The phrase "You are what you eat" is adapted from an 1826 book by a French foodie titled "The Physiology of Taste." And while it may be true, the author missed another noteworthy truth: You are what you drink as well.

Two new studies show how important it is to drink plenty of water and skip soft drinks entirely. (You already know you should only drink alcohol in moderation or not at all).

The first study, published in JAMA Psychiatry, reveals that soft drinks alter the health of your gut biome and the more sodas you drink, the more likely you are to be diagnosed with major depressive disorder.

The researchers suggest that's because sodas increase the amount of a gut bacteria called Eggerthella, which negatively affect gut-brain communication.

The second study explains how dehydration can fuel anxiety and increase your risk of heart disease, diabetes, and depression.

Published in the Journal of Applied Physiology, this research says that people who drink less than 50 ounces of water per day have an amped-up cortisol response to stress that's more than 50% higher than in people who drink that much water daily.

Excess cortisol causes mood shifts, dysregulates glucose control, and increases the risk of cardiovascular problems. I recommend filtered black coffee, water, and tea to keep cortisol levels down.

For more information on how your lifestyle choices can impact your emotions, check out "YOU: The Owner's Manual, revised edition." To reduce your risk of heart disease and diabetes, check out "The Great Age Reboot."