Avocados- THE WONDER FOOD?

BACKGROUND
Have you ever wondered about the health benefits and nutritional properties of avocados?  I am a strong believer that it is important for everyone to have a general idea or at least a healthy curiosity as to what the nutritional properties of the food you are consuming are, and what the resulting health effects, be it good to not so good, will be once the food has been broken down in our bodies. So, in a nutshell, what are these health effects that everyone is raving about in the media when it comes to avocados, and that are often termed "superfoods" in the press?

Whistle-stop tour into the history of avocados and interesting facts: 

• Hass avocados are the most commercially sold avocados worldwide.
• Avocados originated in Mexico, Central or South America, and were first cultivated in Mexico as early as 500 BC.
• The first English language mention of avocado was in 1696. 
• Avocados are farm-to-market food as they require no processing. 
• The avocado's natural skin eliminates the need for packaging and offers some pest resistance, allowing it to be grown in more environmentally sustainable ways.
• Avocados are a medium energy dense fruit as around 80% of their composition consists of water and dietary fibre.

RESEARCH OVERVIEW 
Cardiovascular benefits: 
Monounsaturated fatty acids (MUFAs):
Scientific evidence suggests that avocados promote a healthy heart. A major contributing factor in delivering this health effect may be the rich content of MUFAs naturally present in avocados. The research indicates that MUFA contained in avocados may enhance the bioavailability and absorption in the body of fat-soluble vitamins and phytochemicals. Furthermore, a number of clinical trials pinpoint the fact that avocados may have an important role to play in maintaining healthy blood lipid profiles. The mechanisms by which this physiological effect may be brought about is via the role of MUFAs in potentially reducing levels of low-density lipoprotein (LDL-cholesterol), often referred to as the 'bad' cholesterol. Generally, I am against ascribing such black and white attributes to nutrition i.e. 'good' or 'bad', as nutrition is composed of a complex interplay of many interrelated factors involving complex biological processes. However, this simplistic outlook does have some scientific foundations, as LDL-cholesterol is the type of cholesterol that has been been strongly linked with detrimental vascular consequences including the promotion of heart disease. On the other hand, avocados have also been shown to improve high-density lipoprotein (HDL-cholesterol) status, the so-called 'good-cholesterol', which has not been associated with similar negative health outcomes as LDL-cholesterol. In fact, a healthy level of HDL-cholesterol may be essential in preventing a cardiovascular incidence, such as stroke or heart attack.  So, consuming avocados may contribute to help keeping heart disease at bay.

Avocados are rich in a range of micronutrients (vitamins and minerals):

• Potassium

Avocados also are a good source of the mineral potassium. Clinical evidence suggests that adequate potassium intake may promote blood pressure control in adults, which is of vital importance in ensuring cardiovascular health. 

• Magnesium

Avocados are a good source of the mineral magnesium, which has been shown to act as an important co-factor in many cellular enzymes required in energy metabolism and it may be involved in promoting vascular health, which is closely linked with boosting of heart health. 

• Vitamin C

Avocados are a rich source of vitamin C, also known as ascorbic acid, a powerful water-soluble antioxidant. Vitamin C has been shown to have a broad range of important functions in the body, including the maintenance of healthy connective tissue via the production of collagen. This provides support and structure for other tissues and organs and promotes wound healing. Moreover, the evidence shows that vitamin C plays an important role in immune function. Vitamin C is also a potent antioxidant, reducing free radical formation and oxidative stress, and has been shown to regenerate other antioxidants in the body, including vitamin E. Across the board, the scientific evidence suggests that Vitamin C confers vascular health benefits and arterial plaque stabilisation.

• Vitamin E  

Vitamin E, a fat-soluble vitamin acts as a powerful antioxidant. Research shows that this nutrient may help to limit free radical damage by mopping free radicals away and promote vascular health. 

• Vitamin K

Avocados contain elevated levels of Vitamin K, which helps to ensure that blood coagulates normally to allow for effective wound healing and maintenance of healthy bones.  

• B-vitamins

Avocados contain Folate and vitamin B-6, which have been demonstrated via scientific evidence to keep under control the plasma homocysteine levels. Elevated levels of homocysteine have been associated with higher risks of cardiovascular disease.

Powerful Antioxidant and Anti-inflammatory 
Avocados are rich in phytochemicals (such as carotenoids, phenolic antioxidants and phytosterols), which are naturally occurring compounds, many of which act as antioxidants in the body and have been shown to incur numerous potential health benefits. Antioxidants are present in food and are extracted once consumed in order to bring about a plethora of health effects in the body, including the combating of oxidative stress and inflammation. Indeed, these processes have been implicated in a range of chronic diseases, for example cancer, coronary heart disease and ageing. Antioxidants act by protecting us from harmful substances called free radicals, which are generated when we convert food into energy. Free radicals are also generated in other non food-mediated ways, such as by smoking and exposure via the air. Free radicals are harmful as they have the potential to cause damage to cells and alter genetic make-up. How exactly do antioxidants work? Antioxidants work by preventing the formation of free radicals, or scavenging them after they have been already generated. Each antioxidant will have its own specific function in the body, and each is involved in a highly complicated chemical pathway. 

A deeper look into the different types of phytochemicals:
The carotenoid phytochemicals have been associated with enhanced cardiovascular health via the reduction of LDL-cholesterol. The phenolic antioxidants have been associated with enhanced blood flow and endothelial health, by inhibiting platelet aggregation to help maintain vascular health. Phytosterols, also naturally present in avocados, are known to have various bioactive properties. The most important documented benefit is their blood cholesterol-lowering effect via partial inhibition of intestinal cholesterol absorption. As such, phytochemicals are thought to play a key role in promoting cardiovascular health. 

Healthy Bowel
Avocados are rich in dietary fibre as they are composed of about 80% dietary fibre. This helps to maintain a healthy digestive system. By improving bowel function, dietary fibre can reduce some disorders such as haemorrhoids and may protect against colon cancer. Soluble fibre may also slow digestion and absorption of carbohydrates and consequently reduce the spike in blood glucose that follows a meal and ensuing insulin response. Furthermore, the research indicates that dietary fibre may have a role in prevention of coronary heart disease by improving the blood lipid profiles by reducing total cholesterol levels and LDL-cholesterol. Other benefits of fibre are also good to note: fibre can add bulk to your diet, without adding calories. It can have a satiating effect on appetite and help in weight management. 

Eye Health 
Avocados contain an antioxidant called lutein that may protect against eye conditions such as cataracts and age-related macular degeneration, a leading cause of blindness in elderly people. Lutein is selectively taken up into the macula of the eye (the portion of the eye where light is focused on the lens). 

Sophie's RD opinion- Although avocados may be higher in calories compared to other foods, if consumed in moderation as part of a healthy balanced diet you will really be able to take advantage of the nutritional benefits conferred by nutritionally dense avocados. 

Top Tips 
Mash up some avocado and use it as a healthy alternative in place of: 

• butter or margarines used as spread on your bread
  
• mayonnaise and other shop-bought high calorie & fat salad dressings for salads 
• Make a delicious healthy alternative guacamole dip recipe with raw vegetables:

Ingredients:
1 ripe tomato
2 avocados, very ripe but not bruised
1 small red onion, finely chopped
1 chilli - red or green - deseeded and finely chopped
Juice of 2 large limes

Method 
1. Use a knife to chop up the tomato very finely, then tip into a bowl.  
Halve the avocados (saving a stone) and use a spoon to scoop out the flesh
into the bowl with the tomato. 

2. Tip all the other ingredients into the bowl, then season with salt, pepper and lime juice.
Use a whisk to roughly mash everything together. If not serving straight away, sit 
a stone in the guacamole - this will help to stop it from going brown - cover with 
cling film and chill until needed.

3. Serve with raw vegetables (e.g. carrots, cucumber, celery, radishes)

References 

• http://www.tandfonline.com/doi/pdf/10.1080/10408398.2011.556759
  
• http://www.biomedcentral.com/content/pdf/1475-2891-12-1.pdf
  

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