Claim that fermented dairy products reduce heart attacks leaves us feeling sour – HealthNewsReview.org

Our Review Summary

dairy productsThe study described in this news release is a 20-year observational analysis of a very specific subgroup: Men from Eastern Finland, ages 42-60. The research question is: how do fermented dairy products (like yogurt, kefir, sour milk, cottage cheese, and quark) compare with non-fermented dairy (mostly milk) when it comes to the risk of heart attacks?

The authors of this study of just under 2,000 men report that men who consumed more low-fat/fermented dairy had lower rates of heart attack compared with men who consumed less of those products.

But we get no sense of just how much difference there was between the groups, the volumes of dairy that had to be consumed, or what limitations of the study might make the findings debatable. Further, the release engages in some cause-and-effect language when describing fermented dairy products’ potential affect on cardiovascular health but these kinds of claims can’t be supported by an observational study.

Fortunately, the news release does not use unjustifiable language, and does make it clear that the mechanisms of action behind the study’s findings are not completely understood.

Why This Matters

There is an emerging assumption that fermented dairy products might be “pro-biotic” and, therefore, “heart-friendly.” But, at this time, that remains purely speculative.  There’s currently no proof that any alleged pre-biotic or pro-biotic — or dairy product, for that matter —  protects against heart disease.

Because CHD is a key cause of sickness and death, it is important to understand dietary patterns that might prevent or postpone the disease.  Although this research is interesting, it is not conclusive because of issues discussed below.

Criteria

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

Main findings mentioned include:

  • Men who ate more fermented dairy products had lower rates of CHD.
  • Men who ate more non-fermented dairy had a higher rates of CHD.
  • However, consuming high-fat/fermented dairy products (ie. cheese) was not associated with CHD.

Readers are given no sense of just how much the risk is increased or decreased in these groups.

The only data provided from the study is this:

The risk of CHD was 26% lower in those men who consumed the highest amount of low fat (<3.5%) fermented dairy (compared to the lowest consumption group).

It would be difficult for many readers to put that number into context without knowing how much low-fat/fermented dairy was consumed.

Some data contained in the study might have helped put the numbers in context. According to the tables in the published manuscript, there is a modest reduction from 14 CHD events per 1,000 person years in the low intake group (of fermented dairy) to 10 CHD events per 1,000 person years in the high intake group (of fermented dairy).

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

There are three major limitations of this study that aren’t mentioned.

First, this is a prospective cohort study that can’t completely control for other health variables in the subjects being responsible for some of the changes observed.

Second, the use of a food questionnaire (even with some supervision by nutritionists) is not a completely reliable way to document dairy intake; especially when trying to pinpoint amounts and subtypes of dairy.

Finally, the cohort studied (Eastern Finnish men, ages 42-60) is a very specific subgroup. This limits the generalizability of the results.

The news release addresses none of this.  In the published manuscript the authors describe differences in smoking rates and other dietary patterns in the men who consumed more or less of the dairy types.  These other differences could have accounted for all of the differences in this observational study.

Does the news release establish the true novelty of the approach?

Satisfactory

The news release claims that the new research gives more weight to earlier study findings. It states:

“earlier studies have shown that fermented dairy products have more positive effects on blood lipid profiles and on the risk of heart disease than other dairy products.”

And that

“The new study provides further evidence on the health benefits that fermented dairy products may have over non-fermented ones.”

Links to the earlier studies would have been helpful. As yet, it’s still speculative to claim that fermented dairy products lower the risk of CHD.

Total Score: 3 of 8 Satisfactory

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