More than 50 years ago, a positive relationship was noted between levels of LDL-cholesterol (the so-called “bad cholesterol”), dietary intake of saturated fat and coronary artery disease.
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Dairy products and meat abound in saturated fat. It seemed to make sense, therefore, for people to keep their LDL-cholesterol level as low as possible in order to reduce heart disease. Nutritional recommendations were made for everyone to eat less fat, particularly less saturated fat. It was also recommended that everyone limit their egg intake, since eggs contain a lot of cholesterol. There would be also another benefit from eating less fat. Fat contains twice as many calories per gram as protein and carbohydrate, so eating less fat should help prevent obesity.
These recommendations turned out to be unhelpful in preventing obesity, which has skyrocketed in the United States and many other places around the world, albeit for many reasons. But how effective were they in preventing cardiovascular disease?
Surprisingly, nutrition scientists found it difficult to nail down their effectiveness. The most recent study to examine the influence of saturated fat on coronary artery disease was just published in the prestigious Archives of Internal Medicine.
This was a meta-analysis, and is the largest study on the issue to date. A meta-analysis is a way of combining many studies together so that they can be analyzed statistically as if they were one large study, which improves the ability of researchers to detect small effects. In this instance, 32 studies in which volunteers were observed over time and 27 trials in which the diets of volunteers were changed were analyzed.
As happened with other researchers, these investigators were unable to detect any cardiovascular risk associated with eating saturated fat. A number of nutritional scientists have also pointed out that the scientific evidence linking egg intake to cardiovascular disease is non-existent.
This latest study does not mean that everyone can now over-indulge in butter, cream and fatty meats. A diet very high in fat is not a healthy diet. It also contains a lot of calories and can be obesity-promoting.
What fiber is and why you need it
But if restricting dietary fat in general is not the answer to preventing cardiovascular disease, what is? It is becoming increasingly evident that the answer lies in the quality of carbohydrate.
Carbohydrate quality is determined by a number of factors, but two are of particular importance – fiber content, and content of anti-oxidants.
Dietary fiber is found in plants. It is the non-digestible carbohydrate not broken down in the gut. Dietary fiber influences how full one feels after a meal (this is called satiation), and how long one can last from one meal to the next before feeling hungry (this is called satiety).
Fiber influences satiation by absorbing water while it is in the stomach, causing the stomach to distend and "think" it's full.
Whole grain flour is rich in fiber. This is because it contains bran, which is the fiber–rich part of the grain. To make white flour, the bran is removed, so that white flour contains very little fiber.
Oxidative stress and your heart
Moving onto anti-oxidants, “oxidative stress” is an important concept in disease.
Our cells continually produce super-charged oxygen and nitrogen molecules, which are necessary for normal human physiology. However, if produced in excess, they become a source of oxidative stress and can lead to cellular damage. Smoking and eating a lot of sugar are two important sources of oxidative stress, which can lead over time to heart disease, metabolic syndrome, and even some forms of cancer.
These super-charged molecules are neutralized by endogenous anti-oxidants formed within the body, but dietary anti-oxidants can also be helpful in reducing oxidative stress.
Whole grains contain considerably more anti-oxidants than refined grains; many vegetables and fruits have a high content too; and certain oils, such as olive oil, are also rich in natural anti-oxidants.
In summary, whole grains, vegetables, fruits and beans tend to have a high content of both fiber and anti-oxidants, and there is considerable scientific evidence that these foods are helpful in preventing cardiovascular disease and obesity.
Careless low-fat dieting may actually hurt
There is also evidence that low-fat diets may actually promote cardiovascular disease and obesity in some people. This is because low-fat diets are high-carbohydrate diets.
A low-fat, high-quality carbohydrate diet is excellent, but if the extra carbohydrate consists of sweetened soda, fruit juices and highly-refined snack foods, this may promote heart disease and obesity rather than prevent these conditions.
The Mediterranean diet has been found particularly effective in preventing cardiovascular disease, possibly because of its high content of anti-oxidants. Many Mediterranean foods such as olives, wine and pomegranates are particularly rich in them. Studies of the diet invariably find it more effective in preventing cardiovascular disease than a low-fat diet.
The Israeli diet
What is the relevance of all this to Israelis? In general, the Israeli diet has the potential to be an excellent one, since Israelis eat plenty of vegetables and fruits. By comparison, in the United States, many people, especially children, eat a practically vegetable-free diet, and the snack foods they eat are usually made from highly-refined carbohydrate devoid of fiber. Not surprisingly, the age-adjusted death rate for coronary heart disease is much lower in Israel than many other parts of the world.
However, obesity rates in Israel are rising, with 26% of Israeli adults now meeting the criteria.
Why are people eating more than they did in the past? It's hard to say for sure, but many Israelis are making the same mistake many Americans did. They focus on dietary fat and ignore the quality of the carbohydrate they eat.
Meals and snacks containing mainly highly-refined carbohydrate are less filling than those containing whole grains and vegetables, and this may lead to increased hunger and over-eating. Drinking large amounts of sweetened soda and fruit juices is also a well-documented cause of excessive weight gain. Sweetened soda contains lots of calories but has no effect on satiation. Excessive soda consumption is also linked to heart disease and the development of type 2 diabetes.
These are confusing times for people trying to figure out the best diet for their families, since so many established ideas are being questioned. However, in the final analysis, a diet containing plenty of vegetables, fruits, and whole grains, and only a limited amount of sweetened drinks, approaches a Mediterranean diet.
If Israelis pursued their Mediterranean roots for meal planning, they would have one of the healthiest diets in the world, since the Mediterranean diet has been shown scientifically to provide protection against heart disease, obesity, diabetes, and many other diseases, including forms of cancer, such as breast cancer, and neurological disease, such as Alzheimer’s disease.
Dr. Arnold Slyper is a pediatric endocrinologist who has recently made aliya. He is the author of the book “Saving Your Family From Obesity.” He also has a website eatforhealth.org that provides the scientific background behind many current nutritional controversies.