GI Symbol News with Dr Alan Barclay
Dr Alan Barclay
When it comes to blood cholesterol, both fats and carbohydrates count.
For many years, dietary advice to help people lower their blood cholesterol has focused on the fats in our diets. Specifically, people with high blood cholesterol have been advised to reduce their consumption of foods high in saturated and trans fats and to replace these with foods high in unsaturated fats.
- Foods naturally high in saturated fats include animal foods like fatty meats (sausages, bacon, salami, devon, etc), butter, ghee, cream, hard cheese, and full cream milk.
- Foods high in trans fats include some margarines (e.g., cooking and some cheap table varieties), and cooking fats for deep-frying (particular those used in fast food restaurants) and shortening for baking (pies, pastries, cakes, biscuits/cookies, buns, etc).
- Foods that are high in unsaturated fats, include oily fish (e.g. salmon and mackerel), nuts (e.g. almonds and cashews) and seeds (e.g. sunflower and pumpkin), oils and spreads (e.g. olive, Canola, peanut, sesame, avocado).
Why does this matter? Well, there is very strong evidence that replacing saturated fats with unsaturated fats will lower cholesterol by 0.16 mmol/L and thereby reduce a person’s chance of having a heart attack or stroke by 14%.
Some organisations also advise people to reduce their total fat intake to help them lose weight. This is because fats are the most kilojoule-dense (37 kJ (9 Calories) per gram) of all of the nutrients (carbs provide 16 kJ (4 Calories) per gram and proteins 17 kJ (4 Calories) per gram), and weight loss also helps people to lower their blood cholesterol levels.
While fats are the primary nutrient of interest when it comes to lowering blood cholesterol levels, carbohydrate-containing foods also play an important part. For example, oats, legumes, fruits and vegetables, contain certain kinds of fibre (e.g., beta-glucans) that may help lower blood cholesterol levels by binding it in our guts. In addition to dietary fibre, there is growing evidence that the kind of available carbohydrate (sugars, maltodextrins and starches) that we eat also has an effect on our blood cholesterol levels.
A new systematic review and meta-analysis of 28 randomised controlled trials has provided level 1 evidence that high fibre low GI diets can significantly reduce blood cholesterol (total and LDL) levels by 0.13 mmol/L, independent of weight loss. It is thought that healthy low GI diets lower blood cholesterol levels by decreasing insulin secretion, and thereby reducing the activity of the key enzyme involved in cholesterol synthesis. Importantly, the study found that the average dietary GI needed to be ideally at least 20 units lower than what is normally found in most developed nations. In other words, people with high cholesterol should be aiming for a daily average GI of 45 or less.
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Dr Alan W Barclay, PhD
Chief Scientific Officer
Glycemic Index Foundation (Ltd)
Phone: +61 (0)2 9785 1037
Mob: +61 (0)416 111 046
Fax: +61 (0)2 9785 1037