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ISIS Report 07/09/06

Organic Strawberries Stop Cancer Cells

Latest evidence on why organic foods are good for health. Prof. Joe Cummins and Dr. Mae-Wan Ho

A fully referenced version of this article is posted on ISIS members’ website. Details here

Organic foods a cornucopia of health-promoting compounds

Scientific evidence has been accumulating on the health benefits of organic foods (Are Organic Foods More Healthy?  Organics for Health; Organic Agriculture Helps Fight Cancer; Food Quality? What's That? / Do Animals Like Good Food?) (see Box). 

Box 1

Why organic foods are healthy

Richer in essential minerals such as calcium, magnesium and ion, and trace minerals such as copper [1-3]

Contain more vitamins and micronutrients [3]

Rich in antioxidants and other compounds that fight cancer and heart disease (see main text)

Low in nitrates [4, 5]

Contain little or no harmful pesticide residues (see main text)

Grown without polluting pesticides and fertilizers and hence provide a cleaner environment for health

Contain little or no antibiotics that harm beneficial natural gut bacteria [6]

Contain no harmful artificial food additives such as hydrogenated fats, phosphoric acid aspartame and monosodium glutamate [7]

One important thing about organically grown foods is that they are a cornucopia of health-promoting chemical compounds. A new landmark study shows that organic strawberry extracts inhibited the proliferation of cancer cells more effectively than conventional strawberry extracts.

What is it about organically grown plants that make them rich in secondary metabolites off the main track, which are great for fighting diseases like cancer? Many of these compounds are actually part and parcel of the plant’s own defence against pests and disease.

Bengt Lundegardh and Anna Martensson [8] at the University of Agricultural Sciences Uppsala Sweden believe that the benefits of organically grown foods have a lot to with activating the plant’s defence mechanisms to synthesize its own protective agents because synthetic pesticides are excluded.  An active soil where plants and microbes interact also facilitates the exchange of metabolic compounds such as vitamins and cofactors. In addition, organically grown foods have a richer mineral content, on account of a more balanced nutrient uptake in the absence of artificial fertilizers, which would have provided excesses of easily available nutrients such as nitrates.

Bioactive compounds in foods, especially the plant phenolic antioxidants, are well known to prevent cancer and cardiovascular disease [9]. Phenolics are present in many crops, particularly fruits, and it has become clear that organic foods are richer in cancer fighting antioxidants [10, 11].

Organic strawberry extracts stop cancer cells

Strawberries have been studied extensively for their cancer fighting ability and that is where the benefits of organic fruit cultivation shine through. Swedish researchers at Swedish University of Agricultural Sciences, Alnarp,  and Lund University compared   extracts of five organic and conventional cultivars for their ability to inhibit the proliferation of human colon and breast cancer cells. They found that extracts from organically grown strawberries inhibited cell proliferation more effectively than extracts from the conventionally grown ones, and in both types of cancer cells [12].

The strawberry extracts decreased cell proliferation in a dose-dependent manner between 0.025 to 0.5 percent dry weight of extract to volume of cell culture. At the highest concentration, the organic extracts inhibited proliferation of colon cancer (HT29) cells by 60 percent and breast cancer (MCF-7) cells by 53.1 percent; the corresponding values for conventional strawberry extracts were 49.7 percent and 37.9 percent respectively. The differences between conventional and organic were statistically highly significant.

The most effective extracts at inhibiting cell proliferation contained 48 percent more ascorbate and 5 times more dehydroascorbate. (Vitamin C is ascorbate plus dehydroascorbate.) The organic strawberries also had more antioxidants and a higher ratio of ascorbate to dehydroascorbate.

Compost as a soil supplement increased the level of antioxidant compounds in strawberries [13].   The strawberry extracts, rich in vitamin C and antioxidants, were found to interfere with the mitogen-activated protein kinase (MAPK) signaling cascade that leads to cell division, and to suppress cancer cell proliferation and transformation  [14].

These latest findings on organic strawberries are in line with those on other organic fruits.  Organic yellow plums were found to be richer in phenolic acids when grown in natural meadow or with a ground cover of clover than conventionally grown plums [15]. Plum and clover extracts induced apoptosis (cell death) and reduced the viability of human liver cancer cells [16].

Absence of pesticides another tangible health benefit

Apart from providing secondary metabolites that fight diseases, the absence of pesticide residues in food and feed is another tangible health benefit of organic food. The “green revolution” has boosted food production in developing countries through high inputs of pesticide and fertilizers. Investigators at the Centre for Rural Development and Technology Dehli India studied residues of organochlorine, organophosphorous, carbamate and pyrethroid pesticides in conventionally grown wheat and rice and found that organic wheat and rice had little or no detectable pesticide. Production of wheat and rice under conventional system was higher than organic but this higher production is at the cost of health risk and also poses other hazards to flora and fauna [17].

The National Research Council in the United States concluded in their 1993 report [18] that dietary intake is the major source of pesticide exposure for infants and children in the United States, and this exposure may account for increased pesticide related health risks in children compared to adults (see Box 2).

Box 2

What the US EPA says about pesticides in infants

The US Environmental Protection Agency states [19]: “Laboratory studies show that pesticides can cause health problems, such as birth defects, nerve damage, cancer, and other effects that might occur over a long period of time. However these effects depend on how toxic the pesticide is and how much of it is consumed. Some pesticides also pose unique health risks to children.” 

That is because [20], “their internal organs are still developing and maturing”, and “in relation to their body weight, infants and children eat and drink more than adults, possibly increasing their exposure to pesticides in food and water.” Furthermore, “certain behaviors – such as playing on floors or lawns or putting objects in their mouths – increase a child’s exposure to pesticides used in homes and yards.”

Pesticides may harm the developing child by blocking the absorption of important food nutrients necessary for healthy growth. Furthermore, if the child’s excretory system is not fully developed, the body may not fully remove pesticides. There may also be crucial periods in human development when exposure to toxin can permanently change th way an individual’s system works.

Researchers at the Rollins School of Public Health, Emory University, Atlanta, and Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington in the United States measured dietary exposure in the urine of infants and children before and after they switched from consuming conventional to organic produce and then again back to conventional. They showed that the metabolites of the organophosphates malathion and chlorpyrifos declined to undetectable levels immediately after switching to organic diets, and remained undetectable until they switched back to conventional diets [19]. This supported the earlier conclusion that the children were mostly likely exposed to organophosphate pesticides exclusively through their diets.

Children are not the only ones affected by pesticides. In Denmark, a 1999 study on human sperm and semen quality in relation to organic or conventional diet found that the group consuming mainly organic food had a reduced pesticide intake based on the pesticide levels measured in their food. The researchers concluded that pesticide exposure in the diet did not entail a risk of impaired semen quality [20] even though the group of men not consuming organic food had a significantly lower proportion of morphologically normal sperm, which is generally considered predictive of pregnancy outcome, as abnormal sperms are indicative of DNA damage [21, 22]. It is not clear why the investigators thought that increase in abnormal sperms did not impair semen quality.

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