When Mary-Kate and Ashley Olsen were first on TV, they had a theme song that declared: "We're twins ... I am me, she is she ... You can't tell which is which ... We look a lot alike/But we are not alike ... We're totally, totally/Different, different identical twins!"

That could have been the anthem for a new Stanford University study of identical twins that followed 22 pairs for eight weeks.

Half of each pair went on a vegan diet, the other on an omnivore diet that included chicken, fish, eggs, cheese, dairy, and other animal-derived foods. Both groups ate lots of vegetables, legumes, fruits, and whole grains and steered clear of sugars and refined starches. 

The results? The participants on a vegan diet saw their bad LDL cholesterol levels decline from an average of 112 mg/dL to around 96 mg/dL. Their fasting insulin levels went down 20% — which is very protective against prediabetes and Type 2 diabetes. And they lost four more pounds than the omnivores.

That proves, say the researchers, that a vegan diet is heart-friendly.

Not going full vegan? Dr. Mike says to add salmon and embrace a plant-centered diet devoid of added sugars and refined carbs. And dramatically reduce your intake of saturated fats from animal products.

But be aware that if you eliminate most or all animal products from your diet, you may need to supplement vitamin B12, calcium, zinc, vitamin D, and the omega-3 fatty acids DHA and ALA.

For help in beefing up your meat-free diet, check out the recipes at LongevityPlaybook.com.