The Collison Newsletter December 2013

 

                                POTATOES*  

 

 

The potato plant is a starchy, tuberous crop from the perennial Solanum tuberosum, of the Nightshade or Solanaceae family.

 

Other food members of this family include tomatoes, eggplant, and peppers (or capsicums). Pharmaceutical nightshades include tobacco, mandrake and belladonna.

 

(The Nightshade family is not to be confused with the plant Deadly Nightshade or Atropa belladonna. The foliage and berries of this plant contain alkaloids such as scopolamine and hyoscyamine. The drug atropine is derived from this plant.)

 

The potato is an integral part of much of the world's cuisine, and is the world's fourth-largest food crop, following rice, wheat and corn (maize). China is now the world's largest potato-producing country.

 

The potato is the swollen portion of the underground stem which is called a tuber. The name comes from the Latin word solanum meaning 'soothing'. Whether it is mashed, baked or made into French fries, many people think of the potato as a comfort food, a concept linked to its scientific name.

 

There are about 100 varieties of edible potatoes. They range is size, shape, colour, starch content and flavour. They are often classified as mature potatoes (the large typical ones) and new potatoes (those that are harvested before maturity, and are of a much smaller size).

 

The skin of potatoes is generally brown, red or yellow, and may be smooth or rough, while the flesh is yellow or white. Other less common varieties feature purple-grey skin and a deep violet flesh.

 

The history of potatoes shows that they originated in the Andean mountain region of South America. The Indians living in these areas have cultivated the potato for between 4,000 and 7,000 years. A detailed history to the present can be found at www.whfoods.com.

Nutrition In Potatoes 

The nutritional value of potatoes varies depending on the variety, soil quality etc and, as a result, published figures for the different components of the potato vary. In my book How to Live to 100+ Years Free from Symptoms and Disease, the following nutritional values are set out (similar to other published figures):

 
 
Potato, raw, with skin   -  Nutritional Value per 100gm
  
Water79.8g
Protein2.1g
Fat0.1g
Total carbohydrate17.7g
Fibre0.5g
Energy318kJ (76kcal)
Glycaemic Index78-91
 

The majority of the total carbohydrate is starch, some 90%.

 

Some authors give higher figures for 'dietary fibre', up to 2.2g (per 100g). This is probably due to the fact that a small but significant portion of the starch is resistant to digestion (‘resistant starch’) and so reaches the large intestine essentially intact. This resistant starch is considered to have similar physiological effects and health benefits as fibre.

 

Potatoes are not only very low in fat, but contain no cholesterol, and contain zero trans fats.

 

In addition to the macronutrients set out above, the potato is rich in micronutrients.

 

It contains the following vitamins (amounts per 100g):

B-vitamins: thiamine (B1) 0.08mg, Riboflavin (B2) 0.03mg, Niacin (B3) 1.05mg, Pantothenic acid (B5) 0.3mg, Pyridoxine (B6) 0.3mg.

Vitamin C 19.7mg

Vitamin E 0.01mg (www.ndb.nal.usda.gov).

 

The following minerals are present (amounts per 100g):

Calcium 12mg

Iron 0.78mg

Magnesium 23mg

Manganese 0.15mg

Phosphorus 57mg

Potassium 421mg

Sodium 6mg

Zinc 0.29mg (www.ndb.nal.usda.gov).

 

In addition to the vitamins and minerals, potatoes contain a wide variety of phytochemicals. Analysis has shown that the phenolic content rivals that of broccoli, spinach and Brussels sprouts, and includes flavonoids. Other phytonutrients present in potatoes, such as carotenoids and caffeic acid, have antioxidant properties.

 

The cooking method used can significantly affect the nutrient availability of the potato.

Health Benefits of Potatoes 

Potatoes are a very popular food source. Unfortunately, many people eat potatoes in the form of greasy fries, chips or crisps. Even baked potatoes and potato wedges are served loaded down with fats such as butter, sour cream, melted cheese and bacon pieces. Needless to say, these forms of potatoes are far from healthy. The health benefits set out below apply to potatoes, unadulterated.

 

Potatoes are essentially complex carbohydrate, mainly starch.

 

Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. It is a polysaccharide. It is made up of amylose (20-25%) and amylopectin (75-80%). Glycogen, the glucose store of animals and humans, is a branched version of amylopectin. "Amylum" is Latin for starch.  In photosynthesis, plants use light energy to produce glucose from carbon dioxide. The glucose is stored mainly in the form of starch. The enzymes that break down starch to glucose are known as amylases, found in human saliva and pancreatic secretions.

 

Thus potatoes supply the purest form of glucose molecules ... our fuel. They do have a high glycaemic index, which means that they can spike insulin. Thus the intake of potatoes should be limited if you are sedentary, simply because your metabolism does not need as much glucose. However, if you are physically active, you can consume more starchy foods such as potatoes, and not store them as fat.

 

One medium-size potato has about 418kJ (100kcal), almost no sodium, is very low in fat and is completely cholesterol-free.

 

Potatoes have high levels of potassium. This mineral is part of every body cell. It helps regulate fluids and mineral balance in and out of the cells and, in so doing, helps maintain normal blood pressure. Potassium is a powerful dietary factor that may help lower blood pressure. Potassium is also vital for transmitting nerve impulses and in helping muscles.

 

Potatoes are an excellent source of vitamin C. This vitamin is an antioxidant, stabilising free radicals, thus helping prevent cellular damage. Vitamin C also aids collagen production, assists in iron absorption and helps the body's immune system.

 

Potatoes have a high fibre content as well as resistant starch, essential for bowel health.

 

Phytochemicals are required for a healthy body. See my January 2010 newsletter Phytochemicals for information about these important micronutrients. Potatoes contain significant amounts of phytochemicals, especially antioxidants.

 

Potato skin is important, since about 20% of the potato's nutrition is found in the skin, especially the fibre.

Toxicity of Potatoes 

Potato plants contain toxic compounds known as glycoalkaloids, such as solanine. This is also found in the other members of the nightshade family. These compounds, which protect the plant from its predators, are, in general, concentrated in its leaves, stems, sprouts, and fruits. Exposure to light, physical damage, and age increase the glycoalkaloid content within the tuber, the highest concentrations occurring just underneath the skin. Cooking at high temperatures destroys them. Light exposure causes greening from chlorophyll synthesis, thus giving a visual clue as to areas of the tuber (potato) that may have become more toxic. Do not eat potatoes that have any greening of the skin. Glycoalkaloids may cause headaches, diarrhoea and cramps.

Conclusion 

Potatoes should be part of a healthy well-balanced diet.

 

This does not apply, of course, to potato in the form of fries, chips and crisps, or when adulterated with fats such as butter, cream and bacon pieces.

 

Potatoes are complete foods.

 

One of the earliest publications dealing with the benefits of potatoes set out details of "An experiment in which two adults, a man and a woman, lived over a period of 167 days in nitrogen equilibrium and in good health on a diet in which the nitrogen was practically solely derived from the potato." (The Value of Whole Potato in Human Nutrition, by  S. K. Kon and A. Klein, of the State School of Hygiene, Warsaw, Poland. 1927).

 

Some 85 years later, Dr John McDougall affirms the health benefits of potatoes in his book The Starch Solution (2012, publisher Rodale, distributor Macmillan). In this book, he claims that by eating starches, such as potatoes, "you can easily meet your basic nutritional needs with the exception of vitamin B12 .... No animal protein or dairy need be added for excellent and complete nutrition." (page 15).

 

 

*Copyright 2013: The Huntly Centre.

 Disclaimer: All material in the huntlycentre.com.au website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.

  

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