Folate

Folate, or folic acid, is an essential nutrient for human beings and other vertebrates (animals with backbones). Folate takes part in the synthesis of DNA, the metabolism of proteins, and the subsequent synthesis of amino acids used to produce new body cells and tissues. Folate is vital for normal growth and wound healing. An adequate supply of the vitamin is essential for pregnant women to enable them to create new maternal tissue as well as fetal tissue. In addition, an adequate supply of folate dramatically reduces the risk of spinal cord birth defects. Beans, dark green leafy vegetables, liver, yeast, and various fruits are excellent food sources of folate, and all multivitamin supplements must now provide 400 mcg of folate per dose.

Vitamin B6 (Pyridoxine)

Vitamin B6 is another multiple compound, this one comprising three related chemicals: pyridoxine, pyridoxal, and pyridoxamine. Vitamin B6, a component of enzymes that metabolizes proteins and fats, is essential for getting energy and nutrients from food. It also helps lower blood levels of homocysteine (see Chapter 6), an amino acid produced when you digest proteins. The American Heart Association calls a high level of homocysteine an independent (but not major) risk factor for heart disease, and the American Journal of Clinical Nutrition reported in 2005 that a high homocysteine level may be associated with an age-related decline in memory. Alas, follow up studies show no reduction in the risk of heart disease or improvement in memory in those who reduce their blood levels of homocysteine.
The best food sources of vitamin B6 are liver, chicken, fish, pork, lamb, milk, eggs, unmilled rice, whole grains, soybeans, potatoes, beans, nuts, seeds, and dark green vegetables such as turnip greens. In the United States, bread and other products made with refined grains have added vitamin B6.

Niacin

Niacin is one name for a pair of naturally occurring nutrients, nicotinic acid and nicotinamide. Niacin is essential for proper growth, and like other B vitamins, it’s intimately involved in enzyme reactions. In fact, it’s an integral part of an enzyme that enables oxygen to flow into body tissues. Like thiamin, it gives you a healthy appetite and participates in the metabolism of sugars and fats. Niacin is available either as a preformed nutrient or via the conversion of the amino acid tryptophan. Preformed niacin comes from meat; tryptophan comes from milk and dairy foods. Some niacin is present in grains, but your body can’t absorb it efficiently unless the grain has been treated with lime —the mineral, not the fruit. This is a common practice in Central American and South American countries, where lime is added to cornmeal in making tortillas. In the United States, breads and cereals are routinely fortified with niacin. Your body easily absorbs the added niacin. The term used to describe the niacin RDA is NE (niacin equivalent): 60 milligrams tryptophan = 1 milligram niacin = 1 niacin equivalent (NE).

Lemons, limes, oranges — and bacon?

Check the meat label. Right there it is, plain as day — vitamin C in the form of sodium ascorbate or isoascorbate.
The Food and Drug Administration (FDA) says it has to be there because vitamin C does for meat exactly what it does for your body: It prevents free radicals (incomplete pieces of molecules) from hooking up with each other to form damaging compounds, in this case carcinogens, substances that cause cancer.
Processed meats such as bacon and sausages are preserved with sodium nitrite, which protects the meat from Clostridium botulinum, microorganisms that cause the potentially fatal food poisoning known as botulism.
On its own, sodium nitrite reacts at high temperatures with compounds in meat to form carcinogens called nitrosamines. But like the Lone Ranger, antioxidant vitamin C rides to the rescue, preventing the chemical reaction and keeping the sausage and bacon safe to eat. How’s that for healthy eating, Kemo Sabe?

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. You get riboflavin from foods of animal origin (meat, fish, poultry, eggs, and milk), whole or enriched grain products, brewer’s yeast, and dark green vegetables (like broccoli and spinach).

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.

Vitamin C

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.

Water-soluble vitamins

Vitamin C and the entire roster of B vitamins (thiamin, riboflavin, niacin, vitamin B6, folate, biotin, and pantothenic acid) are usually grouped together simply because they all dissolve in water. 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.

PQQ, a new kind of vitamin

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.