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Dietary Carotenoids Linked to Reduced Risk of Type 2 Diabetes

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April 30, 2013

by Lily Dyke, Contributing Writer

While there are many reasons to adopt a vegan diet, health considerations is one of them. There are various health benefits associated with a vegan diet, largely down to the fact that our diet is lower in total and saturated fat, yet packed with micronutrients. Admittedly we have our critics and we might come under fire from some people for avoiding all animal produce, as potentially this can put us at risk of a deficiency of iron, zinc and vitamin B12; though as we all know, careful food choices and making use of fortified items can turn this into only a theoretical problem. However, our intake of vitamins and minerals from plant foods more than makes up for this, which is why we are less likely to develop heart disease or suffer a stroke. Many people also don’t realize that owing to a high intake of carotenoids from fruit and vegetables we are also at lower risk of developing diabetes. Indeed there is mounting evidence that a link exists between a high concentration of carotenoids in the blood and a lower chance of getting type 2 diabetes. This is particularly relevant, as the condition affects around 8 million Canadians and millions more people across the world, not only causing unpleasant symptoms, but long-term complications such as blindness, kidney failure and nerve damage, which typically knocks at least 10 years off someone’s life expectancy. Here we take a look at the link and which foods are richest in these nutrients.

The connection between diabetes and carotenoids
The risk factors for type 2 diabetes used to be considered to be obesity, inactivity or a genetic predisposition to the disease. However, it is now known that other factors play a role in whether someone will develop the condition. For example, there is mounting evidence that smokers are at higher risk, which may be linked to the fact that they tend to have a lower carotenoid content in their body. This in part may be because taking part in an unhealthy activity such as smoking, they are less conscious of their diet, so consume fewer fruit and vegetables, which may be compounded by the fact that cigarette smoke produces substances that antioxidants such as carotenoids are needed to counteract, thus reducing levels in the body. Antioxidants help to neutralize the effects of free radicals, harmful chemicals produced during reactions within the body that damage cells and contribute to disease risk. Free radicals can trigger inflammation, which is now appreciated to be a risk factor for diabetes, as it increases the likelihood of insulin resistance, where insulin is unable to work effectively leading to an increase in blood sugar levels; this in turn can lead to free radical production and may partly explain why those with diabetes have high levels of free radicals, yet low concentrations of carotenoids.
A number of different molecules make up the group known as carotenoids and these are actually the pigments responsible for the bright colors shown by fruit and vegetables. Lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin have all been shown to lower insulin levels, a sign that the body is controlling its blood sugars well.

Sourcing carotenoids from the diet

  • If you meet the recommended intake of fruit and vegetables – 7 to 10 portions daily – and eat a range of different colored varieties, the chances are that you are already achieving a good intake of carotenoids. However, which are best for each type of carotenoid? Lycopene is responsible for red pigmentation and is richest in tomatoes, especially those that have been cooked or dried. Guavas, watermelon and pink grapefruit are another good bet. Men are particularly wise to up their intake of these foods, as studies have shown lycopene can also reduce prostate cancer risk; it also appears to have a cardio-protective effect.
  • Meanwhile, beat-carotene gives rise to red, orange and yellow pigments; it is also present in green vegetables, but the chlorophyll masks the colour. Good vegetables to opt for include kale, dark green lettuce, spinach, carrots, pumpkin, bell peppers and sweet potatoes, while apricots, oranges, cherries and plums are other rich sources.
  • Orange, yellow and green vegetables are rich in alpha-carotene, with carrots, pumpkin, peas, butternut squash, peppers, cantaloupe melon and tangerines offering among the best supply.
  • Like beta-carotene, beta-cryptoxanthin is converted to vitamin A in the body and is found in greatest amounts in peppers, papayas, oranges, sweetcorn, watermelon, pumpkin and squash.
  • Finally, lutein and zeaxanthin are practically identical structures, but the former provides a green pigment, while the latter a yellow pigment. A diet including plenty of kale, spinach, peas, lettuce, squash, avocados, peaches and tangerines will provide you with both, which are also important in eye health, protecting against two common eye disease of old age - cataracts and macular degeneration.
Including brightly colored fruit and vegetables with each meal will ensure a good intake of carotenoids, which will likely reduce your chance of developing diabetes among other diseases.

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