Alternative diets

Food and water are essential to man: when deprived of food he will die in about 10 weeks and when deprived of water, in about 1 week, depending on the environmental conditions. However, our ancestors managed to survive on an amazing variety of diets so long as certain essential chemical substances were present. McCollum, writing in 1957, considered that by 1940 scientists knew what quantity of macronutrients and micronutrients constituted an adequate diet for man and domestic animals.¹ Their predictions about essential nutrients were tested, and confirmed, by the success of rationing programmes in the UK during World War II, and later by patients who were maintained on long-term parenteral nutrition using pure nutrient solutions. So, we have known for 60 years what rations will enable normal people to avoid dietary deficiency diseases. Now the search is on for the diet that will promote optimum health.

Now, in affluent countries, clinical nutritionists are not concerned with under-nutrition, but with diseases such as heart disease, hypertension, stroke, diabetes, some sex hormone-sensitive cancers and musculoskeletal diseases that are associated with obesity. There is also a vogue for diets that claim to treat diseases caused by toxins (the nature of which are undefined), allergies (most of which are psychologically based, since adverse reactions cannot be elicited by blind testing with the putative allergen) or relative deficiencies of nutrients which, if given in greatly supraphysiological amounts, would support the natural defences against disease. However, it is very difficult to obtain reliable evidence that a given diet promotes optimum health.

The easy research was done before 1940. James Lind, aboard the Salisbury in 1747, assigned 12 seamen with scurvy to six different remedies, but only the two that had a diet supplemented with oranges and lemons recovered in 14 days. Thus, he discovered the antiscorbutic substance later identified as ascorbic acid, or vitamin C. Compare this early simple study with the work now involved in finding out if reduced or modified fat diets protect against cardiovascular disease.² Analysis of 27 studies providing 30901 person-years of data showed that participants involved for more than 2 years showed significant reductions in the rate of cardiovascular events and a suggestion of protection from total mortality.

Many alternative diets claim to cause weight loss, and hence protection against the obesity-related diseases of affluence that are listed above. Some claim that this weight loss can be achieved ‘without dieting’, that is, without consciously restricting energy intake or excluding foods normally eaten. To some extent, these claims are true. Modest weight loss (5–10% of body-weight) in people with obesity-associated medical complications improves glycaemic control in diabetic patients, reduces blood pressure in hypertensive patients, and increases longevity.³,⁴ Substantial weight loss (> 15% of body-weight) provides even greater benefits.⁵ Any diet (alternative or orthodox) that requires the patient to make a conscious change in their eating pattern tends to result in a decrease in total energy intake and hence weight loss. However, it is often doubtful if the magnitude of the weight lost ‘without dieting’ is great enough to earn health benefits, although it may be acceptable for aesthetic reasons. The relation between energy balance and change in body-weight and composition has been investigated under metabolic ward conditions.⁶ In the first week of dieting, weight loss is more rapid owing to loss of water and glycogen, but when the glycogen pool is stabilised in subsequent weeks the energy value of weight lost is 7000 kcal (29 MJ/kg). Even alternative diets obey these rules: for example, in the Hay diet the effect is claimed to depend on the sequence in which foods containing protein, carbohydrate and fat are eaten, but when two isoenergetic and isonitrogenous diets were fed to volunteers either in the normal sequence or in the Hay sequence, the effects on body composition and metabolism were the same.⁷

Alternative nutritional therapies are advocated for the treatment of cancer. The macrobiotic diet, the Gerson diet, the Livingstone diet and the use of vitamin and mineral therapy are the therapies most often suggested. These alternative approaches involve fresh, whole foods, with strong emphasis on a low-fat vegetarian diet. Most are nutritionally adequate, at least for adults. No anti-cancer diet has been shown to cure established cancers, even for cancers whose incidence is decreased by dietary changes.⁸ A gluten-free vegan diet may be of clinical benefit for certain patients with rheumatoid arthritis. This benefit may be related to a reduction in immuno-reactivity to food antigens eliminated by the change in diet.⁹

So, in affluent countries today, what are the major nutrition-related health problems, and what have alternative diets to offer in the treatment or prevention of these conditions? Undoubtedly, the most important public health challenge is obesity and its related diseases.¹⁰ If they supply the essential nutrients, alternative diets that promote wholemeal cereals, fruit and vegetables, and decreased intake of alcohol, may be helpful in causing weight loss, even if the stated objective of the regimen is to remove notional ‘toxins’. Compliance with energy-reduced diets is better if the diet is novel, with an element of magic to maximise the placebo effect.¹¹ Diets that severely restrict carbohydrate cause rapid initial weight loss, since glycogen stores are quickly depleted, but are not effective in the long term and tend to cause undesirable changes in blood lipids. Diets to remove toxins, treat allergies or strengthen immune system by severely restricting certain macronutrients or incorporating large supplements of vitamins or minerals are likely to do more harm than good. Ironically, the diet designed to meet the requirements of food rationing in the UK during World War II may be as close as we will come to the diet for optimum health.

References

1. McCollum EV. A History of Nutrition. Cambridge, Mass: The Riverside Press, 1957.
2. Hooper L, Summerbell CD, Higgins JPT et al. Reduced or modified dietary fat for preventing cardiovascular disease (Cochrane Review), Cochrane Database Syst Rev, . 2002; CD002137
3. Goldstein DJ. Beneficial health effects of modest weight loss. Int J Obes 1992; 16: 397–415.
4. Scottish Intercollegiate Guidelines Network. Obesity in Scotland. Edinburgh: RCP, 1997.
5. Agren G, Narbro K, Naslund I et al. Long-term effects of weight loss on pharmaceutical costs in obese subjects. A report from the SOS intervention study. Int J Obes 2002; 26: 184–92. [Abstract]
6. Garrow JS, Webster JD. Effects on weight and metabolic rate of obese women of a 3.4 MJ (800 kcal) diet. Lancet 1989; 1: 1429–31.
7. Wutzke KD, Heine WE, Köster D et al. Metabolic effects of Hay’s diet. Isotopes Environ Health Stud 2001; 37: 227–37.
8. Weitzman S. Alternative nutritional cancer therapies. Int J Cancer Suppl 1998; 11: 69–72.
9. Hafström I, Ringertz B, Spångberg A et al. A vegan diet free of gluten improves the signs and symptoms of rheumatoid arthritis: the effects on arthritis correlate with a reduction in antibodies to food antigens. Rheumatology 2001; 40: 1175–9. [Abstract]
10. Garrow JS. Obesity. In: Weatherall DJ, Ledingham JGG, Warrell DA (Eds). Oxford Textbook of Medicine. 3rd edn. Oxford: Oxford University Press, 1996. 1301–14.
11. Summerbell CD, Watts C, Higgins JPT, Garrow JS. Out-patient weight-reduction diets should be novel, simple and well-supervised. BMJ 1998; 317: 1487–9.