Diet 2000 – The Truth Behind the Most Famous Health Claims
An Aladdin’s cave of products now exists in our healthfood shops, on the Internet and through specialist suppliers, all claiming to be a key to good health. Books and magazines all give advice about how to live. Every generation has its health fads, and every new guru has a new, improved health regime, claiming to be able to put us on the path to a longer, healthier life. But how do we sort the facts from the fiction?
There are now so many spurious claims out there that it is impossible to address it all in one single newsletter. However, certain beliefs about health, and large areas of received wisdom persist, even in alternative medicine. For this particular issue, as we look towards a healthier millennium, WDDTY thought it appropriate to examine some of the more popular claims that are virtually written in stone to see if there is any actual basis in fact.
Myth no 1: the ideal weight is 15 per cent below normal
Should you dramatically lower your daily calorie intake in order to stay healthy? For women and men on a diet, the answer is always ‘no’. Crash diets are unhelpful and yo-yoing weight increases your risk of being fat in the long term.
However, whenever this question is asked by individuals interested in longevity, the answer is invariably, and strangely, ‘yes’. Longevity research appears to show that those who eat fewer calories – ideally around 1500 calories a day – and who have thinner bodies live longer.
One of the most widely publicised studies into weight and mortality was conducted by Harvard University as part of the Nurses’ Health Study. It showed that, among other things, people who were 15 per cent below their recommended body weight lived longer (N Engl J Med, 1995; 333: 677-85). A few years earlier the same research team reported much the same finding among men (JAMA, 1993; 270: 2823-8). The media reported on these results – because they fit current social prejudices about weight, and not because the study was particularly conclusive.
What most observers failed to note was the other conclusion of the Nurses’ Study – namely, that those women who had maintained a more or less stable weight since the age of 18 had also had the best prospects of a long life. This conclusion squares with the many research papers showing that fluctuating weight not only prevents long-term weight loss but also damages the body’s vital organs (N Engl J Med, 1991; 324:1839-44; BMJ, 1997; 314: 29-34).
There may also have been other factors that turned the Harvard researchers’ conclusions from black and white to grey. In 1990, US guidelines for ‘ideal ‘weight, which had remained unchanged and unevaluated since 1959, were altered. The new guidelines for weight issued by the U.S Department of Agriculture and Health and Human Services showed that a mid-life weight gain of 10-40 pounds was acceptable and unlikely to have a significant impact on health.
Those women who were 15 per cent below current weight guidelines were probably in line with past health weight guidelines and perhaps not underweight at all. To make matters even more confusing, the guidelines changed again, a few years after the publication of this study (see box, p 1).
This may be one reason why the researchers’ main tool for analysis was body mass index (BMI). The BMI is calculated from a combination of your height and your weight. To figure out your BMI, multiply your weight in pounds by 703 and multiply your height in inches by your, height in inches. Then divide the first answer by the second. Researchers prefer it because it is a shorthand which allows them to use a single number to describe the fatness of both a five-foot woman and a six-foot man. To the average man or woman, it is still a meaningless term.
The Harvard researchers used a BMI of 19 as their healthy baseline measurement. Although there was a trend towards greater mortality from, for instance, cardiovascular disease as weight went up, it did not reach significance until women went over a BMI of 27. At this point, the numbers shot up, and a woman with a BMI of 29 or more had four times the risk of heart disease than her leaner counterpart.
To confuse things further, a large number of studies show that gaining a moderate amount of weight in middle age may actually prolong life. Very underweight people may be more likely to die younger because they lack the reserves to withstand illness. Because of this, those who gain a moderate amount of weight (10 to 15 pounds) with age may live longer (Am J Epidemiol, 1995; 141: 312-21).
Some weight gain in middle age may even be protective. For postmenopausal women in particular, a little extra fat in middle age is the primary source of oestrogen production. This not only protects the heart and bones, but eases the characteristic symptoms of menopause. Underweight women report significantly more menopausal symptoms than those who have allowed themselves to put on a moderate amount of weight.
It has long been known that lean women over 50 have the greatest risk of hip fractures – often a result of osteoporosis – due to less padding to absorb the shock of a fall. But experts now believe that weight loss after menopause is also a significant risk factor.
Researchers at the National Institute on Aging followed 3683 women who were at least 67 years old. The women were asked to recall their weight at age 50. Their weight changes and incidences of hip fractures were charted for eight years.
All the women in the study who lost 10 per cent or more of their weight at age 50 doubled their chances of fracturing a hip. The increase was greatest for lean women, however – they doubled their odds with only a 5 per cent or greater weight loss (Arch Intern Med, 1996; 156: 989-94).
In terms most of us can understand, the Harvard researchers found that a weight gain of more than 10 kg (22 lbs) since the age of 18 was associated with an increased risk of mortality in adulthood. Any gain under 22 pounds was not significantly associated with increased mortality risk.
The moral of the tale may be moderation in all things – and moderation even in that. As a review of 13 reports from 11 diverse populations in the US and Europe concluded, ‘. . . the highest mortality rates occur in adults who either have lost weight or have gained excessive weight. The lowest mortality rates are generally associated with modest weight gain’ (Ann Intern Med, 1993; 119: 737-43).
Myth no 2: Vigorous aerobic exercise is the best kind for your heart
A huge amount of data exists on the benefits of being physically active. A physically active person has a life expectancy which is on average seven years longer (Prevent Med, 1972; 1: 109-21). He or she will be prone to less depression and anxiety, and experience better mental efficiency (Br J Sports Med, 1979; 13; 110-17), higher self-esteem (Med Sci Sport, 1970; 2: 213-17), more restful sleep (Psychol Physiol, 1978; 15: 447-50), more relaxation, spontaneity, enthusiasm and better self-acceptance (Am Curr Ther J, 1979; 33: 41-44; J Clin Psychol, 1971; 27: 411-12).
But is there one definitive type of exercise which is of universal benefit? It may be, as in everything else, that exercise needs to be tailored to individual needs. For the man or woman whose heart health is an issue, 20 minutes of aerobic exercise three times a week may work as a preventative. For the woman who is at risk of osteoporosis, weight-bearing exercises which do not put excessive strain on the joints is a better choice.
When researchers looked at brisk walking compared with aerobic exercise, they found that walking was just as good for heart health (N Engl J Med, 1999; 341: 650-8). Walking three or more hours per week was associated with a 30 to 40 per cent reduction in the risk of heart attack.
But two recent reports from America (JAMA, 1999; 281: 327-34, 335-40), involving both men and women, has put much of what we know about exercise into perspective. Researchers comparing lifestyle activity with structured exercise found that a physically active lifestyle is just as effective as structured exercise in maintaining heart health.
Physical activity is defined as any activity which involves the contraction of skeletal muscle in a way which substantially increases energy expenditure has been shown to reduce the risk of heart disease, diabetes, colon cancer and several other major chronic diseases and conditions.
Exercise, such as aerobics classes and keep-fit groups, is a subset of physical activity that is structured, planned and repetitive. Finding 30 minutes a day to walk instead of using the car, to climb the stairs instead of using the lift, even window shopping while walking around the shopping mall proved to be just as effective as traditional forms of exercise. In another recent study, brisk walking was shown to be just as effective as vigorous exercise in preventing coronary events among women (N Engl J Med, 1999; 341: 650-8).
Another study found that washing and waxing the car and other household activities, when undertaken regularly, can extend your life. All it takes is 30 minutes of moderate activity each day (JAMA, 1996; 276: 221-5).
One reason why many exercise regimes have a poor long-term compliance among individuals is that they require a substantial shift in priorities and schedules. The key, it seems, is to fit exercise in with your life, not to structure your life around exercise.
Myth no 3: Cut fat out of your diet and increase your intake of carbohydrates
Fear of fat has led to widespread acceptance of the carbohydrate as the keep-fit generation’s official ‘best’ food. As dietary fat consumption has dropped, so carbohydrate consumption has skyrocketed. But instead of becoming leaner, body weights have continued to rise.
Part of the problem is hidden carbohydrates. Cereals and pulses are sources of carbohydrates, but so are vegetables, fruit, sugar, nuts, seeds, fruit juices and milk. Carbohydrates are known as energy foods because, when metabolised, they supply glucose, a sugar that circulates in our blood, providing energy where the body needs it. Our muscles, and especially our brains, need glucose to function.
But just because carbohydrates are low in fat doesn’t mean they are automatically good for keeping thin. Although they contain fewer calories than fat, they are also more easily stored as fat if they are overconsumed. The body produces insulin in response to the rise in blood sugar, which carbohydrates produce. Insulin removes excess glucose and stores it first as glycogen and then as fat. If we overconsume carbohydrate, especially high levels of refined-grain products such as bread, more insulin is produced and more fat is stored. High insulin levels promote fat storage and block the release of fat-burning glucagon. Even though carbohydrates are in themselves fat-free, they can eventually be stored as fat and prevent your body from burning fat.
Researchers at Harvard School of Public Health found that replacing fats with a high-carbohydrate diet lowered both LDL and HDL cholesterol, and reduced vitamin E and essential fatty acids. The researchers claimed that there is no proof that a low-fat, high-carbohydrate diet reduces the risk of cancer or helps maintain body weight N Engl J Med, 1997; 337: 562-8). Interestingly, a study published years ago in the Lancet actually showed that people on a 2600 kcal per day diet with a low intake of carbohydrates would lose weight, despite the higher fat content of the diet (Lancet, 1956; July 28: 155-61).
Overconsuming carbohydrates doesn’t just affect weight. Consider that:
- Refined carbohydrates are not much more than simple sugars. They have an often dramatic effect on insulin levels and can lead to depression and anxiety.
- These sugars also wreak havoc on the immune system.
- Carbohydrates in the form of wheat are linked with allergies. They have also been linked with cancer, osteoporosis, hypoglycaemia, adrenal exhaustion and parasitic and yeast infections.
- Overconsumption of carbohydrates is also associated with a greater number of food cravings – often resulting in binge-eating.
Nevertheless, carbohydrates are essential to life. Plus, not all carbohydrates have the same effect on insulin secretion. Complex carbohydrates such as those found in whole grains take longer to digest and are less likely to be stored as fats. The slower speed at which they are broken down by digestion means you maintain a much more even blood-sugar level.
Myth no 4: You can’t get enough of soy products
Will the new millennium be the time when we finally switch to a diet rich in soya-based products? Certainly, soya has many proven benefits. It contains, for instance, cancer-preventing isoflavones. It is low in fat and is a reasonable source of non-meat protein. The evidence for soya is so compelling that the US Food and Drug Administration (FDA) recently announced that it will authorise heart-health claims for certain products containing soya. But not all nutritionists are enthusiastic about soy. It is not allowed, for instance on the Gerson regime.
The Western approach to diet is usually all or nothing. Thus, there is a risk that some may end up eating soya products in an over-the-top way which Oriental societies would never consider healthy. Soya has many benefits – it is rich in natural phytoestrogens, low in fat and high in protein. But as a food source, in addition to benefits, it also has many limitations:
- Allergies to soy are almost as common as those to milk.
- Soya contains phytates, which can block the uptake of essential minerals in the intestinal tract, including such important ones as calcium, magnesium, iron and especially zinc. Oriental children who do not consume fish or meat products to counterbalance the effect of their high-phytate, soya- and rice-based diets can suffer nutritional deficiency illnesses as stunting, rickets and other developmental problems.
- Soya contains potent enzyme inhibitors, which block the action of trypsin and other enzymes needed for protein digestion.
- Soya products also contain another chemical, hemagglutinin, which promotes clumping of red blood cells. These clumped red cells are unable to fully take up oxygen and carry it in the bloodstream to all tissues. Hemagglutinin has also been observed to act as a growth depressor.
- Soya inhibits the uptake of essential amino acids such as methionine and leucine, as well as isoleucine and valine. These are all needed to combat stress, avoid depression, synthesise new body protein and maintain a healthy immune system.
- Soya is low in calcium and B vitamins, low levels of which can contribute to osteoporosis.
- Maintaining an adequate intake of vitamin C can counteract the effect of phytates (Am J Clin Nutr, 1989; 49: 140-4). Traditional fermentation of soybeans significantly reduces phytates, and also deactivates hemagglutinin and trypsin inhibitors, while leaving health-promoting substances like isoflavones intact. As a result, soya products like tempeh and miso can be very beneficial. However, in non-fermented soy products such as tofu and soy milk, these occur in an altered form that lacks protective properties. As part of a diet which includes a variety of foods, soya is likely to be a beneficial addition. But you can get too much of a good thing.
Myth no 5: Drink three to five glasses of wine per day and as much water as you can tolerate for optimum health.
It has been suggested recently (even by one of our recent contributors) that three to five glasses of wine a day is good for your heart. There are much confusing data on alcohol and its potential therapeutic uses. What is clear is that there can be no blanket recommendations about alcohol. Moderate drinking is currently defined as a single drink daily for women or two drinks for men. One ‘drink’ is the equivalent of 12 ounces of beer, five ounces of wine, one and a half ounces of 80-proof distilled spirits or one ounce of 100-proof distilled spirits.
But we all respond differently to alcohol, and some of us can experience a decline in health from consuming the ‘moderate’ amounts mentioned above.
Some of the well-documented adverse effects of alcohol include:
- A rise in oestrogen levels. Alcohol interferes with oestrogen metabolism and has been linked to breast cancer. One daily drink can raise a woman’s risk by as much as 11 to 40 per cent (Cancer Causes and Control, 1994; 5: 73-82; J Nat Cancer Inst, 1985; 87: 923-9). Women taking HRT should avoid alcohol – half a glass can nearly double the amounts of oestrogen circulating in the bloodstream (JAMA, 1996; 276: 1747-51).
- A higher risk of liver and gastrointestinal tract malignancies. Alcohol is thought to be responsible for around 2-4 per cent of cancers (J Nat Cancer Inst, 1981; 66:1191-308).
- Heavy beer consumption can increase intake of minerals like nickel, which is implicated in heart problems.
- Even moderate alcohol consumption can destroy the benefits of a diet rich in calcium by diminishing the calcium content in the heart muscle. Studies show that alcohol depletes the body of calcium, magnesium and selenium (Alcohol Alcohol, 1988; 23: 279-82; J Int Med Res, 1991; 19: 410-3). High alcohol consumption can contribute to the development of bone disease, such as osteoporosis and arthritis in men and women (Alcohol Alcohol, 1995; 30: 449-53; Bone Miner Res, 1991; 13: 139-51).
- Alcohol consumption can reduce female fecundity. The more you drink, the less likely you are to conceive (BMJ, 1998; 317: 505-10). The researchers noted that drinkers tended also to be thinner and to smoke more – which also affects conception.
Of all the alcohols, wine is least likely to cause cancer, according to a recent study. It was compared against beer and spirits and considered the least likely of the three to cause upper digestive tract cancer (BMJ, 1998; 317: 844-8).
Nevertheless, even though wine may the least damaging form of alcohol with some heart-health benefits, the potential health hazards of alcohol consumption may far outweigh the potential health benefits of the consumption levels now favoured by the medical profession.
Interestingly, research has shown that three glasses of purple grape juice are just as effective as red wine in reducing blood platelet levels (Townsend Lett Docs, 1997; 168: 52-3), so if you are torn between the damage that alcohol can do and the proven protective effects of wine, why not try the safer alternative?
At the other end of the liquid scale is water. How much we need each day is an issue of ongoing debate. There is scant evidence that drinking extra water is beneficial or even acts as a prophylactic. Adequate hydration can help avoid constipation and keeps the kidneys working optimally to flush toxins out of the body. But excess water is unlikely to be of any more benefit.
On sedentary days, to balance water lost through urination, breathing and sweating, it is said that you should consume half an ounce of liquid for every pound of body weight. So, if you’re 120 pounds, that’s 60 ounces or 7 1/2 eight-ounce cups.
You can get this much by combining drinking water with eating fruits, vegetables and other foods. Equally, most liquids can have some beneficial effect on health.
A recent study showed that men who drink more than 2.4 litres of liquid each day halve their risk of developing bladder cancer. It wasn’t just water that was beneficial. Fruit juice, carbonated liquids, milk, coffee and tea were also acceptable (N Engl J Med, 1999; 340: 1390-7).
Sidebar: A starved body is a perfect one
In June 1998, some 25 million Americans went from being a normal, healthy weight to being overweight overnight. Neither Haagen-Dazs nor Ben & Jerry’s was implicated in the change.
Instead, it came about because of new, stricter recommendations from the federal government to lower the cutoff weights used by doctors to define overweight and obese.
According to the new guidelines, those with a height-to-weight ratio or a body mass index (BMI) of 25 to 30 are considered overweight, while those with a BMI of 30 and above are considered obese. Previously, a person was not considered overweight unless he had a BMI of at least 27.
The Harvard researchers used a BMI of 19 as a healthy indicator. However, the Food and Agriculture Organization (FAO) has proposed that the use of a body mass index (BMI) of less than 18.5 be used as a criterion for assessing the incidence of starvation or chronic energy deficiency on a worldwide basis. In other words, a body mass index hovering around 10 is close to levels considered indicative of starvation, deficiencies of the immune system, illness or death (Nutrition Today, 1996; 31: 38).
Sidebar: Diet vs exercise
Which is better for your heart: exercising or losing weight?
In a randomised, controlled trial, weight loss and aerobic exercise as a means of preventing coronary artery disease were compared over a period of nine months. The 107 subjects were healthy, sedentary, obese, middle-aged and older men.
The men were randomised into either a weight-loss programme or aerobic-exercise groups. The aerobic group experienced an increase in their maximum aerobic capacity. The weight-loss group lost more weight as well as significantly decreasing fasting glucose concentrations compared with the aerobic group.
Weight loss, but not aerobic training, significantly increased HDL cholesterol and decreased blood pressure (Altern Ther Health Med, 1996; 2: 82-83).
Sidebar: 30 apples a day
Eating a variety of fruits and vegetables has traditionally been thought of as the best way to get all the nutrients you need. Unfortunately, most of us only eat a limited selection of fruits and vegetables, and the majority of today’s fruits, vegetables and grains are grown in depleted soil and stored for long periods of time before being sold. One important study which documented the historical decline in the mineral contents of fruits and vegetables between 1930 and 1987 came up with some startling conclusions (Br Food J, 1997; 99: 207-11).
Modern potatoes, for instance, were shown to have 40 per cent less potassium in them than those grown in 1930. Carrots of today contain nearly half the calcium they once did, and 75 per cent less magnesium. Tomatoes contain 90 per cent less copper. Among the fruits, apples contain two-thirds less iron than they once did, as do oranges and apricots. Some 20 common fruits and vegetables showed that foods were less nutritious than they once were.
These figures do not alter the fact that fruit and vegetables are still important sources of nutrients. But for health-conscious individuals, especially vegetarians, increasing the variety of produce eaten combined with a switch to organic foods, be they fruits and vegetables or meats, may be the best way to ensure optimum nutrient intake.
Sidebar: They’re not as bad (or as good) for you as you think
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:
Eggs
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.
Wheat
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).
Nuts
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).
Milk
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).
Potatoes
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.
Salt
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).
Coffee
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).
- This article first appeared in the December 1999 (volume 10 no 9) edition of What Doctors Don’t Tell You.
