Issue 3, September 2002
Milk, Doing Your Body Good?
Jean Lee and Randy Wei
Integrative Biology, Molecular and Cell Biology, University of California at Berkeley
From the "Got Milk" campaign to get people to drink more milk, to
the "Not Milk" campaign decrying the benefits of milk, claims surrounding
milk consumption are constantly debated. Milk producers advocate the
benefits of calcium, vitamin D, and other nutrients, while detractors
mention possible links to cancer or other diseases.
Humans place themselves in the odd position of being the only
animals that consume milk after weaning.
Milk is a familiar, one-of-a-kind beverage consumed by humans and
other animals. But humans place themselves in the odd position of
being the only animals that consume milk after weaning. Moreover,
humans do not drink human milk, but drink the milk of other species,
and do so commonly throughout their adult lives.
New alternatives to milk, such as calcium-enriched juices, soymilk,
and rice milks, have stormed the markets. In Asian markets, powdered
calcium is a popular commodity, often spooned into a pot of rice or
soup. Milk and other dairy products are large parts of many diets
around the world, but are they smart choices in our daily lives? To
answer this, we need an increased awareness of this familiar yet ever-changing
The Calcium Content of Milk
A large part of the ongoing milk advertisement campaign seeks to
persuade people to drink milk for its calcium content. Indeed, calcium
comprises a crucial aspect of human health. Not only is calcium
needed for muscle contraction, but calcium lends to our bone structure,
bone recovery (re-calcification), and bone health as well.
Human locomotion is made possible by rigid skeletons formed from
calcium salts in the ground substance of bone. Less calcium therefore
leads to weakened bones, resulting in the serious condition known
as osteoporosis. Inappropriate levels of calcium can also lead to
kidney stones, seizures, and body spasms. In addition, neurotransmitters
specifically rely on calcium ions to continue to relay chemicals
to areas of the body that need them. Lastly, calcium is an important
factor in the blood coagulation cascade. In short, without calcium,
humans could not survive.
The recommended daily allowance of calcium is approximately 800-1000
mg, although 1200 mg is ideal, according to the most recent update
by the U.S. Food and Drug Administration (FDA). The FDA also notes
that the majority of Americans consume only 500-700 mg per day,
which is not enough. This leads to the debate about milk. Milk contains
calcium, magnesium, zinc, proteins, fat, sugars, and vitamins A
and D, what some call the "perfect package." However, the FDA reminds
consumers not to capitalize on one source of nutrition. It recommends
a variety of foods, the best choices being grains and vegetable
According to a list proposed by the "Not Milk" campaign, milk contains
less calcium per given amount than other foods. Raw turnip greens
or cooked turnips, watercress, and seeds (such as sunflower or sesame)
all contain larger amounts of calcium compared to milk. Compare
the 234 mg of calcium in a 100-gram portion of almonds to the surprisingly
low value of 33-35 g of calcium per 100-gram portion in a typical
milk sample (2% milk fat) from the store.
About 35% of one serving of milk (typically 240 mL) is calcium,
which is a significant portion of the serving, but relatively calcium-poor
when compared to most other sources of calcium, especially green
leafy vegetables and grains. Milk still has more calcium per glass
than some calcium-enriched juices, yet the calcium benefit of milk
is still debated.
Unfortunately, milk and milk products cause an estimated 50% of
the adult population's uncomfortable bloating, gas, cramping and
diarrhea. Lactose intolerance can result from two things: either
through a natural enzyme deficiency, which prevents the body from
digesting milk sugars, or through an allergy to milk itself. The
amount of lactase, the intestinal enzyme responsible for the digestion
of lactose, the sugar found in milk, typically declines naturally
after weaning, unless the body is genetically predisposed to produce
After this decline, the disaccharide lactose cannot be broken down.
Continued avoidance of lactose can send a signal to the intestinal
brush border that lactase is no longer "needed" for activity, and
decline can go further into completion than if the intestines were
fed milk more often. But again, the natural tendency for the majority
of world adult populations is the gradual lessening of enzyme activity.
One solution to the discomfort of lactose intolerance can be the
consumption of dairy products pre-digested by lactase. Another simple
solution is to take milk and dairy items out of the diet. Extensive
cookbooks, such as The Milk-Free Diet Cookbook: Cooking for the
Lactose Intolerant, are available for the lactose-intolerant.
Other animal milks, such as the sweeter goat's milk, contain lower
levels of lactose, making them easier to digest.
What risks come with drinking milk from cows injected with
recombinant Bovine Growth Hormone (rBGH)?
Many dairy producers use rBGH as a way to increase milk production
in their cows, resulting in up to 20% more production.
When Ben and Jerry's Ice Cream decided not to use milk from cows injected
with Monsanto's rBGH, many consumers became more conscious of what
was in their food and milk products. Many dairy producers use rBGH
as a way to increase milk production in their cows, resulting in up
to 20% more production. However, the hormone causes udder inflammation
in cows, which can lead to the contamination of the milk from secreted
pus common in udder inflammation.
Also, antibiotics used to treat inflammation have been discovered
in trace amounts in the milk. Such contamination leads many people
to wonder whether milk is safe for daily human consumption.
In addition, milk produced by rBGH-treated cows has higher concentrations
of insulin-like growth-factor-1 (IGF-1). Higher levels of IGF-1 have
been indicated as a potential risk factor in prostate cancer.
In 1998, Harvard School of Public Health and Brigham and Women's Hospital
reported in Science that men with IGF-1 levels in the highest
quartile of study participants were 4.3% more likely to develop prostate
cancer, compared to men with IGF-1 levels in the lowest quartile.
Such a small increase in prostate cancer risk may or may not deter
people from consuming milk from cows treated with rBGH.
Will I get kidney stones from drinking too much milk?<
Many people drink a glass of milk daily for calcium and other essential
minerals vital for healthy bones. Contrary to popular belief, milk
does not lead to the formation of urinary stones or buildup of mineral
deposits in the kidney. At the University of Chicago, D.R. Webb
showed that even calcium-sensitive patients were able to consume
milk or calcium-fortified orange juice without increasing their
risk of stone formation. Patients drinking 600 mg of calcium in
beverage form developed no kidney stones.
Milk plays an important role in many diets today. Many of us grew
up eating cheese pizza, yogurt, milk and cookies, and cheesecake.
We have grown so comfortable consuming milk and eating milk products
that many do not give a second thought to the possible positive
and negative effects of milk. Overall, milk does do a body good.
The negative side effects of milk are due mainly to the over-consumption
of milk products beyond the recommended daily allowance of 3 8-oz
glasses of milk. Consumers must be aware of both the pros and cons
of drinking milk. Being knowledgeable consumers will empower us
to decide how much we should rely on milk for our nutritional needs
and empower us to be more proactive in creating a well-balanced
and nutritious meal
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Lukin, Jane. The Milk-Free Diet Cookbook: Cooking for the Lactose
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H.S. Adams. Milk and Food Sanitation Practice. 1947. The Commonwealth
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Journal of Young
Investigators. 2002. Volume Six.
Copyright © 2002 by Jean Lee, Randy Wei and JYI. All rights