Ask a Dietitian: June

Send Registered Dietitian Alice Ma your nutrition and food questions at We will do our best to answer every question, and will select for the column those that may be most useful to a larger audience of readers.

I see so many stone fruits this time of year—cherries, apricots, peaches—are there any health benefits unique to these summer staples?

 Alice Ma

Alice Ma

If you’ve ever been told to “Eat a rainbow of fruits and vegetables,” or to include a variety of colors in your diet, this is because every color found in plants is associated with a different type of substance, or phytochemical, that provides a specific health benefit.

While stone fruits are similar to other fruits in that they contain fiber, vitamin C, and potassium, the unique colors of cherries, apricots, and peaches each represent a different phytochemical. Dark red, blue, and purple fruits, such as cherries and plums, contain anthocyanins, a phytochemical with cancer-preventative properties that may also slow memory loss as we age. The red/orange colors of apricots, peaches, and nectarines all come from carotenoids, a phytochemical that supports eye health, reduces inflammation, and controls blood sugar.

That being said, as each fruit differs in their nutrient profile, it’s good (and much more interesting) to include a variety in your diet. Touting one fruit as healthier than another would be like trying to compare apples to oranges (see what I did there?).

I know that kale has been touted as a superfood, but I've recently heard that too much kale can actually cause harm. How much kale is too much kale?

Like many poorly supported nutrition claims, this one probably rose from anecdotal evidence. Last year, one California researcher noticed that many of his patients who reported experiencing fatigue, foggy brain, and skin and hair issues were also eating kale frequently. Kale, as well as other vegetables, has the ability to absorb thallium, a heavy metal that can be toxic if large amounts are present in the blood. Thallium is a heavy metal that occurs in soil, and can enter our bodies through a number of ways (including exposure from hazardous waste sites and smelting plants, cocaine or heroin use, or accidentally consuming rat poison or contaminated fish). These patients had abnormal thallium levels in their blood. Thus, it was inferred that kale was the culprit for the experienced symptoms.

This one incident, however, should not be a cause for concern. As far as kale is concerned, there is currently no scientific research linking high consumption of kale, or any other vegetable, with thallium poisoning symptoms. In other words, thallium poisoning is probably not a good excuse to eat less kale or fewer vegetables. But, keep in mind that large amounts of anything can be dangerous. If kale is the only vegetable you are eating, there’s a chance you’re missing out on nutrients found in other vegetables.

Like with any food, whether it be fruits, vegetables, grains, proteins, or sweets, eating a variety is key to a nutritious and sustainable diet.

Disclaimer: Nutrition, wellness, and general health information is intended only to assist readers. It should not be used as a substitute for medical information. As always, please consult your physician regarding any medical condition.

Alice Ma, is a Co-op volunteer and registered dietitian who will answer your questions about nutrition and food. Alice received her Master’s degree in nutrition and dietetics at the University of Utah. After spending a year serving as an AmeriCorps volunteer in Ellensburg, WA, she became a resident of Moscow and currently works at Washington State University as the Registered Dietitian for Dining Services. Alice is passionate about food, nutrition, and sustainability and is excited about being involved with the Moscow Food Coop and local community.