Good nutrition is not just a question of eating wholesome food. It also entails the consumption of foods in proper combinations. The subject of food combinations is one of the most confused issues in the health literature, and at times the requirements set can be so overwhelming that even the most ardent of health-conscious individuals could become discouraged. Numerous charts and tables are presented and the most exacting combinations prescribed. Common suggestions in this regard are that some foods should only be eaten by themselves, proteins and carbohydrates should not be mixed in a meal, and even that foods grown above the ground should not be combined with foods grown below the ground. If all these suggestions were to be implemented at the same time, meal planning would become very. Nevertheless, certain basic rules pertaining to the subject of food combinations do exist, and can be usefully applied. Some important ones in this regard are: Ensuring a balanced proportion of acid- and alkaline-forming foods in the diet, combining foods that have roughly similar digestion times so as to prevent fermentation and the accumulation of toxins, and selecting food combinations in the overall diet that will provide balanced proportions of macro- and micro-nutrients. To achieve this the kitchen does not have to be changed into a laboratory, and in primitive societies these criteria are met naturally and without the need for advanced training on the subject of nutrition. Combining acid- and alkaline-forming foods
Food can be either acid-forming, or alkaline-forming. The elements in the food, to a large extent, determine whether there will be acidosis or alkalosis after the digesting of the food. Minerals are the main controllers of the acid-alkaline levels once the products of digestion have either been converted to alkaline or acid ash. A list of the acid- and alkaline-forming minerals is presented in table 7.2
Table 7.2. The main acid- and alkaline-forming minerals.
Human blood is slightly alkaline at pH 7,4 and is maintained at this level by acid-base regulatory mechanisms. The lungs and kidneys are the two organs which regulate the acid-base balance. The lungs take care of volatile substances such as CO2, and the kidneys eliminate nonvolatile acids, such as lactic acid, ketone bodies (derived from fatty acid metabolism), sulphuric acid (produced in the metabolism of protein) and phosphoric acid produced in the metabolism of phospholipids. Even slight variations in the blood pH will have a profound effect on the regulation of the acid-base balance. For example, during metabolic acidosis, bone mineral is decomposed in order to contribute to the buffering of the acid load. In one study carried out on mice, it was found that when pH fell below 7.4, then calcium efflux of bone took place, when the pH was above 7.4, then calcium influx into the bone took place whilst at pH 7.4 there was no net flux.18 A diet which is acid-forming is thus a diet which will place excessive demands on the system, and can lead to increased susceptibility to disease. Besides contributing to calcium loss from bone, high-acid diets will lead to impaired immune responses, early aging and eventual renal impairment. In cases of renal impairment there is excessive retention of acidic catabolites such as phosphates and sulphates and in addition ammonia exchange is poor, which leads to further acidosis. In the overall diet it is, therefore, important to choose more alkaline-forming foods than acid-forming foods as presented in figure Fig. 7.2.
Figure 7.2. The suggested ratio of alkaline- to acid-forming foods.
In table 7.3 the main categories of alkaline and acid-forming foods are presented. It is important to note that both alkaline- and acid-forming foods are required in the diet, but the balance should always favour alkalinity as shown in figure 7.2. Moreover, it should be noted that animal products are generally highly acid forming, which is another reason why they should be avoided. Meals that contain large proportions of acid-forming food groups should be balanced with meals containing mainly alkaline-forming foods, particularly fruits.
Table 7.3. Acid and alkaline ash food groups. The figures in brackets represent the percentage alkalinity or acidity. The grouping of fruits and vegetables is listed according to common usage and not biological classification.(From references 19 and 20).
From table 7.3 it is evident that animal products are highly acid-forming, and the invertebrate foods, such as the crabs, lobsters and oysters are the most acid-forming in this category. Diets high in animal products are also rich in purines which lead to uric acid formation and enhance kidney stone formation.21 Grains are mildly acid-forming, but when eaten together with the neutral or alkaline-forming legumes, fruits or vegetables, will not only supply an excellent protein with a well balanced mix of amino acids, but the combination will also be overall alkaline forming.
Of the alkaline-forming foods, the dried fruits are most alkaline forming, and all vegetables and fruits in general, with the exception of plums and cranberries, are alkaline forming. Strange as this may seem, this means that even the lemon with its high organic acid content is overall alkaline forming, because the acids are weak and once metabolized, the lemon has more alkaline than acidic components. The same holds true for all the other acid-tasting fruits in the list. Fruits or vegetables, in addition to a grain legume combination, will thus ensure an overall shift towards alkalinity.
Animal products are particularly acid forming, in view of their high sulphur, and phosphorus content. Purines that are present in animal foods are degraded in the course of their metabolism to uric acid, and the greater the consumption of these foods the greater the uric acid load becomes. People living in Western countries, particularly the affluent classes, are also at greater risk of forming kidney and gallstones.22,23 Both these stone types consist of calcium-oxalate, whereas gallstones, in addition contain cholesterol.
Meat in the diet results in acid urine, which results in negative calcium balance as a result of increased calcium loss in the urine.24 In addition, meat has a significant effect on the acid-base balance of the body, which in turn could lead to substantial bone loss.18,25 The reason for this is probably the high sulphur content of meat, as calcium loss has been attributed to the excretion of sulphate which is derived from amino acid metabolism.26 Combining animal foods such as cheese, eggs and meats with plant foods will lead to fermentation and toxin accumulation, as the digestion of these foods takes much longer than that of the plant foods.
Another source of acidity in the body is oxalic acid in food. Oxalic acid is not metabolized by the body, and combines with calcium to be eliminated as calcium-oxalate. Certain foods and beverages, including tea, cocoa products such as chocolates, peanuts, beets, spinach, rhubarb, Swiss chard, and black pepper, are high in oxalates and can thus also place an acid load on the system.27 As oxalic acid is excreted in the form of calcium oxalate, its elimination entails calcium loss, and there is a tendency to form crystals if consumption of these foods is high.28 It has, however, been found that if vegetarians consume foods high in oxalates, the urine composition of vegetarians is such that the formation of calcium oxalate crystals is inhibited. The relative risk of gallstone formation is 1,9 fold greater in non-vegetarians than in vegetarians, and the risk of kidney stone formation is also less in vegetarians than in non-vegetarians.27 It has also been shown that the problem for non-vegetarians seems to lie in the nature of the animal proteins which they consume,29,30 a vegetarian diet with emphasis on variety, would substantially reduce the acid load on the system.
Combining fruits and vegetables
Fruits and vegetables are both essential components of a healthy diet. Fruits are rich in vitamins and minerals and they require a shorter digestion time than do vegetables, as the principle sugar in fruit is fructose which requires no further digestion. Vegetables, on the other hand consist mainly of complex carbohydrates, and also have a different ratio of soluble to non-soluble fibres.
Because of the differences in composition, fruits and vegetables have different digestion and
stomach retention times and the eating of fruits and vegetables at the same meal can lead to fermentation in the stomach. Symptoms produced by incorrect combinations include flatulence, halitosis and all the conditions associated with an acid system. Vegetables take on average two hours longer to digest than fruits, and it has been suggested that fruits be only eaten by themselves, however, the consensus of opinion is that fruits and vegetables combine well with grains, nuts and legumes but do not combine well with each other. The digestion of the protein component in grains, nuts and legumes in the stomach takes place rapidly and provided that the system is not subjected to free fats, animal proteins, or excessive quantities of high-protein foods, this digestion takes place rapidly enough to prevent fermentation. It is therefore not necessary to eat fruits only by themselves, and a breakfast consisting of grains and fruits is therefore not only compatible, but advisable, particularly for young children who need high energy foods to start the day.
Another issue that can be confusing is the question as to what should be regarded as a fruit and what should be regarded as a vegetable. Biologically the products of a blossom containing seed must be considered fruits, however, in terms of their composition and also their common usage, some biological fruits are more like vegetables in that their principle carbohydrate is not fructose but complex carbohydrates. To confuse the issue even further, some fruits and vegetables are neutral and produce no adverse effects when combined with either fruits or vegetables at the same meal. The neutral vegetables are mainly the high-water content vegetables with very low starch content and the neutral fruits are largely the high fat content fruits such as avocados and olives. In table 7.4 a list of likely compatible and non-compatible combinations is presented. It must be noted, however, that this list is not iron clad as no hard and fast rule exists in this regard, and what works well for one individual may cause discomfort for another. Nevertheless, it is intended to provide a starting point for the selection of compatible combinations.
Table 7.4. Compatible combinations of plant foods.
It is important to vary the diet. Variation must be the watchword for healthful living. Some foods contain components which will suppress the uptake of vitamins and minerals in other foods, so that even if all the elements required by the system should be present in one meal, not all of them may be maximally utilized in that particular combination. By varying the
combinations, however, we not only make life more interesting, but we also ensure a balanced uptake of essential nutrients.
Combining grains and legumes
If a vegan vegetarian diet is followed, protein needs must be met by combining plant protein sources, as plants generally do not contain complete proteins. All plant foods contain some protein, and the digestion of these proteins will contribute to the amino acid pool from which the body will construct its own proteins. The body does not store proteins as such, but the amino acid pool is maintained for a sufficient period of time to augment amino acid requirements from one meal to the next and it is therefore not necessary to obtain all the required amino acids during any one meal. Nevertheless, it is important to ensure that foods containing balanced proportions of all the essential amino acids be consumed over a 24-hour period, even if they are not consumed at the same meal.
Some vegetarians follow very restrictive diets where nutritional needs are supplied by only one, or a few plant food sources such as rice, but such diets will be totally inadequate. Although, the quantities of essential amino acids in plant foods are not the same as those in animal foods, proper combinations will supply all the body’s needs.13,31 One such combination is the combination of grains and legumes, which supplies a protein of exceptional quality. The amino acid profiles of individual grains and legumes do not always supply adequate quantities of the essential amino acids if eaten by themselves, but if eaten together, or separately over a 24-hour period, the amino acid pool will be supplied with all the essential amino acids the body requires.
Grains are relatively low in the amino acid lysine, and supplementation with legumes or nuts will provide excellent protein. Legumes and grains go well together as the simple peanut butter sandwich will demonstrate, and preparing meals that contain both of these plant protein sources will not only provide nourishing meals, but will also give peace of mind. Adequate nutrition for young children is always a matter of concern, and whilst legumes or grains might be adequate for adults, the combination is more than adequate, even for young children. Studies in rats31 and humans confirm that suitably combined vegetarian foods supply up to many times the minimum essential amino acid requirements.32
The concern for adequate proteins often leads to an overemphasis of legumes and nuts in the vegetarian diet, and the proportions in which these foods are consumed are mostly incorrect. Heavy protein dishes consisting largely of legumes, will not only produce flatulence, but will also lead to excessive protein katabolism with its associated problems. When combining grains and legumes, the quantity of grains should exceed that of the legumes or other high protein source. Legume dishes can be made very tasty by incorporating vegetables into the recipe as in the case of casseroles, and this will naturally make the legume dish less concentrated.
Much can be learnt from Eastern, Middle Eastern and Mediterranean cultures regarding the use of whole foods such as whole grains, legumes, seeds and nuts in the preparation of tasty dishes. A whole new range of tastes and textures is available from these foods that will more than compensate for any foods given up in the interest of health.. These foods can be purchased from health shops, but as these are often quite expensive it may be wise (and fun) to scout around farming co-operatives and Eastern markets, particularly Indian, Malaysian and Chinese markets, to obtain the best buys. Furthermore, a few modern kitchen appliances such as a strong blender and mixer will greatly increase the range of dishes that can be prepared, and will also be a time saver. Expensive kitchen appliances are not essential to adopting this lifestyle, as has been proved by the many tribes that have not had the advantages of modern technology at
their disposal but enjoy a healthy lifestyle based on whole foods.