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The Calcium Paradox: Shocking Research About Dairy No One Tells Us

The Calcium Paradox is a term coined by the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (UN) in response to a meta-analysis revealing that hip fracture probability rates were significantly lower in countries with low consumption of dairy and dairy products. The meta-analysis involved 72 studies from 63 countries conducted over a 60-year period between 1950 and 2011.

The criteria to consider when reviewing scientific studies includes:

  • How old is the study?

  • How many people participated?

  • How long were participants studied?

  • Was the study published in a reputable peer-reviewed journal?

  • Who funded the study?

When it comes to studies about nutrition and bone health, here are some additional considerations:

  1. Any long-range study is going to rely on self-reported data. The researchers don’t confine participants to a lab and control everything they eat. Nor can they reach back in time. For example, studies concluding that high milk consumption during adolescence increased the risk for hip fractures later in life are relying on participants’ memory of how much dairy they consumed a teenagers. 

  2. We typically eat a variety of foods. When a study focuses exclusively on one food item, that may overlook the impact of other foods on bone health. For example, whole wheat interferes with the absorption of calcium. So if people consume their calcium in the form of milk atop a bowl of cereal or in a dish of macaroni and cheese, the presence of wheat impedes absorption of the calcium in that meal.

  3. Environmental considerations may impact bone health. Weight-bearing exercise strengthens bones so someone who works in an active job may have stronger bones than someone who sits at a deck all day. Someone who works outside gets plenty of sunshine and vitamin D. An eighteen year study involving 72,000 postmenopausal women concluded that,An adequate vitamin D intake is associated with a lower risk of osteoporotic hip fractures in postmenopausal women. Neither milk nor a high-calcium diet appears to reduce risk.

  4. And finally, do the differences in the milk production process matter? In 1993 the FDA approved a bovine growth hormone that increased milk production in cows by nearly 33% from 15,000 pounds of milk per cow per year to nearly 20,000 pounds of milk per cow per year. That’s nearly 55 pounds of milk per cow per day. But Canada and the EU banned the sale of milk from cows treated with this hormone due to animal welfare concerns. So the milk consumed by people in those countries could be chemically different from milk consumed in the US.

This table shows the annual increase in milk production for cows treated with bovine growth hormone

Let’s return to the Calcium Paradox. Despite all the unknowns such as sunlight exposure and exercise, one thing is still clear -- people in countries with low milk consumption are at a much lower risk for hip fractures.

This trend chart shows positive coorelation between dairy consumption and higher incidence of hip fractures
This graph is from a 2020 review in the New England Journal of Medicine

How much calcium do we need? The answer depends on who you ask. The WHO recommends 500 mg / day, whereas the UK advises slightly higher 700 mg / day. The USDA recommendation is double the WHO recommendation at 1,000 mg / day for people under the age of 50 and 1,200 mg / day for older adults. 

According to a 2020 article in the New England Journal of Medicine, the US Department of Agriculture (USDA) recommendation is based on a study involving 155 adults over a period of 3 weeks which is consistent with information I found on the USDA’s website. This is a very remarkably small population and short duration for measuring nutritional impact on health. While I was on the USDA's site, I ran across an article from 2007 stating that the guidelines may be excessive. Despite this article on the USDA's own website, the official guidance still stands.

The USDA replaced the Food Pyramid with MyPlate in 2011, which recommends three servings of dairy products per day. Interestingly, MyPlate encourages consumption of low-fat dairy products although the article from the New England Journal of Medicine indicates: 

“Among 12,829 adolescents followed for 3 years, intake of low-fat milk was positively associated with gain in body-mass index (BMI, the weight in kilograms divided by the square of the height in meters), but intakes of full-fat milk and dairy fat were not…”. 

This graphic represents the My Plate eating plan from the US FDA

In 2017 Harvard Medical School published their version of My Plate called the Healthy Eating Plate which recommends limiting dairy to 1-2 servings a day. In the accompanying text it states, 

MyPlate recommends dairy at every meal, even though there is little if any evidence that high dairy intakes protect against osteoporosis, and there is considerable evidence that too-high intakes can be harmful.”
Harvard Medical School's Healthy Eating Plate is their recommended alternative to the My Plate eating plan from the US FDA

In closing, this is an excerpt from the conclusion of the 2020 article in the New England Journal of Medicine:

Pending additional research, guidelines for milk and equivalent dairy foods ideally should designate an acceptable intake (such as 0 to 2 servings per day for adults), deemphasize reduced-fat milk as preferable to whole milk, and discourage consumption of sugar-sweetened dairy foods in populations with high rates of overweight and obesity.

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