Is refined sugar any worse than refined starch?
Dr Alan Barclay is an Accredited Practising Dietitian and Nutritionist with over 20 years of experience in clinical dietetics, public health and academia. The amount and type of carbohydrate in food is his particular area of expertise, having completed a PhD in this area in the mid 00s. He is author of several books: Reversing Diabetes, Low GI Diet Diabetes Handbook, Low GI Diet Managing Type 2 Diabetes and The Ultimate Guide to Sugars and Sweeteners; and he is regular blogger for GI News.
In July 2015 we started a conversation with Dr Barclay about starches in Starch the final frontier. He explained the differences between starches, maltodextrins and sugars and how they vary in their glycemic impact. This interview continues on this theme exploring the nutrition impact of starches with a focus on refined starches used in food manufacturing.
What’s the difference between starches found naturally in foods and refined starches added to foods?
Naturally occurring starches are usually part of a food matrix that also contains vitamins, minerals, dietary fibres and other phytonutrients, whereas the refining process typically removes some, if not all of these. The refining process may also raise a starchy foods glycemic index (GI) by making the starch more readily digestible. Highly refined starches like corn flour are nutritionally similar to refined sugars (e.g. sucrose) and have a similar glycemic impact. In summary, refined starches are much like refined sugars.
How are refined starches and sugars listed on food labels?
In Australia and New Zealand, total sugars (naturally occurring and added/refined) are listed in the mandatory nutrition information panel (NIP) on packaged foods and beverages. There have been calls for Australia to follow the United States of America (USA) and include added sugars in the NIP, but to-date regulatory agencies are yet to respond. Although maltodextrins are technically more like starches, they are classified as ‘sugars’ in the FSANZ Food Standards Code (Standard 2.8.1) and included in the NIP under sugars. Starches (naturally occurring and added/refined) are truly the “dark continent” of carbohydrate nutrition as they are not listed in the mandatory NIP and the names of refined starches, although included in the ingredient list, are hard to recognise (see previous article Starch the final frontier). Total starches can be estimated from the NIP, by subtracting total sugars from carbohydrate – a little known fact. There are currently no calls to identify added/refined starches in the NIP, despite their nutritional similarity to added/refined sugars.
Where is the line between starches and dietary fibre, and are “artificial” fibres used as food additives as good as natural fibre?
Some forms of resistant starches (starches that are poorly digested in the human digestive tract) act as dietary fibre and research is emerging that suggests they may have similar health benefits. Good natural sources of resistant starches include legumes, rolled oats, barley and bananas (not over ripe).
The food industry is adding back, or enhancing, the amount of fibre in processed foods – often by adding in isolated or synthetic dietary fibres. We do not know whether the simple addition of isolated or synthetic dietary fibres to processed foods will make them as healthy as foods that are naturally good sources of dietary fibre. Because of this, the USA Food and Drug Administration (FDA) recently narrowed its definition of dietary fibre. The new rule defines “dietary fibre” as “non-digestible soluble and insoluble carbohydrates (with 3 or more monomeric units) and lignin that are intrinsic and intact in plants” and “isolated or synthetic non-digestible carbohydrates (with 3 or more monomeric units) determined by FDA to have physiological effects that are beneficial to human health such as lowering blood glucose and cholesterol levels, increasing feelings of fullness (satiety) resulting in reduced calorie [kilojoule] intake, and improving bowel function.”
What is the state of the evidence with regard to starch and adverse health effects?
Perhaps because starch is not included in Nutrition Information Panels on food labels, and in many countries’ food nutrient databases, there is very little research on the association between starch per se (total or added/refined) and disease risk.
One study from Harvard University did investigate the association between sources of carbohydrate and the risk of developing coronary heart disease (CHD) in two large cohorts: 84,628 female nurses and 42,908 male health professionals followed up over 24-30 years. They found that carbohydrate-containing foods high in refined starches and added sugars were positively associated with CHD (HR 1.10), while carbohydrate from wholegrains reduced risk. Unfortunately they did not analyse refined starches and added sugars separately.
Most research focuses on the health benefits of wholegrains. The overall body of evidence to-date suggests regular consumers of wholegrains have a reduced risk of type 2 diabetes, cardiovascular disease and certain cancers. Wholegrains are not just starch of course – they are good sources of vitamins, minerals, dietary fibre and other phytonutrients, so we cannot assume from these data that refined starch will increase the risk of these chronic diseases. More research is definitely needed.
It is important to note that we have known for a long time that starches, like sugars, increase the risk of dental caries . Unfortunately, this fact is not well publicised by public health organisations who generally focus on sugars and overlook the role of starches in cariogenesis.
Are we eating more refined starches now than previously? Why?
Comparison between the 1995 National Nutrition Survey and 2011/2 Australian Health Survey found total starch consumption has decreased slightly from 140 g per day to 119 g per day in people aged 19 years and over. Unfortunately, we do not know what proportion of total starch is naturally occurring and what is refined/added. Over the same time frame, dietary fibre consumption decreased from 25 g to 24 g per day. Finally, in 2011/2, energy dense, nutrient poor foods made up about one third of the total foods that we consume. Overall, the evidence suggests that refined starch consumption may be increasing in Australia, but more research is needed.
What are some examples of foods with high levels of refined starch?
Highly processed food products with high levels of refined starches and little if any other nutritional benefits include potato crisps, rice crisps and crackers, and extruded savoury snacks (potato thins, cheesy puffs, twists etc). Low-fibre breakfast cereals (e.g. puffed rice, flaked corn) are also a significant source of refined starch, although unlike savoury snack foods, they usually fortified with essential nutrients. Mass produced white bread, white rice and potato chips (French fries) although perhaps not described as “refined” are also sources of high GI starch.
Rice syrup has become a popular alternative sweetener to sucrose. What is rice malt syrup and is it healthier than regular sugar?
Rice malt syrup is a malted-grain sweetener made by fermenting brown rice with enzymes that break down the natural starch content. The sugar composition is around 45% maltose, 3% glucose, and 52% maltotriose – a trisaccharide (or maltodextrin) consisting of three glucose molecules joined together.
It is a syrup (sugar in water), so is more dilute than regular (granulated) sugar (sucrose), and therefore provides slightly less energy (1160 vs 1600 kilojoules per 100 g) and carbohydrate (68 vs 100 g) as regular sugar, but has a higher glycemic index (GI 98 vs 65 for sucrose), essentially the same glycemic load (66 vs 65) and is equally as cariogenic (dental caries causing).
Rice malt syrup is included in the World Health Organisations definition of free sugars and like regular sugar, should be limited to less than 10% of total energy.
 Li Y, Hruby A, Bernstein AM et al. Saturated fats compared with unsaturated fats and sources of carbohydrates in relation to the risk of coronary heart disease: a prospective cohort study. J Am Coll Cardiol 2015;66(14):1538-48.