Black walnut (Juglans nigra) is a type of nut thought to offer a number of health benefits. The tree nut contains tannins, a class of substances with antioxidant and anti-inflammatory properties. Long used in certain systems of herbal medicine, black walnut extract is available in dietary supplement form and is believed to help in the treatment of certain illnesses including infections.
Black walnuts are also commonly eaten in the United States. The tree nut is high in unsaturated fat and protein and provides certain nutritional benefits. Black walnut contains essential fatty acids, including linoleic acid, oleic acid, palmitic acid, stearic acid, and linolenic acid (an omega-3 fatty acid) as well as minerals like magnesium and potassium.
There’s currently a lack of research on the effects of dietary supplements containing black walnut extract. It is too soon to tell if they can provide any health advantage to humans. Additionally, there are different types of black walnuts and extracts from each may provide a different level of benefits (if any) based on their concentration of bioactive agents.
One study investigating antibacterial properties of black walnut found that there was variation between different types cultivars). Researchers examined 22 cultivars and found that one variety (Mystry) exhibited the strongest antibacterial activity.
Regardless of variety, black walnuts, in general, may provide fewer benefits than other types of walnuts.
One small study published in the Journal of Medicinal Food in 2011 compared the cardiovascular effects of black walnuts to those of English walnuts. For the study, 36 people ate about 1.06 ounces of black walnuts or English walnuts every day for 30 days. Study results showed that participants who added English walnuts to their diets experienced greater improvements in several measures of cardiovascular health compared to participants who added black walnuts to their diets.
Lastly, researchers are still investigating how to effectively extract the active compounds from the nut. Without proper extraction methods, supplements containing the bioactive compounds may not provide benefits at all.
Despite the lack of evidence, black walnut is touted as a natural remedy for the following health problems:
There is not enough scientific evidence to support the use of black walnut or black walnut extract for these health benefits.
Due to a lack of research, little is known about the safety of long-term use of supplements containing black walnut extract. However, there’s some concern that black walnut may trigger certain side effects, including diarrhea.
Due to the high tannin content, people with liver or kidney disease or certain gastrointestinal conditions should avoid black walnut. People who are taking blood pressure medication should avoid black walnut. Pregnant or nursing women and children should avoid black walnut supplements.
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