Friday, March 28, 2008

Understanding DNA/RNA

Nucleoproteins are chemicals in the nucleus of every living cell. They’re made of proteins linked to nucleic acids — complex compounds that contain phosphoric acid, a sugar molecule, and nitrogen-containing molecules made from amino acids.
Nucleic acids (molecules found in the chromosomes and other structures in the center of your cells) carry the genetic codes — genes that help determine what you look like, your general intelligence, and who you are. They contain one of two sugars, either ribose or deoxyribose. The nucleic acid containing ribose is called ribonucleic acid (RNA). The nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA).
DNA, a long molecule with two strands twisting about each other (the double helix), carries and transmits the genetic inheritance in your chromosomes. In other words, DNA supplies instructions that determine how your body cells are formed and how they behave. RNA, a single-strand molecule, is created in the cell nucleus according to the pattern determined by the DNA. Then RNA carries the DNA’s instructions to the rest of the cell.
Knowing about DNA is important because it’s the most distinctly “you” thing about your body. Chances that another person on Earth has exactly the same DNA as you are really small. That’s why DNA analysis is used increasingly in identifying criminals or exonerating the innocent. Some people are even proposing that parents store a sample of their children’s DNA so that they’ll have a conclusive way of identifying a missing child, even years later.

What Happens to the Proteins You Eat?

The cells in your digestive tract can absorb only single amino acids or very small chains of two or three amino acids called peptides. So proteins from food are broken into their component amino acids by digestive enzymes —which are, of course, specialized proteins. Then other enzymes in your body cells build new proteins by reassembling the amino acids into specific compounds that your body needs to function. This process is called protein synthesis.
During protein synthesis
  • Amino acids hook up with fats to form lipoproteins, the molecules that ferry cholesterol around and out of the body. Or amino acids may join up with carbohydrates to form the glycoproteins found in the mucus secreted by the digestive tract.
  • Proteins combine with phosphoric acid to produce phosphoproteins, such as casein, a protein in milk.
  • Nucleic acids combine with proteins to create nucleoproteins, which are essential components of the cell nucleus and of cytoplasm, the living material inside each cell.
The carbon, hydrogen, and oxygen that are left over after protein synthesis is complete are converted to glucose and used for energy. The nitrogen residue (ammonia) isn’t used for energy. It’s processed by the liver, which converts the ammonia to urea. Most of the urea produced in the liver is excreted through the kidneys in urine; very small amounts are sloughed off in skin, hair, and nails.

Every day, you turn over (reuse) more proteins than you get from the food you eat, so you need a continuous supply to maintain your protein status. If your diet does not contain sufficient amounts of proteins, you start digesting the proteins in your body, including the proteins in your muscles and — in extreme cases — your heart muscle.

How Your Body Uses Protein?

Your body uses proteins to build new cells, maintain tissues, and synthesize new proteins that make it possible for you to perform basic bodily functions. About half the dietary protein that you consume each day goes into making enzymes, the specialized worker proteins that do specific jobs such as digesting food and assembling or dividing molecules to make new cells and chemical substances. To perform these functions, enzymes often need specific vitamins and minerals.

Your ability to see, think, hear, and move — in fact, to do just about everything that you consider part of a healthy life — requires your nerve cells to send messages back and forth to each other and to other specialized kinds of cells, such as muscle cells. Sending these messages requires chemicals called neurotransmitters. Making neurotransmitters requires — guess what — proteins. Finally, proteins play an important part in the creation of every new cell and every new individual. Your chromosomes consist of nucleoproteins, which are substances made of amino acids and nucleic acids.

Sunday, March 23, 2008

Where Your Body Puts Protein?

The human body is chock-full of proteins. Proteins are present in the outer and inner membranes of every living cell. Here’s where else protein makes an appearance:
  • Your hair, your nails, and the outer layers of your skin are made of the protein keratin. Keratin is a scleroprotein, or a protein resistant to digestive enzymes. So if you bite your nails, you can’t digest them.
  • Muscle tissue contains myosin, actin, myoglobin, and a number of other proteins.
  • Bone has plenty of protein. The outer part of bone is hardened with minerals such as calcium, but the basic, rubbery inner structure is protein; and bone marrow, the soft material inside the bone, also contains protein.
  • Red blood cells contain hemoglobin, a protein compound that carries oxygen throughout the body. Plasma, the clear fluid in blood, contains fat and protein particles known as lipoproteins, which ferry cholesterol around and out of the body.

Saturday, March 22, 2008

The hazard of megadoses

Several common nutrients may be toxic when you scarf them down in megadose servings (amounts several times larger than the RDAs). Not only are large doses of vitamin A linked to birth defects, but they may also cause symptoms similar to a brain tumor. Niacin megadoses may cause liver damage. Megadoses of vitamin B6 may cause (temporary) damage to nerves in arms, legs, fingers, and toes. All these effects are more likely to occur with supplements. Pills slip down easily, but regardless of how hungry you are, you probably won’t eat enough food to reach toxic levels of nutrients. The best statement about the role of supplements in good nutrition may be a paraphrase of Abraham Lincoln’s famous remark about politicians and voters:
“You may fool all the people some of the time; you can even fool some of the people all the time; but you can’t fool all of the people all the time.” If Honest Abe were with us now and were a sensible nutritionist rather than President, he might amend his words: “Supplements are valuable for all people some of the time and for some people all the time, but they’re probably not necessary for all people all the time.”

Food, the best supplement available

If you’re willing to plan and prepare nutritious meals, you can almost always get your nutrients less expensively from fresh fruits, vegetables, whole grains, dairy products, meat, fish, and poultry. Besides, food usually tastes better than supplements.
Food is a package deal containing vitamins, minerals, protein, fat, carbohydrates, and fiber, plus a cornucopia of as-yet-unidentified substances called phytochemicals (phyto = plant, chemicals = well, chemicals) that may be vital to your continuing good health. Think of lycopene, the red pigment in tomatoes that recently was found to reduce the risk of prostate cancer. Think of genistein and daidzein, the estrogen-like substances in soybeans that appear to reduce your risk of heart disease. Who knows what else is hiding in your apples, peaches, pears, and plums? Do you want to be the only one on your block who misses out on these goodies? Of course not. For more about the benefits of phytochemicals.

Wednesday, March 19, 2008

How to avoid supplement hype?

When the label promises something that’s too good to be true — “Buy me! You’ll live forever” — you know it’s too good to be true. The FDA doesn’t permit supplement marketers to claim that their products cure or prevent disease (that would make them medicines that require premarket testing). But the agency does allow claims that affect function, such as “maintains your cholesterol” (the no-no medical claim would be “lowers your cholesterol”). Another potential hype zone is the one labeled “natural,” as in “natural vitamins are better.” If you took Chem 101 in college, you know that the ascorbic acid (vitamin C) in oranges has exactly the same chemical composition as the ascorbic acid some nutritional chemist cooks up in her lab. But the ascorbic acid in a “natural” vitamin pill may come without additives such as coloring agents or fillers used in “regular” vitamin pills. In other words, if you aren’t sensitive to the coloring agents or fillers in plain old pills, don’t spend the extra dollars for “natural.” If you are sensitive, do. What could be simpler?

Supplement expiration date and storage

Over time, all dietary supplements become less potent. Always choose the product with the longest useful shelf life. Pass on the ones that will expire before you can use all the pills, such as the 100-pill bottle with an expiration date 30 days from now.

Even when you buy a product with the correct expiration date, it may be less effective if you don’t keep it in the right place. Some supplements must be refrigerated; the rest you need to store, like any food product, in a cool, dry place. Avoid putting dietary supplements in a cabinet above the stove or refrigerator — true, the fridge is cold inside, but the motor pulsing away outside emits heat.

Unless your doctor prescribes a dietary supplement as medicine, you don’t need products marked “therapeutic,” “extra-strength,” or any variation thereof. Pick one that gives you no more than the RDA for any ingredient.

Understanding Supplement Brand and Ingredient List

Even though the FDA can’t require manufacturers to submit safety and effectiveness data, a respected name on the label offers some assurance of a quality product. It also promises a fresh product; well-known brands generally sell out more quickly. The initials USP (U.S. Pharmacopoeia, a reputable testing organization) are another quality statement, and so are the words “release assured” or “proven release,” which mean the supplement is easily absorbed by your body. Check the supplement label.

In the early 1990s, the FDA introduced the consumer-friendly nutrition food label with its mini-nutrition guide to nutrient content, complete ingredient listings, and dependable information about how eating certain foods may affect your risk of chronic illnesses, such as heart disease and cancer. The FDA’s new supplement labels must list all ingredients. The label for vitamin and mineral products must give you the quantity per nutrient per serving plus the %DV (percentage daily value), the percentage of the RDA (Recommended Dietary Allowance).

The listings for other dietary supplements, such as botanicals (herbs) and phytochemicals, must show the quantity per serving plus the part of the plant from which the ingredient is drawn (root, leaves, and so on). A manufacturer’s own proprietary blend of two or more botanicals must list the weight of the total blend.

Thursday, March 13, 2008

The Sweet trouble

Nobody wants to choke down a yucky supplement, but pills that look or taste like candy may be hazardous to a child’s health. Some nutrients are troublesome — or even deadly — in high doses, especially for kids. For example, the Food and Drug Administration warns the lethal dose for young children may be as low as 3 grams (3,000 milligrams) elemental iron, the amount in 49 tablets with 65 milligrams iron apiece. If you have youngsters in your house, protect them by buying neutraltasting supplements and keeping all pills, nutrient and otherwise, in a safe cabinet, preferably high off the floor and locked tight to resist tiny prying fingers.

Guide on Supplement Safety

The Food and Drug Administration (FDA) regulates food and drugs (no surprise there). Before the agency allows a new food or a new drug on the market, the manufacturer must submit proof that the product is safe. Drug manufacturers must also meet a second test, showing that their new medicine is efficacious, a fancy way of saying that the drug and the dosage in which it’s sold will cure or relieve the condition for which it’s prescribed. Nobody says the drug-regulation system’s perfect. Reality dictates that manufacturers test a drug only on a limited number of people for a limited period of time.

So you can bet that some new drugs will trigger unexpected, serious, maybe even life-threatening side effects when used by thousands of people or taken for longer than the testing period. For proof, look no further than Phen-Fen, a diet drug combination that appeared to control weight safely during premarket testing but turned lethal after it reached pharmacy shelves. But at least the FDA can require that premarket safety and/or effectiveness info be displayed on foods and drugs. Unfortunately, the agency has no such power when it comes to dietary supplements.
In 1994, Congress passed and President Clinton signed into law the Dietary Supplement Health and Education Act, which limits the FDA’s control over dietary supplements. Under this law, The FDA can’t
  • Require premarket tests to prove that supplements are safe and effective
  • Limit the dosage in any dietary supplement
  • Halt or restrict sales of a dietary supplement unless evidence shows that the product has caused illness or injury when used according to the directions on the package; in other words, if you experience a problem after taking slightly more or less of a supplement than directed on the label, the FDA can’t help you.
As a result, the FDA has found it virtually impossible to take products off drugstore shelves even after reports of illness and injury. For example, supplements containing the herb ephedra are reputed to enhance weight loss and sports performance. More than 600 reports of illness and at least 100 deaths have been linked to the use of ephedra supplements. The herb is banned by professional football and college athletics in the U.S. and by the Olympics. However, the FDA didn’t act until February 2003, following the death of Baltimore Orioles pitcher Steve Bechler, who reportedly had been using ephedra products to control his weight.

Bechler’s untimely death rang warning bells across the country, including in Washington, D.C., where the FDA ruled that henceforth every bottle of ephedra must carry strong warnings that the popular herb can cause potentially lethal heart attacks or strokes. In the sports world, ephedra was immediately forbidden in minor league but not major league baseball. The FDA banned all ephedra products, but the ban was partially reversed in April 2005, when a federal judge ruled that products containing low doses of ephedra were safe and could remain on the market. Some in Congress are pressing for a law that would enable FDA to ban any supplements considered even potentially hazardous to your precious health. Stay tuned.

How to meet a woman’s special needs with supplements?

And what about women? At various stages of their reproductive lives, they, too, benefit from supplements-as-insurance:
  • Before menopause: Women, who lose iron each month through menstrual bleeding, rarely get sufficient amounts of iron from a typical American diet providing fewer than 2,000 calories a day. For them, and for women who are often on a diet to lose weight, iron supplements may be the only practical answer. Iron is a mineral element, so it may be called “iron” or “elemental iron” on the label. Iron pills contain a compound of elemental iron (“ferrous” or “ferric,” from ferrum, the Latin word for iron), plus an ingredient such as a sulfur derivative or lactic acid to enable your body to use the iron. On the label, the combination reads “ferrous sulfate” or “ferrous lactate.” Different iron compounds dissolve at different rates in your stomach, yielding different amounts of elemental iron, so supplement labels usually list the iron this way: Ferrous sulfate 325 mg/Elemental iron 65 mg. Translation? This pill has 325 milligrams of ferrous sulfate, yielding 65 milligrams plain old iron. Sometimes the label omits the first part and simply says: Iron 65 mg. If your doctor says, “Take one 325-milligram pill a day,” she means 325 milligrams iron compound, not plain elemental iron.
  • During pregnancy and lactation: Women who are pregnant or nursing often need supplements to provide the nutrients they need to build new maternal and fetal tissue or to produce nutritious breast milk. In addition, supplements of the B vitamin folate now are known to decrease a woman’s risk of giving birth to a child with a neural tube defect (a defect of the spinal cord and column). Never self-prescribe supplements while you’re pregnant. Large amounts of some nutrients may actually be hazardous for your baby. For example, taking megadoses of vitamin A while you’re pregnant can increase the risk of birth defects.
  • Through adulthood: True, women older than 19 can get the calcium they require (1,000 milligrams/day) from four 8-ounce glasses of nonfat skim milk a day, three 8-ounce containers of yogurt made with nonfat milk, 22 ounces of canned salmon (with the soft edible bones; no, you definitely should not eat the hard bones in fresh salmon!), or any combination of the above. However, expecting women to do this nutritional balancing act every single day may be unrealistic. The simple alternative is calcium supplements.

Monday, March 10, 2008

Using supplements as insurance

Healthy people who eat a nutritious diet still may want to use supplements to make sure they’re getting adequate nutrition. Plenty of recent research supports their choice.

Protecting against disease
Taking supplements may reduce the likelihood of some types of cancer and other diseases. After analyzing data from a survey of 871 men and women, epidemiologists at Seattle’s Fred Hutchinson Cancer Center found that people taking a daily multivitamin for more than ten years were 50 percent less likely to develop colon cancer. In addition, selenium supplements seem to reduce the risk of prostate cancer, and vitamin C seems to lower the risk of cataracts.

Supplementing aging appetites
As you grow older, your appetite may decline and your sense of taste and smell may falter. If food no longer tastes as good as it once did, if you have to eat alone all the time and don’t enjoy cooking for one, or if dentures make chewing difficult, you may not be taking in all the foods that you need to get the nutrients you require. Dietary supplements to the rescue! If you’re so rushed that you literally never get to eat a full, balanced meal, you may benefit from supplements regardless of your age.

When food isn’t enough

Illness, age, diet preferences, and some gender-related conditions may put you in a spot where you can’t get all the nutrients you need from food alone.

Digestive illnesses, unfriendly drugs, injury, and chronic illness
Certain metabolic disorders and diseases of the digestive organs (liver, gallbladder, pancreas, and intestines) interfere with the normal digestion of food and the absorption of nutrients. Some medicines may also interfere with normal digestion, meaning you need supplements to make up the difference. People who suffer from certain chronic diseases, who have suffered a major injury (such as a serious burn), or who have just been through surgery may need more nutrients than they can get from food. In these cases, a doctor may prescribe supplements to provide the hard-to-get vitamins, minerals, and other nutrients.
Checking with your doctor or pharmacist before opting for a supplement you hope will have medical effects (make you stronger, smooth your skin, ease your anxiety) is a smart idea. The bad old days when doctors were total ignoramuses about nutrition may not be gone forever, but they’re fading fast. Besides, your doctor is the person most familiar with your health, knows what medications you’re taking, and can warn you of potential side effects.

Vitamin B12 is found only in food from animals, such as meat, milk, and eggs. (Some seaweed does have B12, but the suspicion is that the vitamin comes from microorganisms living in the plant.) Without these foods, vegans —vegetarians who don’t eat any foods of animal origin — almost certainly have to get their vitamin B12 from supplements or fortified foods.

Why People Use Dietary Supplements?

In a country where food is plentiful and affordable, you have to wonder why so many people opt to scarf down pills instead of just plain food. Many people consider vitamin and mineral supplements a quick and easy way to get nutrients without so much shopping and kitchen time and without all the pesky fat and sugars in food. Others take supplements as nutritional insurance. And some even use supplements as substitutes for medical drugs. In general, nutrition experts, including the American Dietetic Association, the National Academy of Sciences, and the National Research Council, prefer that you invest your time and money whipping up meals and snacks that supply the nutrients you need in a balanced, tasty diet. Nonetheless, every expert worth his or her vitamin C admits that in certain circumstances, supplements can be a definite plus.

In 2002, the American Medical Association (AMA), which for decades had turned thumbs down on vitamin supplements, changed its collective mind after a review of 26 years’ worth of scientific studies relating vitamin levels to the risk of chronic illness. Robert H. Fletcher and Kathleen M. Fairfield, the Harvard-based authors of the study, which was published in the Journal of the American Medical Association (JAMA), said, yes, true vitamin-deficiency diseases such as scurvy and beriberi are rare in Western countries. But suboptimal vitamin levels — sciencespeak for slightly less than you need — are a real problem. If “slightly less than you need” sounds slightly less than important, consider this:
  • Suboptimal intake of folate and two other B vitamins (B6 and B12) raises your risk of heart disease, colon cancer, breast cancer, and birth defects.
  • Suboptimal vitamin D intake means a higher risk of rickets and osteoporosis.
  • Suboptimal levels of antioxidant vitamins A, E, and C are linked to a particular form of heart disease and some forms of cancer.
Hence the new AMA rule: “It’s prudent for all adults to take vitamin supplements.”
But just as that bit of info was settling in, a new study said, “Hold it! There’s too much Vitamin A in that pill!” That was followed by more new research on too much vitamin E. As you read this, vitamin manufacturers are tumbling over each other in the race to get new, lower formulations to market.

Thursday, March 6, 2008

Introducing Dietary Supplements

The vitamin pill you may pop each morning is a dietary supplement. So are the calcium antacids many American women consider standard nutrition. Echinacea, the herb reputed to short-circuit your winter cold, is, and so is the vanilla-flavored meal-in-a-can liquid your granny chug-a-lugs every afternoon just before setting off on her daily mile power walk. The FDA classifies each of these as a dietary supplement because they meet the agency’s definition: any pill, tablet, capsule, powder, or liquid you take by mouth that contains a dietary ingredient.
Of course, that raises another question: What’s a dietary ingredient?

  • Vitamins
  • Minerals
  • Herbs
  • Organ tissue, such as desiccated (dried) liver
  • Some hormones, such as melatonin, which is promoted as a sleep aid
  • Metabolites (substances produced when nutrients are digested)
  • Extracts
Dietary supplements may be single-ingredient products, such as vitamin E capsules, or they may be combination products, such as the nutrient-packed protein powders favored by some athletes.

Understanding terms used to describe nutrient recommendations

Nutrient listings use the metric system. RDAs for protein are listed in grams. The RDA and AIs for vitamins and minerals are shown in milligrams (mg) and micrograms (mcg). A milligram is 1⁄1000 of a gram; a microgram is 1⁄1000 of a milligram. Vitamin A, vitamin D, and vitamin E are special cases.

For instance, one form of vitamin A is preformed vitamin A, a form of the nutrient that your body can use right away. Preformed vitamin A, known as retinol, is found in food from animals —liver, milk, and eggs. Carotenoids (red or yellow pigments in plants) also provide vitamin A. But to get vitamin A from carotenoids, your body has to convert the pigments to chemicals similar to retinol. Because retinol is a ready-made nutrient, the RDA for vitamin A is listed in units called retinol equivalents (RE). One mcg (microgram)

RE is approximately equal to 3.33 international units (IU, the former unit of measurement for vitamin A).
Vitamin D consists of three compounds: vitamin D1, vitamin D2, and vitamin D3. Cholecalciferol, the chemical name for vitamin D3, is the most active of the three, so the RDA for vitamin D is measured in equivalents of cholecalciferol. Your body gets vitamin E from two classes of chemicals in food: tocopherols and tocotrienols. The compound with the greatest vitamin E activity is a tocopherol: alpha-tocopherol. The RDA for vitamin E is measured in milligrams of alphatocopherol equivalents (a-TE).

Understanding DRI: Dietary Reference Intake

In 1993, the Food and Nutrition Board’s Dietary Reference Intakes committee established several panels of experts to review the RDAs and other recommendations for major nutrients (vitamins, minerals, and other food components) in light of new research and nutrition information.
The first order of business was to establish a new standard for nutrient recommendations called the Dietary Reference Intake (DRI). DRI is an umbrella term that embraces several categories of nutritional measurements for vitamins, minerals, and other nutrients. It includes the:
  • Estimated Average Requirement (EAR): the amount that meets the nutritional needs of half the people in any one group (such as teenage girls or people older than 70). Nutritionists use the EAR to figure out whether an entire population’s normal diet provides adequate amounts of nutrients.
  • Recommended Dietary Allowance (RDA): The RDA, now based on information provided by the EAR, is still a daily average for individuals, the amount of any one nutrient known to protect against deficiency.
  • Adequate Intake (AI): The AI is a new measurement, providing recommendations for nutrients for which no RDA is set. (Note: AI replaces ESADDI.)
  • Tolerable Upper Intake Level (UL): The UL is the highest amount of a nutrient you can consume each day without risking an adverse effect.
The DRI panel’s first report, listing new recommendations for calcium, phosphorus, magnesium, and fluoride, appeared in 1997. Its most notable change was upping the recommended amount of calcium from 800 mg to 1,000 mg for adults ages 31 to 50 as well as post-menopausal women taking estrogen supplements; for post menopausal women not taking estrogen, the recommendation is 1,500 mg.

The second DRI Panel report appeared in 1998. The report included new recommendations for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. The most important revision was increasing the folate recommendation to 400 mcg a day based on evidence showing that folate reduces a woman’s risk of giving birth to a baby with spinal cord defects and lowers the risk of heart disease for men and women.

As a result of the 1989 DRI Panel report, the FDA ordered food manufacturers to add folate to flour, rice, and other grain products. (Multivitamin products already contain 400 mcg of folate.) In May 1999, data released by the Framingham Heart Study, which has followed heart health among residents of a Boston suburb for nearly half a century, showed a dramatic increase in blood levels of folate. Before the fortification of foods, 22 percent of the study participants had folate deficiencies; after the fortification, the number fell to 2 percent.

A DRI report with revised recommendations for vitamin C, vitamin E, the mineral selenium, beta-carotene, and other antioxidant vitamins was published in 2000. In 2001, new DRIs were released for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. And in 2004, the Institute of Medicine (IOM) released new recommendations for sodium, potassium, chloride, and water, plus a special report on recommendations for two groups of older adults (ages 50 to 70 and 71 and over). Put these findings all together, and they spell out the recommendations.

The complete reports on which this table is based are available online. Go to Prefer hard copy? IOM plans to consolidate the reports into one book to be published late in 2006.
Hankering for more details? Notice something missing? Right — no recommended allowances for protein, fat, carbohydrates and, of course, water.