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揭秘牛奶背后的真相!

放大字體  縮小字體 發布日期:2011-02-22  來源:譯言網  瀏覽次數:2813
核心提示:本文作者在查閱大量科學文獻基礎上,分析了有關牛奶營養健康的是是非非,我們到底需不需要牛奶?看完本文,相信每個人都自會有答案了。


Milk is as pure white as fresh fallen snow and as familiar as a mother's warm touch.  Common sense once led me to believe that if a single food, milk, could sustain a baby as the sole source of nutrients, then it must be “nature's most perfect food.”  Milk builds strong bones – I have learned over and over again – and since the hardest parts of my body are made mostly of calcium, this liquid food must be essential for my strength and stability.  Milk is for life, because they tell me I never outgrow my need for milk.  All these “facts” were the “truth” until I took the trouble to think a little about the subject on my own and to look into the scientific research.  May I share with you some of my surprising discoveries?

Mother's Milk Can Be a Perfect Food
Within the same species – like cow for calf, cat for kitten, mare for foal – mother's milk can be the perfect food for the very young – not, after weaning, for older offspring, and certainly, not for the fully-grown.  All mammals nourish their developing young with this ready-to-eat liquid synthesized by specialized sweat glands, called the mammary glands.  This life-giving fluid contains the nutrients, antibodies and hormones that optimize the chances for growth and survival of the infant.

How essential is mother's milk? Human infants deprived of the advantages of human breast milk have:1
1、Two to four times the risk of sudden infant death syndrome (crib death),
2.  More than 60 times the risk of pneumonia in the first three months of life,2
3.  Ten times the risk of hospitalization during their first year
4.Reduced intelligence as measured by IQ score
5. Behavioral and speech difficulties
 6.An increased chance of suffering from infections, asthma, eczema, type I diabetes, and cancer (lymphoma and leukemia) in early life 
7.A greater risk of heart disease, obesity, diabetes, multiple sclerosis, food allergies, ulcerative colitis, and Crohn’s disease later in life

 
No one argues against the fact that human breast milk is nature’s most perfect food for human babies.  There is also no satisfactory substitute; therefore, every effort should be made to have every infant breast-fed exclusively for six months; and then, with the addition of healthy solid food choices, partially breast-fed until the age of two.  (More information on this is found in The McDougall Program for Women book).

Mother's Milk is Species Specific
The nutritional needs of very young animals are met by the unique qualities of the milk of that particular species.  The composition of this infant food has evolved over millions of years to be ideally suited for that animal.  Let me explain in terms of one essential nutrient: protein.

The amount of protein in the milk of an animal varies to meet the growth demands of the very young – the faster an animal grows the greater the protein needs.

Comparisons of Milk of Different Species3
Animal
Protein*
Growth Rate(days)**
Human
1.2
180
Horse
2.4
60
Cow
3.3
47
Goat
4.1
19
Dog
7.1
8
Cat
9.5
7
Rat
11.8
4.5
* Grams per 100 milliliters (in terms of % of calories, cow's milk has four times more protein than human milk; 21% vs. 5%4)
** Time required to double birth weight

In addition to the much higher protein content, consider the other nutrient differences between cow's milk and human:
Nutrient
Human
mg/100 Cal
Cow
mg/100 Cal
Calcium
45
194
Phosphorus
18
152
Sodium
23
80
Potassium
72
246

Not surprisingly, since a calf doubles its birth weight nearly four times faster than a human infant does, the concentrations of protein and calcium are nearly four times greater.  Rapid growth requires a much higher density of all kinds of nutrients.

Problems of Excess Nutrients
Most people think of health problems in terms of deficiencies of nutrients; this is the reason vitamin and mineral supplements are so popular.  However, I do not see diseases of deficiency in my patients.  For example, I see no vitamin C deficiency (scurvy), B1 deficiency (Beriberi), or protein deficiency in my patients.  Rather, I see diseases of excess – such as excess dietary fat (obesity), cholesterol (heart disease), and salt (hypertension).  Therefore, feeding an overly-concentrated food such as cow's milk to people (infants, children, and adults) promotes diseases of excess.  (Some of you are still thinking cow's milk corrects calcium deficiency in people, preventing osteoporosis.  Be patient, in a moment I will show you this is not true.)

Replacing human breast milk with cow's milk was once tried in the mid-1800s in the United States for emergency situations (such as when a mother died in childbirth).  The result was a quick death for most of the infants, because the high protein content of the cow's milk forced fluid losses from the infant's kidneys, resulting in dehydration.5 Once this problem was recognized, then infant formulas were developed which added sugar to the cow's milk in order to reduce the protein concentration of the cow's milk and make it more resemble human milk.  Some of you may be old enough to remember making or drinking infant formula made from Carnation evaporated cow's milk and Karo syrup (sugar).6 (This is a very unhealthy formula for infants – do not use this).

Consider the purpose of cow's milk.  This is an ideal food to grow a calf from its 60-pound birthweight to a 600-pound young cow, ready to wean.  This is a high “octane” fuel.  One obvious consequence of people eating “calf food” is rapid fat gain – and dairy products are one of the leading contributors to the epidemic of excess body fat affecting 25% of children and 65% of adults in Western populations.  Matters are made even worse when cow's milk is converted into even more concentrated products, like cheeses.

Cow's milk products have some important nutritional deficiencies.4  They are completely devoid of fiber; and contain insufficient amounts of vitamins, like C and niacin, and minerals, like iron, to meet the human body's needs.

False Promise #1: Milk Builds Strong Bones
If you ask people why they drink milk, they'll tell you it's for the calcium. Milk has lots of calcium and its supporters have "milked" that point for all it's worth. One of your first clues that cow's milk is not ideal for bone health comes from comparison of the calcium content of the two kinds of milk (shown above).  Cow's milk has more than four times the calcium content as human breast milk. If this exaggerated amount of calcium is not required during our greatest time of growth – babies double in weight in six months – then why should a concentration of calcium ideal for calves be required when we stop growing bones as adults?  Without a doubt growing the hefty skeleton of a cow takes much more calcium than growing relatively small human bones.

Billions of people worldwide do not consume milk after weaning and they grow normal adult skeletons.7 For example, Bantu women in Africa consume no dairy products at all, and take in only about 250 to 400 mg of calcium each day through vegetable sources8 (about half the recommended daily intake in the U.S.). These women typically have ten children each and breast-feed each one for about 10 months. Yet despite a diet with no dairy products and the tremendous calcium drain of pregnancy and breast-feeding, osteoporosis is virtually unknown among these women.8 When rural African women migrate to cities or move to Western counties and adopt rich, high-calcium diets, osteoporosis becomes common.9 You will soon understand this is because their new diet becomes very high in animal protein.10

The world picture fails to support benefits claimed by the dairy industry.  Countries that have the highest traditional consumption of dairy products (United States, Sweden, Israel, Finland, and the United Kingdom) also have the highest rates of osteoporosis-related hip fractures.11 Places in the world with a traditionally low intake of dairy - Hong Kong, Singapore, countries in rural Africa - have the lowest incidence of osteoporosis.

If calcium is the key and milk is such a great source, why are there still 10 million Americans with osteoporosis?  Long-standing recommendations to increase calcium intakes have had little or no effect on the prevalence of osteoporosis or fractures in the United States.7

Worldwide, the incidence of osteoporosis correlates directly and strongly with animal protein intake.  The highly acidic nature of animal protein is the major cause of bone loss.10 (You can read more about this at www.drmcdougall.com in the February 2003 McDougall Newsletter in the article, “Fish is not health food.”)

False Promise #2: Research Supports Dairy’s Benefits
In September of 2000, two researchers compiled a review of the 57 studies on dairy products and bone health which had been published in the scientific literature since 1985.  This review was published in the American Journal of Clinical Nutrition.12   Not surprisingly, most of this research was financed by the dairy industry.  The researchers reported that 53 percent of the studies showed no benefit from dairy.  Then they excluded studies with weak evidence or poor techniques, which eliminated more than half of the studies. Of the 21 remaining studies, 57 percent again showed no benefit from dairy, and another 14 percent found that dairy products actually weaken bones. Think about that – this means that 71 percent of the scientifically sound research did not support the bone building benefits of dairy products and some showed actual harm.

Randomized controlled studies compare an experimental group with a control group and are considered the most valid form of scientific research.   Of the seven randomized controlled studies which have been completed on the effects of dairy products on bone health, six were financed by the dairy industry.  Only one looked at the benefits of fluid milk on the health of the women most likely to benefit: postmenopausal women.13 At the conclusion of this study, the women in the experimental group, fed three eight-ounce glasses of skim milk daily for a year, were still losing more calcium from their bodies than they were absorbing (they were in negative calcium balance). Even though they consumed more than 1400 mg of calcium daily they still lost twice as much bone as the women in the control group, who were not getting the supplemental milk.  Yet the industry continues to proclaim its pro-milk message from every rooftop.

False Promise #3: Dairy Foods Make Meeting Calcium Recommendations Easy
Recommended intakes of calcium to prevent osteoporosis are now so high that it is difficult, if not impossible, to make up practical diets that meet these recommendations.7   The National Institutes of Health Consensus Conference and The National Osteoporosis Foundation support a calcium intake of 1,500 milligrams per day for postmenopausal women not taking estrogen, and for adults 65 years or older.  Assuming 300-400 mg of calcium comes from starches, vegetables, fruits, eggs, poultry, fish, and meats,4 then 1,200 mg would have to be obtained from dairy products daily.  An average postmenopausal sedentary woman consumes 1500 calories a day.  The amount of dairy required to meet her recommended calcium needs would be:4

* 6 ounces Cheddar cheese (which is 74% fat).  This would mean that 46% of the calories in her diet must be from cheese; or

* One quart (32 ounces) of whole milk (which is 50% fat) which would mean 40% of her diet is from milk; or
* One quart (32 ounces) of non-fat milk (which is 3% fat) which would mean 23% of her diet would be non-fat milk.

The dairy industry is happy about these grand recommendations, but consuming that much cow's milk product daily would replace too many other more filling (satisfying) and nutritious foods, and be unhealthy.

False Promise #4:  We Require 1500 mg of Calcium a Day
Our requirements for calcium are far less than recommended.   Scientific research demonstrates people need as little as 150 to 200 mg/day, even when pregnant or lactating.14

Consider the great variation in calcium intakes and recommendation:
Minimum Requirement Based on Research
150-200 mg
Calcium Intake for Underdeveloped Countries
300-500 mg
Calcium Intake for Average American
500-600 mg
World Health Organization Recommendation
400-500 mg
USA Food and Nutrition Board
1000- 1300 mg
A National Institutes of Health
1000-1500 mg

Why the large variation in figures for calcium intakes and recommendations?  The simple answer is the amount of calcium in the foods you eat has little effect on the quantity of calcium that is eventually taken into the body and on the health of your bones.15

Your intestine will always absorb sufficient calcium to meet your needs from the foods you eat. On a diet low in calcium, the efficiency of mineral absorption is increased, and the intestine takes in more calcium. On a high-calcium diet, more calcium is left in the intestine to be excreted, unused, in the feces.16  The intestine is so “smart” about calcium that it never fails to meet the body’s needs.  If you look over the last hundred years of scientific and nutritional literature you will find there is no evidence that dietary calcium deficiency occurs in humans, even though most people in the world don't drink milk after weaning – because of custom, lactose intolerance, or simply because milk is not generally available in their part of the world. 7,14, 17-20  This means there is no such disease as “dietary calcium deficiency” – think again if your mind drifts to osteoporosis – remember, populations with the lowest calcium intakes have the strongest bones; the least osteoporosis, worldwide.11

False Promise #5: Milk is the Best Food for Bones
The truth is, milk is not the only source of calcium and it is not the best source of calcium.  Consider that the original source of calcium is the ground.  Calcium, and other minerals, are dissolved in watery solutions and absorbed by the roots of plants.  These minerals are then incorporated in the roots, stems, leaves, flowers, and fruits of the plants.  Humans can get plenty of calcium the same way it gets into cow's milk; from the plant foods they eat.

Inappropriate concern about calcium intake may divert attention and resources from more important nutritional issues. Calcium isn't the only nutrient that affects bone health. Studies have shown that potassium and magnesium may be even more critical in preventing bone loss, and that beta-carotene, phosphorus, and fiber play important roles as well.21,22 Plants are excellent sources of these nutrients.  Milk provides no beta-carotene and no dietary fiber.4 Most important, bone health can be more about what you don't eat than what you do eat. Certain foods and substances – like animal proteins, cigarettes, soft drinks, caffeine, and salt – all affect your body's ability to absorb and use calcium vs. the loss of calcium from the body. 23,24

False Promise #6: Milk is Necessary for vitamin D
Some people will point out milk's vitamin D content as evidence of its critical place in a healthy diet. Well, that's a fabrication, too. Vitamin D is not really a vitamin; it's a hormone that the body produces in reaction to sunlight. And it isn't present naturally in milk – it's added as a supplement at the dairy processing factory. This addition was supposedly done to prevent rickets, a painful, deforming bone condition that is caused by vitamin D deficiency. But rickets is really caused by limited exposure to sunlight, and the body levels of vitamin D are only slightly affected by dietary sources.25,26 The amount of sunlight we get during the summer holidays is reflected in our vitamin D levels all year long.  More than 90% of the vitamin D in the body is produced by sunlight.  Exposing the face and arms for as little as 15 minutes 3 times a week provides adequate amounts of vitamin D.  However, this activity is modified by the use of sunscreens and by skin pigmentation.27 So nearly everyone gets enough vitamin D every day just through normal activities – we don't need to drink milk to get it. Plus, vitamin D is fat-soluble, which means it is stored in our body fat for long periods of time – and most importantly, for periods of low sun exposure in the winter months.

Myth #7:  Milk Cures Hypertension
A grant from the National Dairy Council supported a large review of the influence of dietary (dairy products) and nondietary (supplements) calcium supplementation on blood pressure and came to the conclusion “that calcium supplementation leads to a small reduction in systolic (top number) and diastolic (bottom number) blood pressure.”28  Of the 67 studies published, 47 proved eligible for review.  The actual decrease in blood pressure was paltry:  Decreases of 1.44 mmHg systolic and 0.84 mmHg diastolic.  The mechanism causing this almost undetectable reduction in blood pressure from consuming calcium is unknown.

By comparison, our results from the McDougall residential center show a 23/14 mmHg decrease in blood pressure in people with high blood pressure (150/90 mmHg or greater) in less than 10 days; and almost all of these people were taken off all of their blood pressure medication during the 10 days.

False Promise #8:  Milk Prevents Colon Cancer
Colon cancer is one of the most common cancers in the United States and other places where people eat the Western diet.  There is general agreement in the scientific community that this form of cancer is due to the high-meat, high-fat, low-dietary fiber, low-vegetable diet that people eat.29,30  However, among those unfortunate people who eat this unhealthy diet, those who have a higher calcium intake also have a lower risk of colon cancer.  The reason for this may be that calcium in the colon binds and neutralizes cancer-causing substances, such as fats and bile acids, which are produced by the Western diet.31

The recommendation to increase your calcium intake, rather than change to a healthy diet, makes good economic sense for the dairy and calcium supplement industry.  However, as a sensible person, you would come to the conclusion that stopping the cause of colon cancer – the Western diet – should be the focus of your attention.

False Promise #9:  Low-fat Dairy Products are Health Food
Low-fat or skim milk and dairy products are widely consumed today, but in some ways they may be even more of a health hazard than the high-fat versions. The process of skimming the fat from the milk increases the relative proportions of protein and lactose.

Making Low-fat Milk
When the fat is removed from whole milk to make low-fat and skim milk the relative amounts of proteins and carbohydrates (sugars) are increased.4
 
Whole
Low-fat
Skim
Fat
49%
31%
2%
Protein
21%
28%
41%
CHO
30%
41%
57%
CHO = carbohydrate = lactose = milk sugar

Protein causes calcium loss10,11 and is the #1 source of food allergies in people; and the milk sugar (lactose) results in lactose intolerance (diarrhea, stomach cramps and gas). Although skim milk may have less fat, it is still devoid of fiber; and contains insufficient amounts of vitamins, like C and niacin, and minerals, like iron, to meet the human body's needs.4

False Promise #10: Milk Is As Pure White As Fresh Fallen Snow
Milk may be white but it is far from pure.  Unfortunately, some of that white comes from white blood cells – commonly referred to as “pus cells” – which are cells produced by the cow's immune system to fight off infections, especially those of bacterial origin, such as mastitis.  The dairy industry calls these somatic cells and refers to their presence as the somatic cell count (SCC).  The SCC is the number of (mostly) white blood cells per milliliter (cells/ml) of milk.  (There are 20 drops per milliliter; 30 milliliters to an ounce)

Beginning July 1, 1993, the SCC level in milk must be less than 750,000 SCC to comply with the State and Federal Pasteurized Milk Ordinance.32   This means one 8 ounce glass of milk (240 milliliters) can contain 180 million white blood cells and still be fine for you to drink and feed to your family.  In a recent study of milk sold in New York State the average SCC was 363,000 cells/ml.33 These white blood cells were produced by the cow to fight off the 24,400 bacteria/ml found in this milk.

I realize this is a disgusting way to end this article, but I must prepare you for next month’s article concerning the health risks you take for yourself and your family by consuming dairy products, such as obesity, heart disease, cancer, type-I diabetes, food allergies, and the potential for infections with AIDS and leukemia viruses found in almost all vats of milk in the United States.

References:
1)  McDougall J. The McDougall Program for Women. Plume, 2000. Pages 59-70.
2)  Cesar JA.  Impact of breast feeding on admission for pneumonia during postneonatal period in Brazil: nested case-control study.  BMJ. 1999 May 15;318(7194):1316-20.
3)  McDougall J.  The McDougall Plan. New Win Publ. 1983; page 101.
4)  J Pennington.  Bowes & Church’s Food Values of Portions Commonly Used.  17th Ed. Lippincott. Philadelphia- New York. 1998.
5)  Abrams CA.  Hazards of overconcentrated milk formula. Hyperosmolality, disseminated intravascular coagulation and gangrene.  JAMA. 1975 Jun 16;232(11):1136-40.
6)  Belton NR.  Clinical and biochemical assessment of a modified evaporated milk for infant feeding.  Arch Dis Child. 1977 Mar;52(3):167-75.
7)  Hegsted D.  Fractures, calcium and the modern diet.  Am J Clin Nutr 74: 571-3, 2000.
8)  Walker A. The influence of numerous pregnancies and lactations on bone dimensions in South African Bantu and caucasian mothers.  Clin Science 42:l89-196, l972.
9)  Smith R. Epidemiologic Studies of Osteoporosis in Women of Puerto Rico and Southeastern Michigan with Special Reference to Age, Race, National Origin, and to Other Related or Associated Findings. Clin Orthop 45:31-48, 1966.
10)  Barzel US, Massey LK. Excess dietary protein can adversely affect bone.  J Nutr. 1998;128:1051‑3.
11)  Abelow B.  Cross-cultural association between dietary animal protein and hip fracture: a hypothesis.  Calcific Tissue Int 50:14-8, 1992.
12)  Weinsier R.  Dairy foods and bone health: examination of the evidence.
Am J Clin Nutr.
2000 Sep;72(3):681-9.
13)  Recker R.  The effect of milk supplements on calcium metabolism, bone metabolism and calcium balance.  Am J Clin Nutr. 1985 Feb;41(2):254-63.
14)  Paterson C. Calcium requirements in man: a critical review.  Postgrad Med J 54:244-8, 1978.
15)  Kanis J.  The use of calcium in the management of osteoporosis.  Bone 24:279-90, 1999.
16)  Spencer H. Influence of dietary calcium intake on Ca(47) absorption in man. Am J Med 46:197-205, 1969.
17)  Hegsted D.  A study of minimum calcium requirements of adult men.  J Nutr 46:181-120, 1952.
18)  Symposium on human calcium requirements. JAMA 185:588-93, 1963.
19)  Goodhart and Shils, Modern Nutrition in health and disease (Dietotherapy), 5th ed. 1973 p. 274.
20)  Walker A. Osteoporosis and calcium deficiency. Am J Clin Nutr 16:327, 1965.
21)  Tucker KL.  Potassium, magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women.  Am J Clin Nutr. 1999 Apr;69(4):727-36.
22)  New S. Dietary influences on bone mass and bone metabolism: further evidence of a positive link between fruit and vegetable consumption and bone health.   Am J Clin Nutr 71:142-151,2000.
23)  Ilich J. Nutrition in bone health revisited: a story beyond calcium. J Am Coll 19:715-37, 2000.
24)  Cohen A. Review of risk factors for osteoporosis with particular reference to a possible aetiological role of dietary salt.  Food Chem Toxicol. 38:237-53, 2000.
25)  Holick M. Environmental factors that influence the cutaneous production of vitamin D.  Am J Clin Nutr. 1995 Mar;61(3 Suppl):638S-645S.
26)  Stamp T.  Comparison of oral 25-hydroxycholecalciferol, vitamin D, and ultraviolet light as determinants of circulating 25-hydroxyvitamin D. Lancet. 1977 Jun 25;1(8026):1341-3.S
27)  Norris J.  Can the sunshine vitamin shed light on type 1 diabetes?  Lancet 2001 358:1476-77.
28)  The influence of dietary and nondietary calcium supplementation on blood pressure: an updated metaanalysis of randomized controlled trials. Am J Hypertens. 1999 Jan;12(1 Pt 1):84-92.
29)  Weisburger J.  Causes, relevant mechanisms, and prevention of large bowel cancer.
Semin Oncol
. 1991 Aug;18(4):316-36.
30)  Mason JB.  Nutritional chemoprevention of colon cancer.  Semin Gastrointest Dis. 2002 Jul;13(3):143-53.
31)  Holt R.  Dairy foods and prevention of colon cancer: human studies.  J Am Coll Nutr. 1999 Oct;18(5 Suppl):379S-391S.
32)  Adkinson RW.  Implications of proposed changes in bulk tank somatic cell count regulations.  J Dairy Sci. 2001 Feb;84(2):370-4.
33)  van Schaik G.  Trends in somatic cell counts, bacterial counts, and antibiotic residue violations in New York State during 1999-2000.  J Dairy Sci. 2002 Apr;85(4):782-9.

參考譯文:
牛奶如從天而降的雪一樣潔白,讓人想起母親溫暖的懷抱。常識曾讓我相信,既然牛奶可以作為嬰兒唯一的營養來源,那么它一定是天然的最完美的食品。牛奶強壯骨骼──我反復被告知──既然體內最堅硬的骨骼大多由鈣組成,那么富含鈣質的牛奶對于維持我骨骼的力量和平衡來說,是必不可少的。你終生都需要牛奶,因為你身體對牛奶的需求是永不滿足的,乳制品業如此宣傳。這些"事實"一直是"真的",然而,當我花點時間去認真地思考牛奶的作用,并查閱大量的科學文獻后,我得出了一些讓我感到意外的結果。

一、母乳才是最佳食品
例如牛奶對小牛、貓奶對小貓、馬奶對小馬,只有在同一物種之內,母乳才是嬰兒的最佳食品,對于斷奶后、青少年、成年人來說,母乳也不是最佳食品。哺乳動物用乳腺分泌的乳汁來哺育成長中的嬰兒。乳汁含有利于成長和生存所需的營養、抗體、激素。

母乳有多重要?人類嬰兒如果沒有乳汁:
1.患嬰兒猝死綜合癥的機率大2~4倍。
2.在出生后三個月內,患肺炎的風險大60倍。
3.出生后一年內,住院機率大10倍。
4.IQ下降。
5.行為和語言障礙。
6.在生命前期,患感染、哮喘、濕疹、1型糖尿和癌癥(淋巴瘤和白血病)的風險加大。
7.在生命后期,有較大機率患心臟病、肥胖癥、糖尿病、多發性硬化癥、食物過敏、潰瘍性結腸炎和克羅恩病。

母乳是人類嬰兒最理想的食品這一點是毋容置疑的。迄今為止,還沒有滿意的母乳替代品,因此,在出生后前6個月應該盡量只用母乳喂養,然后,在兩歲以前,以健康的固體食品加上一部分母乳喂養。(更多信息請查閱麥克杜格爾婦女手冊)

二、母乳是物種特異性的
嬰兒所需的營養只有在同樣物種的母乳中才含有。母乳的成分通過上萬年的進化才使得其符合該物種嬰兒的需求。讓我以蛋白質這個必需營養成分為例來解釋。

因不同物種嬰兒的生長速度不同,母乳中的蛋白質含量也不同──生長速度越快,所需蛋白質越多。

不同乳汁的蛋白質含量

* 每毫升所需克數(以卡路里的百分比計算,牛奶比人乳的蛋白質含量高4倍:21%比5%)
** 出生后體重增加一倍所需時間

除了蛋白質含量的不同,還有其它營養成分的含量也不同:


不出意料,因為小牛增加一倍出生體重的速度比人類嬰兒快4倍,牛奶中的蛋白質和鈣含量也比人乳高4倍。高的生長速度對于各種營養成分的需求也更多。

三、營養過剩的問題
大多數人認為健康問題是因為缺乏營養而引起的,這是維生素和礦物質補充劑如此暢銷的原因。但是,我的患者中沒有一個是因缺乏營養而患病,比如維生素C缺乏癥(壞血病)、維生素B1缺乏癥(腳氣病)或蛋白質缺乏癥。相反,其中有很多富貴病──比如超量飲食脂肪酸(肥胖)、膽固醇(心臟病)、鹽分(高血壓)。因此,人們(嬰兒、小孩、成人)攝取如牛奶一樣的含有多余營養成分的食品會導致富貴病。(可能你還認為牛奶可以預防鈣缺乏癥,防止骨質疏松。請耐心地往下讀,我會向你證明這是不可信的。)

十九世紀中期,在美國,牛奶只是作為緊急情況下人乳的替代品(比如,母親死于難產)。結果因為牛奶的蛋白質含量過高導致嬰兒腎臟功能障礙,水分從腎臟流失而引發脫水癥,引起大量嬰兒的死亡。該問題發生后,人們在嬰兒配方奶中加入糖分以降低牛奶中蛋白質的含量,使其成分比更接近人類。如果你年紀比較大,可能還會記得沖調或飲用康乃馨牌的奶粉和卡羅牌糖漿組成的嬰兒配方奶(這對于嬰兒來說,是非常不健康的配方奶,請不要再使用)。

考慮一下牛奶的真正用途。它是從出生體重60磅長到600磅準備斷奶的小牛的最佳食物。牛奶是高"辛烷值"的燃料。人們飲用牛奶就會導致一個明顯的結果──快速變胖。在西方國家中,乳制品對于影響25%兒童和65%成年人的超重的流行負主要責任。如果牛奶被制成更高營養含量的食品,如奶酪,其帶來的問題更多。

牛奶中也缺乏一些重要的營養成分。其中,完全缺乏纖維素、缺少維生素和礦物質,比如維生素C、尼克酸、鐵,這些都是人體所需的營養成分。

謊言1:牛奶強壯骨骼
如果你問人們,為什么要喝牛奶?他們通常會說為了其中的鈣。牛奶中含有大量的鈣,于是它的支持者將此證據"擠"出來了。其實,與上面表格中的其它兩種乳汁的鈣含量相比,牛奶不是維持骨骼健康的理性選擇。牛奶中的鈣含量比人乳中的高四倍。如果在我們生命中生長最快的階段(嬰兒在六個月內體重增倍)都不需要如此高含量的鈣,當我們成人停止生長后,為什么還需要如此多的鈣?當然,相對于人類較小的骨骼,牛的骨骼較大,所需的鈣也就多。

世界范圍內上數十億的人斷奶后不再飲用牛奶,成人后,他們的骨骼也是正常的。比如,非洲的班圖婦女完全不飲奶,而是通過蔬菜來獲取每天所需的250~400毫克的鈣(大約是美國推薦攝入量的一半)。這些婦女大多有十個孩子,每個孩子的哺乳期大約是10個月。盡管不飲奶,而且在懷疑和哺乳期間還消耗大量鈣質,她們幾乎都不會出現骨質疏松。但是,當土著非洲婦女移居到大城市或移民到西方國家,遵循富含鈣質的飲食后,骨質疏松癥開始發生。你可能會馬上想到這是因為她們的飲食變得富含動物蛋白了。

不同國家的數據不支持乳制品業宣稱的益處。傳統高消費乳制品的國家(美國、瑞典、以色列、芬蘭、英國)通常有較高的骨質疏松引起的髖骨骨質,而傳統低消費乳制品地區(香港、新加坡、非洲農村)的骨質疏松癥發生率較低。
如果攝取鈣很關鍵,而牛奶又是鈣質的良好來源,為什么還有一千多萬的美國人患骨質疏松癥?增加鈣攝入的這個存在已久的建議對于降低美國骨質疏松或骨質的流行只有有限或完全沒有作用。

世界范圍內,骨質疏松癥的發生與動物蛋白的攝取量有直接和有力的聯系。高度酸性的動物蛋白是引起骨質流失的重要原因。(你可以在www.drmcdougall.com 閱讀麥克杜格爾2003年2月份上的"魚肉不是健康食品"。)

謊言2:研究支持乳制品的益處
2000年九月份,兩位研究者總結了1985年以來發表的關于乳制品和骨骼健康的科學文獻。該綜述發表在美國臨床營養雜志上。不出所料,大多數科學文獻都是由乳制品業提供資金。研究者稱,其中53%的文獻表明乳制品的益處無科學證據。然后,研究者排除了證據差或技術差的研究,這樣至少將一半的研究給排除了。剩下的21個研究中,57%的顯示乳制品的益處無科學證據,其它14%甚至顯示乳制品有害骨骼健康。想一下這意味著什么──71%的科學性良好的研究不支持乳制品的益處,甚至一些顯示有害。

隨機對照實驗比較實驗組和對照組,它被認為是最科學的科學研究。在7個關于乳制品對骨骼健康的隨機對照實驗中,有6個由乳制品業資助。只有一個研究能從液體牛奶中獲益最大的婦女:絕經后的婦女。在這個研究中,實驗組的婦女一年中每天三次飲用8盎司的脫脂牛奶,但是她們仍然流失比吸收更多的鈣(她們的鈣平衡處于負的狀態)。盡管她們每天攝入1400多毫克的鈣,但是和對照組的非飲奶婦女相比,她們的鈣流失速度快兩倍。雖然如此,乳制品業還是繼續不遺余力地宣傳乳制品對骨骼健康的好處。

謊言3:乳制品使你的鈣的攝入量簡單地達到推薦量
防止骨質疏松癥的鈣的推薦攝入量如此之高,以致要通過正常飲食來達到該標準變得很困難(如果不是不可能)。美國國立衛生研究所和國家骨質疏松基金會推薦對于絕境后而又沒有服用雌激素的婦女每天攝取1500毫克的鈣,對于65歲或以上的老年人也要每天攝取1500毫克的鈣。如果其中300~400毫克的鈣來源于碳水化合物、蔬菜、水果、蛋類、禽類、魚肉、肉類,剩下的1200毫克就不得不從乳制品中獲得。一個靜坐生活方式的絕經后的婦女評價每天消耗1500卡路里。如果要達到推薦的鈣攝入量,她所需要食用的乳制品量:

6盎司的切達乳酪(脂肪含量74%)。從乳酪中獲得卡路里將占總卡路里46%;
1夸脫(32盎司)的全脂牛奶(脂肪含量50%),從全脂牛奶中獲得的卡路里將占總卡路里的40%;
1夸脫的脫脂牛奶(32盎司)的脫脂牛奶(脂肪含量3%),從脫脂牛奶中獲得的卡路里將占總卡路里的23%;

乳品業對這些過高的推薦量持樂觀態度,但是每天消耗這么多的牛奶替代其它更加飽腹(滿意)和營養的食物,這是不健康的。

謊言4:每天我們需要1500毫克的鈣
我們真正所需鈣遠遠少于推薦量?茖W研究證明我們每天只需150~200毫克的鈣,即使在懷孕或哺乳期間也是如此。

考慮下鈣攝入量和推薦量不同:


為什么關于鈣的攝入量和推薦量如此不同?簡單地解釋就是你在食物中攝取的鈣對最終吸收進身體和骨骼健康的影響是微小的。

你的腸道總是會從進食的食物中獲取滿足你需求的足量的鈣。如果飲食中的鈣含量低,腸道對鈣吸收的效率增加,這樣就能吸收更多的鈣。如果飲食中鈣含量高,多余的鈣就會在未吸收的狀態下以排泄物的形式排出體外。腸道系統對于鈣吸收的調節十分智能,總是能滿足機體對鈣的需求。如果你追溯營養研究的科學文獻到最近的一百年前,你會發現沒有證據表明食物中鈣缺會發生在人類身上,盡管世界上的大多數人斷奶后并不飲牛奶──可能出于風俗、乳糖不耐受、牛奶不在本地區生產等原因。所以說并不存在"鈣缺乏癥"這個疾病──如果你又想到骨質疏松癥──請記住,世界上,鈣攝入量最低的國家的人卻擁有最強壯的骨骼,最低的骨質疏松發生率。

謊言5:牛奶是骨骼健康的最佳食品
事實上,牛奶并不是鈣的唯一來源,而且也不是最佳來源。鈣的源頭是大地。鈣和其它礦物質溶于水后被植物的根所吸收。然后鈣從根傳遞到莖、葉、花、果。人類也可如鈣進入牛奶的途徑一樣,從植物性飲食中獲取鈣。

對鈣的攝入量的過度關注可能會將人們的注意力和有限的資源從更加重要的營養問題上轉移。鈣不是唯一影響骨骼健康的營養元素。研究顯示,鉀和鎂對于防止骨質流失起到更大的作用,此為β-胡蘿卜素、磷、纖維素也具有重要作用。植物性飲食是獲得這些營養的良好來源。牛奶中不含β-胡蘿卜素和膳食纖維。更為重要的是,你不吃什么要比你吃什么對骨骼健康的影響大。某些食物和物質──比如動物蛋白、煙草、碳酸飲料、咖啡、鹽──都會影響你機體對抗鈣流失,影響你吸收和利用鈣的能力。

謊言6:牛奶對維生素D的獲取是必需的
有些人支持牛奶中的維生素D在健康飲食中扮演一個很重要的角色。但是這不是事實。維生素D不算是真正的維生素,它是一種機體對陽光反應而產生的激素。而且維生素D并不天然存在于牛奶中,他是在牛奶加工過程中被添加的。這是為了預防佝僂病而添加的,佝僂病是一種因維生素D缺乏而引起痛苦的畸形骨骼。實際上,佝僂病是因為日照不足引起的,機體內的維生素水平受飲食因素的影響很小。我們在夏季獲得的日照會影響我們全年的維生素D水平。機體中90%以上的維生素D來源于日照。每周只需3次日照臉部和手臂15分鐘,我們就能獲得足量的維生素D。但是,這個作用會受到防曬霜和膚色的影響;旧,通過日;顒,我們就能獲得滿足每天所需的維生素D,我們并不需要通過飲用牛奶來獲取它。再說,維生素D是脂溶性的,這樣它就可以儲存在我們的機體內很長一段時間,在冬天低日照的情況下,我們也能獲得足量維生素D。

謊言7:牛奶可以治療高血壓
國家奶業委員會通過評價飲食鈣(乳制品)和非飲食鈣(補充劑)的補充對血壓的影響,從而得出一個可以保證的結論"鈣的補充可以輕微降低血壓的收縮壓(最高值)和舒張壓(最低值)"。在67個研究中,有47個符合評價標準。血壓的實際下降值毫無意義:收縮壓降低1.44mmHg,舒張壓降低0.84mmHg。攝入鈣導致血壓輕微下降的機制還不清楚。

相對的是,麥克道格爾居民中心的結果顯示高血壓(150/90mmHg或更高)的人群飲用植物性飲食不到10天,血壓就下降了23/14mmHg。這些人大多數在這10天內都沒服用抗高血壓藥物。

謊言8:牛奶預防結腸癌
結腸癌是美國和其它西方飲食流行地區人們的常見癌癥?茖W界一致認為結腸癌是由高動物蛋白、高脂肪、低膳食纖維、低蔬菜飲食引起的。但是,在這些食用不健康飲食的人群中,鈣攝入量高的人患結腸癌的風險也低?赡艿脑蚴墙Y腸中的鈣結合和中和了引起癌癥的物質,例如西方飲食中存在的脂肪和膽汁酸。

乳制品業建議你攝取更多的鈣,而不是改變飲食習慣,這對于乳制品業和鈣補充劑生產商來說,是有利的。但是,作為理性的人,你應該已經得出結論:停止結腸癌的根本原因──西方飲食──才該是你注意力的中心。

謊言9:低脂牛奶是健康食品
低脂牛奶或脫脂牛奶和其它乳制品如今被廣泛消費,但是從某種意義上說,它們可能比全脂牛奶對健康危害更大。脫脂的過程使得牛奶中的蛋白質和乳糖含量相對地增高。

生產低脂牛奶
當脂肪從全脂牛奶中去除而獲得低脂牛奶和脫脂牛奶后,蛋白質和碳水化合物的量相對應地增加:

CHO = 碳水化合物 = 乳糖 = 牛奶中的糖

牛奶中的蛋白質引起鈣流失,而且是人群中食物過敏的首要原因,牛奶中的糖(乳糖)還會引發乳糖不耐受(腹瀉、胃痛、胃脹氣)。盡管脫脂牛奶含有的脂肪很低,但是還是缺乏纖維素,也缺乏一些重要的維生素和礦物質,例如維生素C和尼克酸、鐵,來滿足人體的需求。

謊言10:牛奶如同天降的雪一樣純潔
牛奶是白色的,但是絕對不是純潔的。不幸的是,牛奶的白色有些來自于白細胞──通常稱為膿細胞──白細胞于牛的免疫系統抵抗感染時產生,特別是因細菌引起的感染,比如乳腺炎。乳制品業把這些細胞稱為體細胞,并通過體細胞計數(SCC)來測量。體細胞計數表示牛奶中每毫升中所含白細胞數。(20滴大約為1毫升,30毫升為1盎司)

從1993年7月1日起,根據國家和聯邦巴氏殺菌奶條例,牛奶中的體細胞計數必須小于750000。這意味著,即使一杯8盎司(240毫升)的牛奶中含有1.8億的白細胞,對于你和家人也是安全的。最近一項對于紐約州銷售的牛奶的調查發現平均體細胞計數大約是363000個/毫升。與此同時發現的還有,牛奶中產生這些白細胞的原因──24400個細菌/毫升。

雖然作為文章的結尾,這個事實可能會令你反胃,但是這是為下個月我們將討論因消費乳制品,你和家人所面臨的健康風險做準備,比如肥胖、心臟病、癌癥、1型糖尿病、食物過敏和因牛奶中含有的病毒而患上艾滋病和白血病。

原文鏈接:http://www.nealhendrickson.com/mcdougall/030400pudairyproductsfalsepromises.htm
更多翻譯詳細信息請點擊:http://www.trans1.cn
編輯:foodtrans

 
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