The Dairy Question

For decades, we were told that milk builds strong bones and belongs in every healthy diet. Then came a wave of books, documentaries and diets telling us to cut it out completely. The truth, as so often in nutrition, lies somewhere in between, and it depends a great deal on who you are, what kind of dairy you choose, and how your body responds to it.

A very modern food

Humans are the only mammals that drink milk after weaning, and the only ones that drink the milk of another species. For most of human history, adults couldn't digest it well. To digest lactose, the natural sugar in milk, we need an enzyme called lactase. Most mammals, and most humans, make less of it after early childhood.

Around 7,500 years ago, in some herding communities of Europe, Africa and the Middle East, a genetic change spread that allowed adults to keep making lactase. Today, around two-thirds of the world's adults still have a reduced ability to digest lactose. It's least common in northern Europe, including the UK, and most common in East Asia, Africa and among Indigenous peoples of the Americas.¹

Long before this change, people found another way to enjoy milk: they fermented it. Friendly bacteria in yoghurt, kefir and cheese digest much of the lactose for us. This is one reason fermented dairy features in so many traditional diets.

What's in milk?

Milk is a remarkably complete food, designed to grow a young animal fast. It provides high-quality protein (mainly casein, with whey), calcium, phosphorus, potassium, vitamins B2 and B12 and, in the UK, a large share of our iodine, which the thyroid needs. It also naturally contains growth factors and small amounts of hormones. Some of these qualities are helpful; others may be less so for adults. It depends on the person. (See The Hormone Web.)

Does dairy really build strong bones?

Calcium is essential for bones, and dairy is a rich source. But the picture is more complicated than the old adverts suggested.

• Countries that drink the most milk, such as those in Scandinavia, also have some of the highest rates of hip fracture in the world. This kind of comparison can't prove cause and effect, as many other factors are involved, such as sunlight, height and how long people live. But it shows that milk alone doesn't guarantee strong bones. (See Living by the Sun.)
• A large study of nearly 100,000 Americans found that drinking more milk as a teenager did not lower the risk of breaking a hip later in life.²
• In a Swedish study of over 100,000 adults, women who drank three or more glasses of milk a day had more fractures and a higher risk of dying during the study than those who drank less. Interestingly, eating more fermented dairy, such as yoghurt and cheese, was linked with lower risks.³ These are observational studies, so they can't prove that milk caused the difference, but they suggest that more milk isn't always better.

Bones depend on a whole team of nutrients, including vitamin D, vitamin K2, magnesium and protein, along with good digestion, balanced hormones and plenty of movement. Dairy can be a useful part of that picture, but it isn't essential. (Read more in Living Bones.)

Not all dairy is equal. Fermented dairy stands apart.

Fermented dairy: a different food

Across the research, one pattern stands out: fermented dairy behaves differently from milk.

• Blood sugar. In a large analysis of three American studies and other research, each daily serving of yoghurt was linked with an 18% lower risk of type 2 diabetes, while milk showed no clear link.⁴
• The gut. Live yoghurt and especially kefir contain friendly bacteria and yeasts, and fermentation breaks down much of the lactose, so many people who struggle with milk find them easier to digest. (Read more in The Master Regulator.)
• Bowel health. The World Cancer Research Fund concludes that dairy foods probably help protect against bowel (colorectal) cancer, likely because of their calcium and, for fermented dairy, effects on the gut.⁵

It's worth knowing that a good deal of dairy research is funded by the dairy industry. That doesn't make it wrong, but it's one reason to look at the overall pattern of evidence, rather than any single study.

Where dairy may not help

• Skin. A review of studies in over 78,000 young people found that drinking milk, especially skimmed milk, was linked with a higher risk of acne.⁶ Milk raises levels of IGF-1, a growth hormone that can stimulate oil glands.⁷ Many people with acne notice a difference when they cut back on milk. (Read more in Skin Deep.)
• Prostate health. The World Cancer Research Fund found limited evidence that diets high in dairy may increase the risk of prostate cancer, possibly through IGF-1 or high calcium intakes.⁵ The evidence isn't strong enough for firm conclusions, but it's a reason for men not to overdo it.
• Digestion. Bloating, wind, loose stools or stomach pain after milk can be signs of lactose intolerance.
• Mucus. Many people feel milk makes mucus thicker, and traditional medicine has long seen dairy as "mucus-forming". In one study of volunteers given a cold virus, milk didn't increase the amount of mucus they produced, though some people do notice a coating, thicker feeling in the mouth and throat.⁸ If you notice it, trust your own experience.

A1 and A2 milk

Cow's milk contains two main types of a protein called beta-casein: A1 and A2. Most modern dairy breeds, such as Holstein-Friesians, produce a mix of both. Older breeds such as Jersey and Guernsey cows, and goats, sheep and buffalo, produce mainly A2.

When A1 casein is digested, it releases a fragment called BCM-7, which some researchers believe may cause digestive discomfort in sensitive people. In one trial, people who felt unwell after milk had fewer digestive symptoms when they drank A2 milk instead of ordinary milk.⁹ The study was funded by a company that sells A2 milk, and more independent research is needed, but it may be worth trying if ordinary milk doesn't suit you.

Goat's and sheep's milk

Goat's and sheep's milk have been enjoyed for thousands of years, particularly around the Mediterranean. Their casein is mostly A2, and the fat is in smaller droplets, which many people find easier to digest. They still contain lactose (a little less than cow's milk), so they don't suit everyone with lactose intolerance. Goat's yoghurt, kefir and cheese, and sheep's cheeses such as feta, pecorino and manchego, are lovely ways to enjoy them.

Choosing better dairy

• Favour fermented. Live yoghurt (homemade is wonderful), kefir and traditional cheeses. Making your own live yoghurt or milk kefir is simple, economical and gives you far more live bacteria than most shop-bought versions.
• Choose organic and grass-fed. A large review found organic milk contains around 50% more omega-3 fats than conventional milk.¹⁰ Organic standards also mean higher animal welfare and limits on antibiotic use. (Read more in Why Eat Organic?)
• Full-fat, in sensible amounts. Full-fat dairy is more satisfying and less processed than skimmed, and research no longer supports the idea that it harms the heart. Skimmed milk was also the type most strongly linked with acne.
• Plain, not sweetened. Flavoured yoghurts and milk drinks can contain as much sugar as a pudding. Add your own fruit instead.
• Think of dairy as a condiment, not a staple. A spoon of yoghurt, a little cheese and a splash of milk in tea is very different from several glasses of milk a day.

Thriving without dairy

Many people around the world are healthy without any dairy. If you avoid it, two nutrients need particular care:

• Calcium: from leafy greens such as kale, broccoli and pak choi, calcium-set tofu, sardines and tinned salmon with their soft bones, tahini, almonds, figs, beans and fortified plant milks.
• Iodine: from fish, shellfish, eggs and seaweed (in moderation). In the UK, milk is one of our main sources of iodine, and many plant milks aren't fortified with it. Organic milk also tends to contain less iodine than conventional milk.¹⁰ Low iodine can affect the thyroid, and it's especially important in pregnancy.

Does dairy suit you?

In traditional systems of medicine, dairy is seen as cooling, moistening and building. It may suit someone who is thin, dry and depleted, but feel heavy and congesting for someone prone to mucus, sluggishness or weight gain. (Read more in The Architecture of Balance.)

Your own body is often the best guide. If you suspect dairy doesn't agree with you, perhaps because of bloating, skin problems, sinus congestion or low energy, a short, structured break of three to four weeks, followed by carefully reintroducing it, can be revealing. It's best done with a practitioner's support, so you can stay well nourished and read the results clearly.

At Rootwise, we don't believe there's one right answer for everyone. For some people, a little good-quality fermented dairy is a nourishing food; for others, it's a hidden cause of digestive or skin troubles. A Rootwise consultation can help you discover which is true for you, and make sure you're well nourished either way.