Lately, evidence has emerged to show that some foods considered 'bad' are actually not so bad for you, and some foods, traditionally considered 'good', may not be as good for us as we'd always believed. These include:
Half the fat in eggs is monounsaturated - like olive oil - which is known to reduce oxidation and counter any cholesterol-raising effect (Curr Opin Lipidol, 1990; 1: 18-22; Am J Clin Nutr, 1992; 55: 400-10). The humble egg is still one of nature's better foods.
In the hunter-gatherer diet of our ancestors, a variety of grains would have been eaten. Today, the most highly consumed grain is wheat - and one potential result of this is a rise in the number of wheat allergies. Wheat bran is one of the most difficult foods to digest - which is why it is sometimes called 'good' fibre. It passes straight through the gut, but because it is not water-soluble, it can lead to dry stools and constipation. Wheat has also been identified by nutritionists such as Annemarie Colbin as a major source of depression and mood swings (Food and Healing, Ballantine, 1996).
The more nuts you eat, the lower your incidence of heart disease, according to 14 years' worth of data in the Nurses' Health Study. Nuts are high in fat, but they also contain the more beneficial monounsaturated fats or polyunsaturated fats, which have been shown to lower blood fat levels. Nuts are also rich in arginine and include high levels of magnesium, copper, folic acid, protein, potassium, fibre and vitamin E (BMJ, 1998; 317: 1332-3, 1341-5).
We assume milk and milk products are a good source of calcium. But many studies show that it is a major allergen and can actually make some conditions worse. High consumption is implicated in heart disease in later life (Lancet, 1999; 353: 1547-57). Researchers speculate that it is the protein, rather than the fat component, which is responsible for clogging arteries. Milk consumption is also ineffective in building bones and preventing colon cancer (Cancer Res, 1994; 54: 3186-90).
These contain useful amounts of vitamin C, thiamine and nicotinic acid. But according to nutritionist Gurun Jonnsson (Gut Reaction, Vermillion, 1998), if overcooked or not chewed properly, the starch in cooked potato can go through the stomach lining and dramatically raise blood glucose levels in some people. Those with diabetes mellitus and arthritis should avoid potatoes for this reason. The entire nightshade family, which includes potatoes, tomatoes, aubergines and bell peppers, is one of the most common of allergens.
A recent re-analysis of 56 studies carried out over 30 years from 1967 to 1997 suggests that salt does not play a major role in hypertension (JAMA, 1998; 279: 1383-91). But don't go mad with the salt shaker just yet. Too much salt has other implications for health, including disturbing the sodium-potassium balance. Too little can be just as harmful, too. Men with the lowest levels of sodium in their urine suffered the greatest number of heart problems over a four-year period. This effect was not found in women (Hypertension, 1995; 25: 1153-4).
A little caffeine can work as a mild beneficial stimulant. But women who drink a lot of coffee have shorter and more frequent periods (Am J Epidemiol, 1999; 149: 550-7). Researchers have also found that cafetiere coffee may increase the risk of heart disease by as much as 20 per cent. Filtered, instant and percolated coffees were safer (BMJ, 1996; 313: 1362-6).