Weighing the costs and benefits of milk consumption: Should kids drink cow’s milk?
© 2009 - 2013 Gwen Dewar, Ph.D., all rights reserved
Should your kids drink milk? There are many benefits of milk consumption.
- For families that rarely or never eat meat, milk and milk products may represent important sources of protein
- Milk can boost calcium and vitamin D levels--both crucial for development and for the prevention of disease
- Milk stimulates growth
- Milk may also boost cognitive performance--either because it
improves general nutrition or because it specifically promotes brain
But milk isn't perfect.
If, like most of the world's population, you are lactose intolerant, you
need to avoid consuming cow's milk products that are uncooked or
More universally, all people, regardless of their capacities to
digest milk sugar, have reason to restrict their intake of milk and milk
cow’s milk is NOT recommended for babies under 12 months (Cribb et al 2011);
- some milk products are high in saturated fat, and saturated fats should be restricted for kids over 24 months;
- some kids might suffer from cow’s milk protein intolerance, which causes gastric distress and other problems;
milk and milk products can inhibit
iron absorption; and
- some researchers speculate that early exposure to cow’s milk might put
kids at increased risk for certain diseases--like diabetes--later in
Do these potential costs outweigh the benefits?
I doubt it. Not if we’re talking about 1 or 2 daily servings of
low-fat yogurt or milk for a child who is at low risk for developing
But don’t take my word for it. Here is an overview of the scientific evidence for--and against--the consumption of cow’s milk.
Dairying in anthropological perspective
For thousands of years, milk has been an important source of protein, fat, and calcium for many people...and not just for people in Europe, India, and the Middle East.
From the steppes of Mongolia to the highlands of East Africa and
Peru--wherever, in fact, humans have herded cattle, goats, horses,
camels, or llamas--humans have added milk products to their diets.
Indeed, the benefits of milk and dairy farming may have given
some populations a big evolutionary advantage. Recent genetic analyses
suggest that the hunter-gatherers of Neolithic Europe were replaced by
dairy farming newcomers around 8,000 years ago (Malmström et al 2009;
Bramanti et al 2009).
But traditions—even apparently adaptive traditions—don’t
always reflect what is ideal for an individual’s long-term health and
Skeletal analyses of early farmers are case in point. Compared
with hunter-gatherers, these farmers were malnourished. If milk helped
early farmers replace hunter-gatherers, it may have done so because it
allowed parents to wean their kids from human milk relatively
early--i.e., before the age of 3 years. This would have increased the
birth rate, but the new agricultural diet didn’t necessarily improve
anyone’s quality of life.
More generally, we have to remember that diets—traditional or
otherwise-- are always constrained by what’s available. In the
civilizations of the ancient Mediterranean, people drank wine or beer
instead of water. A good idea? Not if you have safe, clean water to
drink. But they didn’t. So the benefits of drinking alcohol outweighed
the potential risks.
Where does that leave milk? Research suggests that milk
consumption may benefit many children. But milk consumption may have
costs, too. Whether or not milk is a good choice depends on how you
weigh these costs and benefits. It also depends on what other dietary
options you have.
Benefits of milk consumption
Fortified milk and milk products are important dietary sources of
calcium, vitamin D, vitamin A, vitamin B12, and other micronutrients. In
fact, studies suggest that milk consumption can play a crucial role in
maintaining calcium levels and vitamin D stores (e.g., Maguire et al
2012; Vissers et al 2011), and these nutritional benefits may have major
Recent research suggests that vitamin D insufficiency is a risk
factor for a variety of diseases, including heart disease, diabetes,
cancer, and multiple sclerosis (Holick et al 2005). If so, vitamin
D-fortified milk may help children avoid developing such diseases.
Similarly, milk consumption--by increasing calcium intake--may
protect people from developing hypertension, kidney stones, insulin
resistance syndrome, obesity, cancer, and even lead poisoning (Nicklas
And of course the protein and calcium in cow's milk may
contribute to better overall nutrition and bone health. As summarized by
Janet Rich-Edwards and colleagues (2007), studies show that children
who consume cow's milk products have
- reduced risk of protein malnutrition,
- fewer dental cavities,
- increased mineral content in their bones and fewer bone fractures, and
- reduce risk of developing rickets
Much of the research concerns correlations, but there is
experimental evidence, too. For example, one randomized, controlled
study gave Chinese school girls 330 mL of cow’s milk per day. After two
years, these girls enjoyed small but statistically significant increases
in bone mineral content and bone density compared with girls in a
control group (Du et al 2004).
More than good bones and teeth
The benefits of milk consumption for bones and teeth may not seem
surprising. But there are less well-known benefits There is also
evidence that milk consumption--by increasing calcium intake--protects
people from a variety of dangerous medical conditions, including
hypertension, colon cancer, breast cancer, ovarian cancer, kidney
stones, insulin resistance syndrome, obesity, and lead poisoning (see
Nicklas 2003 for a review with full references).
Growth: One of the benefits of milk consumption?
Milk consumption appears to promote growth, too.
For example, in the Chinese study mentioned above, the
milk-supplemented girls were taller than controls. And many other
studies have documented a correlation between cow’s milk consumption and
height in children (Hoppe et al 2006).
This is true in developing countries—where adding milk to the
diet helps eliminate nutritional deficiencies. But it’s also true in
places where basic nutrition is already pretty good.
For instance, a U.S. study found that preschool children who were
in the top 25% for milk consumption were about a centimeter taller than
their peers (Wiley 2009). Another U.S. study found that milk
consumption was linked with taller teenagers, even after controlling for
age, sex, household income, and ethnicity (Wiley 2005).
How does cow’s milk promote growth?
Possibly, milk drinkers grow more because they are getting more
protein. But there might be more going on. Cow’s milk is a natural
source of growth hormone (GH) and insulin-like growth factor. So some
researchers suspect that milk consumption promotes growth by increasing
circulating levels of GH and IGF-I.
In support of this idea, some surveys have documented a link
between greater milk consumption and higher levels of GH and IGF-I.
And there’s experimental evidence, too. In one study, researchers
gave urban Mongolian school children supplements of whole milk and
tracked their serum levels of GH and IGF-I. After a month of milk
drinking, the kids experienced marked increases in GH and IGF-I levels
(Rich-Edwards 2007). Similar results have been reported in China (Zhu et
al 2005) and Britain (Cadogan et al 1997).
Milk and intelligence?
In addition to better bones and taller kids, milk may also be associated with smarter kids.
For example, when 7-and 8-year-old kids from rural Vietnam were
given milk supplements, they scored better on short term memory tests
than did kids in a control group (Lien do et al 2009).
This might reflect an overall improvement in nutrition. But there
is also the possibility that milk enhances intelligence via growth
factors. According to this idea, growth factors in milk boost brain
development as well as linear body growth.
Intriguing? Yes. But the evidence isn’t yet there. One study
found a link between IQ scores and circulating IGF-I levels in 8- and
9-year olds. However, the study didn’t measure milk consumption, and the
IQ effect was not statistically significant after other variables—like
maternal education—were taken into account (Gunnell et al 2005).
The potential costs of milk consumption
There are several potential costs of drinking milk. Some seem pretty clear-cut. Others are controversial.
Cow’s milk is NOT good for babies under 12 months
Cow’s milk differs from human breast milk in several important ways.
For instance, cow’s milk has more protein, sodium, and potassium than is
healthful for human babies. And it lacks certain essential fatty acids
that human babies need for optimal development.
Moreover, some infants can’t digest cow’s milk protein very well, and it makes them ill.
So giving cow’s milk to babies is not a good idea. It can cause
malnourishment and illness. For these reasons, the American Academy of
Pediatrics (AAP) does not recommend cow’s milk—even whole cow’s milk—for
babies under 12 months.
Some kids have lactose intolerance and/or cow’s milk protein intolerance
Both lactose intolerance and cow’s milk protein intolerance are
associated with symptoms of gastrointestinal distress. But they have
different implications. People who suffer from lactose intolerance need
not avoid all milk products. Fermented milk products, like yogurt and
cheese, are usually acceptable. By contrast, people who suffer from
cow’s milk protein intolerance need to avoid most milk products.
Milk is an iron absorption inhibitor
Experiments demonstrate that the high calcium content of milk can
interfere with a child’s absorption of iron, another mineral that is
crucial for development. To ensure your child isn’t iron deficient, it’s
a good idea to avoid serving milk products and iron-rich foods in the
same meal. It may also be a good idea to limit total milk intake in
young children to two cups per day (Maguire et al 2013). For the
details, see this article on
Kids should limit their intake of saturated fat
Many milk products are high in saturated fats. Is this a problem? It depends on your child’s age.
Human breast milk is high in saturated fats (Giovannini et al
1994), and babies need relatively high levels of fat in their diets for
proper brain development. So if you want to give an older baby cow’s
milk, the American Academy of Pediatricians (AAP) recommends that you
give him whole milk—not skim milk or reduced-fat milk.
For kids over 24 months, these AAP recommends that no more than 10% of daily calories should come from saturated fats.
Speculation: Does IGF-1 have a dark side?
Here's the controversial part. Remember IGF-1, the insulin-like
growth factor mentioned above? It stimulates growth. But it also
stimulates the production of insulin. Studies show that people who
consume milk protein experience a post-meal spike in insulin levels.
This has raised the concern that early milk consumption could
“program" the body produce chronically elevated levels of IGF-1, which
might contribute to development of diseases associated with higher
insulin levels—diseases including diabetes, adult heart disease, and
cancer (Melnik 2009).
But does research to support the idea? So far, the evidence
isn’t very compelling. In fact, some studies suggest that milk
consumption may be more likely to protect kids from disease.
For example, a study of Lithuanian children has reported that
babies given cow’s milk-based formula in the first 3 months were more
likely than others to become diabetic (Skrodeniene et al 2008). But this
study didn’t randomly assign babies to receive cow’s milk formula, so
it’s possible that babies receiving cow’s milk were more likely to have
other risk factors for diabetes.
When Finnish researchers conducted a randomized study, they did not
find that cow’s milk consumption increased diabetes risk (Savilahti and
Saarinen 2009). In fact, there was a trend in the other direction:
Babies who were given cow’s milk-based formula were actually less likely
to develop diabetes.
Similarly, a nationwide study of German preschoolers found that preschoolers who drank more cow’s milk were less likely, not more likely, to develop diabetes (Rosenbauer et al 2007).
Research on adults has reported similar results. In studies that
have controlled for overall diet, body mass index, and physical activity
level, adults who consumed more low-fat milk products were less
likely, not more likely, to develop insulin dependence or diabetes (Choi
et al 2005; Tremblay and Gilbert 2009; German et al 2009).
As for other diseases, studies of adults suggest low-fat milk products might reduce
the risk of high blood pressure. (Wang et al 2008; Appel et al 1997).
Increased adult milk consumption may be linked with higher rates of
nonaggressive colon cancer (Ahn et al 2007). But studies have failed to
find a consistent link between adult milk consumption and breast cancer
(Pala et al 2009).
Why the mixed results?
I don't know. But there are several things that might make it
difficult to tease apart the effects of milk consumption on health.
First, studies suggest that people suffering from vitamin D
deficiency are at higher risk for diabetes (e.g., Huang et al 2012). And
other ingredients in milk--like calcium--are known to protect people
from developing diabetes and heart disease. So even if IGF-1 has a negative effect, the net effect of milk consumption may not be negative.
Second, it’s possible that our genes are involved. Cow’s
milk consumption may more likely to trigger diabetes in kids who are
already genetically predisposed to develop diabetes. This idea is
consistent with the results of a Finnish study (Virtanen et al 2000). If
genetics play a role, then studies might report different outcomes
depending on the genetic backgrounds of people being tested.
Third, the effects of milk may depend on which cows made the milk. Researchers
from Iceland analyzed the milk produced by cows from different
Scandinavian countries (Thorsdottir et al 2000). Compared with cow’s
milk from other countries, Icelandic cow’s milk had the lowest levels of
beta casein A1 and B (proteins thought to trigger diabetes) and the
highest levels of immunoglobulin (a protective antibody). This might
explain why Type 1 diabetes less common in Iceland.
The bottom line?
When it comes to insulin-related diseases, milk may have both healthful and negative effects. More research is needed.
Meanwhile, parents with kids at high risk for diabetes should talk to their doctors about the effects of milk consumption.
But doesn't milk make you fat?
I've heard this claim from Hollywood celebrities, but it's not
well-supported by research. Most studies, including a recent
observational study tracking the development of kids in Hong Kong, have
reported no links between milk consumption and excess body fat (Lin et
What about homogenization?
Commercial milk is homogenized, and some people speculate that the
process might have harmful effects. The idea is that
homogenization--which reduces the size of fat droplets in milk--might
put consumers at greater risk of heart disease or diabetes.
Unfortunately more research is needed to evaluate this hypothesis
(Michalski et al 2007).
...and what about raw milk?
Pasteurized milk is milk that has been heated to kill may
disease-causing bacteria. “Raw milk" refers to milk that has not been
Although some people have claimed that raw milk offers special
health benefits, there is, as yet, little scientific evidence to support
this claim. And the fact remains that raw milk is much more likely than
pasteurized milk to be contaminated with dangerous pathogens (Lejeune
JT and Rajala-Schultz 2009).
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