plant foods and phytochemicals

Possible health benefits of vegetables, fruits, spices, teas and other plant foods include

• increased nutrient density for many minerals and vitamins,

• increased dietary fiber intake

• lower intake of saturated fats and meats

• possible benefits of many phytochemicals present in plant foods

• the products of phytochemical fermentation or metabolism by gut bacteria

different species of beneficial bacteria and other microbes in the adult large intestine (colon)

• action of them lead to production of potentially beneficial substances, especially the fermentation of plant food components

• e.g. production of vitamin K and several B vitamins (biotin + folate)or fatty acids through dietary fibers

includes dairy products and eggs but no meat

• substances produced by plants => non-nutrient components of plants and plant foods that may have health benefits.

• some can influence hormone action, others have antioxidant activity

• but: health benefits are not clear: some phytochemicals have low bio-availability in the digestive tract or they get metabolized rapidly

• increase plant foods: fruits, vegetables, legumes, grain products, herbs, spices, teas

• less often recommended: supplements

  • greater risk of toxicity and possible interference with prescription drugs

  • sometimes more phytochemicals are present in the whole plant or whole food compared to an extract

• sources of phytoestrogens, phytochemicals

• possible health benefits: lower risk of cardiovascular diseases and protection against some types of cancer; high-quality protein

• negative effects: very high consumption: some of substances in soy foods can interfere with absorption of mineral micronutrients (antinutrients)

  • phytoestrogens may increase growth of breast cancer: not recommended for women

  • interfere with normal thyroid function

substances that interfere with nutrient absorption

• phytic acid: can lower absorption of minerals: iron, calcium, zinc, magnesium

  • in many different plant seeds

• oxalic acid: abundant in spinach, rhubarb, and cabbage family: can lower absorption of calcium

• enzyme inhibitors (e.g. in legumes) that can decrease the enzymatic digestion of starches and proteins: amylase and protease inhibitor)

• Lectins: interfere with the absorption of nutrients

• avidin (egg white protein) binds vitamin biotin very tightly and prevents its absorption

• glucosinolates: can lower iodine absorption

• flavonoids: lower minerals such as iron, and zinc, and interfere with enzymatic digestion

can lower levels of some antinutrients and decrease the risk of developing nutrient deficiencies

• fermentation by microbes produce some beneficial phytochemicals

• toxins may also be produces especially if harmful strains of microbes get established during the fermentation process

• in many different plantseeds, can bind some minerals like calcium, iron, zinc, magnesium and prevent their absorption

• is often part of food with high fiber. => leads to lower absorption rate of minerals

• present in spinach and rhubarb

• can lower absorption of calcium

• enzyme inhibitors can decrease enzymatic digestion of starches and proteins => amylase and protease inhibitor

• lectins can lower absorption of nutrients

avidin

• egg white protein

• binds biotin (B7) tightly and prevents its absorption

  • biotin participates in production of fatty acids and in gluconeogenesis (use of fatty acids to release energy)

• glucosinolates can lower iodine absorption

• lower mineral absorption from iron and zinc

• interferes with enzymatic digestion

• e.g. tannins

• increases risk of toxicity and interference with prescription drugs

• possible loss of other phytochemicals during the production

• many unproven health claims => not proven via double-blind placebo-controlled intervention studies

• includes isoflavone (soy) and lignans (flax seeds, sesame seeds)

• hormonal regulation

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• include isoflavone, flavonols

• some have potent antioxidant activities and can affect a range of other cell functions

• some can reduce absorption of some nutrients

• can be sources of vitamin A

• possible that they may decrease risk of some cancers or eye diseases (under research)

• can have damaging abilities as well