One of my favourite superfibres, widely used in Asia but not in the UK, is glucomannan, the soluble fibre in konjac. Glucomannan absorbs 50 times more water than wheat bran, bulking up the food you eat, making you feel fuller for longer. Because of its highly absorbent properties it is very important to take it with a lot of water. This highly absorbent property means two things – firstly, it helps eliminate cholesterol by binding to it in the digestive tract, but the real gold of glucomannan is its ability to lower the glycemic load of a meal, and hence help to lower blood sugar naturally.
A study in Thailand found that giving 1 gram of glucommanan before meals significantly lowered the GL, and the need for insulin, in people with type 2 diabetes. Other studies have shown that glucommanan lowers cholesterol and also stabilises blood sugar, which is associated with improving insulin sensitivity. It’s also a brilliant aid for healthy weight loss. Following reports of weight loss in Japan, a US study reported an additional 1lb weight loss a week when patients took 3g of glucomannan a day.
At the Institute for Optimum Nutrition, we decided to put glucomannan to the test by giving 3g a day to 10 overweight people over a three-month period. None made any apparent change to their diet or exercise regime. Nine completed the trial, with an average weight loss of 6.6lb each. A review of all studies to date, in 2005, concludes ‘At doses of 2-4 g per day, glucomannan was well-tolerated and resulted in significant weight loss in overweight and obese individuals.’ You need about 3 grams, or a flat teaspoon for this kind of effect. This would be the equivalent to three capsules, perhaps two or three times a day, before main meals.
Be aware that, thanks to a quirk in a food law (the Emulsifiers & Stabilisers Act), pure glucomannan is not allowed to be sold in the UK. However, konjac root extract is. Konjac extract contains about 60 per cent glucomannan, so a daily intake of 5g would be equivalent to 3g of glucomannan, hence you’ll need 5 capsules or a heaped teaspoon before meals.
PGX – the king of all superfibres
However, there is something even better. The most exceptional results have been demonstrated for a special type of fibre called PGX®. It is the most highly water absorbing fibre, created by reacting glucomannan with other plant fibres (alginate from seaweed and xanthan gum). PGX is a powder, and is also available in capsules. Having a heaped teaspoon (5 grams) in a glass of water two or three times before meals reduces appetite and substantially reduces the GL of the meal you are about to eat.
In a study by Professor Jenny Brand-Miller, from the University of Sydney, who has been very instrumental in promoting the value of low GL eating, she found that taking 5 grams of PGX powder with water before, with or immediately after breakfast cut the GL of the meal by around a quarter. You can see this effect in the first graph below. What you are trying to do is avoid blood sugar spikes, which means less glucose damage and less need for your body to produce insulin. As you can see, a teaspoon of PGX does this very effectively. In addition, taking 5 grams with the evening meal has a knock-on effect of lowering the GL of breakfast the following day by up to a quarter. You may recall, I have previously explained how the GI of a food is worked out by comparing the blood sugar curve created by glucose versus the food you want to test. In the second graph below you can see the average curve created by glucose, in some healthy volunteers, compared to giving the volunteers both glucose and 5 grams of PGX. As you can see, adding the PGX effectively lowers the GI or GL of the glucose.
The GL lowering effect is even greater when added to a meal. For example, if you have a teaspoon of PGX with a meal containing a serving of rice (see the third graph) you dramatically stabilise the blood sugar spike of the meal, turning it from a mountain into a rolling hill. This is almost the equivalent to halving the GL of the meal. PGX has been shown to be very effective for losing weight. In one study overweight volunteers lost, on average, 13lbs (6kg), and 5 inches (12 cm) off their waist in a 14 week trial, while their total cholesterol dropped by almost 20%, with the ‘bad’ LDL cholesterol dropping by a fifth. It has also been shown to reduce the amount of food you want to eat in the accompanying meal. In a study on diabetic rats adding PGX fibre to their meal significantly reduced insulin resistance, cholesterol levels, damage to kidneys and also resulted in more healthy cells in ......
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