Calcium, magnesium and phosphorus status of elderly inpatients: dietary intake, metabolic balance studies and biochemical status

Magnesium and Hypertension in Old Age

Hypertension is a complex condition in which various actors and mechanisms combine, resulting in cardiovascular and cerebrovascular complications that today represent the most frequent causes of mortality, morbidity, disability, and health expenses worldwide. In recent decades, there has been an exceptional number of experimental, epidemiological, and clinical studies confirming a close relationship between magnesium deficit and high blood pressure. Multiple mechanisms may help to explain the bulk of evidence supporting a protective effect of magnesium against hypertension and its complications. Hypertension increases sharply with advancing age, hence older persons are those most affected by its negative consequences. They are also more frequently at risk of magnesium deficiency by multiple mechanisms, which may, at least in part, explain the higher frequency of hypertension and its long-term complications. The evidence for a favorable effect of magnesium on hypertension risk emphasizes the importance of broadly encouraging the intake of foods such as vegetables, nuts, whole cereals and legumes, optimal dietary sources of magnesium, and avoiding processed foods, which are very poor in magnesium and other fundamental nutrients, in order to prevent hypertension. In some cases, when diet is not enough to maintain an adequate magnesium status, magnesium supplementation may be of benefit and has been shown to be well tolerated.

Dietary intake of older patients in hospital and at home: the validity of patient kept food diaries

OBJECTIVE

To investigate the validity of a patient kept food diary in relation to weighted intakes and to measure dietary intakes of older people both in hospital and after discharge at home.

DESIGN

A randomly selected cohort of hospitalised elderly patients was recruited. All patients were instructed how to keep a record of all food and drink consumed and any leftovers. Food diaries were kept for up to seven days in hospital and for seven days in the community. In 18 consecutive patients dietary records were compared with weighed intake.

SETTING

Associate Teaching Hospital, United Kingdom.

RESULTS

A total of 116 patients participated in the study (median age 77 years, range 66-86 yrs; 49 female). We found significant correlations between food diary and weighted macronutrient intakes both in hospital and in the community. Overall the food diary predicted within+/-17% weighted energy intakes in 70% of individuals. Compared with the National Diet and Nutrition Survey for free-living elderly people in the UK (1998), we found more or less similar energy and micronutrient intakes in hospital, but lower intakes at home.

CONCLUSION

Patients kept food diaries can be used to identify those at risk of undernutrition and monitor those on nutritional support. It can also be used for nutritional education and for achieving dietary goals.

Manganese alters mitochodrial integrity in the hearts of swine marginally deficient in magnesium

It was previously reported that pigs marginally deficient in magnesium (Mg) and fed diets high in manganese (Mn) died suddenly with signs of sudden cardiac death. Manganese, which has properties similar to Mg, may exacerbate Mg-deficiency and be accumulated by mitochondria resulting in ultrastructural damage. The objective of this study was to determine whether deaths of the type previously observed were mediated by adverse interactions of Mn and Mg resulting in ultrastructural damage to the myocardium, alterations in electrocardiographic recordings and tissue retention of Mn, Mg and calcium (Ca). Forty-eight pigs were fed one of six diets in a 2 X 3 factorial arrangement of Mg (100 or 1000 mg Mg/kg) and Mn (5, 50 or 500 mg Mn/kg) for 8 weeks. Left ventricle muscle samples were collected for examination by transmission electron microscopy. No differences in heart muscle ultrastructure were observed between pigs fed low and adequate dietary Mg. However, marked myocardial necrosis and mitochondrial swelling were observed in pigs fed high dietary Mn when combined with low Mg. Feeding low dietary Mg elevated minimum (P < 0.01), maximum (P < 0.05) and average (P < 0.001) heart rates. Low dietary Mg resulted in a 55% probability of a ventricular beat being recorded (P = 0.05) and lower Mg (P < 0.02) and Ca (P < 0.04) contents in heart atria and ventricles. These results suggest that high Mn, when fed in combination with low Mg, disrupts mitochondrial ultrastructure and is associated with the sudden deaths previously reported.

Serum concentration and dietary intake of Mg and Ca in institutionalized elderly people

We determined the serum levels and the dietary intake of Mg and Ca in 93 institutionalized elderly people (24 men and 69 women) in Granada (Spain). The serum samples had mean concentrations of 21.39 +/- 2.08 mg/l magnesium and 93.39 +/- 9.24 mg/l calcium. No significant differences were found in the serum levels of the two minerals as regards the sex of the subjects. Application of linear regression analysis to the serum Mg and Ca levels showed a statistically significant positive correlation (P < 0.05). A low vitamin D intake of these subjects (51.8% of the recommended dietary allowance) was observed. The intakes of Ca and Mg correlated positively together, as well as with the intakes of energy, protein, fibre (in the case of Mg only), iron and phosphorus (P < 0.05). The Ca and energy intake were adequate to their current recommendations, as too was the Ca:P ratio, whereas the diet had a poor supply of fibre, vitamin D and Mg.

Measurement of the daily dietary calcium and magnesium intake in Belgium, using duplicate portion sampling

The daily dietary calcium and magnesium intakes in Belgium were evaluated by sampling duplicate portions of food, destruction in a microwave oven and their calcium and magnesium contents determined by atomic absorption spectroscopy. The mean intake value for calcium (618 +/- 125 mg/day) was found to be less than those values measured in most other countries and was below the recommended daily allowance (RDA). The mean intake value for magnesium (271 +/- 44 mg/day) was similar to levels found in most other countries, but was below the RDA value for healthy adult men (350 mg/day) whilst being adequate for healthy women (280 mg/day).