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Cardiovascular Disease and Milk Products: Summary of Evidence

Contrary to popular belief, according to current scientific evidence, milk products do not appear to increase cardiovascular risk.

By Anne-Marie Hudon, RD, MSc

Nutrition and Health Clinic, Institute of Nutrition and Functional Foods (INAF), Laval University

In collaboration with Louise Corneau, RD, MSc

Research Professional, Institute of Nutrition and Functional Foods (INAF), Laval University

Highlights

  • Milk product consumption appears to be associated with a decreased risk of cardiovascular disease;
  • A number of specific milk components and characteristic have been associated with an improvement in cardiovascular disease risk factors;
  • The presence of saturated fat in milk products does not appear to detract from their protective effect on cardiovascular health;
  • High-fat milk products seem to be as beneficial as low-fat milk products;
  • Depending on the type of milk products consumed, the protective effects may vary.

Introduction

The bad press surrounding saturated fat has often harmed the reputation of milk products. However, more and more scientific evidence suggests that milk product consumption may reduce the risk of cardiovascular disease. In fact, increasing evidence on saturated fat, particularly that from dairy sources, indicates that it may not be associated with the development of cardiovascular disease. Furthermore, milk products contain many components that may be related to the prevention or management of cardiovascular disease risk factors. These components include:

  • Calcium,
  • Potassium,
  • Phosphorus,
  • Vitamin D,
  • Proteins and certain peptides,
  • Fatty acids,
  • Vitamin K2.

The Evidence

A meta-analysis of 17 prospective cohort studies that included over 600,000 participants was conducted to assess the associations between milk product consumption and cardiovascular disease, particularly ischemic heart disease and stroke. For each 200-mL serving of milk consumed, a decrease of 6% in the risk of cardiovascular disease was observed. Moreover, the consumption of total milk products, low-fat milk products or high-fat milk products was not associated with risks of coronary heart disease, and total milk product intake was not associated with the risk of infarction.1

A second meta-analysis, including cohort and retrospective studies, showed a decrease of 15% in the risk of diabetes, 8% in the risk of ischemic heart disease, and 22% in the risk of stroke in individuals with higher milk products consumption compared to those with lower milk products consumption. Although the definition of high intake varied from study to study, in many of them, an intake above 568 mL per day was considered to be high. It should be acknowledged that in this meta-analysis, the heterogeneity of the studies used to evaluate the relationship between milk consumption and the risk of stroke makes the findings inconclusive.2 Furthermore, the same authors observed, based on data from a meta-analysis of 4 case-control studies, a reduction of 26% in the risk of metabolic syndrome in subjects with the highest dairy consumption relative to those with the lowest consumption.3

Data from a meta-analysis of 5 cohort studies with a duration varying from 2 to 15 years and including 11,500 cases of high blood pressure was analyzed to evaluate the relationship between milk product consumption and blood pressure. It should be noted that high blood pressure is considered as one of the main risk factors of cardiovascular disease. The results showed that a high intake of low-fat milk products was associated with a decrease of 16% in the risk of hypertension. Moreover, a decrease of 8% in this risk was associated with a high intake of fluid milk products (milk and yogurt), or 0.5 to 2.7 servings per day, whereas no risk modification was observed with the consumption of hard milk products (cheese).4 Since few studies separately analyzed the various types of milk products, it is difficult to conclude the effects of a specific milk product. However, there is data to suggest that some differences may exist.4

To learn more, consult Hypertension: Summary of Evidence.

Finally, there are many types of saturated fatty acids, and their respective effects on cardiovascular disease risk factors may not be the same.5 With regard to this, a multi-ethnic cohort study indicated that a high intake of saturated milk fat was associated with a lower risk of cardiovascular disease. This inverse association may possibly be greater in the case of high-fat cheese.6

Potential Mechanisms

The popular belief that dairy products are detrimental to health is mainly because of their content in saturated fat. However, although saturated fat intake is generally related to an increase in blood LDL cholesterol concentrations and milk product consumption may be associated with an increase in saturated fat intakes, milk products may not necessarily be related to an increase in the risk of cardiovascular disease but rather possibly with a decrease.6,7 Many components of milk products are thought to play a role in the prevention of cardiovascular disease, which makes the hypothetically harmful effects of the saturated fat that they contain less significant.

The preventive role of milk products against different cardiovascular disease risk factors may be due to various mechanisms, but these remain to be elucidated. Depending on the type of milk products consumed, the associations between milk products and cardiovascular risk may vary.7 The milk product components that most likely play a role in the prevention of cardiovascular disease are calcium, potassium, phosphorus, vitamin D, vitamin K2, various fatty acids and proteins, including certain peptides.1,8 The following table summarizes the various mechanisms that may explain the beneficial association between milk products and cardiovascular disease. Some of these mechanisms are better documented than others.

Potential mechanisms of the beneficial effects of milk products on cardiovascular disease

Major milk product component Hypothesis
Calcium
  • Blood pressure reduction (this is thought to be the case particularly for dietary calcium, especially in people with insufficient intakes)4
  • Reduction in total cholesterol*9
  • Reduction in LDL cholesterol*9
  • Reduction in total cholesterol/HDL cholesterol ratio*9
  • Increase in HDL/LDL ratio*9
  • Weight management9
Potassium
  • Limitation of the increase in blood pressure associated with a high sodium intake4,9
Magnesium
  • Blood pressure control*9
Phosphorus
  • Blood pressure reduction1
Vitamin D
  • Improvement in blood pressure*9
  • Increased insulin sensitivity9
  • Glycemic control (particularly in people who are vitamin D deficient, insulin resistant or diabetic)9
Proteins and certain peptides
  • Blood pressure reduction*4,9
  • Reduction in triglyceride concentrations*9
  • Reduction in total cholesterol*9
  • Reduction in LDL cholesterol*9
  • Increase in satiety level*9
  • Improvement in insulin sensitivity9
Milk fatty acids
  • Blood pressure reduction (oleic acid)9
  • Increase in HDL cholesterol* (conjugated fatty acids, trans-palmitoleic acid, oleic acid)9
  • Reduction in triglyceride concentrations* (trans-palmitoleic acid and oleic acid)9
  • Reduction in LDL cholesterol* (conjugated fatty acids)9
  • Reduction in total cholesterol/HDL cholesterol ratio* (trans-palmitoleic acid)9
  • Decrease in insulin resistance* (trans-palmitoleic acid and oleic acid)9
  • Weight management* (oleic acid is thought to promote the deposit of subcutaneous instead of visceral fat)9
Vitamin K2 (menaquinones)
  • Reduction in blood vessel calcification9
  • Maintenance of blood vessel integrity

The mechanisms that remain most unclear are identified with an asterisk.

Conclusions

Milk products are complex foods. More and more scientific evidence associates them with the prevention of cardiovascular diseases, which is due, among other reasons, to their influence on the risk factors of these diseases. The majority of studies included in the meta-analyses cited above were conducted over a period when low-fat milk products were not very popular, or before the 1990s for the United States and before the 2000s for the United Kingdom,2 which suggests that the beneficial effects of low-fat milk products may possibly not be greater than those of high-fat milk products. However, few studies have compared the separate effects of high-fat milk products with those of low-fat milk products on the prevention of cardiovascular disease. More studies are needed to fully elucidate the relationship between milk product consumption and cardiovascular disease risk.

References

  1. Soedamah-Muthu SS et al. Milk and dairy consumption and incidence of cardiovascular diseases and all-cause mortality: dose-response meta-analysis of prospective cohort studies. Am J Clin Nutr 2011;93(1):158-71.
  2. Elwood PC et al. The consumption of milk and dairy foods and the incidence of vascular disease and diabetes: an overview of the evidence. Lipids 2010;45(10):925-39.
  3. Elwood PC et al. The survival advantage of milk and dairy consumption: an overview of evidence from cohort studies of vascular diseases, diabetes and cancer. J Am Coll Nutr 2008;27(6):723S-34S.
  4. Ralston RA et al. A systematic review and meta-analysis of elevated blood pressure and consumption of dairy foods. J Hum Hypertens 2012;26(1):3-13.
  5. Mensink RP et al. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr 2003;77(5):1146-55.
  6. de Oliveira Otto MC et al. Dietary intake of saturated fat by food source and incident cardiovascular disease: the Multi-Ethnic Study of Atherosclerosis. Am J Clin Nutr 2012;96(2):397-404.
  7. German JB et al. A reappraisal of the impact of dairy foods and milk fat on cardiovascular disease risk. Eur J Nutr 2009;48(4):191-203.
  8. Rice BH et al. Dairy components and risk factors for cardiometabolic syndrome: recent evidence and opportunities for future research. Adv Nutr 2011;2(5):396-407.
  9. Kidd PM. Vitamins D and K as pleiotropic nutrients: clinical importance to the skeletal and cardiovascular systems and preliminary evidence for synergy. Altern Med Rev 2010;15(3):199-222.

Keywords: cardiovascular disease, cardiovascular risk factors, saturated fat

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