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In the news: Lessons from a Tanzanian Diet Study; Carotenoids and Breast Cancer?

Lessons from Tanzania: Better Diet, Less Inflammation & a Healthier Immune System

A study(1,2) conducted by a team of Dutch, German and Tanzanian researchers reports that eating a typical Western diet versus a more traditional diet is associated with slow, prolonged inflammation – a condition that underlies many chronic diseases. These findings help explain why choosing more whole, plant-based foods is a healthier way to go.

In Tanzania, moving from the countryside to cities leads to dietary changes and is accompanied by a rapid increase in chronic diseases – a pattern observed long ago in the US as well. The research team wanted to look at how this rural to urban change in eating habits affects the immune system and inflammation. The traditional rural Tanzanian diet is rich in whole grains, fiber, fruits and vegetables, while the urban, “Westernized” diet contains more processed foods and saturated fats.

The researchers focused on healthy Tanzanians living in a specific city and a group living in the countryside. From participants’ blood samples, the scientists used the latest tools to unlock the function of the immune system and the factors that influence its activity – looking at active RNA molecules and the composition of metabolic products in the blood.

Comparing the blood analysis results of the two groups, they found that metabolites derived from food had an effect on the immune system.

The rural-living group had higher levels of flavonoids and other anti-inflammatory substances in their blood. In contrast, the urban-residing group had immune cells that produced more inflammatory proteins. They also had increased levels of metabolites that are involved in cholesterol metabolism.

In short, the urban dwellers had a more activated immune system and inflammation, which may increase the risk for chronic diseases such as heart disease. In comparison, the traditional Tanzanian diet had a beneficial effect on inflammation and the functioning of the immune system.

Carotenoids: Role Preventing Breast Cancer?

While diet has been linked to development of breast cancer, a new study has focused on women at high-risk for breast cancer and carotenoids – the pigments found in fruits and veggies(3,4).

Harvard researchers measured carotenoids in plasma at an early follow up of the Nurses’ Health Studies for 1,919 women who later developed breast cancer and 1,695 controls who did not. To determine who was at high-risk for breast cancer, a genetic risk score was developed. The density of breast tissue was also determined by pre-diagnosis mammograms. Research has shown that dense breasts can be twice as likely to develop cancer as non-dense breasts and can make it harder for mammograms to detect breast cancer.

The researchers found that, overall, plasma carotenoid concentrations above 142 micrograms/deciliter were associated with a 20% lower breast cancer risk. The association was seen with estrogen receptor positive, but not estrogen receptor negative, breast cancer.

The association was more pronounced in high-risk women. For women with a high genetic risk score, having the highest circulating carotenoids led to a 28% lower risk for breast cancer. Among women with high mammographic dense tissue, the risk was 37% lower for those with the highest plasma carotenoids.

The American Institute for Cancer Research advises women to eat a diet high in veggies, fruit, whole grains and legumes (beans, lentils), and to limit processed foods, sugary drinks and alcohol. The results of this study emphasize the importance of carotenoid-rich fruits and veggies, especially for high-risk women.

References

1. Godfrey S, et al. Urban living in healthy Tanzanians is associated with an inflammatory status driven by dietary and metabolic changes. Nature Immunology. 22 : 287, 2021.
2. Radboud University Medical Center News. ”Less Inflammation with a Traditional Tanzanian Diet Than with a Western Diet”. https://www.radboudumc.nl/en/radboud-institute-for-health-sciences.
3. Peng C, et al. Circulating carotenoids and breast cancer among high-risk individuals. Am J Clin Nutr. 113: 525–533, 2021.
4. McTiernan A. Editorial. Dietary prevention of breast cancer in high-risk women: role of carotenoids. Am J Clin Nutr. 113:499-500, 2021.