Nutrition (24 page)
Several studies also suggest that organically grown fruit and vegetables contain higher amounts of phytochemicals such as carotenoids (e.g. betacarotene, lycopene) and phenols. This is not surprising, given that plants not dosed with synthetic pesticides are likely to need to produce more of their own natural antioxidant defences.
To limit your exposure to dietary agrochemicals, you may want to consider buying organically grown versions when you can. Although organic produce can be more expensive, you can keep your costs down if you buy fruit and vegetables in season rather than those imported at additional cost; buy locally; buy in bulk; buy wholefoods rather than processed foods; eat more plant-based foods and less meat; look out for special offers; join a box scheme that delivers fruit and vegetables to your door from local producers.
The human body evolved on a diet that was high in lean protein derived from animals, game birds and fish. The diet followed by Stone Age hunter-gatherers provided relatively few carbohydrates, most of which came from green leafy vegetables such as purslane (also rich in vitamins C and E – a succulent leaf resembling a fleshy lamb’s lettuce, currently considered a weed in most of the world but still eaten around the Mediterranean and in parts of Asia and Mexico), berries and a few low-glycaemic wild grains, with very little in the way of sugar and refined carbohydrates such as those we eat today. And the fats within the Palaeolithic diet were mostly polyunsaturated omega-3s plus monounsaturates, with far fewer of the omega-6s and saturated fats that we consume now. With the agricultural revolution 10,000 years ago, we started eating more wholegrains and cultivated crops, and becoming less active as humans settled down into subsistence-farming communities. Following the industrial revolution, processing of grains became common and more and more of the fibre- and mineral-rich husks we used to eat were discarded. Within the space of 500 generations, our diet and lifestyle has changed enormously, but the human genome has stayed relatively unchanged. At the same time, modern humans are more than 60 per cent more sedentary than our hunter-gatherer ancestors, but we are still programmed to engage in a greater degree of physical exercise. This mismatch between our current diet and lifestyle and our Palaeolithic genes has been blamed for a multitude of modern health issues such as obesity, high blood pressure, diabetes and coronary heart disease. Many nutritionists, therefore, urge us to return to our roots with a more balanced wholefood diet that more closely resembles the one enjoyed by our great-great ancestors.
Achieving balance
Every cell in your body today – even those in your skeleton – is made up of different molecules to those that were present a year ago. Even the inert parts of your skeleton – the calcium-containing mineral, hydroxyapatite – is turned over slowly at a rate of 10 per cent annually, meaning that every ten years your entire bone-mineral stores are replaced. All these new building blocks ultimately come from your diet. So your food needs to provide all the energy, essential fatty acids, essential amino acids, vitamins and minerals you need for optimum health.
A nutritionally balanced diet is one that provides everything you need, without containing too much or too little of any component. It will contain sufficient
• energy (from carbohydrates, proteins and fats) to fuel your basal metabolic rate, level of physical activity and maintain a healthy weight
• protein (especially the essential amino acids) for tissue repair, regeneration and rejuvenation
• fat (especially the essential fatty acids) for hormone balance and healthy cell membranes throughout the body, including the brain and retina
• vitamins and minerals to meet your daily requirement
• phytochemicals, especially the antioxidants, for immune health
• fibre and probiotics for digestive health
• water, protons and electrolytes to maintain normal hydration, body fluid and acid balance.
Different people require different amounts of each individual nutrient depending on their level of physical activity – both at work and in leisure – their height, weight, age and the genes they have inherited. Healthy-eating guidelines have to meet the needs of all members of the population, and this is not an easy task.
Healthy-eating guidelines
A number of organizations around the world have published healthy-eating guidelines in an attempt to define the optimum healthy diet. These vary in complexity from broad statements aimed at guiding your general choice of food (e.g. eat as wide a variety of foods as possible), to more complex statements that refer to recommended percentage energy intakes from different food groups (e.g. saturated fats should make up no more than 10 per cent of your daily calories). The problem is that neither of these approaches results in a practical understanding of how to eat better. The former is too simplistic to take seriously, and the latter too complex to be clearly understood by most people.
In the UK, the Department of Health launched the Eatwell Plate in 2007 as a visual guide to the relative amounts of each food group your diet should contain (see
Diagram 9
).
Diagram 9
).
The Eatwell Plate shows how much of what you eat should come from each food group. This includes everything you eat during the day, including snacks, and is much easier to understand at a glance. This tool is far more useful in helping people to select a nutritionally balanced diet, as it encourages you to eat the correct proportion of fruit and vegetables; starchy foods such as bread, rice, potatoes and pasta, with an emphasis on choosing wholegrain varieties whenever you can; milk and dairy foods; meat, fish, eggs, beans and other non-dairy sources of protein; along with just a small amount of foods and drinks that are high in fat and/or sugar.
© Crown copyright. Department of Health in association with the Welsh Assembly Government, the Scottish Government and the Food Standards Agency in Northern Ireland.
Another popular depiction of a healthy diet is the food pyramid, adopted in the US in 1992. In the original, the base of the pyramid consisted of starchy carbohydrates (brown rice, wholemeal bread, wholewheat pasta, wholegrain cereals) with a suggestion to eat six to eleven servings per day. Next up is the fruit and vegetable group, with a suggestion to eat three to five servings of vegetables and two to four of fruit per day. Above this are the animal and dairy products, of which it is recommended that you limit these to two to three servings of milk, yogurt and cheese, plus two to three servings of meat, poultry, fish, pulses, eggs and nuts per day. Finally, the apex of the pyramid contains fats, oils, sugars and sweets, which should be used and consumed sparingly (see
Diagram 10
).
Diagram 10
).
© U.S. Department of Agriculture.
MyPyramid.gov
website. Washington, DC.
MyPyramid.gov
website. Washington, DC.
However, this approach was criticized as it does not differentiate between potentially harmful fats such as trans fats and excess saturated fats, and the beneficial monounsaturated fats such as olive oil or omega-3 fish oils. There is also a lack of clarity as the two to three servings of protein-rich foods was intended as a maximum and the two to four portions of fruit as a minimum. As a result, the Food Pyramid was replaced in 2005 by a more personalized version known as MyPyramid (see
Diagram 11
) which also stresses the importance of physical activity.
Diagram 11
) which also stresses the importance of physical activity.
An accompanying website,
www.mypyramid.gov
, provided detailed information about the different food groups and the daily recommended intake for different ages and genders. For example, women aged 19 to 50 years should obtain 6 oz equivalents of grains per day, while men aged 19 to 30 years should aim for 8 oz equivalents, and those aged 31 to 50 should obtain 7 oz equivalents (where 1 oz equivalent is 1 slice of bread, 1 cup of ready-to-eat cereal, ½ cup cooked rice, cooked pasta or cooked cereal), of which at least half should be wholegrain products.
www.mypyramid.gov
, provided detailed information about the different food groups and the daily recommended intake for different ages and genders. For example, women aged 19 to 50 years should obtain 6 oz equivalents of grains per day, while men aged 19 to 30 years should aim for 8 oz equivalents, and those aged 31 to 50 should obtain 7 oz equivalents (where 1 oz equivalent is 1 slice of bread, 1 cup of ready-to-eat cereal, ½ cup cooked rice, cooked pasta or cooked cereal), of which at least half should be wholegrain products.
© U.S. Department of Agriculture.
MyPyramid.gov
website. Washington, DC.
www.mypyramid.gov
(accessed 22 March 2011).
MyPyramid.gov
website. Washington, DC.
www.mypyramid.gov
(accessed 22 March 2011).
Despite being more accurate, this approach was seen by many as unduly complicated. Individuals had to obtain a personalized eating plan by inputting data via the website such as their age, weight, height, gender, level of physical activity and whether or not they wanted to lose some weight. As a result, US nutrition guidelines have now come full circle and returned to a simplistic approach with the introduction of MyPlate, which replaced MyPyramid in June 2011. MyPlate essentially shows a plate divided into four sections, helping people to select a diet that provides around 30 per cent grains, 30 per cent vegetables, 20 per cent fruit and 20 per cent protein. A small additional circle represents dairy intake, such as a glass of low-fat milk or a serving of yogurt. How to use MyPlate is fully explained at
www.choosemyplate.gov
.
www.choosemyplate.gov
.
Why select ‘brown’ wholegrains rather than ‘white’ processed grains?
Wholegrains form the foundation of a healthy diet as they supply energy in the form of starchy carbohydrates, small amounts of protein and healthy fats (mostly monounsaturated, polyunsaturated fatty acids) plus vitamins, minerals, trace elements and fibre. In fact, brown or wholemeal versions of rice, pasta and bread supply twice as much fibre, and have a lower glycaemic load than their more processed ‘white’ counterparts, whose fibre- and mineral-rich husks are stripped out during processing.
Rice is a staple food for over half the world’s population, for whom it provides both energy and an important source of protein. But its nutritional value is greatly reduced when it is milled to remove the bran, which provides fibre, B-group vitamins and minerals such as calcium, zinc and magnesium. The B-group vitamins are locked into the bran and are only released into the grain when cooked. As a result, those who eat white rice may be at risk of the vitamin-B deficiency disease beriberi, while those who eat brown rice, or rice that was parboiled before milling, are not. Parboiled rice is usually referred to as ‘easy cook’ rice.
As a result of the industrial revolution, milling boosted the glycaemic index of dietary carbohydrate leading to an estimated threefold increase in the rise of blood glucose levels after a meal (postprandial glycaemia) and insulin secretion. With the advent of fast foods, confectionery and supersized meals, the glycaemic index of the typical Western diet increased even further, leading to widespread ‘epidemics’ of obesity, glucose intolerance, insulin resistance and Type 2 diabetes.
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