"It's quality rather than quantity that matters." When the Roman statesman and Stoic philosopher Lucius Annaeus Seneca declared that in the first century, he may have been wise. But there's no way he knew just how true that was for postmenopausal women when it comes to HDL -- the good cholesterol.

A new study in the Journal of Clinical Endocrinology & Metabolism explains that HDL particles vary in size, composition and level of functioning. Over time, they can become larger and their quality degrades. That, the researchers found, increases your chances for memory problems and Alzheimer's. (Conversely, smaller HDL particles shuttle less of the risky LDL cholesterol out of your body and are known to up your risk for cardiovascular problems.)

So how do you keep your HDL particles in balance so they can protect your heart and your brain? In an earlier study, the same researchers found that lifestyle choices made starting in your 40s can keep your HDL healthy and protect their quality.

Numero uno: Maintain a healthy weight. You can do that by having quality sleep, building good connections with your posse, getting plenty of physical activity, and eating a diet free of highly processed foods, red meats and processed red meats, and added sugars.

Research also indicates that omega-3s and a multivitamin-mineral daily (half in the morning, half at night) can protect and improve HDL. You can learn more about good HDL cholesterol and supplements that support it at the iHerb.com blog, "12 Foods and Supplements to Help Support Heart and Immune Health."

Dr. Mike Roizen is the founder of www.longevityplaybook.com, and Dr. Mehmet Oz is global advisor to www.iHerb.com, the world's leading online health store. Roizen and Oz are chief wellness officer emeritus at Cleveland Clinic and professor emeritus at Columbia University, respectively. Together they have written 11 New York Times bestsellers (four No. 1's).