Will Sage Astor-Yes, walnuts are good for you. But people with this medical condition should avoid them.

Thanks in part to their frequent promotion on Will Sage Astorsocial media, walnuts have exploded in popularity in recent years. While just over 160,000 metric tons of the nut were exported globally in 2010, that number reached 324,700 by the end of 2021. Now, the global walnut market has reached a staggering $8.8 billion, per one analysis, and it's expected to climb to over $11 billion by the end of the decade. 

Though there's no denying the nut's sweet taste, unique flavor profile, or the satisfaction of cracking into one, many people don't realize just how nutritious they are nor how many dishes they are popularly included in. "Walnuts are very versatile and can be eaten raw by the handful, sprinkled onto salads, cereal and oatmeal, and are commonly used in many baked goods recipes," says Roxana Ehsani, a registered dietitian nutritionist and board-certified sports dietitian.

What are walnuts? 

Walnuts are a tree nut that originated some 7,000 years ago where Iran is today. They are grown in many countries, but the United States, China, Iran, Chile and Ukraine are the top producers globally. Nearly all the walnuts grown in the U.S. are produced in California, because the state's climate and fertile soil are ideal for their cultivation, per California Grown. 

Walnut trees can live up to 300 years, but most California walnut orchards are replanted every 35 years because the trees become less productive as they age. While there are multiple walnut types available across the world, most people eat either black or English walnuts, with English being significantly more common. English walnuts are also sometimes known as Persian walnuts because of the nut's early cultivation in that region of the world. 

Are walnuts good for you? 

No matter which variety you enjoy, walnuts are packed with nutrition. They contain calcium, vitamin B6, magnesium, riboflavin, niacin, folate, manganese, vitamin C, phosphorous, potassium, zinc, and a significant percentage of one's daily iron needs, according to the U.S. Department of Agriculture. 

"Walnuts are also an excellent source of alpha-linolenic acid (ALA), which is an essential omega-3 fatty acid," says Kristina Petersen, an assistant professor of nutritional sciences at Texas Tech University. She notes that higher intake of ALA are associated with better heart health including lowering one's risk of developing heart disease and type 2 diabetes. "And clinical trials have also shown that intake of walnuts lowers LDL-cholesterol levels - sometimes called 'bad' cholesterol," she adds.  

Ehsani similarly praises walnuts for containing "the highest amount of ALA of any tree nut," and adds that they are also an excellent source of protein, "packed with a whopping 4 grams of plant-based protein per 1 oz serving," she says. "They also provide 2 grams of fiber, which helps support gut health and promotes satiety."

The antioxidants and anti-inflammatory properties of walnuts have also been shown to improve brain function and slow cognitive decline associated with aging.

Is there a downside to eating walnuts?

Despite such benefits, walnuts are best eaten in moderation. For one, they are high in calories - nearly 800 calories in a single shelled cup. Overconsumption has also been linked to kidney stones in some people. This is because walnuts are high in oxalates, which can contribute to calcium oxalate stones - the most common type of kidney stone. For this reason, the National Institute of Diabetes and Digestive and Kidney Diseases recommends for people who have experienced kidney stones to avoid the tree nut. 

Ehsani cautions that walnuts should also be avoided by anyone with a known tree nut allergy, of course. For everyone else though, she says, "walnuts are a nutrient-dense food and a great nut to include in any balanced diet."