First, I will discuss a recent paper, which suggested that salt intake should not be our main focus when trying to improve blood pressure. I will then outline evidence for the most significant changes in lifestyle that can improve blood pressure, and reduce our reliance on drugs.
Sugar increases blood pressure more than salt
Recently, a number of media outlets reported that sugar, rather than salt, from processed foods (especially soft drinks) is a major driver for hypertension. These news reports were written in relation to a short article published in the American Journal of Cardiology this month, which outlined some of the potential mechanisms by which sugar-sweetened beverages (SSBs) can increase blood pressure. In this short article, the authors also discuss why the effect of sugar (in particular SSBs) on blood pressure is more important than the effect of salt, which we have historically focused upon in an attempt to reduce the risk of hypertension in the population.
However, this is just the latest part of an ongoing dialogue on this topic, which started with a review article published in February in the same journal. That original review looked at all the studies to date examining the relationship between SSBs and high blood pressure. I will cover three articles from this dialogue, all published in the same journal, in chronological order:
- The original review article.
- A comment by another group of doctors, disagreeing with the conclusions of the original article.
- The most recent comment by a third group of doctors, agreeing with the original review article. This is the comment that prompted the most recent news reports.
1. The original review article: To date, 12 studies have looked at the intake of SSBs, and current or future risk of hypertension. The original review looked across the results of all of these. Conservatively, they concluded that consuming more than 12 fl. Oz. (one can of coke) per day increased the risk of high blood pressure by at least 6%. This includes an average increase in systolic blood pressure (the number of the top – if your blood pressure is 120/80, your systolic blood pressure is 120mmHg) of at least 1.8mmHg. This doesn’t sound like much, but current estimates suggest that decreasing your systolic blood pressure by 2mmHg will reduce your risk of stroke by 10%. On the other end of the scale, some of the studies suggested that for the equivalent of every can of soft drink you consume each day, your risk of high blood pressure could increase by up to 20%! This is lessened in children and adolescents. However, similar effects are seen in all adults, regardless of whether they are at risk of (or currently have) high blood pressure. Find the original article here.
2. Salt drives soft-drink intake: The first comment on the review disagreed with the suggestion that SSBs cause an increase in the risk of high blood pressure. This comment was written by authors of a study published earlier this year, which provides evidence that reducing salt in processed foods in the UK over the past decade has led to a significant decrease in rates of hypertension. Over the same time period, the incidence of deaths from stroke and heart disease in the UK has dropped by around 40%. However, this does not prove that reducing salt has reduced high blood pressure (or caused the subsequent drop in cardiovascular disease). In particular, as salt intake has come down, the population in general has also:
- Stopped smoking as much
- Started eating more plant-based foods
- A high salt intake drives an increase in thirst, so people drink more
- On average, some of those drinks are going to be sugar-sweetened soft drinks
- Soft drinks are the commonest source of added sugar in the Western diet
- As a result of increased thirst due to high salt intake, sugar is just “coming along for the ride”
In this scenario, a different interpretation of the original review would be that the increased blood pressure seen in response to SSB intake is actually just because people are drinking more soft drinks in response to the salt they’re eating. Therefore salt is still the problem.
Consuming sugar also increases insulin levels, which can cause us to store more salt in the body, perpetuating the above cycle. Ultimately, the authors of this comment feel that reducing salt in processed foods is still the key to improving cardiovascular risk in the whole population. Read their original paper here, and comment on the review article here.
3. Sugar drives salt intake: Lastly we come to the second comment, which brought about the recent headlines. These authors provide a counter-argument to the theory that salt intake is still the main cause of hypertension in the Western world. Find the comment here. They argue that sugar intake causes fluctuation in insulin and blood sugar levels, which increases hunger and the drive to eat. If the food that is then eaten also contains a lot of salt, it is in fact the salt that is coming “along for the ride”, and sugar is actually the original bad guy. They even outline a number of potential mechanisms by which sugar can increase blood pressure, which I will discuss below. Interestingly, they suggest that by cutting the salt in food, we will see the following chain of events:
- Reduced salt intake from food, but ongoing need for salt for optimal bodily function
- Increased drive to eat in order to meet required salt intake
- Greater intake of refined and processed foods, as these are the most convenient sources of calories for the general population
- Increased risk developing hypertension, obesity, diabetes and cardiovascular disease!
Though these comments both provide good arguments for changes we can make individually and on a population level, it seems that they are probably missing some of the big picture in an attempt to prove their point.
- Sedentary lifestyle
- Intake of processed food
Clearly we don’t yet know exactly whether salt is driving us to consume (drink) more sugar, or sugar is making us consume and retain more salt, and which of these underlies the increased risk of cardiovascular disease. However, there is zero evidence to suggest that salt outside of processed foods (such as that added to fresh ingredients during home cooking) has any effect on blood pressure.
Sodium from salt is essential for a number of processes in the body, from helping regulate a normal heart beat to making sure that our nerves conduct messages properly. Much of the evidence now shows that salt intake does not cause high blood pressure if we have a good intake of potassium. Salt is added to processed food for flavour or as a preservative, and potassium is generally only found in high quantities in plant foods (potatoes, greens, avocados, and fruit). If people tend to eat a lot of processed food (sacrificing fresh foods), their salt intake will be high, and their potassium intake will be low. As a result, high salt intake could in fact just be an indicator that somebody is eating less potassium-rich food. Only when potassium intake is low does salt intake become a problem.
In fact, many people suggest that we have now gone too far, and that current salt intake guidelines (around 6g/day) are in fact too low for optimal health, and restricting salt too much may even increase the risk of cardiovascular disease. Here is Dr. John Briffa discussing the absence of evidence behind current salt intake guidelines in the UK.
What about sugar? The most recent theory surrounding sugar and high blood pressure focuses on fructose, which makes up roughly 50% of both normal sugar and high fructose corn syrup (HFCS), which is used to sweeten many processed foods, including soft drinks. Those that suggest sugar is increasing our risk of hypertension propose the following mechanisms by which fructose increases blood pressure:
- Stimulation of the feeding centres of the brain, as well as increasing leptin and insulin levels (which I have described here), which can lead to the body storing more salt, and water.
- Increased levels of a toxic metabolic byproduct (methylglyoxal), which can increase free radical production. These free radicals damage blood vessels, which increases blood pressure.
- Methylglyoxal and uric acid (byproducts of fructose metabolism) can both inhibit production of nitric oxide. Nitric oxide normally acts to lower blood pressure.
I have previously covered how fructose can negatively affect normal hunger regulation and increase the drive to eat, particularly in those already at risk of metabolic diseases. However, fructose is probably not the only culprit. We know that giving healthy people a dose of either sucrose (which is 50:50 glucose and fructose) or fructose can cause a transient increase in blood pressure. However, eating fructose as part of fruit (with extra potassium, and lots of fibre) does not increase the risk of high blood pressure. In older people, and those with high blood pressure, glucose on its own can also cause first a rise, and then a fall in blood pressure. Therefore, intake of any large sugar load, regardless of the source, will increase blood pressure transiently.
Moreover, it has recently been discovered that a large variability in your blood pressure (rather than the exact numbers themselves) also increases your risk of cardiovascular disease. Therefore, frequently eating or drinking things that cause your blood pressure to go up (and then down again), will increase your risk of strokes even if you do not have a diagnosis of high blood pressure. If you do have high blood pressure already (or evidence of a metabolic disease such as obesity or type 2 diabetes), your body is already less able to even out changes in blood pressure; and, you will get bigger swings (larger variability) in your blood pressure, which further increases your later risk of strokes.
Summary: Salt probably doesn’t increase your risk of high blood pressure as long as your potassium intake (from fresh veggies) is good. In addition, the sugar can cause both transient and long-term increases in blood pressure via a number of mechanisms, but this seems to only happen as a result of processed sugars, rather than sugar from things like fresh fruit. Cutting salt too much may actually be bad for you, and you should focus instead on increasing potassium intake from fresh food, and reducing sugar and processed carbohydrate intake.
The evidence for reducing death, strokes and heart attacks by reducing blood pressure, both with and without medication, is incredibly compelling. However, if you have been diagnosed with high blood pressure and want to bring it under control without drugs, there are a number of simple measures that anybody can do in order to achieve this. As a comparison, the starting dose (2.5-5mg) of the most common first-line blood pressure drug in the UK, Ramipril, will reduce systolic blood pressure by 6-8mmHg in the average person. Patients with high blood pressure taking drugs like Ramipril get an almost 20% reduced risk in risk of dying from cardiovascular disease, and 10% reduction in risk of dying of any cause. Most (if not all) of this benefit comes from lowering blood pressure.
Amazingly, you can get a similar (or better) benefit from the following:
Eat a whole-foods diet: There are many diets that have been shown to reduce high blood pressure including the DASH (Dietary Approaches to Stop Hypertension), Mediterranean and Low-GI diets. As I explain here, the key thing that these diets have in common is a focus on:
- Fresh whole-foods (which automatically increases fibre and potassium in the diet)
- Elimination of processed foods
Any diet containing foods that dramatically increase blood glucose (not only sugary things, but also refined carbohydrates including bread, pasta, white rice and white potatoes) can increase the risk of high blood pressure. And adding salt to taste will probably not affect your blood pressure at all.
We will argue for years to come over whether the sugar or the salt in processed foods is increasing our risk of high blood pressure. However, I would also argue that for most of us, it doesn’t matter whether it is the salt or the sugar in our processed convenience food that is causing problems, because the solution is still going to be elimination of processed food from the diet.
Nobody can argue with the fact that the DASH diet reduces systolic blood pressure by over 10mmHg in a number of patient groups (more than most blood pressure drugs); and the Mediterranean diet can reduce blood pressure even further in people that are already taking medication for hypertension.
Stop smoking: Stopping smoking for just one week reduces systolic blood pressure by 3.5mmHg. Ignoring all the other benefits of quitting smoking, this alone could reduce your risk of strokes by up to 20%.
Cut out liquid calories: One key factor missing from the theories about sugar and blood pressure above is the fact that most of the evidence comes from studies where a sugary drink is added to the diet. Consuming sugar in any form (sucrose, fructose and glucose) in a liquid form has much more adverse metabolic effects than eating it in solid food. Even in those without high blood pressure, sugary drinks (including fruit juices) will increase blood pressure transiently, and this increase in blood pressure variability also increases your risk of cardiovascular disease. Similarly, alcohol transiently increases blood pressure, and cases of hypertensive strokes in young healthy people after bingeing on alcohol are not uncommon. Vodka and coke = the perfect storm.
Exercise: Probably the most obvious improvement anybody can make. Cardiovascular exercise (equivalent to 30 minutes of brisk walking – an average heart rate of 100 beats per minute) three times per week for 8-12 weeks is enough to reduce blood pressure by the same amount as you would expect from a standard dose of Ramipril. Adding occasional sprint training (as I outline here) may boost this benefit even further. And this effect is even seen in those people who need 3 or more medications to keep their blood pressure under control!
Lose weight: This will be easier than you think if you are eating a whole-foods diet and taking regular exercise. In overweight people with high blood pressure, combining exercise with weight loss can reduce systolic blood pressure by over 12mmHg. This is probably more effective than any single drug.
Though the above approaches are the most robust ways to improve blood pressure, there are a number of other things you can include in your blood pressure-lowering lifestyle:
- Eat more nitrates. A source of nitric oxide, which opens up blood vessels. Nitrates are found in green leafy vegetables, and are particularly abundant in beetroot. An added benefit will include better blood flow to certain areas. You know what I mean…
- More magnesium. In trials of magnesium supplementation, each 240mg (up to around 1g) you take per day can reduce your blood pressure by around 4mmHg. Get yours from leafy greens, nuts and seeds, avocados and dark chocolate.
- Get some sunshine. Vitamin D deficiency is linked with high blood pressure. The best way to improve this is spend some regular unprotected time in the sun (taking care not to burn). If that’s not an option, then 1-2,000IU of daily supplemented vitamin D can have a similar benefit.
- Cut the caffeine. Caffeine causes spikes in blood pressure like sugar and alcohol do, and this effect is greatest in those that already have high blood pressure, and in men.
- Control stress. Cortisol, our main stress hormone, has a large effect on blood pressure. We even give it to people in hospital with very low blood pressure for that exact reason. Those people with a higher cortisol response in the face of a stressful situation have a greater risk of high blood pressure. Make sure you’re sleeping enough, and try mindfulness exercises, which have been proven to reduce blood pressure in people at risk of hypertension.
With the risks associated with hypertension (strokes, heart attacks and early death), it is important to take control of your blood pressure as soon as possible. Though drugs can help achieve this, focusing on removing processed foods and taking regular exercise will not only dramatically reduce your blood pressure, but also reduce your risk of many cancers, as well as obesity and diabetes. In the end, prevention of many diseases will boil down to these simple steps that you can take right now:
- Head out for a brisk walk in the autumn sunshine
- Cook yourself a real dinner including lots of vegetables
- Skip the after-dinner coffee, brandy and cigarettes
- Enjoy some dark chocolate instead
- Get a good night’s sleep
You’ll immediately feel the benefits.
I will be speaking at Health Unplugged, The 1st Paleo UK health and well being conference focusing on ancestral nutrition, fitness and lifestyle. On October 25th in London.
I will be giving a talk entitled: "Is it Paleo - Grains, legumes and dietary dogma" as well as taking part in two panel discussions: "Food as Medicine" (with Dr. Aseem Malhotra) and "Hacking your way to better health".
This is going to be a great event, with a number of my favourite speakers, including Robb Wolf, Terry Wahls, Darryl Edwards, and Chet Morjaria. Click on the Health Unplugged link to book tickets.
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