The Connection Between Dietary Vegetable Oils and Prostate Cancer
A growing body of evidence suggests that vegetable oils rich in omega-6 fatty acids may play an important role in the progression of prostate cancer.
Men who consume diets rich in omega-6 fats were recently found to increase their risk of prostate cancer by 3.54 times.
Evidence is emerging that the ingestion of large quantities of corn oil and other such refined vegetable oils may increase the risk of developing prostate cancer and stimulate the growth of existing prostate cancer cells once developed.
Increased consumption of omega-6 fatty acids, found in corn oil and most of the oils used in bakery products, could be a reason for the rise in incidence of prostate cancer in recent years, according to recent research.
The evidence
Animal studies have demonstrated that polyunsaturated omega-6 fatty acids stimulate carcinogenesis and tumor growth and metastasis in prostate cancer, whereas long-chain omega-3 fatty acids inhibit these processes.
A recent study has demonstrated that omega-6 fatty acids such as the fat found in corn oil promote the growth of prostate tumor cells in the laboratory.
One particular omega-6 fatty acid, arachidonic acid, turns on a gene that leads directly to tumor growth, researchers have found.
"Some of the fat [that] people eat can actually trigger growth of tumors," said lead researcher Millie Hughes-Fulford, director of the Laboratory of Cell Growth.
In a study conducted at the San Francisco VA Medical Center, human prostate tumors grew twice as quickly when omega-6 acids were introduced into cell cultures.
The study in mice found that corn oil and linoleic acid stimulated the growth of prostate cancer cells called DU145.127 Rats fed a diet rich in corn oil (20% of fat intake) were more likely to have fast-growing prostate cancer cells than those on a fat-free diet. An additional study found that rats fed a diet rich in fats obtained from corn oil (20%) were significantly more likely to develop carcinoma of the prostate than those fed a low-fat diet with low levels (5%) of corn oil.110
An additional study in mice using human prostate cancer cells that had been placed in the animals found that a diet rich (18%) in corn oil stimulated the growth of the cancerous cells to a greater extent than in mice who were fed a diet low in corn oil (5%).
Where are omega-6 fatty acids found?
Omega-6 fatty acids are the polyunsaturated vegetable oils (e.g., corn, safflower, soybean, canola, and sunflower oil), which constitute most of the oils consumed in the U.S.
Omega-6 fatty acids are found in most of the oils used in bakery goods, says Hughes-Fulford, who is also an adjunct professor of medicine at the University of California, San Francisco (UCSF). "Which means that if you’re eating a diet high in omega-6 fatty acids, it’s possible that you’re turning on this prostate cancer cascade, which has been shown to be a common denominator in the growth of prostate, colorectal, and some breast cancers."
How do vegetable oils contribute to prostate cancer?
Oils in their natural state are healthful sources of essential fatty acids. Unfortunately, the standard commercial refining process destroys the EFAs and creates high levels of Trans- fatty acids, while removing important natural constituents and protective agents like minerals and vitamin E.
The result is that most commercial vegetable oils contain very little omega-3 linolenic acid and large amounts of the omega-6 linolenic acid.
Vegetable oils have a high omega-6 to omega-3 ratio
In the average American diet, omega-6 rich oils are consumed at levels 25 times greater than the consumption of beneficial oils. Healthy oils are canola oil, olive oil and fish oil. Over the last 60 years, prostate cancer diagnosis has risen at the same levels as the increased usage of omega-6 foods.
The consequences of low omega-3 levels (or a high omega-6 to omega-3 ratio) are hormonal imbalances as well as a host of serious chronic illnesses. Studies conducted at the San Francisco VA Medical Center found that omega-6 fatty acids, such as those found in corn and similar oils, increased the growth rate of prostate cancer cells in the laboratory. According to the study’s author, a diet high in omega-6 and low in omega-3 can turn on a cascade of events that can lead to an increased risk of developing prostate, colorectal, and some breast cancers.
The researchers believe that cancerous tumors may use omega 6 fats as a high-energy food, enabling rapid growth. Omega-3 fats are known to interfere with the various functions of omega-6 fats, they explain, and this was confirmed by the current findings. This effectively removes the cancer’s ‘free lunch’, a fact that may have clinical importance. Eating a diet with the right balance of omega-3 and omega-6 fats may well help to keep prostate cancer within the prostate gland where it may be monitored safely or more easily treated with surgery or radiotherapy, they conclude, adding that a healthy balance of these two types of fat would be about half as much omega-3 as omega-6.
Conclusion
Reducing total fat intake and increasing the ratio of omega-3 to omega-6 fatty acids in the diet may be particularly useful for groups at a relatively high risk for breast or prostate cancer, and may also be useful after surgery to help prevent disease recurrence.
Avoid trans-fats
High blood levels of a trans fatty acid found in partially hydrogenated vegetable oil were linked to an increased risk for nonaggressive prostate cancer in a review of data from the Physicians’ Health Study, Dr. Jorge E. Chavarro reported at the annual meeting of the American Association for Cancer Research.
Last year, a study from Harvard reported that increased intakes of trans-fatty acids may increase the risk of non-aggressive prostate tumors by about 100 per cent.
Writing in the journal Cancer Epidemiology Biomarkers & Prevention, the Boston-based researchers found that the highest blood levels of trans oleic acid and linoleic acids (18:1n-9t and 18:2t) were associated with a 116 and 97 per cent increase in the risk of non-aggressive prostate tumors, respectively, compared to the lowest levels. The study followed almost 15,000 men over 13 years.
Trans fats displace – and cannot replace – the essential fatty acids linoleic acid (omega-6) and linolenic acid (omega-3), which the body needs for a variety of functions, including blood flow regulation. Studies have shown that trans fats also increase low-density lipoproteins (LDLs) in the blood, a factor which some believe contributes to heart disease.
Practical advice
- Cut back on salad dressings, margarine, fried foods, corn and canola oil.
- Avoid hydrogenated and partially hydrogenated oils, rich fatty foods and fried foods.
For frying and baking purposes use:
- Natural saturated fats such as (organic) butter and coconut oil.
- Monounsaturated oils- such as Organic Extra Virgin Olive Oil, Grape seed oil, and Avocado oil. [Avocado oil has a very high smoke point by comparison to other cooking oils, even olive oil].
