The blood-brain barrier prevents substances from entering the brain unless those substances are very small or required for brain function – but there are special areas (organum vasculosum of the lamina terminalis; OVLT) that monitor salt and osmolarity sense contents of blood and salt levels

OVLT detects changes to salt levels in bloodstream and sends signaling cascades accordingly – thirst, regulation of blood pressure, kidney function, secretion of salt

1. Osmotic thirst (concentration of salt in the bloodstream);
2. Hypovolemic thirst (thirst related to drop in blood pressure)

The cascades are set off for concentrations of both high and low sodium in the blood.

• Osmotic and hypovolemic thirst are not just about seeking water – they’re also about seeking salt which can help retain water
• Sodium engages the action potential, which is the firing of electrical signals by neurons
• If you ingest too much water (this requires A LOT of water), you will actually kill yourself because you’ll disrupt the body’s ability to communicate, brain, and neurons

• The kidneys are responsible for retaining and releasing substances in the body such as glucose, amino acids, urea, uric acids, salt, potassium, etc.
• Very general mechanism: blood enters the kidney and responds to hormonal signals to make mechanical or chemical changes to retain or release substances accordingly
• Your urine is filtered blood!
• Vasopressin: anti-diuretic which prevents urination by increasing permeability of distal tubes
• Water follows salt: the kidney holds on to water in the body when it needs salt
• When estrogen levels are high, there’s water retention

• Blood pressure is in part regulated by sodium intake and sodium balance
• An increase in sodium could help combat symptoms of low blood pressure
• Historically, we’ve been taught that a high salt diet may be consequential for brain function
• However, high salt diets are likely related to other unhealthy factors like processed foods, poor balance of carbohydrate and fat, etc.
• A high salt diet can have detrimental health consequences – but – a very low salt diet can also have deleterious health events

• There’s a direct relationship between the stress system (glucocorticoid system) and the salt craving system
• Bringing sodium in the body counteracts or resists stressors in our lives
• If sodium is too low, our ability to combat stressors is impaired
• If you’re feeling anxious, slightly increasing sodium intake can stabilize blood pressure and ability to lean into stressors and challenges
• Additional sodium intake is naturally stimulated by stress

Sodium and potassium work closely together in the body. Recommended ratios of sodium to potassium vary widely

• Diet is an important contextual element to your ideal sodium-potassium ratio
• Low carb dieters excrete more water so lose sodium and potassium at a higher rate and may need to adjust dietary intake accordingly
• If you are time-restricted eating or fasting you may want to consider increasing electrolytes if you ingest caffeine since caffeine is a diuretic
• Rule of thumb: for every ounce of caffeine, drink 1.5x as much water with a touch of sodium

• There’s some evidence that supplementing with magnesium malate can reduce muscle soreness
• Mangesium threonate may promote transition into sleep and cognitive function
• Magnesium bisglycinate is an alternative for magnesium threonate as far as the transition to sleep, but no studies have been done on cognitive function
• Magnesium citrate is an effective laxative