DEAR DR. BLONZ: If blood glucose level is so important -- if it gets too low, we get weak or pass out -- why does the body automatically convert the carbohydrates we eat into fat? Why don't we store carbs like we do fat? -- R.S., Dublin, Calif.

DEAR R.S.: Plants are able to capture energy from the sun, photosynthesizing the sun's energy into carbohydrate using carbon dioxide from the atmosphere. The human body, like that of most other animals, can't do this. Our only source of energy comes from the foods we consume.

Fat gets used as the storage form because it is nature's most concentrated form of metabolic energy, containing over twice the energy per unit weight as proteins or carbohydrates such as glucose. A concentrated form of energy is essential for us because of mobility: If we stored the bulk of our energy as carbohydrate, we would be too bulky to move.

That provides a good contrast to plants, where the basic theme is staying put, sending roots into the soil for nutrients and growing leaves that are exposed to the sun. With sunshine comes more energy for growth, the production of flowers, and the eventual production of seeds for the next generation. Plants take in their "meal" of sunshine and convert their energy into carbohydrate because it takes up the most space per calorie, which then speeds their growth.

Although the "mission" of the plant is to grow rapidly while remaining in one spot, that of the seed is very different. A seed must be light enough to be carried by the wind or on the fur of animals, but after falling to the ground, it needs to have enough stored energy to fuel the process of sending out roots and growing shoots. Seeds' need for concentrated energy explains why they store their enery as fat, as opposed to carbohydrates like mature plants.

You asked about carbohydrate storage in our body. It turns out that there is a small amount in the form of glycogen, which is a branched chain of glucose molecules. Glycogen is stored in the liver and muscles. It gets used as a source of emergency muscle energy, or if the blood sugar level drops too low, but it's not a large amount: The average adult has just over 100 grams in the liver and about 250 grams in all the muscles combined.

DEAR DR. BLONZ: Why should you only take 500 milligrams of calcium at a time? My supplement contains 600 milligrams and I had been taking two at bedtime. I had heard that it is better to take them at bedtime, but now I hear differently. Could you please comment? -- S.A., Seattle

DEAR S.A.: The reason for the calcium limit is that the efficiency of absorption tends to decrease when a single dose exceeds 500 milligrams. Taking larger amounts means that more will end up passing through without being absorbed. It is probably wise to find a way to distribute your calcium in more than one dose, and taking it at mealtime is usually best.

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: My diet is questionable, and I was recently persuaded to start using the antioxidant Pycnogenol by some friends (and a bunch of online advertisements). I thought that this antioxidant might be the best for whatever ails you, but I was wondering what you thought. -- A.S., Puma, Ariz.

DEAR A.S.: I am not certain what you might have heard about Pycnogenol. It is indeed an antioxidant supplement, but I wouldn't say it is "the best" for anything that might ail you. In fact, I wouldn't say that of any one type of antioxidant or supplement.

The body relies on a number of antioxidants, many of which it manufactures from the raw materials present in your diet. Others come from the foods themselves, such as the naturally occurring antioxidant substances found in grains, fruits, greens and other vegetables. These are the precise substances those plants rely on as living organisms, and many are able to be absorbed and work for us, as well. The most important message here is that the key to good health, good nutrition and effective antioxidant protection is to have an entire team working together. Supplements might be able to pitch in if needed, but they cannot do it all. Think of the interactions between the nutrients and phytochemicals in various combinations of whole foods as being like music performed by a symphony orchestra. A "questionable diet" plus a "whatever ails you" supplement should never be thought of as a reasonable alternative.

DEAR DR. BLONZ: I have read of the many health benefits of drinking tea. Are the same benefits derived from iced tea? Also, does the decaffeination process change the beneficial characteristics of the tea? -- D.S., San Diego

DEAR D.S.: There should be no difference in the health benefits between a tea that is consumed iced and one that is taken hot. The decaffeination process, however, is a mixed bag. Some use a steam process, while others remove the caffeine through the use of solvents. One factor to consider is the potential loss of the tea's beneficial phytochemicals, and I would expect there to be a greater loss with the solvent extraction.

One study using animals reported that regular black tea was the most effective in preventing skin cancer, followed by green tea, decaffeinated black tea, and finally decaffeinated green tea. They all had beneficial effects; it was just a matter of degree. Of interest was the suggestion that the caffeine itself might have some anti-cancer properties. There have been studies that have found that adding caffeine back to the decaffeinated tea restored much of its anti-cancer abilities. Indeed, caffeine was even found to have an ability to prevent certain cancers on its own. Please understand that these are specialized research studies where relatively large amounts of tea extracts or solids are given for a short period of time. It is unclear how much we can generalize from these studies.

The bottom line is that tea is a beverage to be enjoyed however you like it.

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 am looking for general advice: I am 70 years old, in good health and hope to stay that way. I do my best to get five or six fruits and vegetables each day and a lot of cereals/grains. I also take a multivitamin that contains between 100 percent and 200 percent of my recommended nutrients. I am at the top end of the normal bracket for cholesterol, so I am very careful with fats. Most of the vegetables I eat, and a lot of the fruits, are raw. Is that good, bad or does it matter? -- J.W., Phoenix

DEAR J.W.: What you are doing sounds great! Having your vegetables raw is neither good, bad nor indifferent; having them at all is what's most important. The way they are prepared is a matter of taste. If you are going to take a supplement, it is best to take it with a meal. The choice of the meal is up to you, but it should contain fat, protein and carbohydrates. As regards your cholesterol, what you are doing with your diet sounds good to me. The one item you haven't mentioned is physical activity, and I would try to stay as active as possible. If you have not previously been active, you should touch base with your doctor before you start.

DEAR DR. BLONZ: I want to know about the no-calorie sweetener called Splenda. What is it? Have studies shown that it is safe for long-term use? -- B.B., Chicago

DEAR B.B.: Splenda is the brand name for the compound known as sucralose, which is a modified form of sucrose, or table sugar. Sucralose is approximately 600 times as sweet as sucrose. It's not absorbed to any appreciable degree, and that means no carbohydrate grams as well as no calories. It does not contribute to tooth decay. It does contain a small amount of a carbohydrate as a bulking agent in packing, but it is less than one gram per serving -- not enough to provoke the release of insulin by the pancreas. The sweetener has been in use in Europe and in Canada since 1991, but only approved for use in the U.S. since 1998.

Sucralose is made through a multi-step process that substitutes chlorides in three places along the sucrose molecule. These tightly bound chlorides change the character of the molecule to the point that it is not recognized as a carbohydrate. Sucralose gets the green light for cooking because, unlike other artificial sweeteners, it does not lose its sweetness when heated.

As for your second question: Is sucralose safe? Safety studies to date reveal no cause for concern. A review in the October 2009 edition of the journal Regulatory Toxicology and Pharmacology has affirmed this fact. As an artificial sweetener, this one looks like a winner, but our history with novel food additives would dictate that it pays to be prudent with this or any artificial sweetener.

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.