Originally posted 2016-02-22 14:43:32.
Many studies indicate that dairy products may protect against heart disease.
To expand and update the evidence base, a team of researchers conducted a meta-analysis, combining the results of 31 previous observational studies.
Below is a detailed overview of their results, recently published in the British Journal of Nutrition.
Eating Dairy May Reduce Heart Disease Risk
Many studies suggest that dairy products may protect against heart disease. Yet most of the available evidence is based on observational studies, which can’t prove causation.
On the other hand, some scientists have suggested that high-fat dairy containing saturated fat may increase the risk of heart disease by raising LDL-cholesterol.
This is controversial, since dairy products have also been shown to raise HDL-cholesterol and reduce blood pressure.
What’s more, emerging evidence indicates that saturated fat does not increase heart disease risk — its effect may simply be neutral.
Other studies suggest that milk fat may have different effects on risk factors for heart disease, depending on what dairy product it comes from.
A group of researchers from EpidStat Institute, USA, did a systematic review and meta-analysis of observational studies examining the association of dairy products and heart disease.
This was a systematic review and meta-analysis of observational studies examining the association between dairy products and heart disease.
A total of 31 prospective cohort studies, including over one million adults, were selected using strict inclusion criteria.
A prospective cohort study is a type of observational study that follows individuals over time, investigating how certain factors affect the rates of a certain outcome.
In the present meta-analysis, the included studies assessed dairy consumption using food frequency questionnaires. They then followed the participants for 5–26 years, while recording all heart disease events.
Outcome values included:
- Heart disease: Diseases of the heart and blood vessels are collectively known as heart disease, or cardiovascular disease. This includes conditions such as heart attacks, coronary heart disease, heart failure and stroke.
- Coronary heart disease (CHD): This disease is characterized by the clogging of the blood vessels that supply the heart with oxygen. It may eventually lead to heart attacks or heart failure.
- Stroke: Also known as brain attack, stroke is when blood flow in the brain is interrupted, leading to cell death. This may be caused by clogged or ruptured blood vessels.
In addition to examining the association of total dairy intake with heart disease, the researchers divided dairy products into categories and did sub-analyses on each of the groups.
These categories included milk, cheese, yogurt, calcium from dairy products, low-fat dairy and full-fat dairy.
Bottom Line: This was a systematic review and meta-analysis examining the association of dairy consumption with heart disease, coronary heart disease and stroke.
Finding 1: Eating Dairy Reduced the Risk of Heart Disease
This study suggests that total dairy intake is associated with a reduced risk of heart disease, coronary heart disease and stroke.
In fact, the reduction in risk may be as high as 5–15%, regardless of fat content.
Additionally, there were no significant differences between intake levels. One serving per day appeared to be as beneficial as three servings.
These results are also supported by previous meta-analyses on the association of dairy products with heart disease, coronary heart disease and stroke.
Bottom Line: Total dairy consumption was associated with a reduced risk of heart disease, coronary heart disease and stroke.
Finding 2: Eating Cheese Reduced the Risk of Heart Disease
Previous studies indicate that eating fermented dairy products, such as cheese, may protect against heart disease.
The present study supports earlier findings, suggesting that cheese may reduce the risk of coronary heart disease by 18% and stroke by 13%.
All levels of intake appeared to be protective.
Bottom Line: Eating cheese was significantly associated with a reduced risk of coronary heart disease and stroke.
Several additional findings were reported, including:
- No benefits from milk: Drinking milk was not associated with a reduced risk of heart disease, coronary heart disease or stroke.
- Calcium reduced stroke risk: Calcium from dairy products was not significantly linked with coronary heart disease. However, it was associated with an estimated 31% reduction in the risk of stroke, on average.
- Yogurt is inconclusive: Due to lack of data, the study couldn’t form any conclusions about the effects of consuming yogurt. More studies are needed.
Bottom Line: Milk consumption was not associated with a reduced risk of heart disease, whereas dairy calcium seemed to protect against coronary heart disease. The effects of eating yogurt are still unclear.
This systematic review and meta-analysis appears to have been well planned and implemented. Nevertheless, it has one important limitation: it used data from observational studies, which can’t prove causation.
For example, people who eat a lot dairy products may simply have healthier lifestyle habits, compared to those who eat less dairy.
However, most of the studies included in this meta-analysis adjusted for dietary and lifestyle factors, and other studies have consistently reported similar associations.
This indicates that the observed associations are at least partly due to the direct effects of dairy consumption on heart disease risk.
Finally, it would have been interesting if the study had looked into the effects of different dairy fats. For example, butter appears to raise LDL-cholesterol to a greater extent than cream, as discussed in our previous research review.
Bottom Line: This study was both well planned and implemented. However, it was based on observational studies, which can’t prove a cause-and-effect relationship.
Summary and Real-Life Application
This study suggests that consuming dairy products may reduce the risk of heart disease, coronary heart disease and stroke.
Among the different types of dairy products, cheese seems to be an especially good choice.
Simply put, eating dairy appears to be healthy for your heart and blood vessels.