肝臟 ` 排毒

排毒
毒是泛指一些油溶性的化學物質, 這些物質隨著脂肪吸收進入血液, 之後便立即達肝臟; 小部份再經循環系統去到每一個器官. 肝臟中的細胞色素P-450氧化酶 CYP (Cytochrome P-450 Oxidase)會把那些油溶性的有害物質加以氧化, 使其水溶性增加, 方便肝臟把毒隨瞻汁遣返小腸, 再隨大便排出體外. 除此之外, 肝臟另一排毒方法是進行生物轉化, 把有毒而又不溶於水的成份轉為水溶性的穀胱甘肰(Glutathione)衍生物.

瀝青和廢氣氛都含Pyrene, 例如Benzo(a)Pyrene BP. BP可致癌. 肝臟用P-450將BP轉變成非水溶性(醌)Quinone; 之後用醌還原酶Quinone Reductase, NQO1將它轉為水溶性再排出體外. 食物中番茄, 葡萄, 咖哩和蒜都能刺激NQO1的生成.

冥想靜坐時用硫化氫(Hydrogen Sulphide)可以用來鍛鍊心肌(Preconditioning), 令它在心肌梗塞時不會受重傷. 同樣道理, 浸在有硫磺味的溫泉中,也可以強心健健體. 吃蒜頭時將它拍扁,可從破裂後的Alliin分子中找到一種細胞內的溶解體Alliinase生物催化劑. 這催化劑能把Alliin轉為一個不穩定的分子Allicin, Allicin再分解, 成為一些可以被細胞吸收,及可以在細胞內衍生硫化氫的化學成分.

服藥時不要用西柚汁送, 因為西柚汁會抑制CYP, 很容易導致藥物過量, 從而中毒. 另一副作用,西柚汁/皮中的西柚苷(Naringin)是黃酮的一種, 它可以抑制一個幫助腸腔吸收帶正電物質的蛋白質,Organic Anion Transporting Protein(OATP).

陳皮的檸苦素(Limonoids, 其中Limonin和Nomilin最有保健作用)能提高肝的生物轉化功能.
<本草綱目>: [陳皮同補藥則補, 同升藥則升, 同降藥則降].

酒如何傷肝
酒精可以被胃壁直接吸收, 過量的酒精可令胃血管內壁(Endothelium)受傷, 從而不能如常分泌一氧化氮(Nitric Oxide)來舒張血管. 整個胃便會因此而缺氧潰瘍. 內皮細胞不若氣管, 沒有軟骨把它們撐開, 必須不斷分泌一氧化氮, 紓緩血管壁上的平滑肌, 才能保持舒張. 長期飲烈酒, 可令血管失去彈性, 從而引致血壓上升, 心臟負荷增加, 心肌慢慢增厚, 形成心臟肥大(Hypertrophy), 之後大有可能造成心衰竭.

至於一次性飲酒過量, 酒精若多到連胃和小腸都不能將其吸收, 酒入大腸灼傷了大腸上皮細胞, 細菌便可走進血管, 直達肝臟, 再釋放出現外毒素和內毒素使肝臟受傷, 發炎, 硬化. 硬化不會致癌, 但因為肝臟或胰臟內有各種酵素酶, 有能力快速消化掉一切纖維; 不過同時那些酵素會挑起一個局部性的免疫風暴, 隨之而來是免疫系統的重撃, 誘發癌變. 例如, 肝臟能分泌一個令細胞増生的蛋白質IGF-1, Insulin-like Growth Factor-1, IGF-會導致肝癌.

有關肝臟功能的五種指標

1. 白蛋白(Albumin) - 白蛋白完全來自肝臟, 若血液中的白蛋白含量下降, 可能表示有慢性肝病,如肝硬化.
2. ALT(Alanine Transaminase) - ALT, AST和ALP稱[肝酵素]. 因為只有肝細胞才有ALT, 若在血液中驗到ALT, 應該是肝受了傷害. 有兩種情況會導致ALT上升: 肝炎病毒感染和薬物/食物中毒.
3. AST(Aspartate Transaminase) - AST是肝, 紅血球, 肌肉的一個酵素, 若發現AST上升但ALT正常, 便是有了肝以外的其它損傷.
4. ALP(Alkaline Phosphatase) - ALP主要是膽管細胞的酵素, 若膽管栓塞(膽石), ALP指標會上升.
5. Bilirubin - 主要來自紅血球的血紅素(Hemoglobin). 在正常情況下, 肝細胞會把Bilirubin轉為水溶性的物質, 藉膽汁經小腸,大腸排出體外. 血液若出現過量的話Bilirubin, 顯示肝的排毒功能可能出現問題.

護肝食品
綠茶素 - 干擾素乙肝病毒
乳薊 - 減低肝硬化
半胱胺酸(Cysteine) - 提高肝細胞抵抗血中有害的氧化物

Essential Fatty Acid

Nomenclature
Fatty acids are straight chain hydrocarbons possessing a carboxyl (COOH) group at one end. Biological fatty acids can be of different lengths, the last position is labelled as a "ω". Since the physiological properties of unsaturated fatty acids largely depend on the position of the first unsaturation relative to the end position and not the carboxylate, the position is signified by (ω minus n). Double bonds are cis and separated by a single methylene (CH2) group unless otherwise noted. So in free fatty acid form, the chemical structure of stearidonic acid is ω-3 18:4 : 18-carbon chain with 4 double bonds, and with the first double bond in the third position from the CH3 end.

Essential fatty acids (EFAs) 

EFAs refers to fatty acids required for biological processes, and not those that only act as fuel. Humans and other animals must ingest because the body requires them for good health but cannot synthesize them. There are two known EFAs for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid). Other fatty acids that are only "conditionally essential" include gamma-linolenic acid (an omega-6 fatty acid), lauric acid (a saturated fatty acid), and palmitoleic acid (a monounsaturated fatty acid).

The biological effects of the ω-3 and ω-6 fatty acids are mediated by their mutual interactions. In the body, essential fatty acids serve multiple functions:

• They are modified to make:
• the classic eicosanoids (affecting inflammation and many other cellular functions)
• the endocannabinoids (affecting mood, behavior and inflammation)
• the lipoxins from ω-6 EFAs and resolvins from ω-3 (in the presence of aspirin, downregulating inflammation.)
• the isofurans, neurofurans, isoprostanes, hepoxilins, epoxyeicosatrienoic acids (EETs) and Neuroprotectin D. 

• They form lipid rafts (affecting cellular signaling).
• They act on DNA (activating or inhibiting transcription factors such as NF-κB, which is linked to pro-inflammatory cytokine production).

1. Almost all the polyunsaturated fats in the human diet are EFAs. Essential fatty acids play an important role in the life and death of cardiac cells. 
2. Low plasma concentrations of DHA predict low concentrations of cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA). It is found that low concentrations of 5-HIAA in the brain is associated with depression and suicide.
3. There are high concentrations of DHA in synaptic membranes of the brain. This is critical for synaptic transmission and membrane fluidity. The omega-6 fatty acid to omega-3 fatty acid ratio is important to avoid imbalance of membrane fluidity. Membrane fluidity affects function of enzymes such as adenylate cyclase and ion channels such as calcium, potassium, and sodium, which in turn affects receptor numbers and functioning, as well as serotonin neurotransmitter levels. Modern Western diets typically have ratios of omega-6 to omega-3 in excess of 10 to 1, some as high as 30 to 1, partly due to corn oil which has an omega-6 to omega-3 ratio of 49:1. The optimal ratio is thought to be 4 to 1 or lower. 

Mammals lack the ability to introduce double bonds in fatty acids beyond carbon 9 and 10, hence ω-6 linoleic acid (18:2,9,12) LA, and the ω-3 linolenic acid (18:3,9,12,15) ALA, are essential for humans in the diet. These two fatty acids cannot be synthesised by humans, as humans lack the desaturase enzymes required for their production. EFAs start with the short chain polyunsaturated fatty acids (SC-PUFA):
 * ω-3 fatty acids: α-Linolenic acid or ALA (18:3)
 * ω-6 fatty acids: Linoleic acid or LA (18:2)
(ω-9 fatty acids (Oleic acid) are not essential in humans, because humans generally possess all the enzymes required for their synthesis)

These two fatty acids form the starting point for the creation of longer and more desaturated fatty acids, which are also referred to as long-chain polyunsaturated fatty acids (LC-PUFA):
ω-3 fatty acids:
 * eicosapentaenoic acid or EPA (20:5)
 * docosahexaenoic acid or DHA (22:6)
ω-6 fatty acids:
 * gamma-linolenic acid or GLA (18:3)
 * dihomo-gamma-linolenic acid or DGLA (20:3)
 * arachidonic acid or AA (20:4)
(Traditionally speaking, the LC-PUFAs are not essential. Because the LC-PUFA are sometimes required, they may be considered "conditionally essential", or not essential to healthy adults.)

Food Sources
Some of the food sources of ω-3 and ω-6 fatty acids are fish and shellfish, flaxseed (linseed), hemp oil, soya oil, canola (rapeseed) oil, chia seeds, pumpkin seeds, sunflower seeds, leafy vegetables, and walnuts. Plant sources of ω-3 contain neither EPA nor DHA. The human body can convert α-linolenic acid (ALA) to EPA and subsequently DHA. This however requires more metabolic work.

Canola Oil
Canola oil is low in saturated fat and contains both omega-6 and omega-3 fatty acids in a ratio of 2:1. If consumed it also reduces Low-density lipoprotein and overall cholesterol levels, and as a significant source of the essential omega-3 fatty acid is associated with reduced all-cause and cardiovascular mortality. It is recognized by many health professional organizations including the American Dietetic Association and American Heart Association. Canola oil has been given a qualified health claim from the United States Food and Drug Administration due to its high levels of cholesterol-lowering fats.

Simple Facts of Egg

The yolk of one large egg (50 g total, 17 g yolk) contains approximately: 2.7 g protein, 0.61 g carbohydrates, and 4.51 g total fat. It also contains about 60 calories and 210 mg cholesterol.

The egg white of one large egg (33 g) contains: 3.6 g of protein, 0.24 g of carbohydrate and 55 milligrams of sodium. It also contains about 17 calories and no cholesterol.
(USDA National Nutrient Database)

Egg Yolk
All of the fat-soluble vitamins (A, D, E, and K) are found in the egg yolk. Egg yolk is one of the few foods naturally containing vitamin D.

The yellow color is due to lutein and zeaxanthin, which are yellow or orange carotenoids known as xanthophylls. Lutein was found to be concentrated in the macula, a small area of the retina responsible for central vision. The hypothesis for the natural concentration is that lutein helps keep the eyes safe from oxidative stress and the high-energy photons of blue light.

The composition (by weight) of the most prevalent fatty acids in egg yolk is typically as follows:
Unsaturated: Oleic acid (47%), Linoleic acid (16%), Palmitoleic acid (5%), Linolenic acid (2%)
Saturated: Palmitic acid (23%), Stearic acid (4%), Myristic acid (1%)

Choline (grouped within the B-complex vitamins) must be consumed through the diet in order for the body to remain healthy. It is used in the synthesis of the constructional components in the body's cell membranes. Dietary recommendations have discouraged people from eating certain high choline foods, such as egg and fatty meats.

Egg White
The egg white is about two-thirds of the total egg's weight out of its shell, with nearly 92% of that weight coming from water. The remaining weight of the egg white comes from protein, trace minerals, fatty material, vitamins, and glucose.

It contains approximately 40 different proteins: 54% Ovalbumin (nourishment; blocks digestive enzymes), 12% Ovotransferrin (binds iron), 11% Ovomucoid (blocks digestive enzymes), 4% Ovoglobulin G2, 4% Ovoglobulin G3, ...

Egg white is a fining agent that can be used in the clarification and stabilization of wine.

The physical stress of beating egg white can create a foam. There are two types of physical stress caused by beating them with a whisk (denaturation):
1. Whisk drags the liquid through itself, creating a force that unfolds the protein molecules.
2. Mixing of air into the whites causes the proteins to come out of their natural state.
These denatured proteins gather together where the air and water meet and create multiple bonds with the other unraveled proteins, and thus become a foam, holding the incorporated air in place. This process is called coagulation (proteins consist of amino acids; some are hydrophilic (attracted to water) and some are hydrophobic (repelled by water)).

Egg vs Peanut (per 100 g)

	Egg, hard-boiled	Peanut
Vitamin A equiv.	140 μg (18%)
Thiamine (vit. B1)	0.066 mg (6%)	0.6 mg (52%)
Niacin (vit. B3)		12.9 mg (86%)
Riboflavin (vit. B2)	0.5 mg (42%)
Pantothenic acid (B5)	1.4 mg (28%)	1.8 mg (36%)
Vitamin B6		0.3 mg (23%)
Folate (vit. B9)	44 μg (11%)	246 μg (62%)
Vitamin B12	1.11 μg (46%)
Choline (B-complex)	225 mg (46%)
Vitamin D	87 IU (15%)
Vitamin E	1.03 mg (7%)
Calcium	50 mg (5%)	62 mg (6%)
Iron	1.2 mg (9%)	2 mg (15%)
Magnesium	10 mg (3%)	184 mg (52%)
Phosphorus	172 mg (25%)	336 mg (48%)
Potassium	126 mg (3%)	332 mg (7%)
Zinc	1.0 mg (11%)	3.3 mg (35%)
Cholesterol	424 mg
Cholesterol (raw yolk)	1240 mg

Protein	Egg, hard-boiled	Peanut
Alanine	0.7	0.997
Arginine	0.755	3.001
Aspartic acid	1.264	3.06
Cystine	0.292	0.322
Glutamic acid	1.644	5.243
Glycine	0.423	1.512
Histidine	0.298	0.634
Isoleucine	0.686	0.882
Leucine	1.075	1.627
Lysine	0.904	0.901
Methionine	0.392	0.308
Phenylalanine	0.668	1.3
Proline	0.501	1.107
Serine	0.936	1.236
Threonine	0.604	0.859
Tryptophan	0.153	0.2445
Tyrosine	0.513	1.02
Valine	0.767	1.052
	12.575	25.3055

花生雞腳湯的生物化學

一場蛋白質的盛宴

Peanut, or groundnut (Arachis hypogaea) are known by many other local names such as earthnut, ground nut, monkey nut, and pig nut. Despite its name and appearance, the peanut is not a nut, but rather a legume. Hypogaea means "under the earth"; after pollination, the flower stalk elongates causing it to bend until the ovary touches the ground. Continued stalk growth then pushes the ovary underground where the mature fruit develops into a legume pod, the peanut.

Most of the edible tissue on the feet consists of skin and tendons, with no muscle. Collagen is a group of naturally occurring proteins found in animals, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendon, ligament and skin, and is also abundant in cornea, cartilage, bone, blood vessels, the gut, and intervertebral disc.

Peanut nutritional value per 100 g (3.5 oz).

Carbohydrates	21 g
Fat	48 g
saturated	7 g
monounsaturated	24 g
polyunsaturated	16 g
Protein	25.3055 g
Water	4.26 g
Thiamine (vit. B1)	0.6 mg (52%)
Niacin (vit. B3)	12.9 mg (86%)
Pantothenic acid (B5)	1.8 mg (36%)
Vitamin B6	0.3 mg (23%)
Folate (vit. B9)	246 μg (62%)
Vitamin C	0.0 mg (0%)
Calcium	62 mg (6%)
Iron	2 mg (15%)
Magnesium	184 mg (52%)
Phosphorus	336 mg (48%)
Potassium	332 mg (7%)
Zinc	3.3 mg (35%)

* Percentages are relative to US recommendations for adults

Protein	25.3055
Glutamic acid	5.243	20.72%
Aspartic acid	3.06	12.09%
Arginine	3.001	11.86%
Leucine	1.627	6.43%
Glycine	1.512	5.97%
Phenylalanine	1.3	5.14%
Serine	1.236	4.88%
Proline	1.107	4.37%
Valine	1.052	4.16%
Tyrosine	1.02	4.03%
Alanine	0.997	3.94%
Lysine	0.901	3.56%
Isoleucine	0.882	3.49%
Threonine	0.859	3.39%
Histidine	0.634	2.51%
Cystine	0.322	1.27%
Methionine	0.308	1.22%
Tryptophan	0.2445	0.97%

Collagen is a composed of a triple helix, which generally consists of two identical chains (α1) and an additional chain that differs slightly in its chemical composition (α2). The most common motifs in the amino acid sequence of collagen are Glycine-Proline-X and Glycine-X-Hydroxyproline, where X is any amino acid other than glycine, proline or hydroxyproline. Abundance in Skin (Residues/1000):

X	Amino Acid	Mammal	Fish
Gly	Glycine	329	339
Pro	Proline	126	108
Ala	Alanine	109	114
Hyp	Hydroxyproline	95	67
Glu	Glutamic acid	74	76
Arg	Arginine	49	52
Asp	Aspartic acid	47	47
Ser	Serine	36	46
Lys	Lysine	29	26
Leu	Leucine	24	23
Val	Valine	22	21
Thr	Threonine	19	26
Phe	Phenylalanine	13	14
Ile	Isoleucine	11	11
Hyl	Hydroxylysine	6	8
Met	Methionine	6	13
His	Histidine	5	7
Tyr	Tyrosine	3	3

Proteinogenic ("protein building") amino acids are amino acids that are precursors to proteins, and are produced by cellular machinery coded for in the genetic code of any organism. There are 22 standard amino acids, but only 21 are found in eukaryotes. Proteinogenic amino acids can be condensed into a polypeptide (the subunit of a protein) through a process called translation (the second stage of protein biosynthesis, part of the overall process of gene expression).

In contrast, non-proteinogenic amino acids are either not incorporated in proteins (like GABA, L-DOPA, or triiodothyronine), or are not produced directly and in isolation by standard cellular machinery (like hydroxyproline and selenomethionine). Non-proteinogenic amino acids are incorporated in nonribosomal peptides, which are not produced by the ribosome during translation.

Humans can synthesize 11 of these 20 from each other or from other molecules of intermediary metabolism. The other 9 must be consumed in the diet and so are thus called essential amino acids. The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Peanut has all 9 essential amino acids. Collagen in animal skin has 8 with tryptophan is missing. Peanut has cystine but collagen does not.

9 Essential Amino Acids

Histidine	Used by many proteins as a regulatory mechanism. However only a few histidines are needed for this, so it is comparatively scarce.
Isoleucine	Their molecules are rigid and have large aliphatic hydrophobic side chains. Their mutual hydrophobic interactions are important for the correct folding of proteins, as these chains tend to be located inside of the protein molecule.
Leucine	Behaves similarly to isoleucine
Lysine	Behaves similar to arginine. Contains a long flexible side-chain with a positively-charged end. DNA-binding proteins have their active regions rich with arginine and lysine. The strong charge makes these two amino acids prone to be located on the outer hydrophilic surfaces of the proteins; when they are found inside, they are usually paired with a corresponding negatively-charged amino acid, e.g., aspartate or glutamate.
Methionine	Always the first amino acid to be incorporated into a protein. It's methyl group, if activated, is used in many reactions where a new carbon atom is being added to another molecule.
Phenylalanine	The biggest amino acids, contain large rigid aromatic group on the side-chain. Like isoleucine, leucine and valine, these are hydrophobic and tend to orient towards the interior of the folded protein molecule.
Threonine	Has a short group ended with a hydroxyl group. Both threonine and serine are very hydrophilic, the outer regions of soluble proteins tend to be rich with them.
Tryptophan	Behaves similarly to phenylalanine and tyrosine. Precursor of serotonin. Naturally fluorescent.
Valine	Behaves similarly to isoleucine

Amino acids that find in peanuts:

Glutamic acid	Behaves similarly to aspartic acid. Has longer, slightly more flexible side chain.
Arginine	Functionally similar to lysine.
Aspartic acid	Usually is located on the outer surface of the protein, making it water-soluble. Binds to positively-charged molecules and ions, often used in enzymes to fix the metal ion.
Cystine	A dimeric amino acid formed by the oxidation of two cysteine residues that covalently link to make a disulfide bond. Through formation of disulfide bonds within and between protein molecules, cystine is a significant determinant of the tertiary structure of most proteins. Cysteine is an α-amino acid. The thiol side chain in cysteine often participates in enzymatic reactions, serving as a nucleophile.

Amino acids that find in collagen:

Glycine	It is not optically active. It is the smallest amino acid, rotates easily, adds flexibility to the protein chain. As too much flexibility is usually not desired, as a structural component it is less common than alanine.
Proline	Can disrupt protein folding structures like α helix or β sheet, forcing the desired kink in the protein chain. Common in collagen, where it often undergoes a post-translational modification to hydroxyproline.
Alanine	Behaves fairly neutrally, and can be located in both hydrophilic regions on the protein outside and the hydrophobic areas inside.
Hydroxyproline	A common non-proteinogenic amino acid. It is produced by hydroxylation of the amino acid proline by the enzyme prolyl hydroxylase following protein synthesis. Although it is not directly incorporated into proteins, hydroxyproline comprises roughly 4% of all amino acids found in animal tissue, more than seven amino acids which are directly incorporated. Hydroxyproline and proline play key roles for collagen stability. They permit the sharp twisting of the collagen helix.
Hydroxylysine	It arises from a post-translational hydroxy modification of lysine. It is most widely known as a component of collagen.

Smoking Point & Olive Oil

Smoking point is the temperature at which bluish smoke coming up from the cooking oil or fat. The oil begins to break down to glycerol and free fatty acids. The glycerol is then further broken down to acrolein. It is the presence of the acrolein that causes the smoke to be extremely irritating to the eyes and throat. Considerably above the temperature of the smoke point is the flash point, the point at which the vapors from the oil can first ignite when mixed with air.

The smoke point of an oil does tend to increase as free fatty acid decreases and degree of refinement increases. Heating oil produces free fatty acid and as heating time increases, more free fatty acids are produced, thereby decreasing smoke point. The smoke point also marks the beginning of both flavour and nutritional degradation. Therefore, it is a key consideration when selecting a fat for frying.

Oil	Quality	Smoking Point
芥花籽油 Canola (rapeseed) oil	High Oleic	246°C
橄欖油 Olive oil	Extra light	242°C
橄欖油 Olive oil	油渣 Pomace	238°C
花生油 Peanut oil	Refined	232°C
玉米油 Corn oil	Refined	232°C
葵花油 Sunflower oil	Refined	227°C
葡萄籽油 Grapeseed oil		216°C
Olive oil, low acidity	Extra virgin	207°C
芥花籽油 Canola oil	Refined	204°C
橄欖油 Olive oil	Virgin	199°C
橄欖油 Olive oil	Extra virgin	191°C
豬油 Lard		188°C
玉米油 Corn oil	Unrefined	178°C
芝麻油 Sesame oil	Unrefined	177°C
花生油 Peanut oil	Unrefined	160°C
葵花油 Sunflower oil	High Oleic	160°C
奶油 Butter		121-149°C
亞麻仁油 Flax seed oil	Unrefined	107°C
葵花油 Sunflower oil	Unrefined	107°C

Olive oil is composed mainly of the mixed triglyceride esters of (monounsaturated) oleic acid (55-83%) and palmitic acid (7.5-20%) and of other fatty acids. Evidence from epidemiological studies also suggests that a higher proportion of monounsaturated fats in the diet is linked with a reduction in the risk of coronary heart disease. Unlike saturated fats, olive oil lowers total cholesterol and LDL levels in the blood. It is also known to lower blood sugar levels and blood pressure.

Olive oil contains a wide variety of valuable antioxidants that are not found in other oils. Hydroxytyrosol (in extra-virgin olive oil) is thought to be the main antioxidant compound in olives. Hydroxytyrosol's oxygen radical absorbance capacity is 40,000 umolTE/g, which is ten times higher than that of green tea, and two times higher than that of CoQ10. Epidemiological studies suggest that olive oil has a protective effect against certain malignant tumours in the breast, prostate, endometrium and digestive tract. Research has revealed that the type rather than the quantity of fat seems to have more implications for cancer incidence.

Olive oil contains a group of related natural products, called natural phenols, with potent antioxidant properties that give extra-virgin unprocessed olive oil its bitter and pungent taste and are esters of tyrosol and hydroxytyrosol, including oleocanthal and oleuropein. Olive oil is a source of at least 30 phenolic compounds. Oleocanthal is a tyrosol ester and its chemical structure is related to oleuropein that is also found in olive oil. Oleocanthal is a non-selective inhibitor of cyclooxygenase (COX) similar to classical NSAIDs like ibuprofen. 50g of olive oil per day is thought to have the same effect as 1/10 of the adult ibuprofen dose. It has been suggested that long-term consumption of small quantities of this compound from olive oil may be responsible in part for the low incidence of heart disease associated with a Mediterranean diet.

Another health benefit of olive oil seems to be its property to displace omega-6 fatty acids, while not having any impact on omega-3 fatty acids. This way, olive oil helps to build a more healthy balance between omega-6 fats and omega-3 fats.

Olive Oil - Commercial grades
Olive paste is churned slowly or mixed to allow the microscopic oil droplets to concentrate. The oil is extracted by means of pressure (traditional) or centrifugation. After extraction the remnant solid substance, called pomace, still contains a small quantity of oil.

• Virgin means the oil was produced by the use of physical means and no chemical treatment. The term virgin oil referring to production is different from Virgin Oil on a retail label. Virgin olive oils contain the highest levels of polyphenols, antioxidants that have been linked with better health.
• Cold pressed or Cold extraction means "that the oil was not heated over a certain temperature (usually 27 °C) during processing, thus retaining more nutrients and undergoing less degradation."
• First cold pressed means "that the fruit of the olive was crushed exactly one time. The cold refers to the temperature range of the fruit at the time it is crushed." There is no "second" press of virgin oil, so the term "first press" means only that the oil was produced in a press vs. other possible methods.
• Refined means that the oil has been chemically treated to neutralize strong tastes (characterized as defects) and neutralize the acid content (free fatty acids). 
• Pure, Light and Extra-Light are terms introduced by manufacturers for refined oils. They do not have less calories than Extra-virgin oil as implied by the names.
• Olive pomace oil means oil extracted from the pomace using solvents, mostly hexane, and by heat.

Olive Oil - retail grades in IOC member nations

• Extra-virgin olive oil comes from virgin oil production only, contains no more than 0.8% acidity, and is judged to have a superior taste. It is used on salads, added at the table to soups and stews and for dipping.
• Virgin olive oil comes from virgin oil production only, has an acidity less than 1.5%, and is judged to have a good taste.
• Olive oil is a blend of virgin and refined production oil, of no more than 2% acidity. It commonly lacks a strong flavor.
• Olive pomace oil is refined pomace olive oil often blended with some virgin oil. It has the same fat composition as regular olive oil. 

Rancidity, is the chemical decomposition of fats, oils and other lipids.

• Hydrolytic rancidity occurs when water splits fatty acid chains away from the glycerol backbone in triglycerides (fats). More fatty acids are freed from the glycerides, increasing the level of free acidity. 
• Oxidative rancidity is associated with the degradation by oxygen in the air. Oxidation primarily occurs with unsaturated fats.Via a free radical process, the double bonds of an unsaturated fatty acid can undergo cleavage, releasing volatile aldehydes and ketones. This process can be suppressed by the exclusion of oxygen or by the addition of antioxidants. 
• Microbial rancidity refers to a process in which microorganisms use their enzymes such as lipases to break down fat. 

Olive Oil - Culinary use

• Extra virgin olive oil is mostly used as a salad dressing. It is also used with foods to be eaten cold. The higher the temperature to which the olive oil is heated, the higher the risk of compromising its taste.
• Choosing a cold-pressed olive oil can be similar to selecting a wine. The flavour of these oils varies considerably and a particular oil may be more suited for a particular dish.
• Refined olive oils are perfectly suited for deep frying foods and should be replaced after several uses.
•  In time, oils deteriorate and become stale. One-year old oil may be still pleasant to the taste, but it is surely less fragrant than fresh oil. After the first year, olive oil should be used for cooking, not for foods to be eaten cold, like salads.

風寒濕虛

風
中醫稱風是「百病之長」。風是寒、濕、燥、熱侵體的先導，是導致患病的主要因素。在自然界風是一種無形的流動的氣體。靜止、平衡的狀態下不會起風，只有在失衡、冷熱不均的條件下才會形成風。所有當我們的身體內部臟器與臟器之間、經絡與臟器之間、經絡與經絡之間出現了冷熱不均，失衡不和諧的時候，寒、濕、燥、熱就會在風的引導下顯現出各種不同的病症。

與人體內的風有關的疾病有很多種，有「善行、善變」的風疹、蕁麻疹，有「風盛則動」的眩暈、震顫、頭頸僵痛、口眼歪斜以及四肢的抽搐、多動，還有容易向上、向外發散的鼻塞流涕、咽癢咳嗽等。

寒
寒為陰，熱為陽。具有陰冷、凝結、阻滯的特性。當寒侵入體後，血液就失去了陽氣的溫煦，就會運行不暢、淤堵不通。寒還有收縮、閉塞的作用。遇寒後筋脈縮緊，四肢屈伸不利。汗毛孔遇寒關閉、堵塞，不易出汗。

不通則痛，疼痛是因寒致病的重要特徵，不論是四肢的關節疼痛還是心痛、胃痛、腹痛、頭痛等，都與寒有直接的關係。寒用熱除，熱是治療一切寒症的法寶，可以在飲食中吃溫熱、辛辣的食物祛寒；可以多穿衣服保暖祛寒；可以用各種物理方法如熱敷、理療、艾燻等對局部加熱祛寒。

• 面色發白、發青、發暗、發黑代表體內可能有寒。顏色越是發暗，就代表寒濕越重。
• 口臭時舌苔發白，代表體內有寒。
• 咳嗽時痰是稀白的，代表體內有寒。
• 流清鼻涕，代表體內有寒。
• 流出的汗是涼汗，代表體內有寒。
• 長濕疹、牛皮癬、白癜風，代表體內有寒。

濕
濕是一種有水分子存在於物體中的表現，反之為乾。當我們的身體內腎氣不足，體溫偏低時，血液循環的速度就會變慢，飲食中的水分以及潮濕環境侵入人體內的水分就不能很快被人體利用，沉重、向下的特性就顯露出來，如四肢酸重、胸悶、胃腹脹悶、大便不成形、嚴重的腹瀉、小便不順暢、小便的量減少，以及下肢水腫、濕疹、婦女白帶多、濁都屬於這種情況。

• 面色發白、發青、發暗、發黑代表體內可能有寒。顏色越是發暗，就代表寒濕越重。
• 舌苔發白，代表體內有寒濕。
• 四肢關節疼痛、頸肩酸痛、肩周炎、腰酸背痛等症狀，代表體內有寒濕。疼痛的部位越多，時間越長，代表體內寒濕越重。

虛
身體虛就是身體素質差，正氣不足，疲勞乏力，各臟器功能低下。虛和實是相對的，身體實就是身體素質好，正氣足，精力充沛，各個臟器功能正常。血少、血稀時出現的就是虛弱的各種病狀。中醫通過察看人的面色、皮膚、毛髮等外在特徵，探摸肢體末端的溫度，觀察眼、耳、鼻、口以及各臟器的功能反應等方式來判斷體內血液總量是否充足，臟器是否「氣血足」。另外，下面這幾種現象也會讓身體虛弱：

• 過度的按摩、刮痧，會讓身體鬆散、沒勁。
• 過度的運動會讓身體疲乏，消耗過多而導致虛弱。
• 過度的性生活，會很快讓身體空虛、軟弱。
• 吃瀉藥及清熱、寒涼的食物引起腹瀉、尿多，會讓身體虛弱。
• 過度活血(如泡熱水澡、蒸氣浴等)，會使流向皮膚的血液過多，內臟空虛，身體會明顯感覺疲乏。

虛火
中醫將「火」分為實火和虛火，夏天天氣炎熱引起身體燥熱，吃了上火的食物後口舌生瘡、大便乾結是實火，虛火是由寒引起的。實火的治療是用清熱、降火的瀉法，虛火則是用補法。虛火用實火醫，就使得寒上加寒、虛上加虛，越治火越大。

身體內的寒重造成的直接後果就是傷腎，引起腎陽不足、腎氣虛，造成各臟器功能下降，血液虧虛。腎在五行中屬水，水是灌溉、滋潤全身的，當人體內這個水不足時，身體會乾燥。臟器如果缺少了水的滋潤，就易摩擦生熱。最典型的是肝臟，肝臟屬木，最需要水的澆灌，而一旦缺水，肝燥、肝火就非常明顯。同時身體內寒濕重還極易造成經絡不通，散熱困難，容易感到悶熱、燥熱。現代人普遍貪涼，大量吃著寒涼的食物還覺得燥熱，是腎氣虛弱、經絡不通造成的。燥熱則會進一步貪涼，就更加重了血管、經絡的收縮、淤堵，這樣就進入了惡性循環的狀態。

頭面部也是最容易上火的部位。腎主骨髓、主腦，腎陽不足、腎氣虛時髓海就空虛，遠端的頭部首先出現缺血，也就是「缺水」了，自然反應的就是乾燥的症狀，如眼睛乾澀、口乾、舌燥、咽乾、咽痛等。再加上口腔、咽喉、鼻腔、耳朵又是暴露在空氣中的器官，較容易受細菌的感染，當頸部及頭面部的血液供應減少後，這裡的免疫功能就下降，會出現各種不適，這樣患鼻炎、咽炎、牙周炎、扁桃體炎、中耳炎的概率就會增加。又由於沒有充足的血液供應，各種炎症很難治癒，就會反反復復發作，成為各種長期不癒的慢性病，如慢性鼻炎、慢性咽炎、慢性牙周炎、慢性中耳炎等。

要去掉身體內的寒濕，要運動，要補腎，用溫熱食物。若虛火大加溫熱就會出現「虛不受補」，所有以要將先虛火打掉，後再用食療補血、補腎。運動使血液循環加快，體溫升高，出汗在排出寒濕的同時也能帶走了虛火、疏通經絡。

中醫辨證學與體質分類

中醫辯證通常指的是整體辨證，是中醫臨床最具特色的一環。辨證是通過診法所獲得的整體各種信息資料，運用臟腑、經絡、病因、病機等基礎理論進行綜合分析，從而辨別病變位置與性質以及正邪情況，作出高度概括。

八綱辨證，是分析疾病共性的辨證方法。八綱指陰、陽、表、裏、寒、熱、虛、實八個辨證綱領。其中，陰陽是總綱，它可以概括其他六綱，即陰證包括裏、虛、寒證，陽證包括表、實、熱證。 醫生運用八綱辨證，對四診，即“望聞問切”，所獲得的所有病情資料，進行分析綜合，從而獲得關于病位、病性、正邪鬥爭盛衰和病證類別的總印象的辨證方法。其中：

• 陰陽辨證，觀察病類；
• 表裏辨證，觀察病位；
• 寒熱辨證，觀察病性。

八證是相互關係，例如：表陽且熱而裏卻是陰且寒，而同屬虛證裡，又再細分為氣虛與血虛，並且有兼證，如肺脾氣虛和肺腎氣虛等，若要深入辨證，其實還分真虛與假虛，這樣的辯證法非一般熟諳中醫者所能辨識。

2009年4月9日，《中醫體質分類與判定》標准正式發布，該標准是我國第一部指導和規範中醫體質研究及應用的文件，旨在爲體質辨識及與中醫體質相關疾病的防治、養生保健、健康管理提供依據，使體質分類科學化、規範化。這套標準將體質分為九個類型：

1. 平和質
2. 氣虛質
3. 陽虛質
4. 陰虛質
5. 痰濕質
6. 濕熱質
7. 血瘀質
8. 氣鬱質
9. 特稟質

經絡與時辰、五行 - 作息有時

經絡與時辰
21:00 - 23:00 亥時 三焦經

亥時三焦通百脈，此時三焦經最旺。如在亥時深度睡眠，百脈可休息生息，對身板十分有益，百歲老人有個共同獨特之處，即亥時困覺。

23:00 - 01:00 子時 膽經

此時膽經最旺，膽汁需要新陳代謝，人在子時前入睡，膽方能完成代謝。"膽有多清，腦有多清"，凡在子時前入睡者，晨醒後腦筋清楚，精神和面紅潤。膽經這時要上床困覺，利于骨髓造血。

01:00 - 03:00 丑時 肝經

此時肝經最旺，"人臥則血歸肝"。若丑時未入睡的話，肝還在輸出能量，就無法完成新陳代謝。所以丑時前未入睡者，臉色青灰，情志倦怠而焦躁，易生肝病。此外，肝主疏泄，過度壓抑至氣血不暢、阻塞易生腫瘤，情志舒暢為養肝第一要件。

03:00 - 05:00 寅時 肺經

此時肺經最旺，"肺朝百脈"，肝于丑時推陳出新，將新穎血液提供給肺，經由肺送往全身。肺經呼吸運作最佳的時候，而此時脈搏最弱。

05:00 - 07:00 卯時 大腸經

此時大腸經最旺，"肺與大腸相表裏"，肺將充足的新穎血液布滿全身，緊接著促進大腸經步入興奮狀況，完成對食品中水分與營養的吸收，排出渣滓。這時起床，大腸蠕動旺盛，適合吃早餐。

07:00 - 09:00 辰時 胃經

此時胃經最旺，此時吃早餐最容易消化。如果胃火過盛，表現爲嘴唇幹，重則豁嘴或生瘡。

09:00 - 11:00 巳时 脾經

此時脾經最旺，"脾開竅于口，其華在唇"。脾的功效好，表現爲消化吸收好，血的質量好，嘴唇紅潤。唇白標志血氣不足，唇暗，唇紫標志寒入脾經。

11:00 - 13:00 中午 心經

此時心經最旺，" 心主神明，開竅于舌，其華在表"。人在中午能睡片刻，對于養心大有益，可以使乃至晚上精神抖擻 。

13:00 - 15:00 未時 小腸經

此時小腸經最旺。未時是小腸最活躍的時候，故午餐應在下午1時前吃。

15:00 - 17:00 申時 膀胱經

此時膀胱經最旺。若膀胱有熱，可致膀胱咳，咳而夜尿證。膀胱經膀胱最活躍的時候，適當多喝水。

17:00 - 19:00 酉時 腎經

此時腎經最旺，"腎藏于生殖之精，腎爲天賦和五藏六腑之精之根"。人體經過申時泄火排毒，腎在酉時步入儲藏精華的階段。腎經適合休息 。

19:00 - 21:00 戌時 心包經
此時心包經最旺，心包經戌時行旺，可斷根心周圍外邪，使心臟處于無缺狀況。心包經旺時宜隨便走走，這時心腦顱神經器官系統最活躍。

五臟與五行
五行：木 火 土 金 水
五臟：肝 心 脾 肺 腎
五體：筋 脈 肉 皮 骨
五華：爪 面 唇 毛 發
五志：怒 喜 思 悲 恐
五液：淚 汗 涎 涕 唾
五味：酸 苦 甘 辛 鹹
五色：青 赤 黃 白 黑
五方：東 南 中 西 北
五季：春 夏 長夏 秋 冬
五氣：風 暑 濕 燥 寒
五化：生 長 化 收 藏
五音：角 徵 宮 商 羽
五官：目 舌 口 鼻 耳

足厥陰肝經

經絡

經絡是運行氣血、聯系臟腑和體表及全身各部的通道，是人體功能的調控系統。

《靈樞·脈度》：“經脈爲裏，支而橫者爲絡，絡之別者爲孫。

“經”是“縱絲”，有路徑的意思，存在于機體內部，貫穿上下，溝通內外；
“絡”是“網絡”，是主路分出的輔路，存在于機體表面，縱橫交錯，遍布全身。

• 經脈可分爲正經和奇經兩類。正經有十二，即手足三陰經和手足三陽經，合稱“十二經脈”，是氣血運行的主要通道。《靈樞·海論》：“夫十二經脈者，內屬于腑臟，外絡于肢節。” 氣血通過經脈即可內至臟腑，外達肌表，營運全身。
• 奇經有八條，即督、任、沖、帶、陰跷、陽跷、陰維、陽維，合稱“奇經八脈”，有統率、聯絡和調節十二經脈的作用。它們與十二正經不同，既不直屬臟腑，又無表裏配合關系，其循行別道奇行，故稱奇經。其功能有：溝通十二經脈之間的聯系；對十二經氣血有蓄積滲灌等調節作用。
• 十二經別，是十二經脈在胸腹及頭部的內行支脈。從十二經脈的四肢部位別出，陽經經別合于本經，陰經經別合于相表裏的陽經。主要是加強十二經脈中相爲表裏的兩經之間的聯系，還由于它通達某些正經未循行到的器官與形體部位，因而能補正經之不足。
• 經筋、皮部聯系肢體筋肉皮膚；浮絡和孫絡聯系人體各細微部分。十二經筋均起始于四肢末端，結聚于關節、骨骼部，走向軀幹頭面。行于體表，不入內臟。

十二經脈在體表的循行分布規律是：

• 凡屬六臟（心、肝、脾、肺、腎和心包）的陰經分布于四肢的內側和胸腹部，其中分布于上肢內側的爲手三陰經，分布于下肢內側的爲足三陰經。手足三陰經的排列順序是：“太陰”在前，“厥陰”在中，“少陰”在後（內踝上八寸以下爲“厥陰”在前，“太陰”在中，“少陰”在後）。
• 凡屬六腑（膽、胃、大腸、小腸、膀胱和三焦）的陽經，多循行于四肢外側、頭面和腰背部，其中分布于上肢外側的爲手三陽經，分布于下肢外側的爲足三陽經。手足三陽經的排列順序是：“陽明”在前，“少陽”居中，“太陽”在後。
• 表裏關系是：手足三陰、三陽，通過經別和別絡互相溝通，組成六對“表裏相合”的關系。其中，足太陽與足少陰爲表裏，足少陽與足厥陰爲表裏，足陽明與足太陰爲表裏。手太陽與手少陰爲表裏，手少陽與手厥陰爲表裏，手陽明與手太陰爲表裏。

氣血通過經脈即可內至臟腑，外達肌表，營運全身。其流注次序是：

手太陰肺經→手陽明大腸經→足陽明胃經→足太陰脾經→手少陰心經→手太陽小腸經

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足厥陰肝經←足少陽膽經←手少陽三焦經←手厥陰心包經←足少陰腎經←足太陽膀胱經

1. 手太陰肺經主要分布在上肢內側前緣。
2. 手陽明大腸經主要分布在上肢外側前緣。
3. 足陽明胃經主要分布在頭面、胸腹第二側線及下肢外側前緣。
4. 足太陰脾經主要分布在胸腹任脈旁開第二側線及下肢內側前緣。
5. 手少陰心經主要分布在上肢內側後緣。
6. 手太陽小腸經主要分布在上肢外側後緣。
7. 足太陽膀胱經主要分布在腰背第一、二側線及下肢外側後緣。
8. 足少陰腎經主要分布在下肢內側後緣及胸腹第一側線。
9. 手厥陰心包經主要分布在上肢內側中間。
10. 手少陽三焦經主要分布在上肢外側中間。
11. 足少陽膽經主要分布在下肢的外側中間。
12. 足厥陰肝經主要分布在下肢內側的中間。

足少陽膽經

五藏六腑

五藏 - 心肝脾肺腎
中醫五藏不局限於解剖概念。主要生理功能是生化和儲藏精、氣、血、津液和神，特點是藏精氣而不瀉，滿而不能實。

• 心與小腸、脈、面、舌等構成心系統。心主血脈是全身血脈的總樞紐，心通過血脈將氣血運送于周身；心又主神志，是精神、意識和思維活動的中心。血脈指血液和脈管以及血液在脈管中的運行。心主血脈是指心氣推動和調節血脈循行於脈中，周流全身的作用，發揮營養和滋潤作用。氣血指人體內氣和血。氣被視為人體的生長發育、藏腑運轉、體內物質運輸、傳遞和排泄的基本推動能源。
• 肝與膽、目、筋、爪等構成肝系統。肝主疏泄，能調節人的情志活動，協助脾胃消化。肝又藏血，有貯藏血液、調節血量的作用。
• 脾與胃、肉、唇、口等構成脾系統。主運化，促進飲食物的消化、吸收和營養物的輸布，爲氣血生化之源，故有後天之本之稱；脾又統血，能統攝血液不致溢出于經脈之外。
• 肺與大腸、皮、毛、鼻等構成肺系統。肺主氣，司呼吸，是人體氣體交換的場所，又能宣發衛氣和津液于全身以溫潤肌腠皮膚。津液是機體一切正常水液的總稱。存在於氣血之中，散布於皮膚、肌肉、孔竅並滲入血脈，清而稀薄，流動性較大，具有濕潤作用的為津；灌注於關節、藏腑、腦髓、孔竅等組織，稠而濃濁，流動性較小，具有滋養作用的為液。
• 腎與膀胱、骨髓、腦、髮、耳等構成腎系統。腎藏精，與人體生長發育和生殖能力密切相關，故有先天之本之稱；腎又主水，在調節人體水液代謝方面起著重要作用。在中醫學中，氣與精雖同屬於生命物質系統範疇，但精是除氣之外的精微物質的總稱，是一個極其重要的具有多層含義的概念。一般而言，精的含義有廣義和狹義之分。先天(狹義)之精又稱生殖之精，稟受於父母，與人的生育繁殖有關。後天(廣義)之精又稱藏腑之精，由藏腑化生水谷精微而成，主人體生長發育。水谷精微泛指人體消化吸收的的營養物質，是人體生命活動的維持和精、氣、血、津的化生的主要物質基礎。

六腑 - 膽、胃、大腸、小腸、三焦、膀胱

腑，古稱  府，有庫府的意思。六腑的主要生理功能是受納、腐熟水谷，泌別清濁，傳化精華，將糟粕排出體外，而不使之存留。所以六腑以和降通暢為順。生理特點是傳化物而不藏，實而不能滿。在病理變化上相互影響，一腑有病，可影響他腑而致病。

生理功能上密切配合，共同完成飲食物的消化、吸收、轉輸和排泄：

飲食物入胃，經胃的腐熟，下移小腸，進一步消化，並泌別清濁，吸收其中的精微物質，大腸接受小腸中的食物殘渣，吸收其中的水分，其余的糟粕經燥化與傳導作用，排出體外，成為糞，膀胱貯存尿液及排泄尿液。在飲食物消化、吸收過程中，膽排泄膽汁入小腸，以助消化。三焦不但是傳化的通道，更重要的是主持諸氣，推動了傳化功能的正常進行。

藏腑概念與解剖學的藏器概念不同，中醫學將三焦單獨列為一腑，並非僅僅是根據解剖，更重要的是根據生理病理現像的聯系而建立起來的一個功能系統。

三焦的功能實際上是五藏六腑全部功能的總體 :
(經絡是運行氣血、聯系藏腑和體表及全身各部的通道，是人體功能的調控系統)

膈以上為上焦，包括心與肺；

橫膈以下到臍為中焦，包括脾與胃；

臍以下至二陰為下焦，包括肝、腎、大小腸、膀胱、女子胞等。其中肝，按其部位來說，應劃歸中焦，但因它與腎關系密切，故將肝和腎一同劃歸下焦。

煲湯的科學

用來煲老火湯的肉類一般都含有豐富蛋白質, 琥珀酸(succinate acid), 氨基酸(amino acid), 核苷酸(nucleotides)等. 當中能溶解於水的含氮浸淫出物,包括肌凝蛋白質(myosins), 肌酸(creatine) , 肌酐(creatinine), 尿素(Urea or carbamide)和氨基酸等非蛋白質含氮物,它們就是湯鮮味的主要來源.

常說用料要新鮮. 以科學角度來講,湯料的鮮是指魚和离畜殺死後3-5小時,此時肉中的各種酶使蛋白質,脂肪等分解為氨基酸,脂肪酸(fatty acid)等人體易于吸收的物質,不但營養豐富,味道也最好.

煲湯要訣:武火燒沸去沫,文火慢煨至湯餘四份三至一半.

水是湯料傳熱的介質,同時也是鮮味的溶劑. 所以水溫的變化,用量的多少,對湯的風味有直接的影響. 一般來說用水量是主要湯料重量的3-4倍,而水溫則長時間維持在攝氏85-100度.開始時湯料與冷水(魚要先煎, 水開後才放)共同受熱,不先放鹽(鹽具滲透作用,令使原料中水分排出,蛋白質凝固,鮮味減少),既不直接用沸水煨湯,也不中途加冷水,以使營養物緩慢溢出,這樣湯色才清澈.

• 草雞肉的蛋白質和脂肪含量在加熱0.5小時後逐漸升高, 到0.75小時脂肪值最高,1.5小時蛋白質值最高.
• 蹄膀的蛋白質和脂肪含量在加熱1小時後明顯增高,之後逐漸降低.
• 鴨肉的蛋白質在加熱1小時後含量基本不變,脂肪含量在0.75小時後最高.

因為長期加熱會破壞湯料中的維生素(攝氏60-80度),所以加熱1.5小時左右可以達致比較理想的營養峯值.若在於湯中加蔬菜應隨放隨吃,以減少維生素C的破壞.

USB Charging

USB 1.x/2.0 standard pinout

Pin 1 : VBUS (red) : +5V

Pin 2 : D- (white) : data -

Pin 3 : D+ (green) : data +

Pin 4: GND (black) : ground

The USB Battery Charging Specification of 2007 defines new types of USB ports, e.g., charging ports. As compared to standard downstream ports, where a portable device can only draw more than 100mA current after digital negotiation with the host or hub, charging ports can supply currents above 0.5A without digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drop its output voltage if the portable device attempts to draw more than the rated current. There is no upper limit for the rated current of a charging downstream port, as long as the connector can handle the current (standard USB 2.0 A-connectors are rated at 1.5 A). The charger port may shut down if the load is too high. The Battery Charging Specification 1.2 of 2010 makes clear, that there are safety limits to the rated current at 5 A coming from USB 2.0.

Charging ports exist in two flavors: charging downstream ports (CDP), supporting data transfers as well, and dedicated charging ports (DCP), without data support. With charging downstream ports, current passing through the thin ground wire may interfere with high-speed data signals. Therefore, current draw may not exceed 900 mA during high-speed data transfer. On a dedicated charging port, the D+ and D- pins are shorted. Before the battery charging specification was defined, there was no standardized way for the portable device to inquire how much current was available. For example, Apple's iPod and iPhone chargers indicate the available current by voltages on the D- and D+ lines. When D+ = D- = 2V, the device may pull up to 500 mA. When D+ = 2.0 V and D- = 2.8 V, the device may pull up to 1000 mA of current.

USB 2.0

One unit load is 100 mA.

A device may draw a maximum of 5 unit loads (500 mA) from a port.

A low-power device draws at most 1 unit load, with minimum operating voltage of 4.4 V.

USB 3.0

One unit load is 150 mA.

A device may draw a maximum of 5 unit loads (900 mA) from a port.

A low-power device draws at most 1 unit load, with minimum operating voltage of 4 V.

Lithium-ion Polymer Battery
LiPo batteries are usually composed of several identical secondary cells in parallel to increase the discharge current capability. The voltage (nominal cell voltage is 3.7V) of a Li-poly cell varies from about 2.7 V (discharged) to about 4.23 V (fully charged), and Li-poly cells have to be protected from overcharge by limiting the applied voltage to no more than 4.235 V per cell used in a series combination.

Example, a circuit produces +5V and +3.3V to power portable devices It allows the port to maintain communications while supplying power, e.g., to charge a Li+ battery.

IC1 - MAX1811 (Li+ battery charger)

• Pulling SELI terminal low sets the charging current to 100mA for low-power USB ports, and pulling high sets 500mA for high-power ports. 
• Pulling SELV high or low configures the chip for charging a 4.2V or 4.1V Li+ battery. To protect the battery, IC1's final charging voltage exhibits 0.5% accuracy. 
• /CHG light up an LED during charging.
• MAX1811 has preconditioning that soft-starts a near-dead battery cell before charging. It is available in 1.4W thermally enhanced 8-pin SO package.
• Battery voltages less than 2.5V activate a 43mA preconditioning mode (/CHG = high impedance). Normal charging resumes when the battery voltage exceeds 2.5V.
• At high input voltages (5.5V) and low cell voltages (2.7V), the MAX1811’s thermal loop may limit the charge current until the cell voltage rises. 

IC2 - step-up DC-DC converter, boosts VBATT to 5V and delivers up to 450mA. The low-battery detection circuitry and true shutdown (limits battery current to less than 2μA) capability protects the Li+ battery.

• The low-battery trip point is set by an external resistive divider between VBATT and GND, connected to LBI. Connecting the low-battery output (LBO) to shutdown (SHDN) causes IC2 to disconnect its load in response to a low battery voltage.
• The n-channel FET at LBO eliminates on/off oscillation (caused by internal source impedance of a Li+ battery) by adding hysteresis to the low-battery detection circuitry. When VBATT goes below 2.9V, LBO opens and allows SHDN to be pulled high, turning on the FET. With the FET turned on, the parallel combination of 1.3MΩ and 249kΩ eliminates oscillation by setting the battery turn-on voltage to 3.3V.

IC3 - step-down converter, bucks 5V to 3.3V, and delivers up to 250mA.

MAX1811 Functional Diagram

About Charge and Discharge

The available capacity of a battery depends upon the rate at which it is discharged.  The capacity printed on a battery is usually the product of 20 hours multiplied by the constant current that a new battery can supply for 20 hours at 68 F° (20 C°), down to a specified terminal voltage per cell. For example, 2000mAh = 100mA x 20h.

Discharge
Peukert's law describes the (approximated) relationship between current, discharge time, and capacity for a lead acid battery: t = Q1 / I^k, where
t = amount of time (in hours) that a battery can sustain
Q1 = capacity at a one-ampere discharge rate, which must be expressed in A·h
I =  current drawn from battery (A)
k = 1.2-1.6 for flooded batteries, 1.1-1.3 for  lead–acid battery
(For low values of I internal self-discharge must be included.)

High-drain loads such as digital cameras can result in delivery of less total energy, as happens with alkaline batteries. For example, a 2000 mA·h battery would not sustain a current of 1 A for a full two hours as its stated capacity implies.

Example, SANYO Eneloop rechargeable battery

Batteries
Degradation usually occurs because electrolyte migrates away from the electrodes or because active material falls off the electrodes.

NiCd batteries suffer the drawback that they should be fully discharged before recharge. Without full discharge, crystals may build up on the electrodes, thus decreasing the active surface area and increasing internal resistance. This decreases battery capacity and causes the "memory effect". These electrode crystals can also penetrate the electrolyte separator, thereby causing shorts. NiMH, although similar in chemistry, does not suffer from memory effect to quite this extent.

The chemistry that eneloop batteries use is Nickel Metal Hydride (NiMH). A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell.

NiMH use positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd, but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. The "metal" M is actually an intermetallic compound. Many different compounds have been developed for this application, but those in current use fall into two classes. The most common is AB₅, where A is a rare earth mixture of lanthanum, cerium, neodymium, praseodymium and B is nickel, cobalt, manganese, and/or aluminium. Any of these compounds serve the same role, reversibly forming a mixture of metal hydride compounds.

Lithium polymer batteries (abbreviate LiPo) devolved from lithium-ion batteries. The primary difference is that the lithium-salt electrolyte is not held in an organic solvent but in a solid polymer composite such as polyethyleneoxide or polyacrylonitrile. The battery is constructed as:

• Positive electrode: LiCoO₂ or LiMn₂O₄
• Separator: Conducting polymer electrolyte (e.g., polyethyleneoxide, PEO)
• Negative electrode: Li or carbon-Li intercalation compound

Charge
NiMH Trickle Charge
A NiCd charger should not be used as an automatic substitute for a NiMH charger. The simplest way to safely charge a NiMH cell is with a fixed low current, with or without a timer. Most manufacturers claim that overcharging is safe at very low currents, below 0.1 C (where C is the current equivalent to the capacity of the battery divided by one hour). The Panasonic (SANYO) NiMH charging manual warns that overcharging for long enough can damage a battery and suggests limiting the total charging time to 10 to 20 hours. Panasonic's handbook also recommends that NiMH batteries on standby are kept charged by a lower duty cycle approach, where a pulse of a higher current is used whenever the battery's voltage drops below 1.3 V. This can extend battery life and use less energy.

ΔV charging method
When the battery is fully charged the voltage across its terminals drops slightly. The charger can detect this and stop charging. This method is often used with NiCd cells which have a large drop in voltage at full charge but the voltage drop is much less pronounced for NiMH and can be non-existent at low charge rates, which can make the approach unreliable. Therefore, with this method, a much higher charging rate can be used than with a trickle charge, up to 1 C. At this charge rate, ΔV is approximately 5–10mV per cell.

Lithium Ion Charging
The chemistry is basically the same for the two types of batteries, so charging methods for lithium polymer batteries can be used for lithium-ion batteries.

Trickle charging is not acceptable for lithium batteries. The Li-ion chemistry cannot accept an overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous.

In order to charge the Li ion battery safely, the basic algorithm is:

• charge at constant current (0.2 C to 0.7 C depending on manufacturer) until the battery reaches 4.2 Vpc (volts per cell), 
• hold the voltage at 4.2 volts until the charge current has dropped to 10% of the initial charge rate. The termination condition is the drop in charge current to 10% (the top charging voltage and the termination current varies slightly with the manufacturer).

Notes:

• The charge cannot be terminated on a voltage. The capacity reached at 4.2 Volts per cell is only 40 to 70% of full capacity unless charged very slowly. For this reason you need to continue to charge until the current drops, and to terminate on the low current.
• Most dedicated lithium polymer chargers use a charge timer for safety; this cuts the charge after a predefined time (typically 90 minutes).

Example, Apple's lithium-ion polymer batteries page
"Most lithium-ion polymer batteries use a fast charge to charge your device to 80% battery capacity, then switch to trickle charging. That’s about two hours of charge time to power an iPod to 80% capacity, then another two hours to fully charge it, if you are not using the iPod while charging. "