Middle-aged women with pre- or stage 1 hypertension assigned to consumed a low-sodium diet experienced reductions in calcium excretion compared to people consuming a high-carbohydrate low-fat diet, according to findings published in the British Journal of Nutrition.
“The fall in urinary calcium excretion on the lower-sodium Dietary Approaches to Stop Hypertension (DASH)-type diet is likely to have a beneficial effect on bone in the long term,” wrote the researchers, led by Caryl Nowson from Deakin University. “This reduction in urinary calcium was driven by the reduction in dietary sodium, but longer-term studies are required to confirm the benefits of this type of dietary pattern.”
Salt – some, but not too much
Salt is of course a vital nutrient and is necessary for the body to function, but the average daily salt consumption in the western world, between 10 and 12g, vastly exceeds recommendations from WHO/FAO of 5 grams per day to control blood pressure levels and reduce hypertension prevalence and related health risks in populations.
In countries like the UK, Ireland and the USA, over 80 per cent of salt intake comes from processed food, and people therefore do not realize they are consuming it.
The largest double-blind trial of modest salt reduction in a free-living population, which showed that moderate reductions do indeed result in clinically relevant and beneficial reductions in blood pressure
The study, published in the American Heart Association’s Hypertension journal found that reducing salt intake from 9.7 to 6.5 grams per day reduced average blood pressure from 146/91 to 141/88 mmHg within six weeks.
The new study indicates that salt reduction may also have benefits for bone health in women at risk of osteoporosis – a condition described by the World Health Organisation as its biggest global healthcare problem.
Ninety-two women aged between 45 and 75 with pre- or stage 1 hypertension were randomly assigned to consume either a low-sodium DASH-type diet or a high-carbohydrate low-fat diet. The former was characterized by a higher basic or alkaline load, while the latter was characterized by a higher acid load. Both diets contained 800 mg dietary calcium per day.
After 14 weeks, the researchers noted that sodium levels in the urine of the women on low-sodium diet fell by 26 per cent, while potassium excretion increased by 6.8 millimoles per day.
Furthermore, compared to the high-carb, low-fat diet, calcium levels in the urine decreased by 0.7 mmol per day in the low-sodium diet group.
Women consuming the hig-carb, low-fat diet also experienced an increased rate of bone turnover, compared with women in the low-sodium group.
“It would be worthwhile to assess if a lower-acid load diet assists in maintaining bone health on a lower-calcium diet, as this is particularly relevant for older individuals who usually find it difficult to consume sufficient dietary calcium from food sources,” concluded the researchers.
Source: British Journal of Nutrition
Volume 102, Pages 1161-1170, doi:10.1017/S0007114509371731
“The effects of a low-sodium base-producing diet including red meat compared with a high-carbohydrate, low-fat diet on bone turnover markers in women aged 45-75 years”
Authors: C.A. Nowson, A. Patchett, N. Wattanapenpaiboon