Jam, like jelly, is a high-calorie, refined CARBOHYDRATE food: A quart of jam typically contains 2 to 2.5 cups of sugar.. Jelly is there-fore a source of refined CARBOHYDRATEand a high-c
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jam A preservative prepared from boiled SUGAR
syrup and crushed or pureed FRUIT Jams need a
single cooking step Fruits like ripe APPLES, QUINCES,
currants, CRANBERRIES, GOOSEBERRIES, and PLUMS
contain PECTIN, a complex carbohydrate that will
gel upon cooling Low-pectin fruit like BLUEBER
-RIES, APRICOTS, CHERRIES, BLACKBERRIES, GRAPES,
and PINEAPPLE or stalks of RHUBARB have to be
mixed with pectin—or pectin-containing fruits—to
obtain a thicker consistency Jam flavor reflects the
amount of sugar used in syrup The less sugar, the
more pronounced the fruity flavor Jam, like jelly,
is a high-calorie, refined CARBOHYDRATE food: A
quart of jam typically contains 2 to 2.5 cups of
sugar (See also NATURAL SWEETENER.)
jaundice A yellowing of skin, mucous
mem-branes, and whites of the eyes due to the buildup
of BILE PIGMENT (bilirubin) in the body Jaundice
itself is not a disease, but indicates an underlying
problem
Three conditions promote jaundice (bilirubin
accumulation) Prehepatic jaundice reflects the
excessive breakdown of red blood cells Bilirubin is
produced during the degradation of the red
pig-ment of the oxygen-carrying protein HEMOGLOBIN
during disposal of aged red blood cells Bilirubin
travels to the LIVER, where it is processed for
ex-cretion In prehepatic jaundice the rate of bilirubin
production exceeds the liver’s ability to process
incoming bilirubin, for example in hemolytic ANE
-MIA
Hepatic jaundice reflects abnormal liver
func-tion HEPATITIS, liver CIRRHOSIS, and certain liver
dis-eases imbalance liver metabolism and decrease the
liver’s ability to process bilirubin
Extrahepatic jaundice occurs when interference
with BILE release from the GALLBLADDER forces
bilirubin to back into the liver Bile duct obstruc-tions commonly include GALLSTONES (See also
DIGESTION; HEME.)
jejunum The middle segment of the small intes-tine The jejunum is about 8 feet long and lies between the DUODENUM (the first 10 inches) and the ILEUM, the last 12 feet of small intestine Like other regions of the small intestine, the jejunum possesses a large surface area due to its highly wrinkled surface It is covered by numerous hair-like protrusions called VILLI Furthermore, each vil-lus cell surface is covered with microscopic projections called MICROVILLI These physiologic features dramatically increase the absorptive area and aid nutrient absorption and assimilation (See also DIGESTION; DIGESTIVE TRACT.)
jelly A sweet, thickened spread composed of boiled FRUIT juice Jellies are used on toast and in biscuits and pastry Commercial jelly contains at least 55 percent fruit Home-prepared jellies can contain as much as 60 percent sugar Jelly is there-fore a source of refined CARBOHYDRATEand a high-calorie food with few nutrients other than sugar Jelly requires two cooking steps In the first, JUICE
is extracted from the fruit and filtered The clear juice is then cooked with sugar until a gel forms Often juices are extracted by pressure cooking However, high temperatures destroy PECTIN, a form
of fiber required for gel formation Pectin is added back in this case (See also EMPTY CALORIES; NAT
-URAL SWEETENER.)
joule The international scientific standard unit for ENERGY measurement used for all branches of science Recommended by the International
Trang 2Orga-nization for Standardization, the joule was adopted
by the U.S Bureau of Standards in 1964 One joule
is equal to 4.184 calories and is a measure of
mechanical energy while the calorie is based on
heat (thermal energy) Nutrition references still use
KILOCALORIESas a measure of energy in foods For
example, caloric values (in kilocalories) of foods
are published by the USDA; they can be converted
to kilojoules (thousands of joules, abbreviated kJ.)
by multiplying the listed calories by 4.184
juice The liquid extract of FRUITS and VEGETA
-BLES Juices typically contain only small amounts of
FIBER and pulp, which are removed by filtration
Juices can be freshly prepared, concentrated,
frozen, canned, or bottled Juices contain sugars,
soluble minerals, and vitamins that can be released
when plant tissues are crushed or pulverized Plant
leaves yield green, chlorophyll-rich juices
Preparing juices at home with juicers is popular
in the United States On the other hand, consumers
spend more than $9 billion on prepared fruit juices
and fruit drinks annually These preparations are
subject to food labeling regulations The U.S FDA
does not require manufacturers to specify the
amount of fruit juice used in a given juice
Manu-facturers must list ingredients in order of
predomi-nance, but not by percentages Listing percentages
of ingredients would indicate the actual ratios of
the more expensive juices such as kiwi, strawberry,
or peach If the product label specifies “juice” only,
then the product contains only pure fruit juice
Any other designation indicates a diluted juice
Apple juice and white grape juice are among the
least expensive juices to produce and are
fre-quently used in mixtures Proposals by the FDA
would require manufacturers to reveal how much
juice is actually in “juice cocktail” or “juice drink.”
A juicer/juice extractor is a popular mechanical
device that extracts juices from vegetables and
fruits Juicers pulverize the vegetable or fruit by
rotary blades The pulp, seeds, and skin are
sepa-rated from the juice by centrifugal filtration In
contrast, blenders combine pulp and juice
Fresh juices provide a convenient way of
increasing consumption of vegetables and fruits
while cutting back on SOFT DRINKS as part of a
healthful diet that includes lower fat, more whole
grains, vegetables, and fresh fruit Eating whole fruits and vegetables can provide essential nutri-ents and lower the risk of cancer and help reduce the risk of diseases associated with deficiencies and aging However, no juice is a panacea Juicing removes most fiber and pulp, which retain signifi-cant amounts of vitamins, minerals, and perhaps as yet unknown materials that promote health Fiber may have beneficial effects, including lowering the risk of colon cancer There are few studies on the stability of vitamins in juices or on the efficacy of vitamins in the extracts
Fresh juices served immediately are better than those stored because oxidation begins to change the color, flavor, and nutritional quality after the juice is made Juice combinations of vegetables may begin to separate soon after they are made The juice is only as good as the produce used; therefore, using organically grown produce and cleaning produce before juicing make sense when whole produce is to be juiced Ginger and mint can improve the flavor of many juice mixtures (See also AGING; BALANCED DIET.)
junk food A highly processed FOOD Compared to unprocessed foods, junk foods generally contain less nutritive value beyond their caloric content due to added sugar, refined starch, fat or oils Junk food therefore represents a major source of “empty calories” in the typical American diet Junk food is often based on refined grains, such as white flour Obvious examples include CHIPS, CRACKERS, dough-nuts, cookies, packaged sweet snacks, and sugar-laden BREAKFAST CEREALS Gelatin desserts, soft ice cream, candy and soft drinks fit into this category
as well One-third of the average American’s diet is junk food, according to a recent study
Potential Problems with Junk Food Diets
Individual foods are neither “good” nor “bad.” Whether a food is appropriate depends on how much and how often it is eaten, as well as on the health and nutritional status of the individual con-suming it Reliance on junk food is often a direct cause of nutrient-deficient diets in the United States Food manufacturing removes many nutri-ents; consequently, junk foods contain less FIBER;
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-NIUM, CALCIUM, CHROMIUM, COPPER, and IRON; and
less vitamins like VITAMIN A, VITAMIN B6, VITAMIN C,
and FOLIC ACIDthan usually found in unprocessed
or minimally processed foods Simultaneously,
food manufacturing adds many materials not
pre-sent in the original whole food, including: salt,
SUGAR, SATURATED FATand OIL, synthetic
preserva-tives like BHA and BHT, artificial colorings, and
fla-vors To partially correct for nutrient losses in
processing, FLOUR and grain products (such as
processed breakfast cereals) are enriched with
NIACIN, THIAMIN, and RIBOFLAVINto bring them up to
the levels found in whole grain However,
enrich-ment replaces few of the vitamins and trace
miner-als, and none of the fiber lost during food
manufacture
Overnutrition is a second consequence of diets
relying on junk foods Junk food is a major source
of surplus calories and saturated fat in the typical
U.S diet, and a high fat intake is directly tied to a
higher risk of CANCER and coronary heart disease
Excessive junk food is a major cause of OBESITY, a
critical health problem in the United States
Satu-rated fats—such as HYDROGENATED VEGETABLE OIL,
COCONUT OILor palm kernel oil, LARD, and BUTTER— generally increase CHOLESTEROL levels, perhaps setting the stage for clogged arteries Characteristi-cally, junk food contains large amounts of refined sweeteners such as high FRUCTOSE CORN SYRUP, DEX
-TROSE, maltose malt sugar, corn sweetener and
HONEY, as well as SUCROSE
On any given day 46 million Americans eat FAST FOOD, which now shapes many children’s eating habits Studies suggest that children between the ages of six and 11 are more likely to eat cookies than fruit for snacks Children between one and five are just as likely to drink powdered and carbonated soft drinks as they are to drink orange juice (See also CONVENIENCE FOOD; FOOD PROCESSING.)
Kant, Ashima “Consumption of Energy-Dense, Nutri-ent-Poor Foods by Adult Americans; Nutritional and Health Implications The Third National Health and
Nutrition Examination Survey, 1988–1994,” American
Journal of Clinical Nutrition 72 (2000): 929–936.
juvenile diabetes See DIABETES MELLITUS
juvenile diabetes 377