Evidence from the nutritional literature shows an inverse association between vegetable intake and diseases such as obesity, type 2 diabetes and cardiovascular disease. The reason that high intakes of vegetables reduces the risk of disease is not fully understood, but may relate to the nutrients they contain. In particular, vegetables tend to have high amounts of dietary fibre and micronutrients, which improves metabolic function. In addition, vegetables are a good source of bioactive phytonutrients, the exact composition of which varies between vegetable types. Current recommendations are to consume more vegetables because too many individuals eat a Western diet that contains fibre poor refined carbohydrates which include added sugar.As well as being a rich source of nutrients, vegetables also possess low amounts of sugar, and this may hold particular health advantages. Legumes may be particularly beneficial in this regard because consumption produces favourable glycaemic effects, which may explain their ability to cause weight loss and prevent the metabolic syndrome that can lead to abdominal obesity.
When considering vegetables it is worth taking time to weigh the advantages and disadvantages of fresh versus frozen produce. Fresh vegetables grown locally are potentially beneficial because the time between harvest and consumption is short. Nutrient losses can occur in vegetables from the time of harvest, and long-term storage can increases these losses considerably. Choosing locally grown produce offers the advantage of eliminating much of this problem and can also reduce the potential for spoilage. Eating fresh vegetables in season also provides benefits because they tend to be cheaper. However, consumption of frozen vegetables holds a number of advantages over consumption of fresh produce. Firstly, storage of frozen vegetables is more convenient because there is no requirement to consume them immediately, and this prevents waste. Secondly, frozen vegetables are often cheaper than fresh alternatives making them more economically viable. However, perhaps most importantly, frozen vegetables have been shown to retain higher levels of vitamins and phytonutrients compared to fresh produce.
For example in one study1, researchers reviewed studies reporting the ascorbic acid content of fresh and frozen vegetables to allow comparisons of the nutrient losses. In general, the nutrient content of frozen vegetables was as good as provided by fresh vegetables, and in some cases was superior. For example, frozen peas had similar nutrient levels to freshly picked peas, but were nutritionally superior to two day old fresh peas. Fresh peas and broccoli only retained their nutrient levels for around 14 days even when refrigerated, but frozen alternatives retained nutrient levels for up to 12 months. Frozen spinach was comparable to the spinach sampled at harvest but superior in terms of nutrient content to spinach available at market. Frozen vegetables tend to be frozen immediately upon picking, and the freezing process stabilises the vitamin structure preventing losses. Fresh vegetables in contrast may be stored for a week or longer before being consumed, and during this time nutrient losses occur. Frozen fruit possesses the same benefits as frozen vegetables, and should therefore also be considered nutritionally superior to fresh produce.
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