The Black-White IQ Gap: Understanding Its Importance and How to Close It

Black-White IQ gap, estimated at around 15 points (Nisbett et al., 2012), is significant because IQ is one of the strongest predictors of critical life outcomes, including educational attainment, income, job performance, and overall health (Brooks-Gunn & Duncan, 1997). Therefore, addressing and closing this gap is essential for promoting the success and well-being of Black individuals. Dismissing its importance is akin to gaslighting, ignoring the evidence of its critical impact.

The Role of Neurodevelopmental Milestones

A strong predictor of future IQ is the timely achievement of neurodevelopmental milestones during early childhood (Shonkoff & Phillips, 2000). Unfortunately, Black children are statistically less likely to meet these milestones on time, reflecting the broader IQ gap (Brooks-Gunn & Duncan, 1997). However, research shows that when children are born to healthy, adequately nourished, and educated mothers, they are much more likely to reach these milestones on time — regardless of race or ethnicity (Fernald et al., 2020). In such cases, the developmental gap completely closes.

The Solution

To close the IQ gap, we need to address the factors preventing Black children from achieving neurodevelopmental milestones on time. This begins with closing the health gap for Black mothers and children, as health disparities are a significant driver of developmental outcomes (Williams & Mohammed, 2009).

The Black-White Health Gap

There is overwhelming evidence of a health gap between Black and White populations (Danese & McEwen, 2012). A major contributor to this gap is chronic inflammation, which is a known driver of adverse health outcomes. Chronic inflammation has been linked to obesity, diabetes, heart disease, cancer, and neurodegenerative conditions (Danese & McEwen, 2012). These conditions disproportionately impact Black individuals, largely due to systemic inequities and environmental stressors (Williams & Mohammed, 2009).

The Perfect Storm

Several dietary factors contribute to the higher inflammation levels in Black populations:

1. The FADS Gene Variant: Over 80% of individuals of African ancestry carry the FADS1 TT genotype, which makes them more efficient at converting linoleic acid (LA) into arachidonic acid (AA) — a precursor to inflammatory compounds (Mathias et al., 2011).
2. High LA Diets: Modern diets, especially in underserved communities, are often rich in omega-6 fatty acids (e.g., from seed oils like soybean and safflower) and low in omega-3s (found in fish and flaxseeds). This imbalance drives inflammation (Simopoulos, 2002).
3. Demonisation of Saturated Fats: Public health guidance has long promoted low saturated fat intake (Hu et al., 2001), but moderate consumption of saturated fats can help balance fatty acid metabolism and improve the efficacy of omega-3s in reducing inflammation (Whelan, 1996).

What Could Happen If Fatty Acids Were Addressed?

Primary Effect: Reducing Inflammation

Balancing dietary fats — reducing omega-6 intake, increasing omega-3 intake, and incorporating moderate saturated fats — could significantly reduce inflammation (Garg ML et al., 1990). For individuals with the FADS1 TT genotype, this would directly improve brain health and function, particularly by:

• Enhancing DHA and EPA accumulation.
• Reducing pro-inflammatory eicosanoids derived from arachidonic acid.

Secondary Effect: Restoring Nutrient Availability and Reducing Susceptibility to Infections and Toxins

Lowering inflammation would improve the availability and utilisation of key nutrients, many of which are critical for cognitive development. These nutrients include:

1. Directly Benefiting from Reduced Inflammation:

• Magnesium: Supports neuronal signalling and cognitive flexibility. African Americans are more likely to have magnesium deficiencies due to dietary patterns (Rosanoff et al., 2012).
• Folate: Essential for DNA synthesis and brain development. Folate deficiency is disproportionately higher among African American women (CDC, 2018).
• Iron: Crucial for oxygen delivery and energy metabolism in the brain. African Americans have higher rates of iron deficiency anemia (Igbinosa et al., 2023).
• Glutathione: Protects neurons from oxidative stress, which is depleted during chronic inflammation. Selenium, which is associated with increased blood glutathione concentration, is not only significantly higher in Whites than in Blacks, but when supplemented with selenium-enriched yeast (247 μg/day for 9 months), blood glutathione concentrations increased by 35% in Whites while remaining unchanged in Blacks (Richie et al., 2011).
• Choline: Pregnant Black American women had significantly lower plasma choline levels (5.48 μM) compared to White women (6.58 μM) at 16 weeks gestation (Hunter et al., 2018).
• Iodine: Non-Hispanic Blacks have significantly lower urinary iodine levels compared to other groups. Data shows levels of 132 mcg/L for Black children versus 179 mcg/L for White children in the National Children’s Study (Caldwell et al., 2011).

1. Reducing Susceptibility to Infections and Toxins:

• Bacterial and Viral Infections: Chronic inflammation increases susceptibility to bacterial and viral infections, which have been linked to impaired cognition (Cohen-Manheim et al., 2015). Black populations experience a higher prevalence of these infections, compounding cognitive disparities:
• HSV-1: Associated with cognitive impairments, including reduced IQ and language deficits. African Americans have a significantly higher prevalence of HSV-1 (58.8%) compared to White Americans (36.9%) (CDC, 2018). Studies have shown HSV-1 infection correlates with lower IQ scores even in healthy individuals (Fruchter et al., 2015).
• HIV: Black/African American individuals are seven times more likely to be living with HIV than White individuals. HIV is associated with neurocognitive impairments, including memory, executive function, and processing speed deficits, further compounding health and cognitive disparities (CDC, 2021).
• Cytomegalovirus (CMV) and Chronic Respiratory Infections: CMV and other chronic respiratory infections, which are more prevalent among Black populations (Staras et al., 2006 and Thakur et al., 2020), have been linked to cognitive deficits (Wennberg et al., 2023 and Torres-Sánchez et al., 2015).
• COVID-19: The pandemic disproportionately impacted Black communities due to systemic inequities, pre-existing conditions, and higher representation in essential service roles. Studies have found that post-COVID cognitive impairments, including IQ reductions, were more prevalent in these populations (Hampshire et al., 2021).
• Environmental Pollutants and Toxins: Chronic inflammation increases vulnerability to environmental toxins (Moreno et al., 2009), with Black communities facing disproportionate exposure to these pollutants (Sampson et al., 2013). These exposures have been consistently linked to impaired cognitive function and neurodevelopmental outcomes (Bellinger, 2016). Even when exposed to similar levels of pollutants, Black individuals often experience greater health impacts due to pre-existing inflammation and systemic inequities (Bellinger, 2008).

Impact of Sleep on Cognition and Inflammation

Poor sleep is strongly associated with both increased systemic inflammation (Irwin et al., 2016) and reduced cognitive performance across multiple domains including working memory, attention, and processing speed (Alhola & Polo-Kantola, 2007; Dzierzewski et al., 2018). Studies consistently show that Black individuals experience significantly higher rates of sleep disturbances, including shorter sleep durations and lower sleep efficiency, compared to White individuals (Jackson et al., 2020; Johnson et al., 2019). Even moderate sleep restriction can produce cognitive deficits equivalent to two full nights of total sleep deprivation (Van Dongen et al., 2003).

Behavioural and Systemic Effects

By improving maternal and child health, reducing inflammation, and enhancing nutrient availability, broader societal effects could emerge:

• Hormonal Regulation: Lower cortisol, higher oxytocin, and balanced testosterone levels improve emotional stability and focus.
• Stable Households: Better health leads to more stable employment, fewer single-parent homes, and reduced criminality.
• Academic Performance: Improved health and household stability allow children to stay focused in school, avoid suspensions, and engage more deeply in learning.
• Learning Motivation: Success in school builds confidence and fosters a virtuous cycle of learning and achievement.

The “IQ Doesn’t Matter” Argument

Some dismiss the relevance of IQ entirely, viewing it as pseudoscience or arguing that it doesn’t offer meaningful insights into intelligence. They may claim that Black individuals scoring lower on IQ tests is irrelevant and that improving these scores would not translate into better life outcomes. This view ignores robust evidence linking IQ to critical outcomes such as educational attainment, income, and job performance (Nisbett et al., 2012).

Conclusion: Why This Matters

The evidence overwhelmingly suggests that addressing inflammation, improving maternal and child health, and closing developmental gaps could have profound impacts on closing the Black-White IQ gap. Acknowledging the importance of IQ as a predictor of life outcomes, while understanding its modifiable nature, provides a path toward equitable opportunities and success.

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