The position we take up in sleep may have a real influence on digestion. Even in ancient times, monks made a habit of lying down after every meal, just ten minutes, to help the process along. Ayurvedic medicine goes further and recommends sleeping on the left side — an old habit whose promised benefits science today confirms only in part.
A recommendation that comes from Ayurvedic medicine
Which side do you usually sleep on? The right, the left, or perhaps flat on your back? Plenty of wellness experts say the best way to sleep is on the left side: sleeping that way, the argument goes, supports the health of most of our organs by making their work easier — blood circulation and digestion among them. Here is the reasoning, point by point, and what science really says about it today.
The oldest tradition of Eastern medicine (Ayurveda), along with Indian alternative medicine, likewise advises sleeping on the left side. The reason given is simple: the left side of the body is said to be the dominant lymphatic side. Most of the body’s lymphatic fluid does in fact drain through the thoracic duct, which sits on the left — that much is anatomical fact. Lymph, the fluid that carries proteins, glucose and other metabolites and waste products, is purified there by the lymph nodes before being channelled towards the left side of the heart. The anatomy is real; what stays hypothetical is the idea that a sleeping position measurably improves that drainage — no solid clinical study has shown it to date. Sleep’s role, on the other hand, is far better established on another front: the beauty of the skin.
Where does the famous study everyone quotes actually come from?
The headline may have surprised you. You may also be one of those people who have never wondered whether sleeping in one position rather than another could be more or less good for the body — and it does matter. Eastern medicine has long recommended sleeping on the left side, and a study published in The Journal of Clinical Gastroenterology is often cited in support, as though it had proved the case through simple principles that the practitioner John Douillard — wrongly presented as “Doctor Doulliard”, when he is a chiropractor and certified Ayurvedic practitioner rather than a physician — sets out as plainly as he can, so that all of us can follow. The link deserves a closer look: that study, published by Katz and colleagues in 1994, actually deals with something far narrower than the whole set of principles — gastro-oesophageal reflux during sleep (see point 2 below), the only one of the five claimed benefits that is solidly established today. Here is that short summary, so you can put it into practice knowing exactly what you are doing.
The 5 reasons given for sleeping on the left side
Let’s take them one by one, separating what anatomy confirms from what research has actually demonstrated.
1. To help lymphatic drainage
The practitioner John Douillard explains that sleeping on the left side means respecting the nature of our body: most of our lymphatic system sits on that side. That, he says, is what allows better drainage, since lymph carries important elements — proteins, glucose, metabolites — that are filtered by the lymph nodes and then carried to the left side of the body. That is how the “first reason” for sleeping on the left is built. But it rests on a presumed respect for our lymphatic system rather than on clinical proof: to date, no study has measured a real lymphatic drainage benefit tied to sleeping position.
2. For anatomical reasons — and above all less reflux at night
You may not remember this, but the stomach and the pancreas sit on the left side of the body. Sleeping on that side lets the body digest better: it is a good way to channel gastric juices and encourage the secretion of pancreatic enzymes. The process can then unfold gradually rather than all at once, as it does when we sleep on the right side. This is where the science is strongest: the 1994 study in the Journal of Clinical Gastroenterology, confirmed since by more recent work, measured that sleeping on the left side clearly reduces the oesophagus’s exposure to stomach acid compared with the right — by more than half, according to a study published in 2000. For people prone to acid reflux, this is now a recognised recommendation.
3. For the wellbeing of the heart
Surprised? Most likely. This study, so the story goes, tells us that 80% of the heart sits on the left side of the body, and that sleeping on that side supports cardiac health in a simple, natural way — chiefly because the lymphatic system, as we said, would drain better in that position, and because the aorta arcs out towards the left to reach the abdomen: the heart, we are told, then pumps more easily and more efficiently, moving blood with less effort. Taking notes? Take a few more, more reliable this time. The 80% figure is exaggerated — in reality, about two-thirds of the heart’s mass sits on the left side of the chest, the rest on the right. In healthy people, no study has shown this position to have a negative effect on how the heart works: the variations seen on electrical traces mostly reflect the mechanical displacement of the organ, not a genuine disorder. The nuance concerns people with heart failure, who sometimes avoid sleeping on the left of their own accord because it feels uncomfortable, according to a study in the Journal of the American College of Cardiology — a point to raise with your doctor if you have a known heart condition.
4. For a restorative nap
If you love a nap, or simply can’t escape one after eating too much, take it on your left side too. It will help your digestion. You will wake up in better shape, less tired, and without intestinal aches. Try it and see the good a short nap on the left side can do — even if, as with a night’s sleep, nothing proves a benefit specific to the nap rather than to a full night. To make the most of that rest, a few calming thoughts before you close your eyes can help as well.
5. For the health of the spleen
The spleen, as you may know, also sits on the left side of the body. This organ is the foundation of our lymphatic system: it is needed to filter the blood and for our lymphatic function to work properly. Sleeping on the left side lets the fluids it holds travel to the spleen more easily, helped along by the gravity that governs us. Most of our lymphatic system does its work on that side — but, as with point 1, this is a hypothesis inherited from Ayurvedic medicine, not a fact measured by medical research.
A more recent line of research: sleep and the brain
One newer avenue of research, absent from earlier versions of this article, deserves a cautious mention. In 2015, a team from Stony Brook University in the United States, publishing in The Journal of Neuroscience, observed by MRI that lying on one side — left or right, with no notable difference between them — helped rodents clear waste from the brain, including the beta-amyloid protein involved in Alzheimer’s disease, better than lying on the back or the stomach. This is an animal study: nothing at this stage allows us to say the same mechanism works the same way in humans, or that it justifies favouring one side over the other. It is a lead, not a proof — and rest for the brain remains precious anyway, whatever position you choose to sleep in.
So, should you sleep on your left side?
You now know that, health-wise, sleeping on the left side is above all recommended in cases of gastro-oesophageal reflux — while the other benefits (lymphatic drainage, heart health, the spleen) remain anatomically plausible leads rather than facts validated by clinical research. For a healthy person, sleeping on the left carries no known risk. If you have a heart condition, better to talk it over with your doctor than follow a general recommendation found online. Are you going to try it tonight?
