How To Ensure Nutritional Adequacy*
Although only 5-6% of females and 1-3% of males claim to be vegetarian, a 2010 Newspoll Survey (commissioned by Sanitarium Health and Wellbeing) found that seven out of 10 Australians are eating more plant-based meals than previously, in the belief that eating less meat and more plant-based foods improves overall health. As with any dietary practice, vegetarian diets need to be well-planned, to ensure that meals are healthy, delicious and nutritionally adequate.
Research has shown that a well planned vegetarian diet can meet nutritional needs for good health and may reduce the risk of:
- Cardiovascular disease
- Metabolic syndrome
- Insulin resistance
- Type 2 diabetes
Vegetarian diets are generally lower in saturated fat and cholesterol, and higher in dietary fibre, antioxidants and phytochemicals, than non-vegetarian diets. It is likely that the combination of these factors provide vegetarians with a significant health advantage.
Choosing plant-based meals is also environmentally beneficial.
Nutrient Content of Foods
All foods contain macronutrients and micronutrients.
The macronutrients, apart from water, are the source of energy, expressed as calories/joules or Calories/kilojoules.
One small calorie (cal) is the energy required to raise the temperature of one gram of water one degree Celsius. One calorie is 4.2 joules. One large Calorie (Cal or kcal) is the energy required to raise the temperature of one kilogram of water one degree Celsius. One Calorie is 4.2 kilojoules.
Phytochemicals, compounds produced by plants such as carotenoids etc.
The micronutrients are essential for health and do not supply energy.
Does a Vegetarian Diet Meet the Nutritional Reference Values for Macronutrients and Micronutrients?
The revised Nutrient Reference Values for Australia and New Zealand including recommended dietary intakes was released in 2006.
Using these reference values, it has been shown that "... well planned vegetarian diets can meet almost all the nutritional needs of children and adults of all ages." It is emphasised that "... vegetarian diets must be well planned to ensure nutritional needs are being met." In the 'clinical focus project' (2012), it has been shown that the lacto-ovo-vegetarian meal plans " meet key requirements with respect to energy; protein; carbohydrate; total fat; saturated, poly- and monounsaturated fats; alpha-linolenic acid; fibre; iron; zinc; calcium; folate; and vitamins A, C, E and B12." (see 40 page report, published in the Medical Journal of Australia, MJA Open 1 Suppl 2 4 June 2012).
Types of Vegetarian Diets
When people think about a vegetarian diet, they typically think about a diet that excludes meat, poultry and fish.
Vegan diet excludes meat, poultry, fish/sea food, eggs and dairy products and foods that contain these products. The follower of veganism is a vegan. Dietary vegans (strict vegetarians) refrain from consuming all animal products. Ethical vegans are those who not only follow a vegan diet but extend their vegan philosophy into other areas of their lives and oppose the use of animals or animal products for any purpose.
Lacto-vegetarian diet excludes meat, fish, poultry and eggs and foods that contain them. It allows dairy products, milk, cheese etc.
Ovo-lacto vegetarian diet excludes meat, fish and poultry but allows dairy products and eggs.
Ovo-vegetarian diet excludes meat, poultry, sea food and dairy products but allows eggs.
Pesco-vegetarian diet excludes meat, poultry, dairy products and eggs but allows fish and sea food.
Semi-vegetarian diet is primarily plant-based but includes meat, poultry, fish, dairy products and eggs on occasion or in small quantities.
The 'clinical focus project' referred to above, published in the Medical Journal of Australia, was based on lacto-ovo-vegetarian meal plans.
There is no doubt that the inclusion of dairy products, eggs and fish and sea foods in the various types of vegetarian diets makes it easier to meet the nutrient reference values deemed necessary for health. However, on a balanced, strict vegan diet, these values can also be met with the possible exception of vitamin B12. However, there are some researchers who believe that the strict vegan diet should be avoided and that either one of the ovo-lacto-pesco-vegetarian diets or the semi-vegetarian diet is best for health.
Nutrients of Concern on a Vegetarian Diet
On a vegetarian diet, energy requirements are easily met. There is no shortage of carbohydrates. There are adequate amounts of fibre, total fat, calcium, folate and vitamins A, C, and E.
Nutrients of concern on a vegetarian diet, especially the vegan diet, include protein, iron, zinc, vitamin B12, and long-chain omega-3 polyunsaturated fatty acids (PUFA's).
1. Protein and Vegetarian Diets
Proteins are large biological molecules consisting of one or more chains of amino acids. Proteins differ from one another primarily in their sequence of amino acids.
Amino acids are biologically important organic compounds made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen and nitrogen as well as other elements found in the side-chains. There are 23 proteinogenic ("protein building") amino acids that combine into peptide chains (polypeptides) which are the building blocks of the vast array of proteins. 20 of these 23 proteinogenic amino acids are known as "standard" amino acids and of these, 9 are essential.
An essential amino acid is an amino acid that cannot be synthesised de novo by humans, and therefore must be supplied in the diet.
After the amino acids, and in particular the 9 essential ones, were identified, proteins were divided into first and second class proteins. First class proteins are ones which contain all essential amino acids in required proportions by the human body. These are typically found in all meats, and, for example, egg albumin. Second class proteins contain only some of the essential proteins, although generally no more than one or two are missing. Vegetable proteins are generally labelled 'second class'.
It is now accepted that this classification of first and second class proteins led to flawed conclusions. First class protein was supposed to be of greater nutritional value. Hence protein from animal sources was 'good' for you, whereas plant protein, being second class was inferior. In actual fact, this classification of first and second class protein has NO validity in the diet as a whole. The amino acid lacking in one plant protein, is present in the protein from another plant/vegetable/fruit etc.
The findings by the authors of the report referred to above, with reference to protein and vegetarian diets, were summarised as follows:
- "A vegetarian diet can easily meet human dietary protein requirements as long as energy needs are met and a variety of foods eaten.
- Vegetarians should obtain protein from a variety of plant sources, including legumes, soy products, grains, nuts and seeds.
- Eggs and dairy products also provide protein for those following a lacto-ovo-vegetarian diet.
- There is no need to consciously combine different plant proteins at each meal as long as a variety of foods are eaten from day to day, because the human body maintains a pool of amino acids which can be used to complement dietary protein.
- The consumption of plant proteins rather than animal proteins by vegetarians may contribute to their reduced risk of chronic diseases such as diabetes and heart disease."
2. Iron and Vegetarian Diets
Iron is an essential nutrient for haemoglobin and myoglobin formation and is vital for health and peak performance. Much of our iron requirement is met through the recycling of the iron in the red cells. The life span of a red cell is about four months. In a period of four months all the red cells with their haemoglobin have been replaced. The amount of iron stored in the body is carefully regulated by intestinal absorption, as we have a limited ability to excrete excess iron.
The dynamics of iron metabolism in the human body, food sources etc. have been set out in detail in my April 2008 newsletter Iron.
The findings of the authors of the report referred to above, with reference to iron and vegetarian diets, are summarised as follows:
- "Vegetarians who eat a varied and well balanced diet are not at any greater risk of iron deficiency anaemia than non-vegetarians.
- A diet rich in whole grains, legumes, nuts, seeds, dried fruits, iron-fortified cereals and leafy green vegetables provides an adequate iron intake.
- Vitamin C and other organic acids enhance non-haem iron absorption, a process that is carefully regulated by the gut.
- People with low iron stores or higher physiological need for iron will tend to absorb more iron and excrete less."
3. Zinc and Vegetarian Diets
Zinc is a trace mineral abundantly distributed throughout all bodily tissues and fluids, and is second only to iron among trace elements in the body. It is essential for multiple aspects of metabolism, including catalytic, structural and regulatory functions, and also plays an important part in the immune system. See my January 2009 newsletter Zinc.
Plant sources of zinc contain phylate and other inhibitors of zinc absorption. Hence vegetarians and vegans may potentially be at risk of zinc deficiency.
The following is the summary of findings about zinc in the above report:
- "Well planned vegetarian diets can provide adequate amounts of zinc from plant sources.
- Vegetarians appear to adapt to lower zinc intakes by increased absorption and retention of zinc.
- Good sources of zinc for vegetarians include while grains, tofu, tempeh, legumes, nuts and seeds, fortified breakfast cereals and dairy products.
- The inhibitory effects of phylate on absorption of zinc can be minimised by modern food-processing methods such as soaking, heating, sprouting, fermenting and leavening.
- Absorption of zinc can be improved by using yeast-based breads and sourdough breads, sprouts and pre-soaked legumes.
- Studies show vegetarians have similar serum zinc concentrations to, and no greater risk of zinc deficiency than, non-vegetarians (despite differences in zinc uptake)."
4. Vitamin B12 and Vegetarian Diets
Vitamin B12 (cyanocobalamin) is an essential vitamin for the synthesis of DNA (and ultimately cell division) and for maintaining nerve myelin integrity. It is found almost exclusively in animal-based products including red meats, poultry, sea food, milk cheese and eggs. As vitamin B12 is produced by bacteria in the large intestines of animals, plant-based foods are generally not a source of vitamin B12. It is therefore a nutrient of concern for vegetarians and particularly for vegans who choose an entirely plant-based diet. A cross-sectional analysis study of 689 men found that more than half of vegans and 7% of vegetarians were deficient in vitamin B12.
It is recommended that vegans and anyone who significantly limit intake of animal-based foods should take vitamin B12-fortified foods or supplements.
Vitamin B12 deficiency has several stages and may be present even if a person does not have anaemia. Anyone following a vegan (especially) or strict vegetarian diet should have their vitamin B12 status regularly assessed to identify a potential problem.
5. Omega-3 Polyunsaturated Fatty Acids and Vegetarian Diets
Fats in foods and in the body contain saturated, monounsaturated and polyunsaturated fatty acids (PUFA's), the latter comprising the omega-6 and omega-3 families.
There are two essential fatty acids (EFA's): linoleic acid (LA), the parent of the omega-6 fatty acid family and alpha-linolenic acid (ALA), the parent of the omega-3 fatty acid family. EFA's cannot be synthesised by the body and therefore must be supplied by the diet. LA and ALA can be converted by enzymes into long-chain PUFA's. LA is the precursor of arachidonic acid (AA), and ALA is the precursor of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The long-chain PUFA's are not technically 'essential' because they can be produced endogenously, but they can become essential if insufficient precursor is available for their production.
Therefore, supplemental sources of DHA and EPA may be needed.
The conclusions as set out in the report referred to above are summarised as follows:
- "While intakes of the omega-3 fatty acid ALA are similar in vegetarians and non-vegetarians, intakes of EPA and DHA are low in vegetarians and virtually absent in vegans.
- ALA is endogenously converted to EPA and DHA, but the process is slow and inefficient and is affected by genetics, age, and dietary composition. Vegetarians can take practical steps to optimise conversion of ALA to EPA and DHA, including reducing intake of linoleic acid.
- We suggest that vegetarians double the current adequate intake of ALA if no direct sources of EPA and DHA are consumed."
Dietary sources of omega-3 polyunsaturated fatty acids:
- ALA is present in chia seeds, flaxseed and flaxseed oil, canola oil, walnuts, hempseed, soybean and oil, wheatgerm and leafy green vegetables.
- EPA and DHA are present in microalgae (plant EPA and DHA) but not blue-green algae, fish and other sea foods, particularly oily fish, meat (from grass-fed animals), eggs and sea vegetables.
Dietary sources of omega-6 polyunsaturated fatty acids:
- LA is present in safflower seed and oil, sunflower seed and oil, sesame seed and oil, walnuts, corn kernel and oil, wheatgerm and soy beans and oil.
Nutrient Density of Foods
Nutrient density is a critical concept in devising and recommending dietary and nutritional advice.
The importance of adequate intake of vitamins, minerals and trace elements is well known. But adequate consumption of phytochemicals is also essential for proper functioning of the body and especially the immune system.
The "Aggregate Nutrient Density Index", ANDI, is a system that ranks a food based on the amounts of nutrients per calorie/joule. The higher the nutrients per calorie/joule the more beneficial the diet is at slowing down the ageing process and improving the quality of life. ANDI is described in detail in my February 2012 newsletter A.N.D.I. Aggregate Nutrient Density Index.
Foods for Health
In my March 2009 newsletter Foods for Health, foods are grouped into four categories based on nutrient density.
The first group of foods are those with the highest nutrient density, and can be eaten "unlimited" (frequently throughout the day):
- Green vegetables
- All raw vegetables
- Non starch cooked vegetables
- Fresh fruits
- Beans and legumes.
The second group of foods are to be eaten "limit daily" (i.e. once a day only):
- Cooked starch vegetables
- Unrefined grains
- Raw nuts and seeds.
The third group of foods are to be eaten "limit weekly" (i.e. once a week only):
- Fat-free dairy
- White meat, poultry
The last group of foods are to be consumed "rarely" or as one author called them, "off limits":
- Red meat
- Refined grains (white flour, white rice)
- All processed and refined foods
- Full-fat dairy
- Refined oils
- Sweets (sugary foods)
- Alcohol, coffee, soft drinks (soda).
It can be seen that "Foods for Health" is essentially a vegetarian diet. It also meets the requirement of a dominantly alkali-forming diet, as described in my September 2005 newsletter Acid/alkaline Balance - The Ideal Diet.
Health is to be found in a dominantly vegetarian diet.
As detailed above, a balanced vegetarian diet meets all the nutrient dietary requirements. An absolutely strict vegan diet is to be undertaken with caution and with reference to the concerns described.
Finally, a plant-based diet is not only good for us (better health), but it is good for the planet. Not everyone needs to or wants to become a vegetarian, but reducing our dependence on meat is a good recipe for health and also for the planet. Diets dominated by plant foods are almost certainly the way of the future, as the current world food system is inequitable and unsustainable.
*Copyright 2013: The Huntly Centre.
Disclaimer: All material in the huntlycentre.com.au website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.
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