Organic & ordinary milk: ‘the same benefits’

US researchers have found that there are no significant differences between organic and conventional milk. Alan Harman reports.

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There is no evidence to support claims that organic dairy products offer more nutritional benefits to children than conventionally produced food, the American Academy of Paediatrics says. According to the academy, it is more important that all milk be pasteurised to reduce the risk of bacterial infections such as salmonella, E. coli and brucellosis.

New research by the academy concludes that there is no evidence of clinically relevant differences between organic and conventional milk. In addition, the bacterial contamination levels of organic milk are not significantly higher than those of conventional milk and there is no evidence that conventional milk contains significantly higher levels of bovine growth hormones (GH).

“Any bovine GH that might remain in conventional milk is not biologically active in humans because of structural differences and susceptibility to digestion in the stomach,” the report states.According to the academy, the composition of dairy products, including milk, is affected by many factors, including the breed of cattle. Bearing this in mind, the results of studies assessing milk composition have to be interpreted with caution. “In general, milk has the same protein, vitamin, trace mineral content and lipids from both organically and conventionally reared cows,” it says.

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Extensive research
The report cites a recent study of antibiotic and micro-organism content, hormone concentration and nutritional values of milk in 334 samples from 48 states labelled as either organic, not treated with bovine GH, or conventional. This found that milk labelled ‘conventional’ had a lower bacterial count than organic or GH-free milk, but the difference was not clinically significant. Estradiol and progesterone concentrations were lower in conventional milk than in organic milk, but GH-free milk had progesterone concentrations similar to conventional milk and estradiol concentrations similar to organic milk.

Macronutrient composition was similar, although organic milk had 0,1% more protein than the other two milk types. The academy says that several studies have shown that organic milk has higher concentrations of anti-oxidants and polyunsaturated fatty acids, but it is important to recognise that milk composition is related to what the cows eat. This differs according to season and whether farms are high or low input.

High-input farms supplement the feed with proprietary minerals and vitamins. Low-input farms follow methods similar to those used in organic farming, but not as strictly. One study comparing these three systems found that milk from low-input organic and low-input conventional systems generally had significantly higher concentrations of nutritionally desirable unsaturated fatty acids and fat-soluble anti-oxidants than milk from high-input systems.

Milk from cows in both organic-certified and conventional low-input systems was significantly higher in conjugated linoleic acid content than milk from conventional high-input systems. Hormone supplementation of farm animals, especially with GH, is a major reason consumers prefer to buy organic foods. But the academy points out that GH is species-specific and has no physiological effect on humans.

Nor was there evidence that the composition of milk (fat, protein, and lactose) or its vitamin and mineral content were altered by GH treatment. The academy adds that milk from oestrogen-treated cows appears to be safe for children. Oestradiol and oestrone concentrations in organic and conventional 1%, 2%, and wholemilk were the same, although the concentrations of sex steroids were higher as the fat content of the milk increased and were lower than endogenous production rates in humans.

The report says while it has been postulated that ingested oestrogen in food derived from sex hormone- treated animals may play a role in earlier development of puberty and increasing the risk of breast cancer, no studies have supported this hypothesis in humans.