Strokes and heart attacks are among the leading causes of mortality and morbidity throughout the world and South Africa is no exception. According to Crause (2012), premature deaths due to heart and blood vessel disease in South Africans between the ages of 35-64 years are predicted to increase by up to 41% by the year 2030. Worryingly, the incidence of stroke is particularly high in our black population and is the major cause of deaths in black South Africans.
Benefits of calcium
A variety of studies have indicated that diets rich in calcium may help to lower high blood pressure, reduce obesity and thus reduce the risk of stroke and cardiovascular disease. On the other hand, two recent meta-analyses of the results of clinical studies where calcium supplements were used to try and lower blood pressure, showed that calcium supplements which do not contain vitamins D and K, may well increase the risk of stroke and heart disease because of deposition of the calcium in blood vessels (Kuanrong et al, 2012).
Understandably studies to investigate these two very different effects of calcium intake, are urgently required. One such study was conducted by Dr Susanna Larsson and her team at the Karolinska Institute in Stockholm, who studied a very large group of Swedish men and women for a period of 10 years to determine if the consumption of low-fat dairy foods is associated with a reduction in the incidence of stroke or not. The researchers found that of the nearly 75 000 subjects, those who had the highest intakes of low-fat dairy products, had the lowest incidence of total stroke and cerebral infarction.
The Dash Diet
Scientists have suspected for some time that consuming low-fat dairy products such as low- or fat-free milk, yoghurt, and cottage cheese, has a protective effect against stroke and other cardiovascular disorders. Hypertension or high blood pressure is one of the leading, but also preventable, causes of stroke. The Dietary Approaches to Stop Hypertension (Dash) diet, which was developed in the USA, includes low-fat dairy products as its number one component, and it has been producing good results in lowering high blood pressure for more than a decade. Therefore, drinking adequate quantities of low-fat milk and eating plenty of low-fat yoghurt and cottage cheese as prescribed in the Dash diet can be expected to not only lower hypertension, but also to prevent stroke.
In 1997, the subjects in this Swedish study completed a 350 item questionnaire about dietary intake and other lifestyle factors. Over the 10 year period, Dr Larsson and her coauthors, tracked how many of the subjects developed strokes (i.e. 4089 cases). They then compared low-fat dairy food intake with the incidence of strokes in the study group and found that there was a statistically significant inverse association between intake of low-fat dairy and strokes. In other words, those men and women who ate the most low-fat dairy foods, were 12% less likely to develop a stroke and 13% less likely to suffer from cerebral infarction than the subjects who ate the least low-fat dairy. High-fat or full-cream milk and dairy products did not have a protective effect against stroke.
Because this was a powerfully designed study (having a very large sample population; careful recording of food intake; and accurate data on stroke incidence obtained from the Swedish Hospital Discharge Registry), it is evident that drinking low-fat milk and eating low-fat dairy foods, can lower the risk of developing strokes. The low-fat dairy foods mentioned in this report which are available in South Africa, include: fat-free milk and yoghurt (0,5% fat), low-fat milk, yoghurt and drinking yoghurt (2% fat), and fat-free cottage cheese (1,5% fat).
Dr Larsson and her team (2012), suggest that nutrients such as the protein and calcium in low-fat dairy products lower blood pressure, combat the metabolic syndrome and protect against strokes. This Swedish study has provided proof that having three or more servings of low-fat dairy per day will help to combat hypertension and may prevent you from having a stroke.
In contrast to the Swedish study described above, the researchers working on the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg), analysed data obtained from nearly 24 000 subjects participating in the so-called Heidelberg cohort of the EPIC Study to evaluate the effects of dietary and supplemental calcium on cardiovascular events (Kuanrong et al, 2012).
Kuanrong and coworkers (2012) followed-up their subjects for 11 years during which time, 354 cases of myocardial infarction and 260 cases of stroke with 267 deaths, were reported in the study population. The subjects with the third highest intakes of dietary calcium had a significantly reduced risk of heart attacks, but use of calcium supplements was once again found to increase the risk of myocardial infarction, as was previously shown in the two meta-analyses.
These results prompted Kuanrong and her team (2012) to conclude that "calcium supplements which might raise MI (myocardial infarction) risk, should be taken with caution".
The results of these two very large and powerful studies indicate that using low-fat dairy products such as fat-free or low-fat milk, yoghurt and cottage cheese as part of a balanced diet may combat hypertension and protect against strokes. Individuals who are not able to use dairy products because of milk allergy or lactose intolerance, and rely on calcium supplements to provide their daily calcium intake, may need to switch to supplements that also contain vitamins D and K, to prevent increasing their risk of heart attacks. The fact that milk and dairy products in Europe and the USA are fortified with vitamin D, may also play a role in providing protection. The time may well have come to encourage producers to also fortify South African dairy products with vitamin D.
- (Dr IV van Heerden, DietDoc, July 2012)
(Crause L (2012). Letter from the Editor. SA Cardiology & Stroke Journal, Vol 6(3):6; Kuanrong L et al (2012). Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg). Heart, Vol 98:920-925; Larsson SC et al (2012). Dairy Consumption and Risk of Stroke in Swedish Women and Men. Published in: Stroke - Journal of the American Heart Association. Published online April 2012)
(Photo of man drinking milk from Shutterstock)
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