Australian Macadamia- The Healthy Nut
Compiled by Ian McConachie
Macadamias are considered the world’s finest nut and are the only native Australian plant to become an international food. Their delicate flavour, versatility and crunchy texture make them a delight to consume. Also they contain a range of nutritious and health promoting constituents and form an important part of a healthy diet. A balance diet containing macadamias promotes good health, longevity and reduction in degenerative diseases.
The image of macadamia and other tree nuts is changing as research, dietary trails and population studies demonstrate their importance as part of healthy diet. This increasing knowledge and understanding of health benefits is likely to alter public perception so that macadamias may be selected primarily for their nutritive and health value apart from their great flavour and texture.
Research from other tree nuts with similar composition is often applicable to macadamias and other tree nuts have been proven to have significant health benefits. The Mediterranean Health Pyramid or diet recommends tree nuts be eaten daily. The good news is you don’t have to think of breaking your diet by eating macadamias. There is a increasing evidence that they have a positive effect on many aspects of our health and they are full of important nutrients including monounsaturated fats, proteins, dietary fibre, minerals, vitamins and phytochemicals.
The Australian Macadamia Society, nutritionists, medical researchers and food scientists are undertaking on research into nutritional and health benefits of macadamias which means available information is being updated.Current projects being undertaken are a full biochemical analysis and nutritional profiling of macadamias and in the USA a phytochemical analysis is close to completion. The Australian research is being funded by macadamia growers together with a subsidy from the Australian Government through Horticulture Australia.
As macadamias are a natural product their composition may vary to the growing district, variety, cultural procedures and growing season. The composition of both raw, dried and roasted Australian macadamias typically contain the following:
Natural oils 75% Moisture 1.5% Carbohydrates 4.7%
Mineral matter – 1.6% including Potassium, Phosphorus, Magnesium< Calcium, Selenium, Zinc, Copper and Iron.
Vitamins- B1, B2, B5, B6, Vit. E, plus niacin and folate.
Phytochemicals- Antioxidants including polyphenols, amino acids, selenium and flavanols plus plant sterols.
Energy Value- 3000 kilojaules per 100g ( 727 calories)
It is most probable that the health benefits of macadamias are increased by synergistic effect between its constituents and enhanced by complex biochemical interrelationships working together in our bodies. While we cannot yet demonstrate the combined effect and benefits of the complex natural constituents, the presence of high levels of monounsaturated oils, a wide range of phytochemicals, vitamins, minerals and dietary fibre should provide benefits beyond those individual components. Macadamias can be described as a functional food as the physiologically active constituents present provide health benefits greater than the base nutrients.
The University of Newcastle has recently completed a project on health benefit of macadamias, which was a dietary study. It demonstrated a significant improvement in markers for oxidative stress, clotting tendency and inflammation. Persons with elevated cholesterol and blood fats. These people also had a slight weight despite an increase in the total amount of fat consumed.
Separate dietary trials in Australia and Hawaii with macadamias have demonstrated a significant reduction in total blood serum cholesterol , a reduction in a total blood triglycerides, reduction of undesirable low density cholesterol and with little or no effect on the desirable high density cholesterol. These are all recognized indicators for the risk of heart disease. A range of tree nuts including macadamias have been shown to lower blood pressure in hypertensive people.
A series of dietary trials on tree nuts throughtout the out coupled with researches has demonstrated a risk reduction with heart disease, certain cancers and related diseases, hypertension as well as promote well being and food satisfaction.
A typical composition is:
Saturated fatty acids 12.5% Polyunsaturated fatty acids 4.0%
Monounsaturated fatty acids 83.5%
The oil in macadamias is largely monounsaturated which is often described as the “ good oil”. Macadamias contain a higher percentage of monounsaturated oils than any other natural product. Macadamia oil is similar to olive oil in its composition and use. Macadamias are low in damaging saturated fats, low in polyunsaturated fats which oxidize readily and are high in momounsaturated fats. Consuming less fat has been a health message but the type of fat is much more important than total fats. Diets containing moderate fat levels promote satiety and have been shown to be sustainable and enjoyable in the long term. Low fat diets have often been shown to be unsatisfying and difficult to maintain. The desirable Mediterranean Health Pyramid has 40% of the food energy coming from fat.
Macadamias contain significant levels of protein which are a essential component of our diet and in our bodies form muscle and connective tissues, hair and nails, are part or our blood and act positively on many aspects of our health.
The protein in macadamias comprise essential and non essential amino acids. Macadamias contain all the essential amino acids, with most present at optimum levels.
Dietary fibre is becoming better understood and thus more important in human health. Dietary fibre was once called roughage and comprises complex carbohydrates including many types of both soluble and insoluble fibre. In macadamias the walls from millions of cells in each kernel essentially comprise the dietary fibre. Complex carbohydrates include hemicelluloses, lignans, cellulose and gums. Dietary fibre are those carbohydrates resistant to acid and enzymatic attack in the estomach and first intestine and thus pass through into the digestive tract where they promote desirable intestinal bacteria and beneficial physiological processes.
Dietary fibre promotes satiety, provides roughage, slows digestions and reduces hunger and may assist in reducing constipation and diverticular diseases, reduce hemorrhoids, bowel cancers and irritable bowel syndrome. It functions in conjunction with other constituents of macadamia and plays a role in reducing the risk of cardiovascular diseases, cancers and diabetes.
Macadamia contains approximately 7% dietary fibre and current research is attempting to better understand the components that comprise this.
Most of the simple carbohidrates are present as sucrose, fructose, glucose and maltose plus some starch based carbohydrates. Carbohydrate supplies energy to the body.
Macadamia contain a wide range of minerals, which contribute to our bodies requirements. Typical levels are:
Potassium 360mg per 100g Magnesium 120mg per 100g
Phosphorus 200mg per 100g Calcium 70 mg per 100g
Smaller amounts of sodium, selenium, iron, manganese, copper and zinc are present.
Potassium is associated with fluid balance and volume. Others functions are in carbohydrate metabolism, protein synthesis, muscle contraction and nerve impulses.
Phosphorus plays a variety of roles including mineralisation of bones and teeth, energy metabolism, absorption and transport of nutrients and as a component of DNA and RNA.
Magnesium has many functions in the body. It interacts with other elements and plays a role in bone metabolism, glucose and fatty acid metabolism and in protein synthesis. Magnesium is a important in nervous activity and muscle contraction.
Calcium is the major component in bone, bone formation and teeth. It plays an important part in many other body processes.
Selenium is becoming increasingly more relevant due to being part of a key enzyme in a major antioxidant and its joint functions with Vitamin E. It has been recognized as having an anti cancer effect and may behave as an anti-inflammatory agent and assist in the control of rheumatoid arthritis.
Macadamias contain small but significant amounts of a range of vitamins. Typical levels are:
Vitamin E 12mg per 100g
Vitamin B1 ( thiamin) 0.7mg per 100g
Vitamin B 5 ( pantothenic acid) 1 mg per 100g
Vitamin B 6 0.4 mg per 100g
Vitamin B 2 ( riboflavin) 0.1mg per 100g
Niacin 2 mg per 100g
Folate ( folic acid) 10mcg( microgram) per 100g
Vitamin E content varies largely due to the freshness of the kernel and is present as derivatives of Vitamin E. It acts as an important antioxidant, protects cell walls and red blood cells.
Vitamin B1 is a co enzyme important in releasing energy from carbohydrates. Vitamin b 5 promotes a healthy nervous system and releases energy. Vitamin B 6 is involved with protein metabolism and is more important in pregnancy, the elderly and with heavy drinkers. Vitamin B2 is important in growth of the tissues, healthy skin and eyes.
Niacin converts food into energy and promotes healthy skin. Folate assists in forming red blood cells and in utilization of protein. It is regarded as essential in pregnancy in minimizing birth defects.
Phytochemicals are an important group of natural chemicals of plant origin that are becoming increasingly important in our health. They are trace constituents that are not nutrients as such but play an important role in maintaining health. Their chemistry is complex and interrelated. There are many thousands of phytochemicals which is a new form of science were our knowledge will rapidly increase. They can be compared with the discovery of vitamins nearly 100 years ago.
Research is a currently being undertaken to identify and better understand their role in macadamias and a number of different types have been found. A wide range has been found in other tree nuts and it is reasonable to expect that at least some of these wiil be present in macadamias.
Phytochemicals exhibit physiological effects and may modify risk factors with a number of diseases.
The main class present in macadamias are antioxidants. Antioxidants are scavengers of free radicals and play a significant role in protecting living systems from oxidation and damage. They may minimize diseases such as cancer, cardiovascular disease and others.
Macadamias contain a range of antioxidants including Vitamin E as tocopherols and tocotrienol,epicatechin( which is the principle antioxidant in tea), the amino acids methionine and cysteine and selenium.Others antioxidants have been detected in lesser amounts.
Macadamias also contain phytosterols(plant sterols)which are believed to lower total serum cholesterol and the undesirable low density cholesterol. Macadamias contain a range of serols constituents of which, sitosterol is the most significant.
Are macadamias fattening?
Some people fear that nuts may be fattening because of their oil content. They make our food tasty and promote satiety. It has been demonstrated that low fat diets are unsatisfying and difficult to maintain. The substitution of nuts for other foods in dietary trials did not result in any weight gain.
A dietary trial at Harvard University compared a low fat, low calorie diet with a low calorie diet containing ample fat from nuts and olive oil. Over 12 months both groups lost an averageof 4.5 kgs with the dietscontainig nuts more successful in keeping weight off after a further 6 months and the participants showed no change in blood preasure.The summary concluded that healthyfats can be part of a weight loss program,as long as total calories are controlled. When adding calories to a reducing diet it is essential to choose foods such as nuts that are rich in monounsaturated fats, vitamins, minerals, dietary fibre, and phytochemical as well as flavour.
Article published in Australian Macadamia Society News Bulletin.