Milk: Is this as safe as we think it is?

Most people have milk in their diet but few meet the recommended daily quantities. Experts are now advising us to rethink these guidelines and explain why milk might not be as safe as we thought.

Milk may not be as good for our health as we once assumed, according to the recent research.
Milk may not be as good for our health as we once assumed, according to the recent research.

The reputation of dairy milk took a bit of a beating, with the likes of oat, almond and soy milk celebrated as environmentally friendly alternatives.

But cow’s milk remains a firm favorite for many people of all ages — sloshed over toast, as a frothy coffee companion, or enjoyed as a bedtime beverage.

The US Dietary Guidelines 2015-2020 recommends that individuals aged 9 years and over consume 3 cup-equivalents of fat-free and low-fat (1%) dairy products. U.S. put together according to the guideline. Health and Human Services Department, and U.S. Agriculture department, that includes milk, yogurt, cheese and fortified soy milk.

Yet the average dairy quantity U.S. adults consume is about 1.6 cups per day, far short of the recommended levels.

Does that mean that we should all look to our dairy consumption to increase?

New England Journal of Medicine experts don’t think so. Alternatively, they challenge the quality of the evidence on which these guidelines are based and suggest alternative ways to provide us with the nutrients required for our wellbeing.

Strength of evidence is ‘limited’

The debate about milk is, in fact, not a new one. 

Back in 2014, Connie M Weaver, emeritus professor and former head of the Nutrition Science Department at Purdue University in West Lafayette, IN, wrote an article in The American Journal of Clinical Nutrition highlighting the lack of good quality evidence in support of the dairy recommendations.

In her post, partly funded by Danone Institute International, Weaver alludes to the historic reasons behind the importance of milk to our diet.

“Dairy products are crucial to most recommendations on dietary advice. These have a package of essential nutrients and bioactive health constituents that are hard to get in diets with little or limited use of dairy products,” writes Weaver.

“Since the agrarian revolution, when energy sources changed from plant foods relatively high in calcium in hunter-gatherers ‘ diets to low-calcium cereal crops, the main source of dietary calcium was milk,” she continues.

Milk has been used in every American variation. Since its first publication in 1917, Dietary Guidelines The Dietary Guidelines for Americans Advisory Committee reviews the guide every 5 years, reviewing the evidence available.

Weaver cites research that shows how following a dairy-free diet in the form of a U.S.- style Western diet left adolescents aged 9–18 years struggling to achieve the necessary calcium intake.

In order to meet the daily intake of nutrients, milk and cheese contribute “46.3 percent of calcium, 11.6 percent of potassium, and 7.9 percent of magnesium in the American diet.”

However, as far as health in general is concerned, Weaver writes, “the strength of evidence for dairy consumption and wellbeing is constrained by the lack of adequately conducted randomized controlled experiments.”

Human health and the environment

Fast forward to 2020 and a new review paper takes up the argument in the New England Journal of Medicine.

Dr. Walter C. Willett and Dr. David S. Ludwig, both of whom hold positions at Harvard T.H. Chain School of Public Health and the Harvard Medical School in Boston, MA, address milk merits. We also pose questions about the potential risk it can bear to eat.

Both Dr. Willett, an epidemiology and nutrition professor, and Dr. Ludwig, an endocrinologist, claim no applicable conflicts of interest or funding by industry for their research.

Nccmed asked Dr. Willett why he is interested in studying the relationship between milk and health consumption.

“This is an important topic, as milk is one of the few items explicitly included in the U.S. and many other countries ‘ dietary guidelines, and the recommended amount in the U.S. (3 glasses per day or equivalent amounts of cheese or other dairy products) will represent a significant part of the overall diet,” he explained.

“However, research over the past several decades did not clearly support the need for such large intakes for fracture prevention, which was the main justification, and some questions about the harm were posed,” he added. “And we thought it would be useful to have an summary of the data on risks and benefits,”

But health is not the sole concern of Dr. Willett.

“Milk also has a strong environmental footprint, especially the production of greenhouse gases, and if everyone drank 3 glasses a day this would make it very difficult to prevent extreme global warming,” he explained. “This should be remembered, at least, when making decisions regarding milk production and consumption.”

Milk studies have ‘serious limitations’

The professors demonstrate in their report the contributions milk can make to the multitude of aspects of our wellbeing.

Many people probably get the many acquainted with bone health.

Milk is a ready source of calcium, a vital mineral for the production and maintenance of good bone function. Yet the research that set the daily guidelines for how much milk we should consume, and by extension calcium, were very small.

“The basis for the U.S. milk consumption recommendations stems from studies assessing the balance of calcium intake and excretion in only 155 adults in whom the average calcium intake required to maintain a balance was 741 mg per day,” the professors write in their article.

“These balance studies have other serious limitations, including short duration (2 to 3 weeks) and high usual intakes of calcium,” they continue.

The evidence is not in favor of milk consumption to reduce the risk of hip fractures, they explain further.

Alternatively, they point out that countries with high intakes of milk and calcium also have the highest rates of hip fracture.

They refer to a 2014 study by Dr. Willett in JAMA Pediatrics that examined men’s risk of hip fracture in relation to how much milk they drank during their teen years.

The results showed that higher intake of milk later in life leads to increased risk of hip fractures.

Two other examples are how quickly and how tall we grow. Research has established a link between consumption of these and milk. Yet when drawing conclusions at this point, the professors urge caution.

“The health effects of accelerated growth and greater height for adults are complex,” they write. “High stature is associated with lower cardiovascular disease risks but with higher cancer risks, hip fractures and pulmonary emboli.”

Weight, heart health, and cancer

Afterwards, Dr. Willett and Dr. Ludwig turned their attention to a host of other facets of our wellbeing that may or may not impact milk consumption.

Several studies have examined whether milk consumption is beneficial for adult and child weight management. Professors say that these have shown no “significant effects.”

They also point out that “contrary to U.S. Department of Agriculture (USDA) guidance on selecting low-fat dairy, low-fat milk does not appear to have benefits over whole milk for weight control— and in babies, available evidence suggests greater weight gain with low-fat milk than with full-fat milk.”

They also argue that there is weak evidence supporting a favorable effect of milk on high blood pressure and cholesterol levels, and that studies do not support milk as a risk factor for type 1 or type 2 diabetes.

Studies have shown mixed results as they looked at cancer. Several studies have linked milk consumption to a lower risk of developing colorectal cancer, likely because of the high calcium levels found in milk. Nevertheless, other studies have indicated elevated breast, prostate, and endometrial cancer levels.

But when it comes to heart disease, they said, “Moderate consumption of dairy foods will minimize cardiovascular disease by providing nutritional value and lowering glycemic load for people living in low-income countries with very high starch diets.”

Recommendation does not ‘appear to be justified’

So, what’s the overall take on milk for the professors?

“In our view, the current recommendation to considerably raise dairy food consumption to 3 or more servings per day does not seem warranted,” they conclude in the report.

The amount of milk a person should be consuming depends on individual circumstances, they say.

“If someone eats a high-quality diet of refined starch and sugar, as is common in many[ low-income] populations around the world, milk can fill some significant nutritional gaps,” Dr. Willett told Nccmed. “However, if the diet consistency is otherwise good, there will be far less additional nutritional benefits of milk.”

But what does this mean for our intakes of calcium and vitamin D?

“When milk consumption is low, the two nutrients of primary concern, calcium and vitamin D (which are of particular concern at higher latitudes) can be obtained from other foods or supplements without the potential adverse effects of dairy foods,” the professors conclude in their paper.

And here’s how they recommend that we get this done:

“For calcium, alternative dietary sources include kale, broccoli, tofu, nuts, beans, and fortified orange juice; for vitamin D, supplements can provide adequate intake at a far lower cost than fortified milk.”

— Dr. Walter C. Willett and Dr. David S. Ludwig

Should we drink milk or not?

When NCcmed asked Dr. Willett whether he thinks people should consider avoiding milk, he explained: “In our review, we concluded that milk is not an essential part of a healthy diet, but it is compatible with good health when consuming modest amounts. So we suggested a possible range for health from zero to about 2 servings per day for adults.”

“I think flexibility is good because for many reasons, different people have different preferences,” he continued.

“For environmental reasons, keeping this to about 1 serving a day on average would be important. This is actually not very different from current consumption, which is about 1.6 servings a day; going to 3 servings a day as has been recommended would be a radical change and is not necessary,” Dr. Willett concluded.

“Milk is deeply woven into the culture of many populations in cold climates because this was a way to provide nutrition year-round when many other foods were not available. In most of the world, people do not consume milk as adults, and it is not essential.”

— Dr. Walter C. Willett

NCcmed also spoke about Dr. Willet’s and Dr. Ludwig’s article and all things milk to Adda Bjarnadóttir, who is a registered dietitian nutritionist in Iceland and our in-house nutrition expert, about.

In, how well is the general public aware of the recommended guidelines on milk?

“I think most people are aware of the advice but don’t really take it to heart,” commented Bjarnadóttir. “This policy is also special, so that it can not be applied to all. A lot of the world’s population doesn’t accept milk, so dairy isn’t part of their daily routine.”

‘The dose makes the potion’

What kind of research would Bjarnadóttir like to see in the future to help clarify any connections between our health and milk?

“A good amount of research on milk and dairy is already available, and it’s one of those things that can be hard to study and get concrete results,” she explained.

“Milk intake in ordinary milk consumers vs. milk intake in people who are not used to drinking or do not tolerate milk will yield very conflicting and unreliable outcomes. There are also many confounding factors to consider, like the status of micronutrients and the intakes of macronutrients,” she continued. “Milk can give people who have a lower protein and, for example, calcium intake much more benefit than people who usually have higher intakes.”

“Actually, the dosage determines the formula. Consuming too much or too little of everything can have adverse effects on health.“

“For future research, I agree that we would obtain the most reliable information in well-defined randomized controlled trials in well-established groups of people of different ages with different normal intakes and well-recorded nutrient status,” Bjarnadóttir suggested.

“These findings, combined with longitudinal observational studies in well-established groups of people with a set normal milk intake, will give us some good data to work with.”

So, does Bjarnadóttir think we should drink milk or steer clear of that?

“While milk is not a necessary component of a healthy diet, I think if you tolerate milk and dairy, they can definitely be safe dietary additions. Milk is high in protein, nutrient rich and readily available,” she said.

“My advice would be to limit your intake to no more than 2 servings per day, and to encourage the consumption of non-sweetened, full-fat dairy such as yogurt or whole dairy. That being said, there are plenty of other ways to get the nutrients contained in milk and lead a very healthy life if you don’t like or tolerate dairy.”

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