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'Nick has a go' take two ...



Further to 'Nick has a go' (GreenHealth Watch Magazine Edition 52 page 7) ... 

I made good progress towards consuming ten 80 gram (g) portions of vegetables and fruit (V&F) a day, but began to feel very full. I will spare you the details. Suffice it to say that my body's waste disposal system began to challenge my house's waste disposal system. The solution was obvious but unwelcome - reduce the volume of cereal, meat and fish I was eating.

But then I thought ...
  • if I were to accept a lower target of, say, eight portions of V&F a day, and
  • bearing in mind the advice that most V&F bring a unique contribution of nutrition to the feast
... which V&F that I regularly eat would I stop eating? Was there any almost 'dead wood' V&F in my current diet? From what I'd heard and read previously there were two obvious candidates - parsnips and potatoes - so I decided to research them in more detail. I found out the following ...

Parsnips - minerals and vitamins
Neither boiled nor raw parsnips are a rich source of minerals or vitamins. One portion (80g) of raw parsnips delivers just over one seventh (14%) of the US Daily Value (DV) for vitamin B9 (folate), and just over one fifth (22%) of the US DVs for vitamin C, vitamin K and the trace element manganese. Boiling parsnips reduces those levels to: just over one tenth (11%) of the DV for vitamin B9 (folate), just under one fifth (17%) of the DV for vitamin C, and just under an eighth (12%) of the DV for the trace element manganese.

Parsnips - other phytonutrients
Parsnips, like their close relatives carrots, contain:
  • the anti-oxidants falcarino, falcarindiol, panaxydiol and methyl-falcarindiol which, found scientists at the University of Newcastle (Tyne and Wear):
    • possess anti-inflammatory, anti-fungal and anti-cancer functions which, at least in rats
    • slow the development of colon cancer and acute lymphoblastic leukaemia (ALL)1
  • the anti-oxide flavonoids kaempferol, quercetin and rutin (which protect the heart and boost the immune system)
  • the anti-inflammatory and bronchodilator* terpene beta-pinene improving:
    • airflow to the lungs
    • short-term memory when used in conjunction with tetrahydrocannabinol(THC)
    • alertness
  • limonene (also found in the peels of citrus fruits and other plants), which is often added to medicines to promote (i) weight loss, (ii) prevent and (iii) treat cancer and bronchitis
  • alpha-thujene, a possible anti-inflammatory
  • isorhamnetin, a flavanol and anti-oxidant which has been found to (e.g.):
    • promote the elasticity of the artery walls; protect against high blood pressure and heart cell damage
    • protect against the development of oesophageal, liver and lung cancer
  • a very little dietary fibre (80g delivers 4% of the DV)
Parsnips - toxicity
Both raw and boiled parsnip root may be eaten safely, but the shoots and leaves must be handled with care as their sap is toxic. These (shoots and leaves) contain:
  • furanocoumarins as:
    • a defence against herbivore pests and
    • photosensitive chemicals that cause the condition phytophotodermatitis, which is a form of chemical burn rather than an allergic reaction
  • isobergapten, which can:
  • block the liver enzyme P450
    • interact with some medications
  • limonene, which is known to:
    • irritate the skin, sometimes causing allergic dermatitis
    • irritate the eyes
and, if consumed
    • irritate the gastro-intestinal tract
  • significant amounts of psoralen, which can:
    • damage genes
    • cause skin reactions in sunlight
    • become potential cancer-causing agents after exposure to sunlight
In the researchers' opinion: "It is apparent that consumption of moderate quantities of this vegetable by man ... may present some toxicological risk."

Peeling parsnips reduces their psoralen levels by a third (30%), which still leaves worrisome levels, and also has the disadvantage of reducing the already relatively low levels of any nutrients in the skin. Cooking did not reduce psoralen levels.

Parsnips - Footnotes
(i) Top and tail the parsnip root (where pesticide residues tend to accumulate).
(ii) Do not peel the rest of the root if at all possible. Although it may contain pesticide residues (unless organically grown), it is in and just beneath the skin where most of the parsnips' phytonutrients lie.

Potatoes - minerals and vitamins
Neither are potatoes a rich source of minerals and vitamins. According to SelfNutritionData:2
Baked potatoes in their skins are the richest form: 80g delivers 16% of the DV for vitamin B6, 13% of the DV for vitamin C and 16% of the DV for potassium. Boiled potatoes in their skins only get a mention for their B6 (80 grams deliver 12% of the DV). 'Chips' only get a mention for their vitamin C ((80 grams deliver 12% of the DV
  • the only mineral/vitamin worth a mention delivered by 80g of French Fries is vitamin C (17% of the DV)
Potatoes - other phytonutrients
Potatoes also containe.g. 2,3
  • phenolenic compounds, including phenolenic acids (like chlorogenic acid (see below), caffeic acid and quinic acid), tannins, stilbenes, coumarins and lignans
  • flavonoids (like catechin), of which the sub-classes are flavones, flavonols (like quercetin and kaempferol rutinose), flavanone, flavan-3-ols, anthocyanins and isoflavones
  • polyphenols (anti-oxidant, anti-proliferative (e.g. of malignant cancer cells)) and anti-cancer (e.g. breast cancer)
  • chlorogenic acid, which is particularly beneficial to human health, being anti-oxidant, anti-cancer, anti-inflammatory, analgesic, anti-microbial, neuro-protective, cardio-protective, anti-proliferative, insulin sensitivity-increasing, gut glucose absorption- reducing and gluconeogenesis-preventing
  • aglycones, petanin, cyanidin - all anti-oxidants
  • the blood pressure-lowering compounds kukoamines
  • modest amounts of the full range of essential amino acids and polyamine
Potatoes - toxicity
Potatoes contain glycoalkaloids, principally a-solanine and a-chaconine, and principally in and just beneath the skin:
  • A-solanine is much more toxic than a-chaconine
  • The glycoalkaloid content varies between 2.4 mg and 80 mg per 80g of potato, depending on (a) the cultivar/species and (b) the storage temperature
  • The recommended upper daily consumption of glycoalkaloids is 16 mg
  • A person weighing 80 kilograms who ate 100g of potato skins containing 180mg of a-solanine would probably experience symptoms of a-solanine toxicity
Potatoes contain very high concentrations of asparagine (9,270 parts per billion) which, when cooked at high temperature, (e.g. chips and French Fries) transforms into dangerous levels of acrylamide. Eating French Fries (and probably British-style "chips") twice or more a week may double the risk of premature death

Potatoes - Footnotes
(i) "New" potatoes contain higher levels of phytonutrients than mature potatoes.
(ii) Most of potatoes' nutrients rest in or just beneath the skin. Potatoes peeled for inclusion in processed foods/'ready meals' (e.g. "chips", fish cakes) therefore contain very low nutrient levels.
(iii) Extract of potato peel is now being used in the development of natural anti-oxidants used to prolong the shelf-life of processed foods, including those containing meat and fish.

References
1Inhibitory effects of feeding with carrots or (-) - falcarinol on development of azoxymethane-induced preneoplastic lesions in the rat colon. Kobaek-Larsen,M et al. Journal of agricultural and food chemistry 2005;53(5):1823-27
2SelfNutritionData. https://nutritiondata.self.com
3Beneficial phytochemical in potato - a review. Rajarthnam, E et al. Food Research International 2013;50(2):487-496
4Phenolic compounds in the potato and its by-products: an overview. Akyol, H et al. International Journal of Molecular Sciences 2016;17(6):835
(17594)  Nick Anderson. Green Health Watch Magazine 53 7.10.2018
 
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