Читать книгу Why Men Don’t Iron: The New Reality of Gender Differences - Anne Moir - Страница 14

In 1995 three Arkansas nutrition scientists published an analysis of 43 menus that were to be used in a diet manual – a manual that conscientiously met the US Government’s 1990 Dietary Guidelines for Americans.³⁶ To these health-conscious menus they added 11 more from various Arkansas hospitals and discovered that only one in nine of the 54 menus met the 1989 Recommended Dietary Allowance (RDAs) of zinc for men (set by the Food and Nutrition Board of the National Research Council). Four times more men than women were a fifth or more below their daily recommended zinc allowance. Low levels of zinc lead to a decline in the ability to taste and smell one’s food.³⁷ Loss of taste can mean food is not enjoyed and so less is eaten and so the deficiency increases. Night sight deteriorates. New tissue growth slows. Mild zinc deficiencies have been shown to stunt the growth of Canadian³⁸ and American³⁹ infants and preschool children.

The Arkansas authors point out that the continued shift to fish, chicken and legumes ‘may lead to zinc levels even lower than those previously found in the American diet’.⁴⁰ They conclude that the many dietary calls for the public to cut back on saturated fats may be having a negative impact on mineral utilization. ‘Foods rich in zinc and iron may be further limited when people lower the fat content of their diet.’⁴¹ In this they are supported by other research.⁴² The Arkansas researchers discovered that the single main reason why there still seemed enough iron in most of the diets was because of the inclusion of breakfast cereals in the menus, and such cereals typically contain artificial supplements. Such a dependence on manufactured supplements seems at odds with the dietary grail of holistic, all-natural, ‘organic’ ingredients.

Half of the Arkansas menus failed to meet male needs for Vitamin B6. One in seven men – no women – were a third below the recommended intake. Vitamin B6 is involved in the brain’s synthesis of neurotransmitters, and abnormalities can occur within two weeks of a B6-free diet.⁴³ The lack of vitamin B6 indicates a protein shortage, but instead of recommending more eggs or meat on the menu, the nutritionists urged an increase in the consumption of legumes: pulses, mung beans, lentils, chick peas, soya beans or tofu. The nutritionists recognized that there is a distaste for these foods, much more marked among men than in women,⁴⁴ but that was not thought to be a barrier. ‘Legumes are not acceptable food items to many patients,’ the nutritionists noted, ‘this is clearly an area that could be addressed by nutrition education.’⁴⁵ Here is heard the clear voice of the female-dominated nutrition industry: men show symptoms of protein deficiency, meat will cure the deficiency, but legumes, though far less efficient providers of protein, are deemed to be ‘healthier’. He needs red meat? Let him eat tofu.

There are deeply worrying aspects of the officially sanctioned American diet. Nutrition scientists aim to manipulate the average diet to make it ever more healthy, and some of them even accept that it must also be tasty.⁴⁶ So far so good. Yet when the diet fails to deliver the goods – when the needed nutrients are unavailable in the approved food – the nutritionists still refuse to increase the amount of meat in the diet, despite their own evidence that it was the reduction of meat which created the problem in the first place. Rather than rethink the diet in the light of current research, their advice is to increase the legumes and whole grains on the menu.⁴⁷

What is not mentioned by the three Arkansas nutritionists is that the USA’s recommended dietary allowance of zinc for men is a fifth higher than the Canadian recommendation and a third higher than the British. Canadian and British RDAs for zinc intake are based on a mixed diet of animal protein supplemented by unrefined cereals. The American RDA for 1989 was based on a diet containing foods with a moderate to low availability of zinc, which implies a near-vegetarian diet.⁴⁸

Suggested daily vitamin and mineral allowances are set on the high side and are subject to constant debate. People’s needs differ. Most people need less than the recommended daily allowances, a few will need more, but there is common agreement that when a person consumes less than 70% of the RDA there is cause for concern.⁴⁹ Yet a survey of older Americans discovered that 40% of them, both men and women, were falling below this critical level for zinc ingestion. A high proportion of the men also failed to reach the critical level for consumption of Vitamin A.⁵⁰ There is a common belief that Vitamin A can be obtained from dark-green leafy vegetables, but even spinach, comparatively high though it is in Vitamin A, still falls far below the levels available from foods of animal origin.⁵¹

Men need 45% more zinc in their diet than women (unless pregnant or breast-feeding). He needs more zinc because its essential for making androgens – the male hormones that he has ten times more of than her. But where is he going to find that zinc? The problem is compounded because the body’s store of zinc is negligible. We do store some, but most of it is in our bone and skeletal muscle and is difficult to release. Typically, only one-thousandth of our zinc is found circulating in the plasma (from where it can be taken up and put to use), so there is no ‘store’ of zinc in the conventional sense.⁵² Fortunately it usually takes many months for a diet low in zinc to result in any deficiency,⁵³ but research presented to the Nordic Symposium on Trace Elements in Human Health and Disease in Norway, in 1994, warned that ‘subtle deleterious changes seem to occur at much lower zinc intakes than was previously thought.’

The USA’s officially recommended dietary intake for zinc is based on a semi-vegetarian diet. Yet if there is an adequate amount of meat in the diet, the level of zinc-rich foods you need to eat is far lower, because the zinc in meat is much more easily absorbed by the body than the zinc in unrefined cereals. There is a good reason. Unrefined cereals contain a substance called phytic acid.⁵⁴ Wholemeal bread, an obvious example, is phytate rich. Phytates, or phytic acids, block the uptake of both iron and zinc. The speaker at the Nordic conference found that ‘from diets with a high content of phytate, less than 15% is typically absorbed while in refined animal protein-based diets up to 40% is absorbed.’⁵⁵

‘What if some readers think that they haven’t enough of some mineral and go and buy iron pills or whatever to boost their intake?’ asks Bill

‘Too much zinc cuts iron in the blood,’ Anne replies, ‘causing an anaemia that won’t go away with iron supplements. But at least on a balanced diet you won’t overdose.’

‘And vegetarians?’

‘Better consult a sensible doctor.’