It's possible, even likely, that you or someone you know has hypertension. It's possible that you or they have been told by the doctor to cut back on salt. If not, it's still possible that you're cutting back on salt because that's the prevailing wisdom for controlling blood pressure.
As we all know, sodium is lost in sweat. The more we sweat, the more we lose. Long and / or intense trainings or hot environments result in greater sweat production and greater sodium loss. Symptoms of low sodium can include disorientation, nausea, fatigue, even seizures or collapse. Even in a controlled indoor environment, warm outdoor temperatures can increase sweating.
As important as sodium levels are, it's obviously not a good idea to cut back on salt without giving the prescribing MD know that you're working out, taking fitness classes, and often sweating profusely in them. In warmer weather, this becomes even more important.
But this post is not just about salt. Blood pressure may go up with a high-carb diet because of the increased insulin carbs trigger. There are several mechanisms by which high levels of insulin can raise blood pressure.
High insulin levels increase sympathetic nervous system activity, leading to vasoconstriction. That increases both heart rate and blood pressure.
Insulin also stimulates the multiplication (proliferation) of the smooth muscle cells lining the arteries. That may narrow the size of the arterial opening (lumen) and increase blood pressure, sort of in the same way that a narrow hose increases water pressure.
Insulin promotes the production of serotonin, a brain chemical that's also a vasoconstrictor. Vasoconstriction can raise blood pressure. The relationship between insulin levels and serotonin production is pretty much linear, so the more insulin secreted – say, in response to a high-carb diet – the more serotonin is produced. The more serotonin, the more vasoconstriction, and so on.
High insulin levels may also increase production of series 2 prostaglandins, which are hormones that control cellular functions. Among them numerous negative health consequences, Series 2 prostaglandins cause inflammation and increase blood pressure.
So which dietary recommendations can help to lower blood pressure?
First, it's always a good idea to stay away from simple (or as I like to call them, junky) carbs and limit alcohol. That can help to keep insulin levels from skyrocketing.
A second good idea is to avoid all-carb meals / snacks. Meals and snacks that include protein and healthy, unsaturated fats have less impact on insulin levels.
Third, avoid processed (also junky) foods that are loaded with sodium. We consumers can not control the quantity.
Finally, modify – but do not eliminate – salt. We need it to replace what we lose in a session session. The upper limit is 2300 mg, or 1500 mg for older or hypertension -prone individuals. But for someone who sweats profusely, it might be possible to exceed those limits safely to a degree. It's also possible to go too low, and one way of gauging that is by urine production. If you feel you can not hold 50% of your water intake, that's a sign that you could need more salt.
As you may be aware, there's a long-standing table salt / sea salt debt raging. Some sources maintain that the natural minerals in sea salt reduce the overall sodium content. Or that the larger size of sea salt crystals reduces the amount of salt in a teaspoon. Or that the more intense flavor of some sea salts encourages reduced consumption. These factors are said to make sea salt more healthy, but the arguments appear to be inconclusive.
Sea salt users may be advised to take a kelp tablet daily to compensate for the absence of iodine that's typically added to table salt. Or to buy sea salt with added iodine. Iodine's necessary to prevent goiter.
Rather than join the Great Salt Debate, my point in this post is to encourage moderate consumption of salt among those who are regularly exercising and concerned with hypertension, primarily to avoid the negative consequences of low sodium.
Even more importantly, I'd encourage smart consumption of the best carbs to avoid the various mechanisms – related to insulin secret – that can and DO cause hypertension, despite a low-sodium diet.