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 email@example.com. Due to the volume of mail, personal replies cannot be provided.