Are leftovers or re-heated foods bad for me?

Ayurveda harps on about leftovers and frozen foods saying that they weaken digestion (agni), cause toxins (ama) and are low in ‘life force’ (prana). If used regularly, these foods would contribute to a number digestive diseases including irritable bowel syndrome (IBS) and the like. Is there any truth to this? Are reheated foods and leftovers really a problem?

I am always on the lookout for little bits of modern science that help to validate the science of ayurveda, which is why I am going to blether on for a while about resistant starches which are produced when carbohydrate foods (wheat, rice, potatoes etc.) are prepared in certain ways.

What are resistant starches?

According to WikiPedia (

Resistant starch (RS) is starch that escapes digestion in the small intestine of healthy individuals. Resistant starch is considered the third type of dietary fibre, as it can deliver some of the benefits of insoluble fibre and some of the benefits of soluble fibre.

Some carbohydrates, such as sugars and most starch, are rapidly digested and absorbed as glucose into the body through the small intestine and subsequently used for short-term energy needs or stored. Resistant starch, on the other hand, resists digestion and passes through to the large intestine where it acts like dietary fibre.

Resistant starch has been categorized into four types:

. RS1 Physically inaccessible or digestible resistant starch, such as that found in seeds or legumes and unprocessed whole grains

. RS2 Resistant starch that occurs in its natural granular form, such as uncooked potato, green banana flour and high amylose corn

. RS3 Resistant starch that is formed when starch-containing foods are cooked and cooled such as in bread, cornflakes and cooked-and-chilled potatoes or retrograded high amylose corn

. RS4 Starches that have been chemically modified to resist digestion. This type of resistant starches can have a wide variety of structures and are not found in nature.

I am interested in the third kind – RS3 – because ayurveda teaches us that eating leftovers, or even eating cooked food that has cooled down, is harder to digest, and may cause an accumulation toxins called ‘ama’ which literally means “born of undigested food”.

The idea in ayurveda is that ama contributes too many diseases. It is thought inhibit the normal flow of life through the body’s organs and energy channels.

Science seems quite certain that a certain amount of dietary fibre is beneficial for, among other things, the health of the colon. But some research shows that too much undigested foodstuff in the colon can cause excess fermentation which might trigger conditions such as IBS:

Colonic-gas production, particularly of hydrogen, is greater in patients with IBS than in controls, and both symptoms and gas production are reduced by an exclusion diet. This reduction may be associated with alterations in the activity of hydrogen-consuming bacteria. Fermentation may be an important factor in the pathogenesis on IBS.[1]

What produces resistant starches?

It seems that the level of resistant starch increases in carbohydrate foods (grains, vegetables and fruits) when they are:

. cooked then cooled then eaten (bread, potato salad)

. cooked, cooled, then reheated (all kinds of reheated leftovers or pre-made foods, or fast foods)[2]

. or foods that are cooked without any water (such as cornflakes, puffed rice, and many other breakfast cereals)

Whether cooked, or raw, ayurveda also teaches that cold foods are harder to digest and can increase ama. From a biochemical point of view, resistant starches might well be part of the picture.

Yeah yeah, but what does this mean for me?

Ok – here some practical advice that you can follow for optimal digestion according to ayurveda. This will be especially useful if you are suffering from chronic flatulence, constipation or diarrhea, digestive weakness, digestive ‘toxins’ (often shows with a thick tongue coating first thing in the morning) or a condition such as IBS:

1. Eat more freshly prepared cooked foods made from whole grains and vegetables that are served warm
(see my One Pot Meal demo for example)

2. Avoid eating foods that have been reheated or frozen such as leftovers or most restaurant foods.

3. Go easy on bread, pasta, couscous salad, potato salad

4. Avoid eating commercial breakfast cereals, or crisp-breads like ryeveta, rice cakes or crackers.

Alex Duncan,

Gardoussel Retreat, France


[1] T. King, et al. Abnormal colonic fermentation in irritable bowel syndrome. The Lancet. Volume 352, Issue 9135, Pages 1187-1189.

[2] Wolfgang Scheppach, et al (2001). Beneficial health effects of low-digestible carbohydrate consumption. British Journal of Nutrition.