Salt is necessary for life, and has been used since ancient times as a seasoning, preservative, disinfectant, ceremonial offering, and unit of exchange. The Bible repeatedly references salt to signify permanence, loyalty, durability, fidelity, usefulness, value, and purification. Throughout history, salt has been valued highly, until recently.
We hear so many conflicting stories about the impact of salt in health. No wonder we're all confused. That's why I'm pleased to see a new publication explaining why the data are so inconsistent (O'Donnell et al., 2013). The good news is that, with certain exceptions, salt is good for you, unless your sodium intake is excessive (over 5 grams per day). And, even then, the hazard ratio is not dangerously elevated until intake exceeds 8 grams per day. That's a lot of salt. You would have to be chugging the shaker to get that much, or eating an inordinate amount of junk food or restaurant food. At the other end of the curve, sodium intakes of less than 2 grams per day are also linked to cardiovascular disease (CVD). The bottom line is that moderate salt intake is good for you. Enjoy it, but exercise a little discipline.
Many factors besides sodium affect the risk of CVD. Some high-sodium diets contain nutrients that protect the heart, like vitamins, minerals, essential oils, antioxidants and anti-inflammatory agents. For example, Japan's traditional high sodium diet was associated with the lowest risk of CVD, since it is rich in fish and vegetables (Shimazu et al., 2007). Other high-sodium diets (fast, processed junk foods) are low in protective factors and are linked to high CVD risk. These variables contribute greatly to the inconsistency in studies on salt intake. The most important dietary factor that may modify the link is potassium intake (Morris et al., 2006). The lowest rate of CVD is found in those with moderate sodium and high potassium intake (O'Donnell et al., 2011). Potassium intake is also a barometer for a healthy diet, since many foods linked to reduced CVD risk are potassium rich, especially fruits and vegetables. Antioxidants like vitamins C, E, carotenoids (beta-carotene, lycopene, lutein, zeaxanthin, astaxanthin), and numerous substances from plants also protect heart health, as do an assortment of essential minerals, fibers, and oils.
My favorite high-potassium foods are coconut water and sweet potatoes. However, white potatoes and bananas are carbohydrate dense, and are not the best source of potassium for people dealing with obesity and other metabolic conditions. The one exception is purple fingerlings with skins attached -- prepared any way but fried. These provide many more antioxidants, fiber, and minerals due to the greater amounts of skin per serving. Eat them in moderation with organic butter.
The Salt Police
The Center for Science in the Public Interest (CSPI) believes that salt is the single most harmful substance in the food supply. Processed foods and restaurant meals provide nearly 80% of the sodium intake in the modern diet. That's about 4 grams of sodium daily on average, or twice the recommended limit. These scientists claim that cutting sodium consumption by half could save roughly 150,000 lives per year and reduce health care costs by roughly $1.5 trillion over 20 years. They recommend that consumers eat less-salty foods; that food manufacturers/restaurants should reduce salt in their products; and that government should set limits on salt content, encourage the food industry to use less salt, require warning notices on menus, and improve labeling of packaged foods.
While acknowledging the good intentions of these scientists, I firmly believe they are on the wrong track and are misleading the public. While it is true that the modern diet contains entirely too much salt, and that people would benefit greatly by improving their diet, salt is not even close to the most harmful substance in our food. Instead, that distinction goes to sugar and refined carbohydrates, which have increased in the diet in parallel with the epidemic of obesity, heart disease, and diabetes. Bad fats also trump salt when it comes to their negative impact on heart health and inflammation. Placing so much emphasis on reducing salt detracts from far more dangerous substances in food, which is very unfortunate. To their credit, CSPI does urge safe limits on sugar intake as well but, in my opinion, they should focus more on this effort and less on denigrating salt.
The science on salt intake and CVD is highly inconsistent, and varies greatly from one region to another. A meta-analysis of 13 clinical studies worldwide reported a significant association between sodium and CVD (Strazzullo et al., 2009). The association was strong in regions with high intake, but not in regions with moderate intake (Alderman & Cohen, 2012). Countries like Japan and Finland have some of the highest sodium intake, but also exhibit some of the highest life expectancy. Regarding stroke, there is an association with salt in Asia, but not in Europe or North America. Marked reductions in stroke have occurred in the US over the last few decades, without a reduction in sodium intake (Bernstein & Willett, 2010). There seems to be no method to the salt-phobia madness.
Certain populations or individuals may be at increased CVD risk with sodium intake. Salt-sensitive people respond favorably (e.g., reduced blood pressure) to sodium reduction. Ethnicity, blood pressure level, and obesity may modify the association between sodium intake and CVD. Genetic underpinnings for salt sensitivity are likely, but have yet to be determined.
Elevated blood pressure may have many determinants besides high sodium intake, including low potassium, fruit and vegetable, and antioxidant intake, obesity, and lack of physical activity. Strategies that address all these parameters would likely be more effective in lowering blood pressure than focusing on sodium alone.
People with CVD may be more susceptible to extreme sodium intake, and may benefit most from salt reduction. However, low sodium intake has also been linked to increased mortality in congestive heart-failure patients. In fact, low sodium may be as detrimental to this population as high sodium intake. Moderation is key, not strict salt reduction.
So, we see that salt is a controversial subject, and gets a bad rap from the so-called experts. Yet, salt provides sodium, which is necessary for life. Sodium enables muscle contraction and expansion, nerve stimulation, adrenal function, energy production, and many other biological processes. Salt also provides chloride, which helps produce acids for digestion, and is necessary for brain function and growth.