Cancer and Low-Fat Diets

In the early 1970s, tests were performed on laboratory animals. These tests were not meant to compare low-fat versus high-fat diet, but rather to verify the beneficial effect of vegetable oils. So, saturated fat was replaced by polyunsaturates. The outcome was quite surprising, it suggested that vegetable oils can cause cancer.

In the Honolulu Heart Program, investigators compared a high-fat to a low-fat diet, in order to test the conventional wisdom of lower cholesterol levels being beneficial for heart-disease. The results were not what they expected: there was less mortality in the high-fat group.

In this study the high-fat diet was associated with:

• lower risk of total mortality
• lower risk of cancer mortality
• lower risk of stroke mortality.

The low-fat diet was associated with:

• higher total mortality
• higher risk of heart-disease death.

"Only the group with low cholesterol concentration at both examinations had a significant association with mortality." (The Lancet)

In the 1970s, the MRFIT (Multiple Risk Intervention Trial) led by Jeremiah Stamler 12,000 men were randomized into two groups:

      1. Special Care (SI) group

• They were counselled to quit smoking, 21% of them did so.
• They took medication to lower blood pressure.
• They were eating a "healthy low-fat" diet consisting of skim milk, margarine (instead of butter) one or two eggs per week. There were avoiding red meat, cakes, puddings and pastries.

      2. Usual Care (UC) group

• They were left to solve their health issues as they desired. 
• There was a reduction in smoking of 6%.

The results after 7 years and $115 million: the Special Care group ended up with more lung cancer, despite the fact that there were less smokers. 

"Because it was hard to believe that quitting smoking increased rates of lung cancer, the MRFIT investigators  suggested the possibility that the lower cholesterol levels in the [Special Care group] 'might explain [their] higher lung cancer mortality'. And, indeed, serum cholesterol showed a 'marginally significant inverse association' with lung-cancer mortality."
                                                                       - Gary Taubes

A slightly higher total mortality in the treatment group (Special Care group) than among the men who had been smoking, and eating whatever they wanted, had been observed. The opposite of what one would expect. This situation was reported in a Wall Street Journal article: "Heart Attacks: A Test Collapses".

Other investigations showing associations between low cholesterol and cancer:

John Higginson (Founding Director, International Agency for Research on Cancer) reported that breast cancer was 4 times more prevalent in Copenhagen than in rural Denmark, yet fat consumption was half in urban areas compared to the countryside.

The Framigham Study:

"Serum cholesterol measured at base line was found to be associated with the risk of both fatal cancer and all cancers occurring in the subsequent 18 years in men [...]. This inverse association seems particularly strong for colon cancer in men."

The Lancet reports about the mortality in Honolulu:

"[...] elderly people with persistent low cholesterol are more likely to die from cancer [...]"

The Evans County study:

"Kark et al. reported an inverse association between cholesterol and cancer incidence, in the Evans County study population, followed for a period of fourteen years."

In Puerto Rico:

"Serum cholesterol measured at the first examination in 1965 was found to vary inversely with subsequent mortality from cancer."

The Nurses Health Study (1982) was a prospective study led by Walter Willett (Harvard), investigators followed 89,000 nurses around the United States. Dr David Hunter (co-author of the study) concluded:

"We found no evidence that the risk of breast cancer was greater with higher fat intake." (Chicago Tribune)

In 1991, the National Institute of Health launched the $700 million Women's Health Initiative with 49,000 women between the age of 50-79. Here are the two groups:

      1. 29,000 women on their usual diet 

• They ate whatever they wanted.
• They did not receive any kind of counseling on nutrition and health.

      2. 20,000 women on a low-fat diet

• They ate more vegetables and fresh fruits.
• They consumed on average 120 calories less than the other group.
• They took part in an intensive nutritional and behavioral program, in order to avoid sugary, processed foods and alcohol.

The results did not show any association between a "healthy" low-fat diet and the incidence of breast and colorectal cancer. (Low-fat diets did not reduce risk of colorectal or breast cancer, CVD in postmenopausal women)

"The results, published in the Journal of the American Medical Association, showed no benefits for a low-fat diet. Women assigned to this eating strategy did not appear to gain protection against breast cancer,(1) colorectal cancer,(2) or cardiovascular disease.(3) And after eight years, their weights were generally the same as those of women following their usual diets." (Low-Fat Diet Not a Cure-All, Harvard)

These results haven't stopped health authorities from recommending a low-fat dietary approach to entire populations, in order to avoid cancer.

About cancer cells, please go my previous post: Sugar and Cancer.