Phytonutrients for your dog

Found in a range of colorful vegetables and fruits, phytonutrients offer significant antioxidant effects that can help with many canine health problems, from age-related issues to chronic diseases like cancer. 

In the last issue of Animal Wellness (V20I4), we looked at micronutrients, the common vitamins and minerals your dog needs to stay healthy. Now we’ll zero in on the lesser-known phytonutrients, plant-based nutrients essential to animal (and human) well-being. Although phytonutrients are not required for your dog’s growth or development, they contribute to overall long-term health. Higher levels of phytonutrients can even help prevent or reverse chronic disease, and decrease problems associated with aging.

Phytonutrients abound in fruits and vegetables

Thousands of phytonutrients are found in plants, and there is no single chemical category for all of them. Some, like sulforaphane, are in a category by themselves. Others, like flavonoids and carotenoids, are large groups with numerous compounds — over 5,000 flavonoids alone have been identified. Fortunately, a much smaller number have been shown to play the biggest part in maintaining health, and the fruits and vegetables containing the highest concentrations of these phytonutrients have been identified.

Phytonutrients are why diets high in fruits and vegetables are healthier than average diets supplemented with synthetic vitamins. Even supplementing the diet with vegetable and fruit powders offers proven health benefits for humans. Animal guardians also note that their dogs do better on diets that contain fresh whole foods, including vegetables and fruits.

Phytonutrients are mostly responsible for vibrant plant colors, especially dark green, rich red, orange, blue and purple. So it makes sense that fruits and vegetables with the most phytonutrients are dark leafy greens, berries (red, blue and purple), oranges and veggies such as yams and winter squash with orange and yellow flesh. The nutrients reside in the colored parts of the food, so red apple peel has a higher concentration of phytonutrients than the rest of the apple. Red-fleshed fruits like raspberries have nutrients spread throughout the fruit. In short, if you want to add some phytonutrient-rich fruits and veggies to your companion’s diet, go for the bright colors. (Just be sure to avoid fruits and veggies that are toxic to dogs, such as grapes of any color, as well as raisins.)

2 stand-alone phytonutrients

  1. Sulforaphane is found in the broccoli family. The highest levels are found in broccoli sprouts, but there are large amounts in the plants themselves, including broccoli, kale, cauliflower, collard greens and others in this family. Sulforaphane offers some of the strongest anti-cancer effects of all phytonutrients. Commercially-frozen broccoli does not contain a usable form, but adding a little daikon (Japanese radish) fixes that problem. Most pills are not reliable when it comes to the correct form or quantity of sulforaphane.
  2. Resveratrol lies at the root of the “French paradox”, and is why the French can eat high-fat foods such as cheese and butter without suffering heart disease. Resveratrol is a red-purple pigment found in the skins of red grapes, and in berries such as blueberries and cranberries. Resveratrol is an excellent anti-inflammatory nutrient with anti-aging and broad anti-cancer activities. This nutrient has been shown to prevent cancer at three stages — in pro-cancer environments (such as cases of repeated sunburn), in the beginnings of tumor growth, and in slowing the rapid growth phase.


The carotenoid family of phytonutrients is especially good for skin and eye problems. Carotenoids are fat-soluble, which means they are absorbed better if given with a healthy fat or oil, such as fish, olive, avocado or almond oils. They are highest in foods with a red or orange color, such as carrots, sweet potatoes, tomatoes, winter squash, cantaloupe, red peppers and papaya. They are also found in kale and other dark green leafy and cruciferous vegetables.

  • Unlike most nutrients, the lycopene found in tomatoes is released in greater quantities when the tomatoes are cooked. This is especially true when they’re cooked in an oil. Interestingly, canned tomatoes do not have this increased level of lycopene, probably because the canning temperature is so high. Lycopene is an especially good cancer fighter, and may help with memory problems (and with Alzheimer’s disease in humans).
  • Another carotenoid, beta carotene, has an antioxidant effect when given in low doses. But when given in very high doses, it actually has a pro-oxidant effect. The pro-oxidant form has a pro-inflammatory action, which helps cancer cells invade and multiply more rapidly. Rather than giving your animal pure beta carotene, its beneficial effects on the skin and eyes are best administered by giving him carrot powder, which contains a balance of carotenoids at a dose that helps the body.
  • A third carotenoid is the red-orange pigment astaxanthin. It’s found in algae; in krill, which eat those algae; and in salmon, which eat the krill. Astaxanthin is primarily responsible for the bright orange color of wild-caught salmon; it only shows up as a very pale color in farm-raised salmon. This carotenoid helps vision by specifically protecting the cells of the retina. It has a similar effect on brain cells, and can help with age-related memory problems in older animals. It also improves exercise performance in human competitive cyclists, and could help canine athletes as well.


Many people associate the word “bioflavonoids” with oranges and vitamin C. Bioflavonoids may also be called flavonoids, which makes the main name of this family a little confusing. The bioflavonoid family also contains flavonols and flavones, so many call the version found in oranges and other citrus fruits by the term “citrus bioflavonoids.”

The flavonoid family has a strong antioxidant effect. Because of this, they have anti-inflammatory and anti-cancer effects. In humans they are also especially good for the health of the heart and blood vessels.

  • Citrus bioflavonoids are found at high concentrations in peels, not only of oranges but also other citrus fruits like lemons, limes, tangerines and grapefruit. Besides the standard antioxidant action, these bioflavonoids are especially good at protecting the respiratory system, and they boost the action of vitamin C.
  • Rutin is a flavonoid found in buckwheat, olives, asparagus and raspberry. It is especially useful for decreasing bruising and reducing blood clots in the case of stroke.
  • Quercitin is found in leafy greens, tomatoes, berries and broccoli. It is one of the most widely distributed and abundant plant nutrients, with strong antioxidant effects. It has been found helpful for allergies, chronic fatigue and autoimmune problems.
  • Procyanidins are found in pine bark and in grape seeds. They are also found in apples; however, amounts vary greatly, depending on the variety of apple, and do not depend on the level of pigment. For example, Granny Smith apples have more procyanidins than McIntosh apples, but Red Delicious apples have more than both. Procyandians are especially good for memory problems associated with old age, and for high cholesterol. They may also help with high blood pressure.

What are phytonutrients good for?

The best-known of all phytonutrients (see above) have a number of things in common. They offer high antioxidant activity. Consequently, they are anti-inflammatory and have at least some anti-cancer action (either by helping prevent or treat it, or both, depending on the nutrient).

Phytonutrients can also assist with muscle strength in older animals, and help promote healthy aging. In humans (and probably in cats as well), they can help modulate blood sugar levels to control Type II diabetes. Some phytonutrients are especially helpful for specific problems, such as cataracts or respiratory disease.

Phytonutrients work best in groups

Just because phytonutrients do great things, it does not mean you can choose just one for you or your dog and get all the help you need. Many separate chemical pathways lead to inflammation, cancer and aging, and a single phytonutrient does not cover every one. So for the best effect, you need a variety of phytonutrients to cover the broadest number of pathways.

In addition, many phytonutrients have one or more additional benefits, so if you use only one for your dog, you will not get the full range of effects possible. In plants, phytonutrients come in groups, so it’s best to use them the same way. Animals were designed to eat whole foods, not individual pills.

In general, phytonutrients offer health benefits that help with chronic disease. You may want to give your dog a specific phytonutrient for a specific problem. To get the same benefits that humans derive from a diet high in fruits and vegetables, consider high quality fruit and vegetable powders as the easiest way to get a lot of nutrients into your dog at once. Some dogs also enjoy fresh vegetables and/or fruits added to their diet. Experiment with a few and see what your dog likes. Phytonutrients can benefit all animals, especially during their golden years.