Back to Cardiovascular Disease

Metabolic Syndrome

Synopsis

It affects approximately one quarter of the adult population in the Western world.

Although a lifestyle that includes a healthy diet and regular exercise is very important in managing this condition, the impact of specific foods on its development is not well understood. To date, emerging evidence from large population-based studies has indicated that adequate or higher intakes of milk products may be protective. The exact mechanisms by which milk products may confer a protective effect are still unclear. Several components or aspects of milk products may be responsible for this beneficial role, such as their low glycemic index and their content in the following nutrients:

• Calcium,
• Protein,
• Bioactive peptides,
• Conjugated linoleic acid (CLA), found in dairy fat,
• Magnesium,
• Potassium,
• Vitamin D.

The Evidence

The association between milk consumption, lifestyle, components of metabolic syndrome and insulin resistance was examined in a cross-sectional study of 365 school-aged children (mean age 10 years) from two elementary schools in lower-income suburbs of Buenos Aires, Argentina.¹

• Children who consumed ≥ 4 servings/day of milk (mainly whole milk) had a significantly better profile in terms of waist circumference, systolic blood pressure and insulin resistance compared to those who consumed ≤ 1 serving/day after controlling for important confounders;
• A higher intake of milk was associated with healthier lifestyle habits;
• After adjusting for other aspects of a healthy diet and lifestyle, milk consumption was still inversely and significantly associated with insulin resistance but consumption of fruit and vegetables was not.

In a prospective cohort study of 2,512 men (45 to 59 years) from the United Kingdom, milk and milk product consumption was associated with a significantly reduced risk of developing metabolic syndrome.²

• Men who drank 1 pint (16 ounces) of milk or more per day had a 62% reduced risk of developing the syndrome compared to men who drank little or no milk (relative risk [RR] = 0.38, p_trend = 0.02);
• Men with the highest total dairy product intake (milk, cheese, cream, butter, yogurt) had a 60% reduced risk of developing the syndrome compared to men with the lowest intakes (RR = 0.40, p_trend = 0.003).

In a population-based cross-sectional study of 827 adults (357 men, 470 women) in Tehran, increased milk product consumption was associated with a reduced risk of developing metabolic syndrome.³

• Subjects in the highest quartile of dairy consumption (≥ 3.1 servings/day of milk, yogurt and/or cheese) were least likely to have metabolic syndrome (odds ratio = 0.69, p_trend < 0.02);
• Greater milk product intake was associated with lower Body Mass Index (BMI) (highest quartile = 24.0 kg/m² compared to lowest quartile = 26.7 kg/m²) and with a healthier diet in general, which included greater amounts of fibre, fruit, vegetables and whole grains.

The Coronary Artery Risk Development in Young Adults (CARDIA) Study, a 10-year prospective cohort study of 3,157 adults ages 18 to 30 years, also showed that an increased intake of milk products was significantly associated with a lower incidence of developing metabolic syndrome and each of its components among individuals who were overweight (BMI ≥ 25 kg/m2) at baseline.⁴

• Those who consumed the highest number of servings of milk products (≥ 5 servings/day), regardless of fat content, had a significant 72% reduced risk of developing metabolic syndrome than those who consumed the least amount (< 1.5 servings/day);
• The associations were dose-dependent: each daily serving of milk products was associated with a significant 21% lower odds of developing metabolic syndrome.

A large-scale cross-sectional study specifically designed to assess the types of food associated with metabolic syndrome also suggested an inverse association of both milk products and bread in men (n = 2,439), but not in women (n = 2,537), after adjustment for age, energy intake and waist:hip ratio.⁵

• Individuals who consumed ≥ 1 servings of milk products had a significant 40% lower prevalence of metabolic syndrome;
• All components were significantly lower in men who consumed milk products than in those who did not;
• The inverse association of milk intake and metabolic syndrome in women was limited to only one component of the syndrome (diastolic blood pressure).

In contrast to the aforementioned studies is one that involved 4,024 British women aged 60 to 79 years. This secondary cross-sectional analysis of data from the British Women’s Heart and Health Study found that women who never drank milk had a lower risk of developing metabolic syndrome compared to those who drank milk. The odds ratio was 0.55, p_trend = 0.03.⁶ One of the limitations of this study is that they did not assess quantities of milk consumed or intake of other milk products. As well, this study was not originally designed to test the hypothesis of milk intake and the risk of metabolic syndrome and is therefore not as robust in the assessment of this relationship compared to the previously mentioned studies.

In another cross-sectional study involving 1,896 older Dutch adult men and women (50 to 75 years), higher total dairy consumption tended to be associated with lower blood pressure and lower triglyceride levels but not with weight or other components of metabolic syndrome.⁷

TABLE 1
Clinical Identification of Metabolic Syndrome8 (criteria = 3 or more risk factors)

Risk factor	Defining level
Abdominal obesity	Waist circumference
Men	> 102 cm
Women	> 88 cm
Triglyceride level	≥ 1.7 mmol/l
HDL-Cholesterol level
Men	< 1.0 mmol/l
Women	< 1.3 mmol/l
Blood pressure	≥ 130/85 mm Hg
Fasting glucose level	6.2-7.0 mmol/l

 

Potential Mechanisms

The potential mechanisms by which milk product consumption may reduce the risk for developing metabolic syndrome remain to be elucidated. There is evidence from several studies demonstrating a beneficial role for increased milk product consumption on components of metabolic syndrome, especially hypertension and obesity .

Some of the potential mechanisms by which milk products may protect against the development of metabolic syndrome are outlined in the paper by van Meijl et al.⁸ For example, calcium may exert its effects on metabolic syndrome by modulating serum lipid levels, body weight, fat mass and blood pressure.⁹

Conclusions

There is very good emerging evidence to suggest that adequate or higher intakes of milk and milk products may reduce the risk of developing metabolic syndrome.

Randomized controlled trials and mechanistic studies are needed to provide more definitive answers.

Keywords: cardiovascular disease, metabolic syndrome, type 2 diabetes

Related Articles

• Stroke

  Large population studies, including some prospective cohort studies, indicate a beneficial role for milk product intake in the prevention of stroke.

  Continue reading

• Cardiovascular Disease

  The evidence to date does not support an association between milk product consumption and an increased risk of cardiovascular disease.

  Continue reading