Do you live longer if you eat more salt?
Eating more salt does not lead to a longer life. At the individual level, it demonstrably increases the risk of cardiovascular disease, and salt restriction lowers blood pressure and the risk of premature death.
Eating more salt and living longer do not go hand in hand. A comparison of 181 countries might seem to suggest the opposite: countries with a higher salt intake have, on average, a longer healthy life expectancy, with a difference of 2.6 years per gram of extra sodium per day. But the authors of that study themselves warn that no dietary advice should be drawn from this. Wealthy countries simply eat more salt and also have better healthcare, higher incomes and a healthier diet. The association says nothing about cause and effect.
At the individual level, the research tells a very different story. Every additional gram of sodium per day increases the risk of cardiovascular disease by around 4% and the risk of stroke by around 6%. Eating less sodium reduces the risk of death from cardiovascular disease (relative risk 0.83) and all-cause mortality (relative risk 0.88). This has been demonstrated in multiple large analyses that consistently point in the same direction.
The clearest evidence concerns blood pressure. Eating fewer than 6 grams of salt per day lowers blood pressure by an average of more than 3 mmHg and can reduce the need for blood-pressure-lowering medication by around 30%. Finland shows what this can mean at a population level over time: average salt intake there fell by one third over thirty years, while blood pressure dropped by more than 10 mmHg and mortality from stroke and heart attack fell by 75 to 80%. Other factors certainly also played a role in this.
Excess salt also damages blood vessels through pathways independent of blood pressure: it disrupts the production of substances that relax blood vessels and makes the vessel wall stiffer. In people with kidney disease, salt restriction makes an especially significant difference: it reduces fluid retention and enhances the effect of kidney-protective medications. In heart failure, the benefit of salt restriction is less clear: randomised studies find no demonstrable reduction in mortality or hospital admissions, although patients sometimes do feel better.
The answer is based on multiple large analyses of dozens of studies combined, supplemented by thirty years of population research in Finland and mechanistic studies in humans and animals. The evidence that salt increases cardiovascular risk at the individual level, and that salt restriction lowers blood pressure, is robust. The Finnish population study is convincing in scale but cannot rule out other factors. In heart failure, the available studies are relatively small and varied in design, which makes the evidence there weaker. The ecological country-level comparison has been described by the authors themselves as unsuitable as a basis for dietary advice.
Does extra salt help with fatigue during fasting?
Baking soda (sodium bicarbonate) reduced fatigue in trained men who had fasted and then exercised, but this was found in only one small study and says nothing about everyday fasting-related fatigue. Ordinary table salt has not been studied for this purpose.
Is there a relationship between changing body odour and Alzheimer's disease?
Loss of smell is a well-documented early sign of Alzheimer's disease, and changes in body odour are being investigated as a possible marker, but a clinically usable 'smell test' for Alzheimer's disease does not yet exist.
Does eating an avocado every day improve the diversity of your gut microbiome?
Eating an avocado every day likely increases the diversity of your gut bacteria, although the evidence comes primarily from people with overweight. If you have a healthy weight, the effect has not yet been demonstrated.