The next time someone tells you to mind your p's and q's, don't take offense. The subject may be nutrition, not manners — pyrroloquinoline quinone (PQQ), the first new vitamin in more than half a century. The water-soluble compound, identified at the University of Texas in 1979 and labeled a vitamin four years later by researchers at Tokyo's Institute of Physical and Chemical Research, is widely available in plant foods such as green tea, green bell peppers, papaya, spinach, carrots, cabbage, and bananas. Animal studies show a connection between PQQ and an enzyme used by mammals to digest lysine, an amino acid found in proteins. The vitamin is essential for some bacteria and maybe even mice. And you? Well, if you need it, you need very, very little. The amounts of other vitamins are measured in milligrams (thousandths of a gram) or micrograms (millionths of a gram). But PQQ is measured in nanograms (billionths of a gram) — 1/1,000,000,000.Which is about as itty-bitty as it gets.
The ability to dissolve in water is an important point, because that means large amounts of these nutrients can't be stored in your body. If you take in more than you need to perform specific bodily tasks, you will simply pee away virtually all the excess. The good news is that these vitamins rarely cause side effects. The bad news is that you have to take enough of these vitamins every day to protect yourself against deficiencies.
Vitamin C, which also is referred to as ascorbic acid, is essential for the development and maintenance of connective tissue (the fat, muscle, and bone framework of the human body). Vitamin C speeds the production of new cells in wound healing, protects your immune system, helps you fight off infection, reduces the severity of allergic reactions, and plays a role in the syntheses of hormones and other body chemicals. For more on this important nutrient, see the sidebar "A special case: The continuing saga of Vitamin C," further on in this chapter.
Thiamin (vitamin B1)
Call it thiamin. Call it B1. Just don't call it late for lunch (or any other meal). This sulfur (thia) and nitrogen (amin) compound, the first of the B vitamins to be isolated and identified, helps ensure a healthy appetite. It acts as a coenzyme (a substance that works along with other enzymes) essential to at least four different processes by which your body extracts energy from carbohydrates. And thiamin also is a mild diuretic (something that makes you urinate more).
Although thiamin is found in every body tissue, the highest concentrations are in your vital organs — heart, liver, and kidneys.
The richest dietary sources of thiamin are unrefined cereals and grains, lean pork, beans, nuts, and seeds. In the United States, refined flours, stripped of their thiamin, are a nutritional reality, so most Americans get most of their thiamin from breads and cereals enriched with additional B1.
Riboflavin (vitamin B2)
Riboflavin (vitamin B2), the second B vitamin to be identified, was once called "vitamin G." Its present name is derivative of its chemical structure, a carbon-hydrogen-oxygen skeleton that includes ribitol (a sugar) attached to a flavonoid (a substance from plants containing a pigment called flavone).
Like thiamin, riboflavin is a coenzyme. Without it, your body can't digest and use proteins and carbohydrates. Like vitamin A, it protects the health of mucous membranes — the moist tissues that line the eyes, mouth, nose, throat, vagina, and rectum.
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