The metabolic syndrome describes a cluster of metabolic dysfunctions that result from consuming a poor quality diet. The metabolic syndrome is characterised by peripheral and central insulin resistance, non-alcoholic fatty liver, abdominal obesity, as well as lipoprotein and glucose abnormalities. Development of the metabolic syndrome increases the risk of obesity, type 2 diabetes and cardiovascular disease considerably. The Western diet is increasingly being seen as the major causative factor in the development of the metabolic syndrome, as it contains foods that drive insulin resistance, while also being absent of the foods that are protective. Fruits and vegetables appear to offer protection against the development of the metabolic syndrome although the exact reason is not clear. Two possible suggestions are that fruits and vegetables provide antioxidant nutrients and also have beneficial glycaemic effects. In this regard berries offer some of the best protection against the development of metabolic syndrome.
The beneficial effects of berries are well reported in the nutritional literature, and many longitudinal epidemiological studies have investigated the associations between berry consumption and diseases associated with the metabolic syndrome. For example, in one such study1, researchers assessed the association between berry consumption and the risk of type 2 diabetes in over two thousand Finnish men. The results of the study showed that berry consumption was associated with a significant reduction in the risk of developing type 2 diabetes in those with the highest berry consumption compared to those with the lowest berry consumption. However, berry juices were not protective and neither were other fruit juices, or whole fruits or vegetables. These results therefore suggest that berries are protective of type 2 diabetes and this may relate to specific properties they possess when consumed regularly as part of a healthy diet. So what might the beneficial effects of berries be in relation to type 2 diabetes?
Berries contain high amounts of polyphenols called anthocyanins. Anthocyanins are bioavailable and may have antioxidant effects in humans. Evidence does suggest that antioxidants can counteract the detrimental effects of certain Western lifestyle diseases. However, other fruits and vegetables are rich in polyphenols, and berry juices also contain these antioxidants, but neither were associated with a reduction in the risk of type 2 diabetes in this study. Alternatively, it might be the beneficial glycaemic effects of berries that are responsible for their protective effects against type 2 diabetes. Berries are particularly beneficial at slowing the absorption of glucose to the blood (here) and this may be protective of blood sugar disorders such as type 2 diabetes. The reason for the blood glucose lowering effects of berries is not fully understood but may relate to either the polyphenolic content, the sugar content, or the fibre content. However, it is likely that all three components work synergistically to reduce postprandial glycaemia.
Dr Robert Barrington’s Nutritional Recommendation: evidence supports a role for berries in disease prevention. Many different types of berries have been investigated and generally all commonly available edible berries have been shown to possess similar health benefits. Berries are rich in red, purple and blue colours and this reflects the high concentrations of anthocyanin flavonoids in their skins. These anthocyanins likely contribute significantly to the health benefits of berry consumption. Supplements of anthocyanins are available, but the whole fruits are superior for two main reasons. Firstly, the amount of anthocyanins in the supplements is much smaller than can be obtained from eating even modest amounts of whole berries. Secondly, it is not clear which component of the berries is beneficial, and so it makes sense to eat the whole fruit to ensure that the beneficial compound or compounds is consumed. Mixing different types of berry also makes sense as different anthocyanins might have differing but synergistic effects.
RdB
