Here are my BAD 6 (foods and drinks to minimize or cut out entirely because they undermine performance) and my BIG 6 (foods and drinks to add or increase in your diet for boosted recovery or performance).

The BAD 6:

1. Alcohol. I used to drink 5+ times a week, but have cut out booze entirely for the last few years during race build-up. This hands-down has to be #1. The benefits of cutting alcohol are enormous—sleep better, recover better, stay better hydrated, lose weight (if you want). But it’s also the hardest to be honest with ourselves about. My challenge to all marathon runners: no drinks for the at least 6 weeks prior to race day – take a break from booze and make your next drink a celebratory post-race beverage. 
2. Ultra-Processed Foods. UPFs make up SO much of the Standard American Diet that it’s hard to avoid them. Things to especially avoid: soda, processed meat like deli meat and hot dogs, chips, fries, candy, and other foods that trick our brains into wanting them though they’re terrible for us. Your body is a machine: run it on cleaner fuel – you’ll feel better, recover quicker, and ultimately run faster.
3. Fatty Meat. Since you probably already hate me at this point, I’ll just double-down – cut out burgers, bacon, sausages, and fatty steaks. These cause extra inflammation, slow digestion, and impair sleep because extra energy goes to breaking them down instead of repairing your muscles. Sorry not sorry 🙂
4. Dairy. Ok it’s pretty hard to cut out ALL of these and the above 3 are more important to cut out than dairy. That said, dairy can cause digestive issues—similar to fatty meat. It slows digestion and requires more energy for your body to process than, say, tofu or chickpeas.
5. Energy Drinks. These are technically ultra-processed but deserve their own call-out given how prolific they are. Many have an unreasonable amount of caffeine in addition to insane amounts of sugar. Yes, caffeine will help on race day (and I’ll take a lot during the race) but you don’t need or want that much caffeine (or added sugar) in your diet on a regular basis.
6. Spicy Food. This is a bit more debatable but if you’re not used to spicy food, it can irritate your digestion if eaten the night before a long run or big workout. Best to moderate and eat spicy stuff at times that aren’t right before big sessions.

The BIG 6:

1. Sweet Potatoes and Potatoes. The king and queen of complex carbs! In addition to lots of carbs, SPs give us vitamins and antioxidants, while potatoes give us potassium and both are easily digested.
2. Berries (esp blueberries, blackberries, raspberries, strawberries). Berries are rich in polyphenols, which aid in recovery and can even boost performance. To get an extra dose of polyphenols, I supplement with Quercetin on big days, but berries are the best natural source.
3. Leafy greens (esp spinach, kale, arugula, and watercress). So much good stuff in here – nitrates, iron, vitamins, antioxidants, magnesium, and so on. 
4. Legumes / Pulses (chickpeas, lentils, beans, peas). As a vegetarian, where do I get my protein from? Most of it comes from legumes, some comes from veg (like broccoli, avo, corn), and then I supplement with vegan protein powder (one of a few UPF exceptions I grant myself…no one’s perfect!).
5. Beetroot. Ok, tough toss-up between Beetroot and Banana for the last spot but Beetroot deserves a special shoutout b/c folks may be less aware of its benefits. High in nitrates (which studies show improve endurance), beetroot actually has strong scientific evidence showing it improves performance if taken a few hours before a hard workout or race. I add some beetroot powder to my electrolyte drink before big sessions.
6. Tea. Different teas bring different benefits. I’m sipping green tea while writing this up – similarly packed with polyphenols and antioxidants. Other teas are great as well: rooibos, spicy chai, matcha, chamomile, even black tea.

Deserving honorable mentions for the ‘good’ list go to 100% peanut butter, bananas, almonds, mango, chia and flax seeds, brown rice, and whole wheat pasta. Truth be told, most plants go in the ‘good’ pile – the more plant-based runners can eat the better, provided they’re getting enough protein (1.2-1.8g per kg of body weight) and enough calories in general.