Ann Ralph

The dominance of salt in manufactured food in the sodium intake of affluent societies.

Statistical analyses suggest that 25-50% of the salt intake of Western populations is derived from the discretionary use of cooking and table salt. Yet direct estimates of discretionary salt use by a lithium technique show that in one community in Britain this source contributed only 15% to total intake. The estimates of discretionary salt use in Finland, the United States, and Britain have been exaggerated because salt losses in cooking water were not considered. Only about a quarter of cooking salt actually enters the consumed food; allowance for this in statistical calculations makes data on dietary intake similar to those assessed from urinary sodium excretion. Daily salt intake in Britain averages about 10.7 g for adult men and 8.0 g for women, figures similar to those from countries in northern Europe. The natural salt content of food provides about 10% intake, the remaining 75% being derived from salt added by manufacturers; drinking water provides a negligible amount. Any programme for reducing the salt consumption of a population should therefore concentrate primarily on a reduction in the salt used during food processing.

The importance of dietary polyamines in cell regeneration and growth

The polyamines putrescine, spermidine and spermine are essential for cell renewal and, therefore, are needed to keep the body healthy. It was previously believed that polyamines are synthesized by every cell in the body when required. However, in the present paper evidence is provided to show that, as in the case of the essential amino acids, the diet can supply sufficient amounts of polyamines to support cell renewal and growth. Systematic analysis of different foods was carried out and from the data obtained, the average daily polyamine consumption of British adults was calculated to be in the range 350-500 mumol/person per d. The major sources of putrescine were fruit, cheese and non-green vegetables. All foods contributed similar amounts of spermidine to the diet, although levels were generally higher in green vegetables. Meat was the richest source of spermine. However, only a part of the polyamines supplied by the diet is available for use by the body. Based on experiments with rats it was established that polyamines were readily taken up from the gut lumen, probably by passive diffusion, and were partly metabolized during the process of absorption. More than 80% of the putrescine was converted to other polyamines and non-polyamine metabolites, mostly to amino acids. The enzyme responsible for controlling the bioavailability of putrescine was diamine oxidase (EC 1.4.3.6). For spermidine and spermine, however, about 70-80% of the intragastrically intubated dose remained in the original form. Considering the limitations on bioavailability (metabolism and conversion), the amounts of polyamines supplied by the average daily diet in Britain should satisfy metabolic requirements.

Polyamines in food-implications for growth and health

Abstract Different types of food (fruits, vegetables, meat, and milk products) were analyzed by high pressure liquid chromatography to determine their polyamine (putrescine, spermidine, and spermine) contents. All foods contained some polyamines, although the concentrations in different individual food components were variable. As was established earlier using 14C-labeled putrescine, spermidine, and spermine, polyamines are readily taken up by the gut and enter the systemic circulation. Food appears to constitute a major source of polyamines for humans and animals. The distribution of polyamines in the body, as determined by measuring the accumulation of 14C-spermidine in different tissues of the rat, was correlated with the metabolic activity and growth of particular organs. Thus, phytohemagglutinin induced both extensive hyperplastic growth and the preferential accumulation of labeled spermidine in the gut. Correspondingly, when skeletal muscle growth was promoted by the β-antagonist, clenbuterol, 14C-spermidine was sequestered by the hind leg gastrocnemius muscle. It is concluded that food polyamines are not only necessary for normal body metabolism, but are also used and directed preferentially to tissues and organs that have been stimulated to grow by metabolic signals.

The influence of meal composition on post-lunch changes in performance efficiency and mood

Effects of meal composition on post-lunch changes in performance efficiency and mood were examined. Lunch had an effect on mood, with subjects feeling more lethargic, feeble, clumsy, muzzy, dreamy, bored and mentally slow after the meal. However, the composition of the lunch did not influence this effect. High starch and high sugar meals slowed reactions to visual stimuli presented in the periphery, whereas consumption of a high protein lunch was associated with greater susceptibility to distraction from stimuli close to the target. These results show that protein and carbohydrate meals affect different aspects of attention. That is, the behavioural effects of a meal depend both on its composition and on the particular nature of the activity being carried out.

Influences of meal size on post-lunch changes in performance efficiency, mood, and cardiovascular function

This study examined the effects of the size of the meal on post-lunch changes in attention, mood, blood pressure and pulse. Thirty-five females subjects were tested before and after lunch. One group (n = 12) were than given a normal-sized lunch, another (n = 11) were given a lunch designed to contain 40% more energy than their individual requirement and the third group (n = 12) had a lunch with an energy content 40% less than the estimated requirement. After lunch all groups of subjects reported that they felt more feeble, dreamy and bored, and less alert, excited, clear-headed, energetic, quick-witted, friendly, sociable and elated. However, the size of the meal did not alter the extent of the pre/post-meal differences. Similarly, there was no effect of meal size on pulse rate or blood pressure, although pre/post-meal differences were observed. In contrast, subjects who had a larger lunch than normal made more errors on focussed attention and search tasks (especially the search task) than those who had a normal-sized lunch or one which was smaller than normal.

Energy Needs of the Elderly

A discussion of human energy needs in the elderly as well as in other age groups raises the issue of what we mean by the term “needs.” A recent international report on energy and protein requirements (FAO/WHO/UNU, 1985) has dealt in some detail with this question, but the analysis warrants further emphasis because the question of needs is particularly relevant to the elderly. Indeed, most of the literature that purports to assess the adequacy of diets in the elderly ignores the principles of energy requirements. This chapter sets out a collection of some of the literature on energy requirements, supplemented where there are deficiencies by unpublished data collected as part of a current study of the nutritional status of elderly men and women in Italy (A. Ferro-Luzzi, unpublished data). The implications of these studies are then considered and set in the context of the new approach to assessing energy needs embodied in the recent FAO/WHO/UNU (1985) report.

Dietary fats and cancer

Abstract Dietary fat may be a promoter, not an initiator of carcinogenesis. Animal studies suggest that the fat:carcinogenesis link is dominated by increased energy intakes and growth rates on high fat diets. Energy restriction reduces the effect. Restricting food intakes and growth rates in humans is unrealistic but low fat, high nutrient diets may reduce overweight and prevent cancer. Polyunsaturated fatty acids promote cancer up to a dietary concentration of 5%; further increases have little effect. Free radical damage to DNA by carcinogens is reduced by scavengers and modulated by dietary factors. Cross cultural associations, time trend and migrant studies are compatible with a link between fat intake and cancers of colon, breast, ovary, endometrium and prostate. Fat increases often involve the reciprocal fall in complex carbohydrates and their associated antioxidants and non-nutritive modulators of carcinogenesis, which are increasingly recognized as important. New tests can assess DNA damage.

The Hypolipidaemic Effect of Different Diets

Saturated fatty acids are still accepted as stimulating and polyunsaturated fatty acids (PUFAs) as reducing total cholesterol and low density lipoprotein cholesterol levels; these changes seem to be mediated by modulating LDL receptor reactivity and therefore the uptake of cholesterol. Confusion remains on the role of individual fatty acids with stearic and medium chain fatty acids considered ineffective in raising cholesterol levels. Lauric and myristic acids dominate with palmitic acid traditionally linked to high cholesterol levels. New studies suggest a modest effect of palmitic but studies with formula feeding are probably flawed because of the absence of dietary fibre; these polysaccharides increase cholesterol catabolism, reduce its absorption and may promote the hypolipidaemic effects of PUFAs. The impact of hyperlipidaemia on coronary heart disease may be particularly dependent on the genetically controlled apoproteins in the lipoproteins but dietary effects on the turnover and reactivity of these proteins is unresolved; these proteins may have fibrinolytic and thrombotic effects.