When You Heat Natural Plant-Based Foods You Can Get Cancer-Causing Acrylamide
June 09, 2012
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By Dr. Mercola
Acrylamide, a cancer-causing and potentially neurotoxic chemical, is created when carbohydrate-rich foods are cooked at high temperatures, whether baked, fried, roasted, grilled or toasted.
Some of the worst offenders include potato chips and French fries, but many foods cooked or processed at temperatures above 250 F/120 C may contain acrylamide.
As a general rule, the chemical is formed when food is heated enough to produce a fairly dry and brown/yellow surface … so if you're eating cooked foods that contain this characteristic, even if it was once a "healthy" natural food, like a sweet potato, it could be increasing your risk of cancer significantly.
Researchers Have Known About Acrylamide for a Decade
Once believed to be only an industrial product used in plastics, cosmetics and water treatment facilities, as well as found in cigarette smoke, it was not until 2002 that researchers realized acrylamide was present in our food. I remember the news stories very clearly 10 years and was really quite surprised and shocked at the announcements at the time, as it seemed very surreal.
Reaction products of acrylamide were regularly detected in people that had no known exposure to the chemical, and levels approaching 100 μg – representing a considerable cancer risk – were found among Swedish adults. Looking for a possible source, researchers hypothesized that acrylamide was formed at elevated temperatures in cooking – and they were right.
Writing in the Journal of Agricultural and Food Chemistry,i researchers found moderate levels of acrylamide (5−50 μg/kg) in heated protein-rich foods and higher levels (150−4000 μg/kg) in carbohydrate-rich foods, including potato, beetroot, and also certain heated commercial potato products and crispbread. Unheated or boiled foods showed undetectable levels (<5 μg/kg) of acrylamide, leading researchers to conclude:
"Consumption habits indicate that the acrylamide levels in the studied heated foods could lead to a daily intake of a few tens of micrograms."
In 2003, researchers analyzed the acrylamide levels of some common Swedish foods such as processed potato products, bread, breakfast cereals, biscuits, cookies, snacks and coffee. They estimated the average daily intake of the chemical to be 31 μg/day, which they said could be associated with potential health risks according to U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO) data.ii
WARNING: Some Potato Chips Contain Acrylamide in Levels 900 Times Over the Legal Limit
Acrylamide forms from a reaction between sugars and an amino acid (asparagine) during high-temperature cooking. While many foods – from coffee and breakfast cereal to bread – contain it, the highest levels have been detected in starchy plant-based foods, particularly French fries and potato chips. The federal limit for acrylamide in drinking water is 0.5 parts per billion, or about 0.12 micrograms in an eight-ounce glass of water.
However, a six-ounce serving of French fries can contain 60 micrograms of acrylamide, or about 500 times over the allowable limit.
Similarly, potato chips are notoriously high in this dangerous chemical. So high, in fact, that in 2005 the state of California actually sued potato chip makers for failing to warn California consumers about the health risks of acrylamide in their products. A settlement was reached in 2008 when Frito-Lay and several other potato chip makers agreed to reduce the acrylamide levels in their chips to 275 parts per billion (ppb) by 2011, which is low enough to avoid needing a cancer warning label.iii
A 2005 report issued by the California-based Environmental Law Foundation (ELF) also revealed the risks of eating potato chips, as all potato chip products tested exceeded the legal limit of acrylamide by a minimum of 39 times, and as much as 910 times!iv And baked chips, which are often regarded as healthier, may contain more than three times the level of acrylamide as regular chips, according to U.S. Food and Drug Administration Data (FDA).v
You're probably already aware that French fries and potato chips are not health foods, but remember that acrylamide is formed not only when foods are fried, but also when they are baked. According to the FDA's data, Ore Ida Golden Fries contained 107 ppb of acrylamide in the regular fried version and a far higher 1,098 when baked – so you can't assume that a food is low in acrylamide as long as it isn't fried or charred to a crisp.
Exposure to Acrylamide Increases Cancer Risk
Animal studies have shown that exposure to acrylamide increases the risk of several types of cancer,vi and the International Agency for Research on Cancer considers acrylamide a "probable human carcinogen." A link has also been found between acrylamide-hemoglobin levels and estrogen receptor positive breast cancer,vii and increased risks of postmenopausal endometrial and ovarian cancer with increasing dietary acrylamide intake.viii
Acrylamide has also been linked to nerve damage and other neurotoxic effects, including neurological problems in workers handling the substance. While the EPA regulates acrylamide in drinking water and the FDA regulates the amount of acrylamide residue in materials that may come in contact with food, they do not currently have any guidelines limiting the chemical in food itself.
It would be a good start if they did, but only a start, as a three-year long EU project, known as Heat-Generated Food Toxicants (HEATOX),ix the findings of which were published at the end of 2007, found there are more than 800 heat-induced compounds, of which 52 are potential carcinogens.
Can You Reduce Your Exposure to Cancer-Causing Acrylamide?
Acrylamide levels vary greatly among processed foods, even among different batches of the same food item. The chemical has so far only been found in foods heated above 250 F/120 C, which includes most processed foods. Basing your diet on whole foods, with the majority or a significant portion eaten raw or only lightly cooked is therefore one of the best ways to avoid this cancer-causing cooking byproduct.
For the times when you do cook your food, here are some tips to keep in mind:
- Frying, baking and broiling appear to be the worst offenders, while boiling or steaming appear to be much safer
- Longer cooking times increase acrylamide, so the shorter the duration of cooking, the better
- Soaking raw potatoes in water for 15-30 minutes prior to roasting may help reduce acrylamide formation during cooking
- The darker brown the food, the more acrylamide it contains (for instance, dark brown toast compared to light brown toast)
- Acrylamide is found primarily in plant-based foods, such as potatoes and grain products (not typically in meat, dairy or seafood)
In addition, the HEATOX scientists discovered that you're far less likely to ingest dangerous levels of the toxin when you eat home-cooked foods compared to industrially or restaurant-prepared foods. And when you do eat at home, the best advice they could give was to avoid overcooking your food.
This is an important health "rule" to live by, as along with containing numerous dangerous cooking byproducts, heavily-cooked or processed foods are dead and largely devoid of nutritional value. I believe it's really wise to strive to get as much raw food in your diet as possible. I personally try to eat about 85 percent of my food raw, including raw eggs.