The classification of vegetables can be tricky when it comes to foods that are part of a cancer-preventative diet. Some of this is due to the fact that when research looks at the relationship between vegetable intake and cancer risk, it often focuses on non-starchy vegetables, like carrots and mushrooms, while excluding starchy vegetables like potatoes and squash. This practice has inadvertently given starchy vegetables an (undeserved) bad rap.
Starchy versus non-starchy vegetable classification is broadly based on the parts of a plant that are consumed. Separating vegetables into these two categories also highlights differences in nutrient content and how each contributes to a healthy diet.
Non-starchy vegetables are generally thought of in three categories:
- Green, leafy vegetables — spinach, kale, chard, and lettuces
- Brassica vegetables – broccoli, cauliflower, bok choy, cabbage, etc.
- Allium vegetables — onions, garlic, and leeks
Starchy vegetables, on the other hand, have a higher starch (or sugar) content and are considered dietary staples similar to rice or other grains. Starchy vegetables include some tubers and roots, such as potatoes and sweet potatoes (yams), cassava, sago yams, and taro. Although botanically they are classified as fruit, plantains are also classified as starchy vegetables.
While starchy vegetables are concentrated sources of starch, they are less starchy than grains. Other root vegetables like carrots, beets, parsnips, turnips, and rutabagas are classified as non-starchy vegetables.
Together, starchy and non-starchy vegetables provide excellent sources of fiber, vitamins, and nutrients. In addition to all these great nutrients, vegetables also contain phytonutrients that provide potential additional health benefits such as reducing chronic inflammation — a known driver of cancer progression.
If a person is at risk for or has diabetes, a high intake of starchy vegetables has the potential to raise blood glucose levels. This can be offset by consuming this group of vegetables in their whole food form and leaving the skins on the vegetables to increase the overall fiber content in these foods.
Non-starchy vegetables don’t increase blood glucose in the same way that starchy vegetables do and are often suggested as good choices for people who are actively managing their blood sugar levels.
While there are differences between non-starchy and starchy vegetables, all vegetables consumed in their whole form are good choices for a cancer-protective diet. We recommend people aim for 3 cups of non-starchy vegetables per day and vary the types of non-starchy vegetables to include the rainbow of color to ensure you are getting the spectrum of phytonutrients along with vitamins and minerals.
We recommend including starchy vegetables as you would a grain and vary the types of starchy vegetables, grains, and legumes you consume daily. A general recommendation is to aim for ½ to 1 cup of starchy vegetables or grains per day.