Sometimes two is better than one, especially when it comes to nutrition. While we all know there are certain food combinations that taste good together (think fries and ketchup), nutrition experts have discovered that certain food combinations can also make us healthier. "[When certain foods are combined], the nutrients in one food help you better absorb the nutrients in another food," says holistic nutritionist Joy McCarthy.

Called "food synergy," these pairings of nutrient-rich foods can help boost your energy and long-term health. Try these 4 food combinations to supercharge your health and productivity:

1. Support brain health and boost energy with iron + vitamin C.
"Iron is a very important [nutrient] for thinking, memory and also for energy," says McCarthy. If you've ever suffered from anemia (an iron deficiency), you know that low iron can make you feel like you've been run over by a freight train. "Your muscles aren't oxygenating properly when you're low on iron," says McCarthy.

Dark leafy greens such as spinach, kale or arugula are a great source of iron, but plant-based iron is better absorbed when consumed with vitamin C. Add blueberries, raspberries or strawberries to a salad with spinach leaves to boost your iron consumption.

2. Support heart health and reduce stress with green tea + lemon.
Antioxidants called polyphenols in green tea are better absorbed when combined with vitamin C. "[Polyphenols] promote heart health by helping to lower cholesterol [and help] prevent cancer," says McCarthy.

Vitamin C has another benefit for entrepreneurs, helping to keep adequate blood flow to the brain, something commonly affected by stress. "You may notice if you're stressed, your short term memory is weaker," says McCarthy. Lemons have a high concentration of vitamin C and combined with the antioxidants of green tea, packs a powerful health punch.

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3. Boost your immune system with vitamin A + healthy fats.
Busy entrepreneurs don't have the time to get sick. Keeping your immune system strong is essential to protecting your business from illness. "Vitamin A is very important for your white blood cells [which] keep your immune system strong," says McCarthy.
Orange-colored foods such as carrots, squash, cantaloupe or orange peppers are good sources of vitamin A. Vitamin A is a fat-soluble vitamin that is stored in the body until needed, and is best absorbed when eaten with healthy fats, such as avocado, olive oil, nuts, seeds or fish.

4. Boost your brain power with vitamin D + calcium.
Calcium is an important mineral for strengthening the brain's neurotransmitters. "When a chemical signal arrives at a brain cell, it’s the job of calcium ions to deliver that signal from the outside of the cell to the inside,” says McCarthy. Strengthening your brain’s neurotransmitters means you’ll be better able to think on your feet.

Sources of calcium include dairy products, green vegetables such as broccoli or leafy greens, and seeds or nuts. But eating these foods alone won't give you the brain-boosting benefits of calcium. Add a hard-boiled egg to your salad for optimal brain power as calcium is best absorbed with the aid of Vitamin D-rich foods such as eggs, sardines and salmon.

Related: Sharpen Your Memory with Brain-Healthy Foods