In a memorable scene from the 1977 film ‘Pumping Iron,’ Arnold Schwarzenegger is asked his opinion about drinking milk. ‘Milk is for babies,’ he replies. Now governor of California, he’d doubtless modify his politically incorrect stance. After all, no governor would want to harm the dairy industry in a fiscally insecure state.
Arnold’s pronouncement about milk has a sound scientific basis’at least in regard to babies. Mother’s milk is not only a near-perfect food but also the initial preferred source of complete nutrition for all mammals, including humans.
Not only does it come in the most attractive container ever devised by nature, but it also supplies a newborn with everything it needs to thrive and grow. Mother’s milk contains myriad unique nutritional and immune factors, though they’re limited to the initial stages of life. After that we switch to cow’s milk.
According to the American Dairy council, ‘Milk is for every body.’ Few would argue about the superiority of the milk protein whey, which is numero uno in biological value. Dairy products are also the premier source of calcium, vital for strong bones and a variety of bodily functions. Even so, a growing faction of antimilk advocates echo Arnold’s sentiments, claiming that milk is not essential for adults and may cause more problems than we realize.
Eggs are even more maligned than milk. Their high cholesterol content indicts them as an express route to cardiovascular disease (CVD). And if the cholesterol doesn’t kill you, the salmonella in eggs will make you want to die; salmonella causes acute gastroenteritis, better known as food poisoning. Although other foods, including meats and poultry, can cause food poisoning, eggs are almost synonymous with it. So what’s up with eggs and milk’good or bad?
What’s in Milk?
Milk consists of 87.4 percent water; 12.6 percent milk solids, including 3.7 percent fat in whole milk; 3.4 percent protein; 4.8 percent lactose, or sugar; and 0.7 percent minerals. Milk has two protein types: 80 percent of the protein is casein, and 20 percent is whey. Casein and whey, in turn, come in various subtypes, such as alpha, beta, gamma and kappa in casein, and beta-lactoglobulin and alpha-lactalbumin in whey. Smaller proteins, known as bioactive peptides, show up in each subtype.
Milk’s bioactive peptides have generated the most excitement in nutrition science. You may have seen some of these peptides, such as lactoferrin and glycomacropeptide (GMP), mentioned in ads for milk-based protein supplements. They make it unique among foods. Nature put them there for a definite purpose: to enable an immature mammal, whether human or bovine, to survive in an unfamiliar, potentially hostile environment. Many bioactive peptides offer growth-promoting properties.
Casein contains a number of interesting peptides. Opioid peptides work like the painkiller morphine. Peptides naturally occurring in casein are known as casomorphins, and casokinin inhibits an enzyme called angiotensin-converting enzyme (ACE), the key to a biochemical cascade that results in elevated blood pressure. Drugs called ACE inhibitors are available by prescription but can produce serious side effects. Casokinin seems work in a similar manner, minus the side effects.
A kappa-casein fragment called casopiastrin interferes with the activity of platelets, which are blood-clotting agents. That’s significant because a wayward blood clot in a partially blocked or occluded artery initiates most heart attacks and strokes.
The opioid peptides of casein slow down intestinal motility, which partly explains the slower digestion rate of casein. That process appears to help treat conditions characterized by too-rapid intestinal movement, such as diarrhea. Opioids may also exert analgesic, or painkilling, action. Other bioactive peptides in casein stimulate immune-cell activity, helping to protect against the effects of bacteria and viruses’a vital function in newborns, who depend on these milk peptides to protect them against disease.
The whey fraction of milk protein contains a number of fascinating peptides. Lactoferrin offers potent protection against various strains of bacteria. It binds to iron, which bacteria require to multiply, and promotes iron uptake in the body. A derivative peptide called lactoferricin also destroys various forms of bacteria, as well as Candida albicans, or yeast infections.
Animal studies have shown that whey peptides exert potent anticancer effects. A study that fed rats whey resulted in significantly decreased incidence of colon cancer. Whey is also a rich source of the amino acid glutamine, which is used as fuel by immune cells. The high level of another amino acid in whey, cysteine, leads to increased synthesis of glutathione, a major antioxidant, particularly in the liver. ALL Glycomacropeptide increased satiety or reduced hunger sensations in animal studies, evidently by promoting the release of a gut hormone called cholecystokinin, which signals the brain to turn off appetite. Unfortunately, human studies haven’t found any effect of GMP on appetite.
While numerous studies have noted the activity of milk bioactive peptides in both isolated-cell (in vitro) and animal studies, there remains little evidence that they affect human adults. Infants have a far more permeable digestive system and can absorb larger proteins intact, including such hormones as insulinlike growth factor 1 (IGF-1). Adults, though, can’t do that. Most larger protein peptides don’t survive the gut’s harsh acid environment and simply degrade into their native amino-acid structures, negating bioactivity.
Got Problems With Milk?
Antimilk factions recite a litany of problems related to milk consumption. They note that cows are routinely injected with bovine growth hormone, leading to elevated levels of IGF-1 in milk. Breast- and prostate-cancer patients have higher levels of IGF-1, but scientists haven’t figured out whether that means IGF-1 is a marker for the disease or is made by tumor cells to promote cancer spread. That’s because IGF-1 prevents apoptosis, a process that amounts to the tumors’ killing themselves.
A peptide hormone, IGF-1 is nothing more than a specific long chain of amino acids. So when you take it orally, it must pass through the digestive system, where it works like any other protein and degrades into its constituent amino acids. When that happens, all hormone activity is lost. That explains why drug forms of IGF-1 are injected. The odds of obtaining any significant hormonal effects from oral IGF-1 are near zero in adults, although it could theoretically happen in infants.
On the other hand, studies with rats show that casein fosters IGF-1 uptake through the gut. Casein inhibits proteolytic, or protein-digesting, enzymes that would normally degrade the amino-acid chain of IGF-1 and nullify its hormonal activity. Even if IGF-1 somehow gets through the intestinal barrier, it still must travel to the liver, where it degrades, which is something that antimilk activists never discuss. The liver synthesizes far more IGF-1 each day than a person could ever consume in milk. Meanwhile, teenagers, who produce the highest levels of IGF-1, also have the lowest cancer rates.
Some studies implicate dairy products in prostate cancer because of their high calcium content. The mechanism involves a lowered level of vitamin D, which exerts protective effects against prostate cancer. High calcium intake blunts the conversion of vitamin D into a form that protects against prostate cancer, but it remains unclear how much calcium is needed to cause that. It would only happen to those who are deficient in vitamin D. Simply taking in enough vitamin D would offset the problem. The trace mineral selenium also helps activate vitamin D.
Research shows that most commercial milk is obtained from pregnant cows, which have the highest levels of estrogen, known to play a role in prostate-cancer onset. Some of the estrogen is passed on in the milk, but most of it rapidly degrades after it’s drunk, and it has no significant hormonal effects in men. In fact, all men routinely produce far greater amounts of estrogen in their own bodies as a result of aromatization of testosterone, whereby the ubiquitous aromatase enzyme converts free testosterone in the blood into estrogen.
Milk has a number of natural factors that offer cancer protection, including conjugated linoleic acid (CLA), which shows potent anticancer effects in animal studies, and sphingomyelin, which helps prevent colon cancer in animals.1
Another critique of milk is that it may cause cardiovascular disease. One recent study did show that a beta-casein fragment of milk has atherogenic effects,2 but its subjects were rabbits, which are far more prone to atherosclerosis than humans. Their bodies cannot handle cholesterol.
The weight of evidence is against labeling milk a cardiovascular danger.3 The Masai people in Africa drink several quarts of milk daily yet show a low incidence of CVD.4 Most studies show that, if anything, milk appears to protect against it.5
The only critiques of milk that have merit involve food allergies. Some people are allergic to either milk protein or milk sugar (lactose), and the lactose-intolerant can still use fermented milk products, such as true yogurt, in which lactose is degraded. These days, milk is available with added lactase enzyme, making lactose an even lesser problem.
Milk increases glycemic index when drunk with other foods.6 Some amino acids in it increase insulin release, but that may be advantageous, since insulin turns off the appetite after meals. The Yolk’s on You
Eggs have long been castigated as a major source of dietary cholesterol, and since higher blood cholesterol levels are linked to CVD, it’s best to limit egg intake’old news, and just plain wrong. The idea that dietary cholesterol leads to elevated blood cholesterol has proved false. Your body can absorb only about 2 percent of cholesterol from food, not enough to play a significant role in CVD for most people.
Thirteen patients at Highland Hospital in Oakland, California, ate the equivalent of 15 egg yolks a day for three weeks. Nobody except two bedridden obese patients showed any significant increase in blood cholesterol levels. Another four patients in the study showed decreased blood cholesterol at the end of the study.
A 1991 case study reported in the New England Journal of Medicine described an 88-year-old man who ate 25 eggs a day for many years yet showed no signs of CVD. Researchers from Kansas State University found three years ago that eggs contain their own built-in cholesterol inhibitor: phosphotidylcholine, better known as lecithin. That study confirmed what folk-medicine advocates have said for years, that the natural lecithin contained in eggs prevented the rise in cholesterol.
The true culprit in promotion of CVD isn’t dietary cholesterol but saturated fat, which the liver uses as a substrate, or starting material, for cholesterol production. A large egg, which has 71 total calories, contains five grams of fat but only 1.5 grams of saturated fat.
Yolks are another area of controversy. Bodybuilders routinely discard egg yolks, eating only the whites under the notion that the white of an egg is pure protein and all the fat is in the yolk. That’s a significant nutritional error.
The yolk, which contains all of the fat and half of the protein of an egg, accounts for 33 percent of its liquid weight. Most of the vitamins and minerals in an egg are also in the yolk, including the richest natural source of choline (other than lecithin), at 280 milligrams.
Egg whites contain half the protein in an egg and some of the vitamins and minerals. Eating raw egg whites has been implicated in causing a deficiency of the B-complex vitamin biotin. Raw whites contain avidin, an element that locks on to biotin and prevents its uptake. But you’d need to eat 24 raw egg whites a day on a long-term basis to make a dent in biotin absorption.
Even the salmonella issue may be overblown. According to a study conducted by the U.S. Department of Agriculture, only 0.003 percent of eggs contain salmonella. So a person who regularly eats eggs will likely encounter a salmonella-tainted unit once every 42 years.
Until whey appeared on the market, eggs were considered the premier food-protein source. They have a biological value of 93.7 percent compared to 84.5 percent for whole milk, 76 percent for fish and 74.3 percent for meat. Eggs are also nutrient-dense relative to their caloric content. They provide lutein and zeaxanthin, carotenoids that help prevent macular degeneration, the leading cause of blindness in older people. Newer forms of commercial eggs come out of hens on a special diet of increased omega-3 fatty acids’between 150 and 350 milligrams, compared to 60 milligrams in a ‘normal’ egg. The same hens are also on vitamin E, which helps stabilize the highly polyunsaturated structure of omega-3, making it less prone to oxidation. Since about 90 percent of Americans are deficient in omega-3s and often shy away from such other natural fatty-acid food sources as flaxseed and fatty fish, eggs may play a significant role in combating the problem.
Milk and eggs remain the major sources of food protein for bodybuilders. For those who eschew eating beef, milk and eggs supply the quality protein needed for bodybuilding progress, and they promote long-term health and fitness. So they are for every body, not just babies.
References
1 Gill, H.S., et al. (2000). Anticancer properties of milk. Brit J Nutr. Supp 1:S161-S166.
2 Tailford, K.A., et al. (2003). A casein variant in cow’s milk is atherogenic. Atherosclerosis. 170:13-9.
3 Ness, A.R., et al. (2001). Milk, coronary heart disease and mortality. J Epidemiol Commun Health. 55:379-82.
4 Biss, K., et al. (1971). Some unique biological characteristics of the Masai of East Africa. N Eng J Med. 28:694-9.
5 Pfeuffer, M., et al. (2000). Bioactive substances in milk with properties decreasing risk of cardiovascular diseases. Brit J Nutr. Supp 1:S153-S159.
6 Liljeberg, H., et al. (2001). Milk as a supplement to mixed meals may elevate postprandial insulinemia. Eur J Nutr. 55:994-999. IM
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