PERSPECTIVES WITH DR ALAN BARCLAY

A GRAIN OF SALT
For nearly four decades, dietary guidelines around the world have advised us to avoid consuming too much salt, or words to that effect. The salt they are talking about is sodium chloride, which has been used by humans for millennia, and is still the most common source of sodium today accounting for around 90% of all sodium consumed in developed nations. The guidelines are based on the relatively large body of evidence from randomised controlled trials (RCTs) that provides compelling evidence that reducing sodium consumption decreases blood pressure, which is a major risk factor for heart disease, stroke and other cardiovascular diseases.

Long-term observational studies also indicate that increased sodium consumption is associated with an increased risk of developing cardiovascular diseases. However, emerging evidence from observational studies is also indicating that excessive restriction of sodium is associated with an increased risk of cardiovascular disease, suggesting that there is a U shaped relationship between sodium and cardiovascular health.

While consuming less sodium does lower blood pressure, the combination of a lower-sodium, high-potassium diet is even more beneficial, with greater reductions in both systolic and diastolic blood pressure demonstrated in systematic reviews of RCTs, compared to low sodium diets alone, without any potential negative effects. Indeed, systematic reviews of RCTs now provide level 1 evidence that balancing the sodium : potassium ratio is effective in lowering blood pressure in people with and without high blood pressure, and is also associated with decreased risk of cardiovascular diseases in observational studies.

The WHO recommends a sodium : potassium ratio of no greater than 1 : 1. In other words, each day we should be aiming to consume at least as much potassium in our diet as sodium, to counter-balance any potential negative effects on blood pressure and cardiovascular disease risk. So keep up the fruit and veg!

This key recommendation is not well known perhaps because government regulatory food bodies don’t require potassium to be included in mandatory nutrition facts / information panels, and because public health campaigns focus very much on reducing salt intake rather than increasing potassium intake. However, in Australia and New Zealand, FSANZ requires the manufacturer to list the potassium content in the Nutrition Information Panel if they make a marketing claim about the salt / sodium content of a food or beverage. In this case, all you need to do is look for products that have more potassium than sodium – it’s as simple as that.

To help you follow WHO guidelines for sodium and potassium, the recipes in GI News include the sodium : potassium ratio in the nutritional analysis. Our recent books (Reversing Diabetes and The Good Carbs Cookbook, both published by Murdoch Books) also include the sodium : potassium ratio. Of course, recipes are rarely the complete meal, but if you see that sodium is higher than potassium, you know it’s important to up the potassium with a salad, some leafy greens, a piece of pumpkin or some sweet potato. It’s as easy as that.

But few cookbook recipes come with a nutritional analysis, and fewer the sodium : potassium ratio. So, here are some top sources of potassium to help you up your intake:

• leafy green vegetables, such as bok choy (pak choy), silverbeet (Swiss chard) and English spinach 
• vine fruits, such as tomatoes, cucumbers, zucchini (courgette), eggplant (aubergine) and pumpkin (winter squash) 
• root vegetables, such as potatoes, sweet potatoes and carrots. 
• Unprocessed bran 

Moderately good sources of potassium include:

• beans (for example, baked beans, kidney beans, black beans) 
• green peas 
• dried fruits 
• fresh fruits, such as apples, oranges and bananas. 

Milk, yoghurt, wholegrains and meat (beef, lamb, pork, chicken) also contain some potassium as does good old canned salmon, although not as much as vegetables and fruits.

The take-home: It is more important to balance out your sodium and potassium intake than to focus on the salt content alone. As usual, the one-nutrient-at-a-time approach will not ensure optimal nutrition.

Alan Barclay, PhD is a consultant dietitian. He worked for Diabetes Australia (NSW) from 1998–2014 and is a member of the editorial board of Diabetes Management Journal (Diabetes Australia). He is author/co-author of more than 30 scientific publications, and author/co-author of  Reversing Diabetes (Murdoch Books), The Low GI Diet: Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment, New York).