Citas de “Nutrition For Dummies, 5th Edition” de Carol Ann Rinzler

The first step is for an enzyme in your fat cells to break up stored triglycerides (the form of fat in adipose tissue). The enzyme action releases glycerol and fatty acids, which travel through your blood to body cells, where they combine with oxygen to produce heat/energy, plus water — lots of water — and the waste product carbon dioxide.

As anyone who has used a high-protein/high-fat/low-carb weight-loss diet such as the Atkins regimen can tell you, in addition to all that water, burning fat without glucose produces a second waste product called ketones. In extreme cases, high concentrations of ketones (a condition known as ketosis) alter the acid/alkaline balance (or pH) of your blood and may trip you into a coma. Left untreated, ketosis can lead to death. Medically, this condition is most common among people with diabetes. For people on a low-carb diet, the more likely sign of ketosis is stinky urine or breath that smells like acetone (nail polish remover)
When the fat moves down your digestive tract into your small intestine, an intestinal hormone called cholecystokinin alerts your gallbladder to release bile. Bile is an emulsifier, a substance that enables fat to mix with water so that lipases can start breaking the fat into glycerol and fatty acids. These smaller fragments may be stored in special cells (fat cells) in adipose tissue, or they may be absorbed into cells in the intestinal wall, where one of the following happens:

They’re combined with oxygen (or burned) to produce heat/energy, water, and the waste product carbon dioxide.
Although dietary fat has more energy (calories) per gram than protein and carbohydrates, your body has a more difficult time pulling the energy out of fatty foods than out of foods high in protein and carbs.

Imagine a chain of long balloons — the kind people twist into shapes that resemble dachshunds, flowers, and other amusing things. When you drop one of these balloons into water, it floats. That’s exactly what happens when you swallow fat-rich foods. The fat floats on top of the watery food-and-liquid mixture in your stomach, which limits the effects of lipases, the enzymes that break fats apart so you can digest them. As a result, fat is digested more slowly than proteins and carbohydrates, so you feel fuller, a condition called satiety (pronounced say-ty-eh-tee) longer after eating high-fat food
A healthy body needs fats to build body tissues and manufacture biochemicals, such as hormones. Some of the adipose (fatty) tissue in your body is plain to see. For example, even though your skin covers it, you can see the fat deposits in female breasts, hips, thighs, buttocks, and belly or on the male abdomen and shoulders
A component of myelin, the fatty material that sheathes nerve cells and makes it possible for them to send the electrical messages that enable you to think, see, speak, move, and perform the multitude of tasks natural to a living body (Your brain is about 60 percent fat, giving a whole new meaning to the term “fat head.”)
A protein deficiency may also affect red blood cells. The cells live for only 120 days, so the body needs a regular supply of protein to make new ones. People who do not get enough protein may become anemic, having fewer red blood cells than they need. Other signs of protein deficiency are fluid retention (the big belly on a starving child), hair loss, and muscle wasting caused by the body’s attempt to protect itself by digesting the proteins in its own muscle tissue, a phenomenon that explains why victims of starvation are, literally, skin and bones.
Liquid fats are called oils; solid fats are called, well, fat, and the fat in food is called dietary fat
With the exception of cholesterol (a fatty substance that has no calories and provides no energy), dietary fats are high-energy nutrients. Gram for gram, fats have more than twice as much energy potential (calories) as protein and carbohydrates: 9 calories per fat gram versus 4 calories per gram for the other two. (For more calorie information, see Chapter 3.)
Some nutritionists think soy proteins are even better than the proteins in eggs and milk, because the proteins in soy come with no cholesterol and very little of the saturated fat known to clog your arteries and raise your risk of heart attack. Better yet, more than 20 recent studies suggest that adding soy foods to your diet can actually lower your cholesterol levels
For example, eggs are 11 percent protein, and dry beans are 22 percent protein. However, the proteins in beans don’t provide sufficient amounts of all the essential amino acids, so they (the beans) are not as nutritionally complete as proteins from animal foods. The prime exception is the soybean, a legume that’s packed with abundant amounts of all of the amino acids essential for adults. Soybeans are an excellent source of proteins for vegetarians, especially vegans, which are vegetarians who avoid all products of animal origin, including milk and eggs
Vegans (those who do not eat any foods from animals, including dairy products) get the protein they need from a cup of oatmeal (6 grams) with a cup of soymilk (7 grams), 2 tablespoons peanut butter (8 grams) sandwiched on one large pita (5–6 grams), 6 ounces soy milk yogurt (6 grams), 6 ounces tofu (13 grams) with 1 cup cooked brown rice (5 grams), and 1 cup steamed broccoli (5 grams)
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
To make all the proteins that your body needs, you require 22 different amino acids. Ten are considered essential, which means you can’t synthesize them in your body and must obtain them from food. (Two of these, arginine and histidine, are essential only for children.) Several more are nonessential: If you don’t get them in food, you can manufacture them yourself from fats, carbohydrates, and other amino acids. Three — glutamine, ornithine, and taurine — are somewhere in between essential and nonessential for human beings: They’re essential only under certain conditions, such as with injury or disease
Unlike other vegetables, including other beans, soybeans have complete proteins with sufficient amounts of all the amino acids essential to human health. In fact, food experts rank soy proteins on par with egg whites and casein (the protein in milk), the two proteins easiest for your body to absorb and use (see Table 7-1)
Your hair, your nails, and the outer layers of your skin are made of keratin, a scleroprotein, or a protein resistant to digestive enzymes. If you bite your nails, you can’t digest them.
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
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.
Nothing succeeds like success, of course. Fairly soon, other universities began ordering up some Gatorade for their teams, pro teams bought in, and, by 1983, Gatorade was the official sports drink of the NFL — a title it holds to this day. Eventually, the hydrating liquid for serious athletes morphed into an “energy drink” for amateur athletes with nutrient-packed beverages promising to increase performance and, sometimes, just keep a person awake and alert. Not surprising, one of the most common ingredients in these beverages is the original awake-and-alert substance, caffeine, as in coffee or guarana, a caffeinated berry native to Brazil and Venezuela. Other prominent ingredients are taurine, an amino acid whose name comes from the Latin word for bull, a clear hint of strength, and ginseng, the reputed healing herb. And often, vitamins — primarily the Bs — are also in the mix. And sometimes there is sugar to sweeten an otherwise bland cocktail. The value of the herbs in these products is questionable, as is the value of vitamins for healthy people who eat a varied diet
Stick with a safe dose. 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
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 United States 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 then banned all ephedra products, and despite a challenge from an ephedra manufacturer, the ban was upheld by the U.S. Court of Appeals for the Tenth Circuit in 2006
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