Are you wary of dairy? HFG senior nutritionist Rose Carr pours over the facts to bust the myths surrounding this staple food.
Most of us were brought up eating and drinking dairy products, such as milk, yoghurt and cheese. Some of us even have memories (fond or otherwise!) of the national free-school-milk program that ran from 1950 to 1973.
But how do dairy foods affect our health? You may have heard the popular theory that most of us have a mild milk intolerance, and that this intolerance is the culprit behind many common conditions, from tummy bloat to teen acne. You may have also read that some scientific studies suggest that dairy foods cause cancer, whereas others claim they actually prevent it.
A more common concern is that dairy foods promote weight gain, so when people decide to eat ‘healthily’ and slim down, they often ditch dairy foods — along with all their health benefits.
To muddy the milk picture even more, the research on this topic can be confusing or conflicting, so let’s take a look at the current evidence to get a clearer idea.
Why are dairy foods important?
Dairy foods contain a wide range of nutrients. They provide useful amounts of protein, along with vitamins riboflavin (B2) and B12 to maintain energy levels, the minerals calcium and phosphorus for strong teeth and bones, and zinc and iodine for immunity and better brain function.
On the downside, full-fat dairy foods can also be very high in fat, much of which is the saturated kind that’s associated with heart disease. And a high fat content equals more kilojoules, too.
Is there a link between dairy products and weight gain?
Some people, especially women, limit their intake of dairy foods in an attempt to control their weight.
In 2012, The American Journal of Clinical Nutrition published a review that looked at weight loss in association with dairy, and it concluded that “the addition of dairy to diets promotes neither weight gain nor weight loss”. In other words, if you’re worried about gaining weight, there’s no point in avoiding dairy products.
Can dairy foods cause heart disease?
Most of us are aware of the health message that we should lower our saturated-fat intake to reduce our risk of cardiovascular disease. We’ve learned how to choose reduced-fat dairy foods and to trim visible white fat from our meat, which has also been good for our hearts.
Even full-fat dairy foods may do our hearts no harm, according to Harvard University researcher Marcia de Oliveira Otto, though she does acknowledge that there may be other risks. After studying the effects of diet on heart health for more than a decade, she not only concluded that there was no evidence that dairy foods could cause cardiovascular disease, but also found a link between cheese consumption and a reduced risk of heart disease. Why? Well, the beneficial effect of cheese seems to be related to the whole food, not just the calcium. But for now, de Oliveira Otto warns that more evidence is required, and that it’s too early to think about changing the current guidelines that urge people to opt for reduced-fat dairy products.
In fact, the connection between saturated fat and health is a bit of a grey area, as it may depend on either the specific types of saturated fats in different foods or on other nutrients in the foods that contain these saturated fats.
And Professor Manohar Garg, from The University of Newcastle, proposes yet another theory: He says that high dietary levels of omega-3 fatty acids could limit the negative impact of saturated fats on our health. Some animal studies support his theory, but we need much more evidence to understand its relevance to human beings. Until we learn a lot more about these theories, the safest move for your heart health is to continue to use reduced-fat dairy.
What’s the link between dairy foods and bone health?
Think of your skeleton as the framework of a house: once it’s in place, you don’t expect it to change. But our bones are living tissue, so our bodies are constantly producing new tissue and disposing of the old. As we grow up, we make more tissue than we discard, but we soon reach ‘peak bone mass’ — the time when the body has the most bone tissue it will ever produce. Different areas of bone reach peak bone mass at different times, but by our early 20s, the body has achieved roughly 90 per cent, and by the time we’re in our 30s, it’s done. After that, we gradually lose bone tissue. And as we know, people with poor bone density are more likely to develop osteoporosis as they age.
Osteoporosis affects at least 600,000 Australians, and, unfortunately, its risk rises as we age. One in two women and one in four men over the age of 60 will suffer a fracture as a result of a reduction in bone mass and density during their lifetime.
To enjoy healthy bones throughout life, we first need to achieve the best peak bone mass that we can when we’re young, and then to ensure we lose as little of our bone tissue as possible in the following years. Dairy products, especially milk, help, because they’re a rich, easily absorbed source of calcium, which is essential to the continual process of building bone.
It’s easy to include dairy in our diets, yet many of us don’t consume as much calcium as we need for strong bones — and calcium is relatively scarce in other food groups. The problem is that more than 60 per cent of Australian women consume less than the recommended dietary intake for calcium.
The simple solution is to eat more reduced-fat dairy foods, such as milk, cheese and yoghurt. If you choose not to consume dairy, for whatever reason, you need to consciously ensure you’re getting enough calcium from other sources, such as canned fish with edible bones, leafy green vegetables, nuts and seeds, and calcium-fortified soy and rice milks.
Do our dairy needs change as we age?
Yes — as we get older, we need to increase our calcium intake to combat the bone loss that comes with age. Women over the age of 50 and men over the age of 70 should aim to consume 1300mg of calcium per day; people who are younger need 1000mg a day.
Studies of postmenopausal women show that a high calcium intake not only slows the rate of bone loss, but may also reduce the risk of fracture. Nearly four in five women over the age of 65 fail to get even 1000mg, so it’s important to eat rich sources of high-quality calcium, such as reduced-fat dairy products.
Calcium supplements can help you meet higher requirements, and you may need them if you’re at risk of osteoporosis. Always check supplement labels for their pure calcium content, and opt for a brand that provides more than 200mg per tablet. It’s best to take a supplement that also contains vitamin D, as D helps the body absorb calcium. If you’re thinking of taking a supplement, talk to your doctor or pharmacist about the dosage that’s right for you.
For most of us, consuming reduced-fat dairy foods remains the best way to meet our calcium requirements. Dairy foods are filling and nutrient dense, and they have a low GI, all of which makes them a valuable part of a healthy, balanced diet.
How much is enough?
The recommended daily intake for calcium is:
1000mg for women under 50 and men under 70
1300mg for women over 51 and men over 71
A serve of dairy equals:
1 cup (250ml) milk
2 slices (40g) cheese
Aim to eat two to three serves of reduced-fat dairy foods every day
1. Seventy-five per cent of people can’t digest dairy
Lactose is a natural milk sugar in dairy products. People who find it difficult to digest this sugar are lactose intolerant, which means they’re lacking in lactase, the enzyme the body needs to digest lactose. (Lactose intolerance can also follow a bout of gastrointestinal illness, but this usually passes as the gut bacteria recover.)
Your ethnicity directly affects your chances of having lactose intolerance. In Australia, up to 5 per cent of Caucasians and 75 per cent of non-Caucasians can’t tolerate lactose. In Asia, Africa and South America, more than 50 per cent of people have lactose intolerance, and in some Asian countries, the rate is nearly 100 per cent.
Most people with lactose intolerance still produce some lactase, which means they can consume small amounts of milk and other dairy products on a daily basis without experiencing any discomfort. In fact, many people can drink up to a cup of milk a day, but most lactose-intolerant individuals better tolerate foods such as cheese and yoghurt, as these contain less lactose.
2. Cheese causes constipation
No — eating cheese won’t constipate you. When Finnish researchers put nursing-home residents on a high-cheese diet and a separate no-cheese diet (both of which ran for three weeks), they noted no changes in either digestion time or degree of constipation — and this was despite a tenfold increase in the cheese consumption of subjects following the high-cheese diet! Consequently, the researchers rejected the practice of avoiding cheese to prevent constipation.
Still, it’s important to note that cheese has no fibre. If you eat so much cheese that you haven’t got room for fibre-rich foods, it’s time to find a better balance in your diet. You can also help keep your bowels healthy by drinking enough water and exercising regularly.
3. Cheese triggers bad dreams
Many people think that English novelist Charles Dickens is the source of this particular cheese myth, because his character Scrooge blames his nocturnal visions on the crumb of cheese he eats before going to bed in A Christmas Carol.
A more modern-day suspect upholding this particular myth is a mid-century antidepressant, the side effects of which can include nightmares. Before experts fully understood this drug, they implicated cheese as the culprit. (Today, people taking this drug are warned against eating cheese, as the combination can be fatal.)
There’s been little research into the relationship between cheese and nightmares, possibly because most academics don’t believe any such relationship exists. The British Cheese Board is rumoured to have conducted a study on the subject, but it hasn’t appeared in any peer-reviewed journals, and therefore seems to be more of a marketing exercise.
4. Milk contains harmful hormones
No, but cow’s milk contains various natural bioactive hormones, such as insulin-like growth factor 1 (IGF-1). Some experts say that milk’s IGF-1 content makes a negligible contribution to blood levels of IGF-1, but the hormone continues to interest researchers, especially in relation to prostate cancer.
US manufacturers often use a synthetic bovine growth hormone (as well as naturally occurring hormones) to increase milk production. But this practice is banned in Australia, New Zealand and the European Union.
5. Dairy products cause cancer
Some people think consuming large amounts of dairy protein may increase the risk of breast and prostate cancers. In 2007, the World Cancer Research Fund (WCRF), UK, undertook the most comprehensive review of all of the scientific evidence on diet, lifestyle and cancer prevention.
Its report acknowledges that diet is a difficult area to study because of the variety of foods and the complexity of our meals. In addition, researchers found conflicting evidence surrounding any links between dairy foods and cancer, so they’re without guidelines for dairy consumption as regards cancer prevention.
More recent reviews support recommendations that having three daily serves of milk and dairy products is safe and does not appear to increase overall cancer risk.
In 2011, scientists at New Zealand’s University of Otago reported that schoolchildren who drank milk every day reduced their risk of bowel cancer in adulthood by 30 per cent. (Previous studies in adults have suggested that calcium consumption may reduce bowel-cancer risk.)
As a result, the WCRF updated its findings the same year, noting a “probable”, as opposed to “convincing”, link between milk and calcium consumption and reduced colorectal-cancer risk.
Did you know? One in two Australian women over the age of 60 will suffer a fracture as a result of reduced bone density during her lifetime.