Gut Health: Research
Diet swap A study in swapping the diets of 20 rural Africans with the equivalent number of Americans for two weeks, led to some surprising results…
Ursula Arens Writer; Nutrition & Dietetics
Ursula has spent most of her career in industry as a company nutritionist for a food retailer and a pharmaceutical company. She was also a nutrition scientist at the British Nutrition Foundation for seven years. Ursula helps guide the NHD features agenda as well as contributing features and reviews.
A year ago, it was a great day for some 20 rural Africans living near the town of Empangeni in Kwa Zulu Natal South Africa. Some American researchers asked (paraphrased), “Would you like to eat an American diet (for free) for two weeks?” The answer could only be an enthusiastic yes, even when the priceto-be-paid, the butt-clenching procedure of colonoscopy, was revealed. At the opposite end of the globe, for some 20 African-Americans living in Pittsburgh Pennsylvania there was perhaps less appeal for the offer of the diet swap experiment; an all-you-can-eat typical African diet, but with perhaps the benefit of better health. The study of the diet swap between 20 rural Africans and 20 big-city Americans for the modest period of two weeks gained much interest in the media when published in April 2015, and mostly because there was astonishment about the speed of change to gut measures. Was a change of diet really such a fast-acting modifier on the colonic environment? It appears so. Lead researcher Professor O’Keefe, from the Department of Medicine and the University of Pittsburgh, concluded that the diet swap resulted in remarkable reciprocal changes in both groups in many of the colonic mucosal biomarkers of cancer risk (3). Colon cancer rates are more than 13fold higher in African Americans compared to rural South Africans, and differences in diet are likely to be the main factor. American diets are high in fat and animal protein and low in fibre and a typical African diet features the inverse. But are the risk factors associated with differences in disease rates, long-term
and cumulative effects from life-long dietary patterns? Or can modifications of diet result in near-instant measurable changes to gut environments? The typical African American diet would be familiar to many British dietitians; lots of prepared meat items such as hamburger, hotdogs, ribs or steak married to lots of refined and fatty starch, such as fries, white pasta or fried potato. Colour on a plate is more likely from ketchup or mustard than fruits or vegetables. The typical rural South African diet is small embellishments around the central base of phutu/mielie meal (also called pap or very confusingly and perhaps ironically, ‘African salad’) (2). This polenta-like staple may have very small additions of vegetables or fermented milk for flavour, but the only other usual additions to the diet are beans and cabbage/onion/spinach. Fruits may be seasonally available (bananas/ pineapple/guava), but these will only be occasional items, along with salad items such a tomatoes. Chicken, meat and sausages are much relished and appreciated, but are generally considered expensive foods for special days. After assessment for general good health and absence of exclusion criteria, 20 Americans and 20 Africans did a diet swap. The subjects were all middle aged (mean = 55 years) and most were overweight (mean BMIs = 28), although the Africans were shorter and lighter than the Americans. Diet were carefully prepared and measured and intakes observed: amounts consumed were ad libitum, but small additions of juice were added in situations where weight loss was observed in the two-week period. NHDmag.com June 2015 - Issue 105
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