats are the main fatty acid in vegetable oils, including soy, sunflower and corn oil. One type of omega-3 is found in some vegetables, and a different type is found in seafood. As a general rule, there tends to be an excess of omega-6 fatty acids, and an inadequate amount of omega-3s, in the typical American diet.

Fats can be thought of as long chains of carbon atoms. Omega-3 is a term that refers to the location of the first double bond along the carbon chain: in this case, the third carbon. Omega-6 fats have their first double bond on the sixth carbon.

The location of that first double bond is critical in determining what the body does with a fatty acid, and this is particularly important with the omega-3 fats. The two important omega-3 fats are EPA and DHA, which are 20 and 22 carbons long, respectively. These are the omega-3s associated with blood-pressure benefits, anti-inflammatory effects and a reduced risk of heart disease. (There is a list of fish oil benefits at tinyurl.com/3d8fe9l.)

The omega-3 fat found in your hemp milk -- and in other plant sources such as flaxseed, canola, soy and walnuts -- is only 18 carbons long. It is still an omega-3, but the body has to put it through an extensive "lengthening" process to make it into EPA and DHA. This, it turns out, is an inefficient process. Most of the omega-3s of plant origin get burned for energy, with only a small fraction getting converted into the longer-chain varieties.

The bottom line is that if you want the most effective source of EPA and DHA omega-3 fats, fish is the way to go.

DEAR DR. BLONZ: I heard about some great benefits of drinking lemonade made from real lemons, especially if it helps you consume the juice from at least two lemons daily. My question is, could that result in a loss of calcium, or have any other harmful effects? -- M., via email

DEAR M.: Regarding calcium loss from the body, there is no basis for concern about adding lemon juice, especially the amount provided by two lemons, to your daily diet. About the only side issue might be for the teeth if the lemon juice (or any acidic food) were allowed to stay in contact with the teeth for an extended period. But once swallowed, it's all good.

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: Is there any problem with eating fish, especially salmon, if you have gout? If so, does the problem also apply to fish-oil supplements? I also read that high doses of vitamin C are not recommended for gout patients. Can you shed any light on this? -- L.L., Seattle

DEAR L.L.: Gout is a form of arthritis (inflammation of the joints) that is brought about when there is an excess of uric acid in the blood, which gives rise to deposits of sharp crystals in and around joints. Usually, the first joint affected is the most remote one from the heart -- the big toe -- but gout can affect other joints, as well.

Uric acid is a normal metabolic intermediate that gets produced during the breakdown of certain compounds. Normal kidney function will eliminate uric acid. Gout can develop when the body produces too much, or when the kidneys, for some reason, are not able to do their job. Why this happens is not known, but it is thought there may be a genetic predisposition.

There are prescription medications to help with gout, but an important step is to cut down on foods known to give rise to uric acid during their metabolic breakdown. Purines are substances that turn into uric acid, so those at risk for gout are typically put on a low-purine diet. Some fish and shellfish are high in purine, including sardines, herring, anchovies, cod, trout, haddock, mussels and scallops. Salmon is considered moderate, not high, in purine. Fish oil does not contain purine.

To find out more, consult articles on gout at the Arthritis Foundation (tinyurl.com/nmzytqf) and the National Institutes of Health (tinyurl.com/3ulmzb).

DEAR DR. BLONZ: I recently took a loaf of bread out of the freezer, and it had mold on it. Of course I did not eat it, but was wondering how this could be possible. -- M.M., San Dimas, California

DEAR M.M.: Mold spores tend to be all over the place, and bread is not a sterile food. If your bread had already been opened when you froze it, it is likely a few mold spores were present. There could have also been some mold in the packaging that was used. You don't mention how long the bread was in the freezer, how it was defrosted or how much mold you found. There could have been a small amount of growth during the freezing process. Other factors could be a power outage during the loaf's life in the freezer, or if the loaf was near the freezer door and it was opened often.

Moisture in bread tends to move from the interior to the surface during the freezing process. This helps explain ice crystals that form in the package. During the defrosting process, any ice crystals present will create a high-moisture environment in the package as it returns to room temperature, which is an ideal situation for the mold to spring back to life.

It is difficult to say for sure what happened, but the key is whether this is an isolated incident or a regular occurrence with breads and other foods in your freezer. If it's the latter, you have some detective work to do.

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: In my new apartment, I am living with a group that primarily eats raw foods. Their explanation is that "cooking removes the vitamins and minerals." These are my friends, so while I detect a slight bit of sanctimony, there is no serious rejection of the fact that I am an omnivore. Is eating nothing but raw foods, or even mostly raw foods, a good idea? One of my roommates says her new diet is really helping her lose weight. What are the pluses and minuses? -- S.T., Oakland, California

DEAR S.T.: Diets that strictly limit what you can eat can result in weight loss simply because you are paying closer attention to the foods you select. When you stick to raw, you definitely limit the types and amounts of foods you can eat. As for whether a raw food diet is a good idea, it depends on how it is done.

First, let's add some perspective to any blanket statement that cooking removes vitamins and minerals. Minerals are not affected at all, and while the levels of a few vitamins are reduced by heat (notably vitamin C, thiamine and folic acid), most are not affected. Cooking can actually help make other nutrients more bioavailable. Proper cooking also makes certain foods easier to digest. The idea that cooking destroys certain vitamins is not a serious issue if the food involved is not the main source of that nutrient. We get our vitamin C, for example, from fruits, not from cooked foods. Cooking can help make foods safer, helping to destroy foodborne organisms as well as some natural toxicants.

There is absolutely nothing wrong with eating raw foods. It can be an exciting way to eat, but it is not something that should be embraced blindly. It takes information and effort to do it correctly, as the body still requires a full complement of nutrients.

DEAR DR. BLONZ: I am in my 30s, with two children, and I have been taking multivitamins for most of my adult life. My mother has just been diagnosed with osteoporosis, and I want to add 1,200 milligrams of calcium to build my bones before I start to lose them. Is there a best time of day to take calcium and multivitamins? At present, I take mine after breakfast so I can flush out the excess vitamins with water throughout the day. -- T.M., Eureka, California

DEAR T.M.: There is definite wisdom to building bones during the first decades of life while the door is open. If you are going to take a calcium supplement based on calcium carbonate (the most common type), it is best to take it with or after a meal. Don't take more than 500 milligrams at a time, as this is about as much as your body can handle at once. Also consider calcium-rich foods, such as yogurt, or calcium-fortified beverages, such as orange juice.

Your multivitamin should include vitamin D, an important nutrient for bone health. Experts are now recommending up to 1,000 IU daily for adults. An active lifestyle, with weight-bearing exercise, plays a big role in building bones. It tells your body that your bones are needed, and the body responds by keeping them strong. There is a more detailed discussion of calcium at tinyurl.com/866w4sa.

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.