How many different plant foods did you eat in the last 7 days?

The average American consumes just 5. Dr Jeff Leach, of the Human Food Project, says good health starts with 25 per week. He aims for 55 to 70 (my breakfast alone has 20). A robust, well populated gut microbiome of diverse friendly bacteria is now linked with less risk for obesity, gut and mood disorders, heart disease and cancer.

There are 4 types of plant foods:

1) Fruits and vegetables

2) Grains – eg oats

3) Legumes – eg chickpeas

4) Nuts and seeds – eg almonds, tahini.

Unless you have a serious intolerance to an entire family of food, you should eat from a wide variety of each type. To help counteract the sloth of habit, each week when you do the shopping, buy at least one fruit, veg, nut, seed, grain or legume (dried peas, beans, lentils, soy) that you don’t usually have.

The benefits are many. Each plant has a unique profile of vitamins, minerals, antioxidants, carbohydrates, proteins and fats eager to keep you well. Additionally, only plants contain fibre. Some have soluble fibre (eg as in linseed, chia, slippery elm, psyllium, legumes including peanuts, oats) to act as a sponge to soak up impurities (such as heavy metals, excess cholesterol and unwanted hormones). Most plants have insoluble fibre that acts as a coarse broom to sweep out faecal matter (eg as in fruit, veg, wholegrains). Nuts and seeds have both types of fibre.

Another key health factor to some plants is resistant starch (RS). Most starches are broken down into sugar in the small intestine. This passes into the bloodstream and can spike blood sugar (or glucose – same thing) and insulin levels. They are used for short term energy needs or are stored. In contrast, resistant starch resists digestion and passes into the large intestine where it acts as a prebiotic. Bacteria feast on it. They turn it into short chain fatty acids (SCFA).

One type of SCFA is butyrate, which the US National Cancer Institute states is anti-inflammatory and immuno-regulatory. Butyrate can inhibit tumour cell proliferation and induce apoptosis (destruction) in colorectal cancer cells. RS isn’t new, but understanding it is. Despite the ‘starch’ part of its name, due to its resistance to digestion, RS is classified as a form of fibre.

SCFA can have many benefits, including:

• Improved insulin and blood sugar levels (BSL)
• Increased nutrient circulation
• Lowered growth of pathogenic bacteria
• Better absorption of minerals (especially calcium)
• Less absorption of toxic or carcinogenic compounds, which improves immunity
• Triggering leptin and glucagon hormones, which reduce the urge to eat, helping weight maintenance
• Elevated satiety (feeling satisfied and full with smaller meals)
• Increased bulk and water to stool, which helps regulate bowel function

There are 3 types of carbohydrates: fibre, starches and sugars. Starches have 2 types. Slowly digested starches are high in amylose, which has a tight, linear structure and so breaks down gradually (eg sushi rice) and helps regulate BSL. In contrast, amylopectin is widely branched with more surface area for speedy digestion (eg jasmine rice) and possible energy ups and downs.

However, what you eat with these foods has a significant impact. Protein, fat and fibre help slow digestion and regulate insulin and BSL. So a plate of plain rice, bread, potato or pasta will be a bland, poor choice. Instead add hummus and salad; curried egg and veg; fish or tofu and veg in peanut sauce or pesto. Other BSL regulators are crunchiness (eg raw or lightly cooked veg, coarse seeds, cracked grains in bread) and culinary acids such as lemon and vinegar (eg sauces, toppings, dressings). These too slow digestion while adding flavour, texture and nutrients.

The amount of SCFAs in the bowel is related to the amount and type of carbohydrate you consume. Resistant starch also increases when food is: not overcooked; less processed (so choose oat porridge over white toast); is cooked and cooled (such as with a potato, rice or pasta salad; or when cooked and later reheated, or cooked from frozen – RS can triple); and when fruit is firm rather than soft and overripe (especially true of bananas; green ones can have 7 times the RS of ripe ones).

RS helps weight management in several ways. While whole and highly processed food can have the same kilojoules, you absorb fewer of them when food is less refined. Since RS is not completely digested, you extract only about half the calories or kilojoules. Plus more chewing and digestion burn up fuel. You fill up, not out.

One study gave people similar looking sandwiches of equal kilojoules. One had highly processed bread and cheese spread. One had multigrain bread and cheddar. The latter burned up 46.8% more energy (as measured in kilojoules) during digestion! More evidence that it is highly processed foods – not carbs, or naturally resistant starches – which encourage weight gain and its attendant health problems.

Top RS Foods (in descending order)
• Buckwheat, oats and cassava
• Cooked and cooled potato, sweet potato
• 100% rye bread, especially sourdough
• White beans
• Lentils, green peas, chickpeas then kidney beans
• Green bananas
• 100% rye crackers
• Barley
• Corn tortillas; muesli
• Millet; brown rice
• Pasta (with white wheat flour; not gluten-free)
• Muesli bars with oats
• Sourdough wheat bread
• Cooked potato and taro
• Whole wheat bread, carrot and parsnip

See here for a more extensive chart.