These are things I buy for my cats on a regular basis, to keep them happy and healthy.
I scrape the food into a bowl or large cup (usually use an empty, washed-out plastic quart sized continer... the chia seeds make the thole thing gelatinous so it barely sticks to the sides). Then I add about 1/2 tsp. of the probiotics, and mix it all up (it's easier to blend the probiotics in evenly, if you do this first). Then I add about 2 tbsp of chia seeds (I used to add just one, but now I give more), 1/2 tsp of astragalus root powder (hoping it lengthens their telomeres and can make them liver longer). Lately, I have been adding Brewer's yeast, because it really does seem to help them with fleas! (You can see the story, HERE).
One more thing - I also try to add about 1/4 tbsp of peas and carrots, or dandelions from my yard (they have SO many health benefits), blended in my nutribullet with about 1/4 cup filtered water, because if I don't blend it, they'll spit it out. They have a lot of energy after they eat this. It may sound odd to add vegetables to cat food, but the fiber really helps them, and one of the world's oldest living dogs is on a vegetarian diet! You can read about that HERE.

Trader Joes Tuna for Cats 8 Pack
NOTE: I am soooo bummed. The week of June 1st, I learned that Trader Joe's is going to be disontinuing this brand!! They are looking for a new distributor, because the old manufacturer is retiring (I think) or going out of business, for some reason. The people at TJs know that there are cat owners like me, who LOVE this brand, so hopefully they will find a decent replacement, soon.
This Purina One cat food is the best DRY cat food I've ever gotten for these kitties. It has really made a noticeable difference in their energy level, and seems to be 10x better than the cheap, dangerous, kidney-failing stuff in a light blue bag that I used to get from Costco (which has since been discontinued). Lately, because I have been on a budget, I don't always give them the wet food every day, but I give them dry food for a few days and then give them a round of the wet food recipe mentioned above, so that they can get everything out of their digestive system. The chia seeds and probiotics really help with that a lot.
Purina ONE Tender Selects Blend With Real Salmon Dry Cat Food
You can get Chia seeds WAY cheaper, at Costco, for about 8 bucks a bag. At one point they were just about $8 on Amazon, too, but it seems the price went up. Chia seeds are loaded with nutritional benefits. The word "chia" means strength! So I give the cats quite a bit of these. I add 2 tbsp to their wet food (TOTAL... so it's about 1/2 tbsp per cat).
Nutiva Organic, non-GMO, Raw, Premium Black Chia Seeds, 32 Ounce
This is the brand of digestive enzymes I've been giving the cats for about 4 or 5 years now. It really seems to help them, and they barf less when they have it. I used to buy the 1 lb jar, but I just discovered that they sell a 10 oz. bag, which is the same stuff (I guess it costs more to put it in this thick plastic container). I like to save the old jars anyway, so I will probably just transfer the contents of the bag into the empty containers I'd saved.
NaturVet – Digestive Enzymes - Plus Probiotics & Prebiotics – Helps Support Diet Change & A Healthy Digestive Tract – for Dogs & Cats – 10 oz Powder
Please note: It took me a while to realize, the Probiotics in the bag look cheaper at first, but that's because it has more PREbiotics than PRObiotics. There's more fiber in the bag, and you need 2 teaspoons to equal one serving, whereas you just need 1/4 teaspoon of the probiotics (in the plastic container) with no prebiotics. I tend to use flaxseed and chia seeds for fiber, on my own, anyway, so I think it's probably cheaper to go with the plastic container, if you buy this on a regular basis. Just my opinion.
Pet Ultimates Probiotics for Cats - 20 Species - Stops Diarrhea
& Vomiting, Cuts Litterbox Smell
In the past I've just bought this 2 lb bag, but think I will go with the 10 lb bag next time, as I seemed to go through the last bag pretty quick, and use this stuff in my own smoothies. It actually can give me a buzz like coffee, if I drink it on an empty stomach.
Food Grade Diatomaceous Earth 10 Lbs
I use about 1/2 tsp of this in their wet food, hoping they will live longer : )
Starwest Botanicals: Organic Astragalus Root Powder, 1 Lb
Jeanne used to feed these to Buster all the time, and she said it really made his fur nice, so I will be getting some of these for my own kitties at some point, when I can afford it : )
I used to get chicken flavored greenies, but recently learned that chicken is one of the biggest things that can cause pet allergies, so I am switching to salmon.
FELINE GREENIES Dental Treats For Cats Oven Roasted Chicken Flavor 11 Ounces With Natural Ingredients Plus Vitamins, Minerals, And Other Nutrients
Update February 2022:
This may not be the healthiest food on the planet, but the good thing about it is that I can mix healthy stuff into it, and my cats will eat it. My cat Bert, in particular, needs to have extra stuff in his food, to stay healthy. Lately I've been giving him the following:
In a small bowl, I put an entire 3 oz can of wet food, to be divided among my 3 cats.
I have fully moved to crazy cat lady status now, because I actually microwave my cat Bert's plate, since I discovered that he eats more if I do this. Bert is at that age where he's getting to be borderline senile and has lost a bit of his appetite, so I have to use little tricks to get him to eat more. Cats do like their food warm. While he's eating, I even kind of hover over him and push his wet food together (when he's about halfway done) so that it's in a "lump," as he will also eat more if it's in a lump, vs. spread out all over the plate. There was a day when I didn't have to do this at all, and he would lick the plate clean (as my other cats still do) but I guess as they get older, they get more fussy.
Here's the entire routine I've been doing for the past few months, which seems to be working well, and Bert no longer has to have IV fluids anymore (knock wood this keeps up).
I'll boil a small amount of water.
Then, get out a small clear bowl, add a 3 oz. can of PATE (they don't care for any other kind of food and tend to just eat the gravy from the "feast" type so I no longer buy it). At the same time, I heat up a plate for 20 seconds in the microwave, so it's very warm but not too hot.
I mash up the contents of the whole can of food in the clear bowl, then add about 2 tbsp of the hot water to the food. Mix thoroughly. Then, I add about 1/2 tsp. ground chia seeds (kept refrigerated) to the mixture. Mix thoroughly.
When it's all mixed and everything is lukewarm, I add a teaspoon of NaturVet Probiotics, shown on this page. It's important to add this only after the food is mixed with the hot water, because adding it before the hot water would cause the probiotics to die if they come into contact with boiling hot water, but it's fine if they're in a lukewarm environment.
Then I divide the mixture in half. Bert (who is 17 and needs the special food) gets half, while the other 2 cats split the other half (it's just a treat for them; they don't need fancy stuff). I put my other 2 cats' food on 2 plates and can give it to them now if they're around, or after Bert is fed.
Bert's portion is still in the bowl. I mix in, for him: 2 capsules of Slippery Elm (I save the empty capsules in a box for when I take oregano oil to kill covid), a dropper full of Chlorella (to keep his iron up), a dropperful of Liquid Vitamins, and a dropperful of liquid glucosamine. I am currently out of Urinary Tract Support by Vetflix, but will be ordering some more.
Fancy Feast Classic Tender Beef Feast Canned Cat Food, 3 oz, 12 Cans
Big thanks to my sister and friend Rob who have helped me to feed the kitties when I go back home to visit my Mom! : )
I've been looking for a good brand of glucosamine and was really impressed by these reviews, so I have a feeling I will be ordering this regularly.
Best Paw Nutrition Bacon Flavor Liquid Glucosamine for Dogs and Cats