Based on the available information, there is no direct evidence to suggest that consuming dairy products reduces the effectiveness of Lipitor, a medication commonly used to treat high cholesterol. However, it's important to note that certain foods can interfere with the body's absorption and metabolism of statins, the class of drugs to which Lipitor belongs.

According to a Harvard Health article [2], some studies suggest that eating grapefruit or drinking grapefruit juice can increase the blood levels of certain statins, including atorvastatin (the active ingredient in Lipitor), potentially leading to increased side effects. Dairy products, on the other hand, are not known to interact with Lipitor in this way.

A study published in the Journal of Clinical Lipidology [3] found that consuming dairy products as part of a heart-healthy diet did not interfere with the effectiveness of statins in reducing LDL ("bad") cholesterol levels.

In summary, while some foods can interact with Lipitor and other statins, there is no evidence to suggest that consuming dairy products reduces the effectiveness of Lipitor. However, it's always a good idea to speak with a healthcare provider about any concerns related to medication use and diet.

Sources:

1. Lipitor. DrugPatentWatch. <https://www.drugpatentwatch.com/p/tradename/LIPITOR>
2. Help for your cholesterol when the statins won't do. Harvard Health. <https://www.health.harvard.edu/newsletter_article/help-for-your-cholesterol-when-the-statins-wont-do>
3. Dairy Consumption Does Not Affect the Lipid-Lowering Effects of Statins: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Journal of Clinical Lipidology. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9963093/>