What is the recommended daily intake of Brazil nuts in grams for an adult?

Recommended Daily Intake of Brazil Nuts

The recommended daily intake of Brazil nuts for an adult is 1-2 nuts per day (approximately 5-10 grams), which provides sufficient selenium without exceeding safe limits. 1, 2, 3

Rationale for Limited Consumption

Brazil nuts contain exceptionally high amounts of selenium, making them both beneficial and potentially harmful depending on consumption levels:

• A single Brazil nut (approximately 5g) from high-selenium regions can provide the entire recommended daily allowance of selenium 2
• Mean selenium levels in commercially available Brazil nuts range between 28-49 mg/kg, with up to 8-fold variation between individual nuts 2
• Consuming the standard serving size of 30g (approximately 6 nuts) may exceed the allowable daily intake of selenium (400 μg) or even approach toxicity thresholds (1200 μg) 2

Selenium Content and Variability

The selenium content in Brazil nuts varies significantly based on geographical origin:

• Brazil nuts from Amazonas state can contain up to 68.15 mg/kg of selenium, while those from Mato Grosso state may contain as little as 2.07 mg/kg 4
• A single Brazil nut could provide from 11% to 288% of the daily selenium requirement (70 μg) for an adult man, depending on its origin 4
• Soil acidity plays a major role in selenium uptake by Brazil nut trees, affecting the selenium content of the nuts 4

Health Benefits vs. Risks

Benefits:

• Consumption of just 2 Brazil nuts daily has been shown to be as effective as 100 μg of selenomethionine supplements for increasing selenium status 3
• Brazil nuts can significantly increase plasma selenium (by 64.2%) and enhance glutathione peroxidase activity, an important antioxidant enzyme 3
• A 6-month study showed improved verbal fluency and constructional praxis in older adults with mild cognitive impairment who consumed one Brazil nut daily 5

Risks:

• Brazil nuts contain high levels of radium isotopes (Ra-226 and Ra-228) that emit alpha and beta radiation 6
• Daily consumption of 1-2 Brazil nuts could result in an effective radiation dose of ~88-220 μSv/year, with uncertain health implications 6
• Excessive selenium intake can lead to toxicity, with symptoms including hair and nail loss, skin lesions, and nervous system abnormalities 2

Practical Recommendations

1. Limit consumption to 1-2 Brazil nuts per day to obtain selenium benefits while avoiding potential toxicity 2, 3
2. Consider consuming Brazil nuts as part of mixed nuts rather than alone to reduce the risk of excessive selenium intake 2
3. Be aware that the standard serving size of 30g (approximately 6 nuts) may provide excessive selenium and should be avoided for regular consumption 2
4. Those with adequate selenium status or those taking selenium supplements should be particularly cautious with Brazil nut consumption

Special Considerations

• Vegetarians and vegans in regions with low soil selenium levels may particularly benefit from controlled Brazil nut consumption 6
• Due to the high variability in selenium content, consistent daily intake of Brazil nuts should be approached with caution 2, 4
• The radiation exposure from regular Brazil nut consumption appears to be neither clearly harmful nor clearly harmless based on current evidence 6