Lemons limes oranges and bacon

Check the meat label. Right there it is, plain as day — vitamin C in the form of sodium ascor-bate 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?

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).

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).

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.

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 B12

Vitamin B12 (cyanocobalamin) makes healthy red blood cells. Vitamin B12 protects myelin, the fatty material that covers your nerves and enables you to transmit electrical impulses (messages) between nerve cells. These messages make it possible for you to see, hear, think, move, and do all the things a healthy body does each day. In 2005, the Canadian Medical Association Journal reported that low blood levels of B12 in older people are linked to higher levels of homocysteine (a minor risk factor for heart disease; see previous, "Vitamin B6 [Pyridoxine]").

Vitamin B12 is unique. First, it's the only vitamin that contains a mineral, cobalt. (Cyanocobalamin, a cobalt compound, is commonly used as "vitamin B12" in vitamin pills and nutritional supplements.) Second, it's a vitamin that can't be made by higher plants (the ones that give us fruits and vegetables). Like vitamin K, vitamin B12 is made by beneficial bacteria living in your small intestine. Meat, fish, poultry, milk products, and eggs are good sources of vitamin B12. Grains don't naturally contain vitamin B12, but like other B vitamins, it's added to grain products in the United States.

Biotin

Biotin is a B-vitamin, a component of enzymes that ferry carbon and oxygen atoms between cells. Biotin helps you metabolize fats and carbohydrates and is essential for synthesizing fatty acids and amino acids needed for healthy growth. And it seems to prevent a buildup of fat deposits that may interfere with the proper functioning of liver and kidneys. (No, biotin won't keep fat from settling in more visible places, such as your hips.)

The best food sources of biotin are liver, egg yolk, yeast, nuts, and beans. If your diet doesn't give you all the biotin you need, bacteria in your gut will synthesize enough to make up the difference. No RDA exists for biotin, but the Food and Nutrition Board has established an Adequate Intake (AI), which means a safe and effective daily dose.

Pantothenic acid

Pantothenic acid, another B-vitamin, is vital to enzyme reactions that enable you to use carbohydrates and create steroid biochemicals such as hormones. Pantothenic acid also helps stabilize blood sugar levels, defends against infection, and protects hemoglobin (the protein in red blood cells that carries oxygen through the body), as well as nerve, brain, and muscle tissue. You get pantothenic acid from meat, fish and poultry, beans, whole grain cereals, and fortified grain products. As with biotin, the Food and Nutrition Board has established an Adequate Intake (AI) for pantothenic acid.

Choline

Choline is not a vitamin, a mineral, a protein, a carbohydrate, or a fat, but it's usually lumped in with the B-vitamins, so heeeeere's choline!

In 1998, 138 years after this nutrient first was identified, the Institute of Medicine (IOM) finally declared it essential for human beings. The IOM had good reasons for doing so. Choline keeps body cells healthy. It's used to make acetylcholine, a chemical that enables brain cells to exchange messages. It protects the heart and lowers the risk of liver cancer. And new research at the University of North Carolina (Chapel Hill) shows that choline plays a role in developing and maintaining the ability to think and remember, at least among rat pups and other beasties born to lab animals that were given choline supplements while pregnant. Follow-up studies showed that prenatal choline supplements helped the animals grow bigger brain cells.

True, no one knows whether this would also be true for human pups, er, babies, but some researchers advise pregnant women to eat a varied diet, because getting choline from basic stuff like eggs, meat, and milk is so easy.

IOM's Food and Nutrition Board, the group that sets the RDAs, has established an AI (Adequate Intake) for choline.

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