Dietary Intake and Cancer in Sub-Saharan Africa: A Critical Review of Epidemiological Studies

The global diet quality score (GDQS) of foods consumed by Nigerian adults

BACKGROUND

Poor diet quality is a significant and modifiable risk factor associated with numerous non-communicable diseases. Despite its critical importance, there is a paucity of comprehensive data concerning diet quality in Nigeria. In this study, we evaluated the healthiness of food intake among Nigerian adults to identify the factors associated with them and seasonal variations in food consumption patterns.

METHODS

We used a validated semi-quantitative Food Frequency Questionnaire (FFQ). to collect dietary data from adults in Ibadan, Nigeria, on four occasions over two years. We assessed food intake healthiness using the Global Diet Quality Score (GDQS), which ranges from 0 to 49 based on 25 food groups, and its sub-metrics GDQS + (0-32, 16 food groups) and GDQS - (0-17, 9 food groups). We used Generalized Linear Models (GLMs) to examine the relationships between GDQS, demographic factors, and participants' dietary habits.

RESULTS

There were 205 participants (110 women, 95 men) with mean(SD) age of 45.0(13.4) years and mean(SD) GDQS of 29.0(4.0). Some 91.7% of the participants had a GDQS ≥ 23, signifying a low risk of poor diet quality. The multivariable analysis showed that the GDQS of those who frequently consumed home-cooked meal was higher than those who did not by 2.04 (95%CI: 0.11 to 4.07). The GDQS + of men was higher than women by 1.64 (95%CI: 0.11 to 3.03). The GDQS - of men was 0.88 lower than that of women (95%CI: - 1.53 to - 0.24), while younger participants (< 40 years) had lower GDQS - compared to older (60 + years) participants (2.51, 95%CI: - 1.58 to - 3.43) indicating a higher intake of unhealthy foods by these groups. Most participants (~ 95%) reported low intake of cruciferous vegetable.

CONCLUSIONS

Despite the overall healthiness of foods consumed by Nigerian adults and low risk of poor diet quality across seasons, men and younger adults tend to consume more unhealthy foods and fewer home cooked meals. Both genders, irrespective of age, had low intakes of cruciferous vegetables. These findings highlight opportunities for targeted interventions to improve the overall healthiness of dietary intakes among Nigerian adults.

The Policy of Compulsory Large-Scale Food Fortification in Sub-Saharan Africa

Food fortification with micronutrients was initially justified in developed countries by a lack of availability of micronutrients in staple crops, mainly due to soil exhaustion. However, in Sub-Saharan arable lands, soil fatigue is not predominant, and communities consume mostly home-grown, organic, non-processed crops. Sub-Saharan food systems are nevertheless deeply entwined with food insecurity, driver of illnesses. Family production can promote subsistence, food stability, and self-sufficiency, the main SSA setback being the vicious cycle of poverty and the lack of dietary variety, contributing to malnutrition. Poverty reduction and women's education are significant strategies for reducing child and adolescent undernourishment. Fortification of foods consumed daily by individuals makes sense and can minimize, if not entirely, eliminate deficiencies. Compulsory mass fortification of foods in Sub-Saharan Africa (SSA) with single micronutrients is, however, controversial since they work in synergy among each other and with the food matrix, for optimal absorption and metabolism. Since the causes of malnutrition are many, caused by diverse, unequal, and unjust food distribution, interrelated with political, social, cultural, or economic factors, education status of the population, season and climatic changes, and effectiveness of nutrition programs, just food fortification cannot solve the composite of all these elements. Further, compulsory fortification is excessive, unproductive, and likely harmful to human health, while many challenges remain in assessing the quality of available premixes. Furthermore, aiming at dietary diversification is the best approach of increasing trace element intake from commonly accessible and easily available food sources.

Validity and Reproducibility of a Semiquantitative Food Frequency Questionnaire and Food Picture Book in Nigeria

Background

Increasing noncommunicable diseases in Nigeria are partly related to dietary factors. However, the lack of validated nutrition assessment tools hinders the conduct of nutritional epidemiology research in this population.

Objectives

To develop a Food Frequency Questionnaire (FFQ) and Food Picture Book (FPB) for Nigerian adults, and to assess its reproducibility and validity compared with 24-h dietary recalls (24DRs) during different seasons in the year.

Methods

We compiled 202 foods for the FFQ through focus groups and consultations with local dietitians. We created an FPB with standardized food portion images to enhance the accuracy of reports of dietary intakes. We administered the FFQs to 205 purposively selected adults in Ibadan, Nigeria at ∼6 monthly intervals between November 2018 and October 2020. We evaluated the FFQ's reproducibility and validity compared with 24DR across the dry and rainy seasons by examining the consumption of common food and mixed dishes. We computed the Spearman's correlation coefficients (SCC), intraclass correlation coefficients (ICC), and Wilcoxon signed-rank tests, and generated Bland and Altman plots.

Results

Overall, we studied 110 women (53.7%) and 95 men (46.3%) with a mean age of 45.0 ± 13.4 y (mean ± SD). The reproducibility tests showed a mean ± SD SCC of 0.39 ± 0.14 and mean ± SD ICC of 0.32 ± 0.12. Higher mean ± SD SCC values were noted for cereal products (0.43 ± 0.09), starchy roots and tubers (0.45 ± 0.17), and soups (0.44 ± 0.20). Conversely, lower mean ± SD SCC values were observed for milk products (0.29 ± 0.02), solid fats (0.29 ± 0.26), and fish (0.22 ± 0.19). Regarding validity tests, the overall mean ± SD SCC was 0.27 ± 0.16 and mean ± SD ICC was 0.26 ± 0.16. We observed seasonal variations in intakes of fruits, cassava flour-based products, and nuts, although most foods did not show significant differences in intakes between seasons.

Conclusions

Our FFQ and FPB demonstrated moderate correlations and seasonal variations in intakes of certain foods, emphasizing the need to account for seasonality in dietary intakes in nutritional studies in Nigeria and similar countries.

A matched case-control study of bean intake and breast cancer risk in urbanized Nigerian women

PURPOSE

Bean intake has been associated with reduced risk of breast cancer, however; only a few studies considered molecular subtypes status and none in African women living in Sub-Saharan Africa (SSA). Therefore, the purpose of this study was to examine the associations between dietary intake of beans and breast cancer including its subtypes in Nigerian women.

METHODS

Overall, 472 newly diagnosed patients with primary invasive breast cancer were age-matched (± 5 years) with 472 controls from the Nigerian Integrative Epidemiology of Breast Cancer (NIBBLE) Study from 01/2014 to 07/2016. We collected the dietary intake of beans using a food frequency questionnaire (FFQ). Beans_alone intake was categorized into three levels never (never in the past year), low (≤ 1 portion/week), and high intake (> 1 portion/week). We used conditional and unconditional logistic regression models to estimate the Odds Ratio (OR) and 95% Confidence Intervals (CI) of beans_alone intake and the risk of breast cancer and by its molecular subtypes, respectively.

RESULTS

The mean (SD) age of cases was 44.4(10.0) and of controls was 43.5(9.5) years. In the case group, more than half (51.1%) have never consumed beans_alone in the past year compared to 39.0% in the control group. The multivariable models showed inverse associations between beans_alone (high vs. none) and breast cancer (OR = 0.55; 95%CI: 0.36-0.86, p-trend = 0.03), triple-negative (OR = 0.51 95%CI: 0.28-0.95, p-trend = 0.02) and marginally associated with hormone receptor-positive (OR = 0.53, 95%CI: 0.29-0.96, p-trend = 0.06).

CONCLUSION

Dietary intake of beans_alone may play a significant role in reducing the incidence of breast cancer, particularly of the more aggressive molecular subtype, triple-negative, in African women living in SSA.

The African Female Breast Cancer Epidemiology Study Protocol

Breast cancer is now the commonest cancer in most sub-Saharan African countries. Few studies of the epidemiology and genomics of breast cancer and its molecular subtypes in these countries have been done. The African Female Breast Cancer Epidemiology (AFBRECANE) study, a part of the Human Heredity and Health in Africa (H3Africa) initiative, is designed to study the genomics and epidemiology of breast cancer and its molecular subtypes in Nigerian women. We link recruitment of breast cancer cases at study sites with population-based cancer registries activities to enable ascertainment of the incidence of breast cancer and its molecular subtypes. We use centralized laboratory processing to characterize the histopathological and molecular diagnosis of breast cancer and its subtypes using multiple technologies. By combining genome-wide association study (GWAS) data from this study with that generated from 12,000 women participating in our prospective cohort study of cervical cancer, we conduct GWAS of breast cancer in an entirely indigenous African population. We test associations between dietary intakes and breast cancer and focus on vitamin D which we measure using dietary intakes, serum vitamin D, and Mendelian randomization. This paper describes the AFBRECANE project, its design, objectives and anticipated contributions to knowledge and understanding of breast cancer.