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|All Health and Nutrition Bites|
Calcium & Vitamin D Supplements:
The Risk/Benefit Ratio
Not long ago I got an email from a Dr. Gourmet reader who was frustrated by some of my answers to Ask Dr. Gourmet questions. For example, the question about whether drinking diet soda is linked to obesity. There isn't a lot of evidence, and it certainly doesn't show that drinking diet soda will cause obesity, but it doesn't look like drinking soda of any kind is all that great an idea, especially when coffee, tea and water is definitely great for you.
Drinking milk may be bad for your bones
For years, if not decades, we have been told to drink our milk in order to build strong bones. Milk is a good source of calcium, Vitamin D, and phosphorus, all important nutrients for bone formation and maintenance, so many people are told that they should drink at least three glasses a day to help prevent fractures and osteoporosis.
Need to improve your cholesterol profile? Make sure you get enough calcium
One recent study involving weight loss appears to show that high calcium intake, whether in pill or dairy food form, will help reduce blood pressure and improve one's cholesterol profile. So was it the weight loss that did it, or the calcium in the dairy? Scientists at Laval University in Canada designed a study to help make that distinction (Am J Clin Nutr 2007;85:54-9).
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Today's article is another one that I've seen all over the news: the headlines imply that adding more dairy products to the Mediterranean Diet improves metabolic scores such as blood pressures, cholesterol scores, and insulin and glucose levels. From the abstract's conclusion:
Following a MedDiet with additional dairy foods led to significant changes in markers of cardiovascular risk over 8 wk. The MedDiet supplemented with dairy may be appropriate for an improvement in cardiovascular risk factors in a population at risk for CVD [cardiovascular disease] (Am J Clin Nutr 2018;108:1166-1182).
The authors recruited 41 men and women between the ages of 45 and 75 who were at risk of cardiovascular disease. In an order assigned randomly, the participants followed either a modified Mediterranean Diet (supplemented with additional dairy products that provided the recommended daily supply of calcium) for eight weeks, or a Low Fat control diet for eight weeks. The two diet periods were separated by an 8-week washout period, during which the participants returned to their usual diets. The subjects met with dietitians biweekly to discuss their assigned diets to help with maintaining their assigned diet, and turned in dietary records as well.
At the start and end of both diet periods the participants underwent blood pressure testing as well as having blood drawn for cholesterol and other scores. They also underwent body composition testing to measure their lean and fat mass.
In this study the authors found that a MedDiet supplemented with additional dairy improved systolic blood pressures, increased HDL cholesterol (the good kind of cholesterol), and lowered triglycerides. No differences were seen for diastolic blood pressures, total cholesterol, LDL cholesterol, insulin, or glucose scores. On the surface the study seems valid, if small: a randomized, controlled crossover trial would seem the best way to find out if one diet is superior to another.
Until you get access to the full paper and read the full article.
I might not have sought out this particular article if I had not seen a retweet in my Twitter feed. The person retweeted Dr. Gregory Miller, PhD, who simply said, "Dairy Foods Can Fit Into a Mediterranean Diet." Accurate enough, but I noticed that his Twitter handle is @drdairy50. He works for the National Dairy Council: it's his job to promote dairy consumption.
Dr. Miller is not listed as an author on the study and likely had nothing to do with the study himself since it was performed in Australia, but I'm wary of industry employees like Dr. Miller who are paid to lend the weight of their expertise to various food industries. So I read the article and noted a few troubling points.
First, the study was funded by a Dairy Australia Research Grant. To be fair, the article also states that "Dairy Australia had no role in the study design, implementation, analysis, or interpretation of data." Although Dairy Australia does not appear to have supplied dairy products for the study, The Almond Board of Australia donated almonds and other manufacturers donated cheese, extra-virgin olive oil, legumes, tuna, and salmon. Not something that can in and of itself condemn the quality of an article, but something to bear in mind. This is, after all, why we require such disclosures.
Second, the authors made adjustments to the Mediterranean Diet over and above supplementing the diet with additional dairy products. Their Mediterranean Diet was based on that used in the PREDIMED study that I've reported on here, here, here, here, here, here, and here. Instead of the participants being advised to consume at least 4 Tablespoons of extra-virgin olive oil daily, the Australians only consumed at least 1 Tablespoon per day, "in order to increase the palatability and sustainability of the MedDairy intervention."
Third, the comparison diet was a low fat diet. Participants were instructed to follow their regular diet, but choose low fat versions of foods and follow "LF [low fat] cooking methods," consuming less than 20ml of oil per day and less than 2 teaspoons of butter or margarine per day. They were not instructed to avoid "biscuits, pastry, and ice cream," but to choose low-fat alternatives.
It's true that for a long time those at risk of cardiovascular disease were instructed to follow a low fat diet. And certainly the "low fat" diet instructions described in this study sound very much like the kind of advice we physicians might have given regarding a low-fat diet.
But we now know that such a diet is not the best diet for heart disease: the overwhelming preponderance of evidence points to a Mediterranean Diet as the most effective and sustainable diet for those at risk of heart disease. This isn't even news: all the way back in 2006 I reported on a (also somewhat flawed) study that suggested that the Mediterranean Diet to be superior to an American Heart Association low-fat diet in reducing the risk factors for heart disease. Comparing a Mediterranean Diet - even one adjusted like this one - to a low-fat diet is a sure thing: of course the MedDiet is going to show better results!
Further, while there's some evidence that consuming full-fat dairy products might reduce your risk of diabetes, increasing your intake of higher fat dairy products has been shown to be related with greater weight gain over a 12-year period.
Lastly, although the authors seem to be very concerned about making sure Australians consume enough calcium, they conveniently ignore the long list of foods that are also high in calcium that are not dairy products, including fortified cereals and orange juice; spinach, collard greens, turnip greens, and Swiss chard; almonds; and even sesame seeds. By no means are dairy products the only significant source of calcium in people's diets, and you don't have to consume dairy products to get enough calcium (here's an Ask Dr. Gourmet question on whether you need to drink milk to get enough calcium).
This study would be far more useful if it were not comparing a Mediterranean Diet with less olive oil and more dairy with a low-fat diet. If you want to know if adding dairy to a Mediterranean Diet will still affect metabolic and other scores positively, then compare a "usual diet" versus a standard Mediterranean Diet versus a Mediterranean Diet plus additional dairy.
Even if the better metabolic scores versus a low-fat diet are in spite of the addition to the amount of dairy products (testifying to the power of the Mediterranean Diet), the fact remains that dairy's effects on health are mixed and there are sources of calcium that are not dairy that are easily incorporated into a Mediterranean Diet. Assuming that a Mediterranean Diet is deficient in calcium is specious at best.
First posted: December 19, 2018