Fat substitutes - a note of caution from the AHA
question the efficacy of fat replacers such as olestra, at the same
time as highlighting a number of serious side effects relating to
vitamin and mineral absorption.
Fat substitutes have been in the news a lot in the last few weeks, and rarely has the news been good. Just yesterday Danisco issued a statement reiterating the safety of its salatrim fat replacer after a damning report in the Danish press, while a week earlier Procter & Gamble concluded the sale of the plant where it makes its olestra substitute after the ingredient failed to live up to expectations.
While much of the bad press about fat replacers has centred on the side effects, which are said to include stomach cramps and diarrhoea, little has been said about their efficacy, until now. A new report from the American Heart Association (AHA) has claimed that the fat replacers have only a minor benefit to health, as most of the people who use them fail to lose weight.
The study, published in Circulation: Journal of the American Heart Association, showed that while 90 per cent of the US adult population consumed low- or reduced-fat foods and beverages, many of which contain fat substitutes, the number of overweight individuals continued to increase.
Judith Wylie-Rosett, a member of the American Heart Association's Nutrition Committee and author of the report, said: "The bottom line is that foods made with fat substitutes, used in moderation, may provide some flexibility in food selection, but are not an effective strategy on their own for weight control. Often, reduced-fat versions of products have the same or even more calories than their full-fat versions."
The report is not totally damning, however. Wylie-Rosett said that the use of fat substitutes seemed to have led to an overall trend for less fat in the diet, and the US government's target of reducing fat consumption to no more than 30 per cent of total calories is nearly a reality. Data suggests that the modern American consumes around 34 per cent of total calories from fat, compared to 40-42 per cent in the 1950s.
"We've done well in getting out the message about reducing fat intake," said Wylie-Rosett. "Now we must put the emphasis on obesity, which has doubled in the last 20 years. During the 1990s the number of people in the United States with diagnosed diabetes increased by about 33 per cent. Almost all of this increase is related to the rise in obesity."
She continued: "Americans are confused about reduced fat products in general - for example, there is a common misperception that if you consume lower-fat versions of products you don't have to worry about portion size or total calories. Eating smaller portions of food and increasing physical activity are still the most effective ways to lose weight and maintain a healthy weight."
She said that one of the most worrying side effects of the growth of fat replacers was an increase in the number of so-called fat free products such as confectionery and biscuits on the market. "These foods should be consumed in moderation. There is nothing wrong with enjoying a reduced-fat confection, but it should be a treat, rather than a major source of calories in the daily menu," said Wylie-Rosett.
"A healthy diet, like the one recommended by the American Heart Association, doesn't just limit fat, but also emphasises foods such as fruits, vegetables, whole grains and other foods that have positive benefits for health, such as dietary fibre, vitamins and minerals."
Wylie-Rosett's study focused on more than just olestra and salatrim - in fact it looked at 13 different kinds of fat substitutes, including six derived from carbohydrate, two from protein and five from fat. Those formulated from carbohydrates such as polydextrose and gums, or protein such as modified whey (used in low-fat baked goods and dairy products) have little or no effect on digestion, absorption or metabolism of vitamins and minerals, her study found. Some fat-based substitutes, such as caprenin and salatrim, used in baked goods and dairy products, also appear to have no deleterious effect on metabolism, she added.
She was particularly concerned about olestra, however, because her study showed that it reduced the absorption of fat-soluble nutrients, such as carotenoids, and the fat-soluble vitamins A, D, E and K. Vitamins A and E are antioxidants, which research has linked to a decrease in coronary heart disease, while the body uses vitamin K in the blood clotting process and vitamin D is needed for normal calcium absorption and metabolism. She said that in order to compensate for this side-effect, any food product containing olestra would have to contain added vitamins and nutrients.
She added that little was known about the potential interactions between olestra and medications and ingredients in food products that could affect fat-soluble nutrient movement and absorption rates in the gastrointestinal tract. She reiterated that olestra had already been shown to cause diarrhoea, and that large quantities of vitamins could also be lost to the body because of this.
Wylie-Rosett concluded that while the jury was still out on the effectiveness of fat replacers, primarily because there simply was not enough data yet available, the most sensible course of action for overweight individuals was to follow the healthy eating guidelines set out by organisations such as the AHA and to eat products containing fat replacers only in moderation.
