According to the sources provided, there is no direct evidence to suggest that alcohol can reduce the effectiveness of niacin. However, it is important to note that alcohol consumption can have negative effects on the body, and may interact with niacin in other ways.

Niacin, also known as vitamin B3, is commonly used to treat high cholesterol and triglyceride levels, as well as to reduce the risk of heart disease. It works by increasing the levels of good cholesterol (HDL) in the body and decreasing the levels of bad cholesterol (LDL). [2]

Alcohol, on the other hand, is a depressant that can have a negative impact on the liver, pancreas, and other organs. It can also interfere with the absorption of nutrients, including vitamins and minerals. [1]

While there is no direct evidence to suggest that alcohol can reduce the effectiveness of niacin, it is possible that alcohol consumption could interfere with the body's ability to absorb and utilize the vitamin. Additionally, alcohol use can contribute to high cholesterol and triglyceride levels, which may counteract the benefits of niacin supplementation. [3]

Overall, it is important to maintain a healthy lifestyle and limit alcohol consumption in order to maximize the benefits of niacin and other vitamins and supplements. It is also recommended to consult with a healthcare professional before starting any new supplement regimen.

Sources:
[1] Drug Patent Watch. (2021). Alcohol. Retrieved from https://www.drugpatentwatch.com/p/tradename/ALCOHOL
[2] Mayo Clinic. (2021). Niacin. Retrieved from https://www.mayoclinic.org/drugs-supplements-niacin/art-20364984
[3] National Center for Biotechnology Information. (2020). Niacin. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK557728/