Beans and lentils

Beans and lentils are fantastic prebiotic foods. They are classed as legumes, which means that they come from the Fabaceae family of plants. Pulses are the dried seeds of the legume. Beans and lentils are a rich source of fibre. A fibre is the part of a plant that does not get digested in the upper intestine. It reaches the lower intestine or colon intact.

A starch is a sugar polymer, which means it's made up of repeating chains of sugars, typically over 200 units (an oligosaccharide typically has smaller chains of less than 10). This is where it gets a bit confusing (if it's not already). There are three types of fibre: soluble, insoluble and resistant starch. So, the resistant starch is not technically fibre but a starch.

Soluble fibre and resistant starch have similar properties in that they are loved by gut microbes which ferment them to form SCFAs - remember BOB and AA from the Dr Ese Fasting talk. Insoluble fibre isn’t as metabolically active as soluble fibre but it does increase faecal bulk and increases the frequency of bowel opening. All types of fibre, by their action on the gall bladder, enhance the detoxification of harmful substances.

From the graph you’ll see that beans and lentils are a better source of fibre/resistant starch than boiled potatoes and chips. However, we are unlikely be eating enough fibre and resistant starch. Northern Europeans typically eat 3-6 gms per day, the Chinese 10-15 gms per day and black South Africans around over 30 gms per day.

The fibre and resistant starch in beans and lentils are not digested in the upper intestine. Their sugars are ‘locked’ into complex structures that our body finds hard to deal with.  This means that the sugars are not readily released into our blood stream. Beans and lentils therefore are able to slow the release of glucose into the blood stream which also keeps insulin levels down.

Black beans are a rich source of antioxidants which means that they scavenge free radicals that cause inflammation in the tissues. Compared to chickpeas and lentils, black beans also come up tops when it comes to SCFA production.

We hear a lot of talk about needing to eat an ‘alkaline diet’ and so the graph that gives us a look at what beans and lentils do to the colon pH (acidity) can seem counter intuitive. From the graph, black beans, in particular, can have a substantial pH lowering effect on the colon. This means that it increases the acidity of the colon environment. This may seem like bad news but in fact it represents the opposite. The benefit of lowering the pH is that it discourages the growth of harmful microbes and encourages the growth of beneficial microbes such as lactobacilli and bifidobacteria.

How should we look to incorporate more beans and lentils into our lives?

We’re often put off because of the gassy side effects of beans. This is usually because our gut microbes are not used to dealing with such complicated food. Start with small amounts and make sure that the beans have been soaked overnight and even fermented. Changing the water frequently when washing them can also help avoid stomach reactions. Think about making a fermented spicy relish to use as a garnish for foods. This way you can have a little bit with your meals on a regular basis. Home made humous is a simple and easy way to enjoy chickpeas. This too can be used as a starter with raw veggies or added as a side to the main meal. Throw some beans into meat stews. Think of stews with coconut, beans, peas and fish.

Nutrients

• Oligosaccharides
• Fibre (soluble and insoluble)
• Resistant starch
• Phenolic (antioxidants)

Prebiotic effects

• Blood sugar & insulin control
• Satiety
• Short chain fatty acids (SCFAs)
• Inflammation control

Conclusion

Beans and lentils are an important prebiotic food and we probably don’t eat enough of them. Introduce beans and lentils into your life - slowly at first if you’re not used to eating them.