I grew up in a milk-drinking home. My sister and I were not allowed to leave the dinner table unless we finished a glass of 2% milk. During the winter holidays, we got to put a single Hershey’s kiss at the bottom, a special incentive to empty the glass. As a kid, I didn’t particularly LIKE milk. But nonetheless I drank it. After all, this was the 90s. The days of “Milk – it does the body good”, and the height of the “Got milk?” campaign (did anyone else collect these ads?). We never questioned milk’s nutritional benefits.
Fast forward to 2016. The nutrition world has become a hostile place. Anti-GMO, the Paleo fanatics, detox diets, vegans, low-carb/high-fat, the “dangers” of high-fructose corn syrup, artificial sweeteners, and food additives. Seems food and diets have become as divisive as religion in some groups. And defending dogma has become more important that standing up for science. Fearmongering has taken over and created an environment wrought with distrust of the mainstream. My nutrition training didn’t prepare me for the heated discussions, the daily need to defend science-based nutrition advice. Social media has served as a particularly efficient battleground for the nutrition wars. The word “troll” has taken on a whole new meaning (they’re no longer the neon-haired figures we collected in middle school).
And there are some serious dairy haters out there. Lots of “experts” weigh in the appropriateness or healthfulness of milk. Whether it’s a criticism of the dairy industry’s influence on milk intake recommendations, the use of growth hormones or antibiotics, or the “unnatural” practice of drinking milk from another species, dairy is now a hot debate (which is just a weird thing to say).
I have been getting so many inquiries about milk from patients lately, so I thought I’d address some of them here. Then I will summarize what currently available quality research suggests about milk consumption.
- “Think about it – Humans are the only species that drink the milk of another animal.” Um, OK… Let’s suspend reality for a minute and pretend that statement is actually true. Is that supposed to freak me out? Humans have learned how to procure and alter their food in MANY ways, and in the process we have improved the nutritional quality of our overall diets over the course of human history, leading to improved health, longer lifespans, and less unnecessary deaths*. We chop, blend, and crush our food. We cook our food, which makes a larger variety of food sources palatable and safe. We’ve learned to grow it in a controlled, fruitful manner in order to feed the growing population on Earth. And anyway, humans are NOT the only animal to drink the milk of another species. Cats and dogs drink cow’s milk if you give it to them. All baby mammals actually have the ability to digest a variety of species’ milks. Orphaned piglets can survive and thrive if allowed to nurse from a lactating cow. Most animals, including humans, become lactose intolerant when they reach adulthood (not that it stops us from eating ice cream and cheese). However, a change in technology altered this genetic norm. Humans started domesticating cattle and drinking its milk thousands of years ago, which coincides with the explosion of lactase persistence in humans (the ability to digest lactose into adulthood). This suggests milk provided nutritional benefits, improved survival and the passing on of the lactase persistence gene, and thus the lactase persistence gene was increasingly naturally selected for.1 There’s nothing “unnatural” about drinking milk into adulthood if you tolerate it.
- “You shouldn’t drink skim milk because when they remove the fat, they add sugar to make up for it.” I really do not understand where this idea came from. But I hear it like once a week. If you Google it, you’ll find websites and blogs of MEDICAL DOCTORS that claim this. I even heard the hosts of one of my favorite** podcasts (Stuff You Should Know) say it and it broke my heart because now I wonder what other lies they’ve told me. It’s just not true, unless you’re buying flavored (chocolate, vanilla, strawberry) skim milk. Skim milk is made by skimming the fat out of whole milk. The milk is then fortified with vitamin A (since this vitamin dissolves in fat and thus is removed when fat is removed) and vitamin D (never was in the milk to begin with but helps with the absorption of calcium). And that’s it. An 8 ounce glass of plain skim milk has 12 grams of sugar. An 8 ounce glass of plain whole milk has 12 grams of sugar. Next time you’re in the grocery store, take a look.
- “Full fat dairy is more nutritious because the nutrients in milk are fat-soluble and need fat to be absorbed.” This one means well, but is only half true. The essential fat-soluble vitamins are A, D, E, and K. Whole milk is a natural source of vitamin A, but has very little natural vitamin D, E, and K. Since vitamin A is fat-soluble, it is removed with the fat when skim milk is made, so skim milk must be fortified with enough vitamin A to match the vitamin A content naturally present in whole milk (this is required by law)2. In addition, all types of milk are fortified with vitamin D as well (in the United States). Again, this is because science has taught us that vitamin D helps with calcium absorption in the intestines. The type of vitamins A and D used in milk fortification are readily available for breakdown by human digestive enzymes, even in the absence of fat.2,3*** Regarding the other nutrients in milk (calcium, potassium, phosphorus, etc), they are all water-soluble, meaning they are not lost when you skim the fat off of whole milk.
So do we need dairy at all? The major health benefit dairy provides is its calcium content.
Calcium is an essential mineral (we need it to live, but can’t endogenously make it so we have to eat it) that has long been associated with bone health in humans. Our bones and teeth contain 99% of our body’s calcium, and bone strength is associated with the bones’ calcium content. The remaining 1% is in the blood and helps with muscle contraction (keeps our heart pumping). Calcium deficiency leads to weak bones and osteoporosis.
Our bones are dynamic body tissue. Every day we build bone, and every day we destroy bone – this is the process of bone remodeling. Until the age of about 30, bone remodeling favors the building up of bones (putting calcium into the bones to strengthen them). After that, bone breakdown (sucking calcium out of bones) tends to exceed the rate of bone building. This is why fractures and falls are more prevalent in the elderly population. The leeching of calcium from bones is even more prominent in the deficient state. That 1% in the blood is VERY tightly controlled. If calcium intake is chronically low, the body must pull calcium from the bones to maintain that 1% and keep your heart functioning. Hence, bone loss occurs more rapidly and osteoporosis sets in earlier in life.
The idea that calcium intake can build bones is supported by data from calcium retention studies which basically show that if you give someone calcium it will in turn increase the calcium density in their bones. The more you give, the more gets deposited into the bones, until a point is reached when calcium deposition in bones is maxed out. This is where we get our daily recommendations from (here in the US, it’s between 1000 and 1200 mg/day depending on age).
Dairy naysayers claim that everything we think we know about calcium and bone health is wrong. They assert that the recommendation to eat 3 servings of dairy a day is excessive and influenced by the dairy industry. They also claim that research does NOT support calcium’s protective role.4-6 Problem is, the studies they cite are almost all observational studies where a group of people is followed over a certain period of time and a correlation is analyzed between the number of broken bones they suffer and the amount of calcium from food and supplements they take in. These studies have major limitations. Some of the studies only ask about food and supplement habits three times over the course of 12 or more years.
I’m not saying those data need to be completely trashed. I’m just saying we really aren’t sure yet. Clearly we need more well-designed experimental studies.
A certain amount of calcium intake is key in premature bone loss and osteoporosis, but it is not the only factor. As mentioned earlier, calcium needs vitamin D to be well-absorbed. Research has shown that when calcium and vitamin D are given together, it reduces the risk of fractures7,8. Taking a calcium supplement alone, especially if you are deficient in vitamin D or live in a part of the world with limited exposure to regular sunlight, may offer you no benefit to bone health. Weight bearing exercise like walking, running, biking, and playing some sports also helps keep calcium in bones. A high salt diet can increase the amount of calcium excreted in the urine and potentially lead to calcium deficiency (and kidney stones, if you are prone!). Vitamin K has also been studied with regards to its role in bone health (jury’s still out on this one).
If I’m counseling a healthy person that just wants to lose weight, I encourage some milk or dairy in moderation, and I don’t really care if it’s whole, 2%, or nonfat (I enjoy a nice 1% myself). Yes, whole milk has more calories, but they are relatively high-quality calories because they also provide essential vitamins, minerals, and protein. Oftentimes a diet recall will reveal that a glass of whole milk a day is the LEAST concerning eating habit my patients have.
There are also instances when I recommend dairy avoidance: lactose intolerance, milk protein allergy, inflammatory bowel disease (for some people), irritable bowel syndrome (for some people), and coronary artery disease (recommend skim milk only) are among them.
Luckily you can get milk’s nutrients from other foods if you don’t want to (or can’t) eat dairy products. You can get calcium from broccoli, kale, collards, legumes, soy or almond milk, tofu, dried figs, fortified cereals, fortified orange juice, canned salmon with bones, canned mackerel, and canned sardines (bonus points for the fish because they also contain vitamin D). You can get vitamin D from sunlight exposure without sunscreen. Get 10 minutes a day if you are fair-skinned. If you are darker-toned and live in the north, you may need a little longer or you may want to take a supplement (ask your doctor to check your blood level of vitamin D first and only supplement if it’s low).
Final thoughts: Don’t believe everything you read on the internet, even if a doctor wrote it. Especially if it sounds hostile, threatening, or it’s attempting to strike fear in the reader. And beware of the word “proven”. A true practitioner of science-based medicine will never claim that a single study or even a small pool of studies (especially if they are observational in nature) can “prove” any theory. We can have “evidence” that “supports” a theory or hypothesis, but “proof” actually doesn’t exist in science.
* The very recent period of ultra-processed, nutrient-poor foods notwithstanding.
** I should say “former” favorite; I’ve stopped listening.
*** This is in contrast to limited bioavailability of the naturally-occurring forms of vitamin A, D, E, and K in plants. It is best to consume your plant sources of fat-soluble vitamins with a little fat (like extra virgin olive oil). This fat stimulates the release of bile into the intestine which helps break down food, extract vitamins, and improve absorption.9
- http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Milk/ucm301969.htm –
Other articles that I used as references for this post: