Billie Eilish, Woody Harrelson, and Mayim Bialik are all vegans — and they look like they're thriving.

But according to a study in the journal Nutrients, 53% of vegans don't eat a healthy diet. They dine on processed fish and meat alternatives, savory vegan snacks, sauces, cakes and other sweets, convenience foods, fruit juices, and refined grains. 

Those vegans who primarily chose unhealthy foods have a 29% higher risk of overall mortality, up to 51% higher risk of being overweight or obese, a 29% higher risk of cardiovascular disease, and 74% higher risk of Type 2 diabetes than vegans who eat a healthy diet containing far more vegetables, fruit, protein alternatives, 100% whole grains, and healthy oils and fats.

A healthful diet also needs to supply vitamin B12, calcium, iodine, and iron. So if you’re a vegan, you may need supplements.

And you need to eat plants with lots of ALA (an omega-3 fatty acid), which is found in flax, chia seeds, avocados, and walnuts. That's because the body can convert ALA to EPA and DHA, two omega-3s that help fight inflammation and boost immune and heart health.

However, salmon, sea trout, sardines, and herring deliver omega-3s directly — that's why I'm plant-based, not vegan.

If you're vegan, be sure to pay careful attention to your food sources.