DrG's Medisense Feature Article
18081-Exotic_Fruits
Exotic Fruits
– Nutrition Trove or Hype?
by Ann Gerhardt, MD
August 2018
Print Version
Rambutan looks like an alien’s egg that might hatch and kill
us
all. Even the fruit’s white, pulpy flesh is
creepy. Why would one eat it, except out of
curiosity? With no
obvious vitamin content,
nutrition certainly is no motivator. Should we should just
take a picture and devour a banana?
Until the nutrition community, and subsequently the rest of the
population, woke up to the notion that plant foods contain healthy
polyphenols, vegetables like iceberg lettuce and celery
didn’t
get much respect. At first glance, iceberg lettuce wins the
useless contest. A list of celery’s nutritional
content,
were it to have a label, would look bleak. A whole stalk has
essentially no fat, minerals or protein and only 2-3% of the Daily
Value recommended for Vitamins A and C.
That changed when scientists identified plant foods’
polyphenolic
health value. Vegetables like celery, containing flavonols,
flavones, dihydrostilbenoids, phenolic acids, phytosterols and
furanocoumarins, suddenly became healthy. Those
unhealthy-sounding chemicals give the plant and those of us who eat
them an anti-oxidant, anti-inflammatory and possibly anti-tumor and
anti-bacterial boost.
Some exotic/tropical fruits lack well-known nutrients, as seen in the
Table, but the Internet often touts them as wonder foods.
Miraculous health claims derive from traditional herbal medicine lore
and may or may not be justified. We need science to confirm
or
refute those claims and identify plant foods’ chemical
components
which confer health benefits. Good science takes much longer
than
it does to make an unjustified health claim.
Science hasn’t analyzed the phytochemical content of every
fruit
to the same extent. What follows, therefore, probably
woefully
underreports the nutritional content of these fruits. Guava
reigns as queen in recognizable nutrients. It also is a rich
source of healthy carotenoids, anthocyanins and flavanols, and supplies
moderate amounts of folate, magnesium and manganese. The
juice
has much less nutritional value than whole fruit but would at least
retain the water-soluble vitamins.
Mangos supply a veritable treasure trove of phytochemicals –
carotenoids, catechins, tannins, terpenes, flavonoids, alkaloids and
phenols. It’s unclear to me if we’ve
found more of
these nutrients in mango because it’s better studied or
because
nature actually packed it with more of them. Papaya also
contains
considerable quantities of micronutrient, - magnesium, folate,
carotenoids, isothiocyanates, alkaloids and tannins. Kiwi
fruit
is rich in folate and anti-oxidant flavones and flavonols.
Starfruit has a measurable amount of vitamin B5, copper and
potassium. It also contains beneficial flavonoids, alkaloids
and
phenols. As a rich source of oxalates, people with kidney
stones
should avoid it, which is not hard to do in the mainland
U.S. It also potently inhibits the
liver’s role a
detoxifier, which might seriously alter medication levels in the body
of a regular starfruit consumer. The inhibition is even
greater
than that of grapefruit, which we routinely advise against for patients
taking affected medications.
Passion fruit contains a slew of phytochemicals, some of which might
affect medication metabolism. Its alkaloids inhibit monoamine
oxidase, important for metabolism of some anti-depressants and
catecholamines like adrenaline. Theobromine and coumarin have
medicinal effects that are likely insignificant unless one develops a
passion for passion fruit.
The edible part of purple mangosteen contains a few
bioflavonoids. In the early 2000s, purveyors of its juice
made a
lot of money after creating a mangosteen fad. Read my 2006
analysis of it at
http://www.healthychoicesformindandbody.org/Medisense_Articles/06126-Mangosteen_Mania.pdf.
In addition to potassium and vitamins C and B6, jackfruit supplies
useful amounts of magnesium, manganese and
carotenoids.
Breadfruit contains anti-microbial phenols, but its not clear that they
would be absorbed well enough to help fight an infection.
Longan is either too obscure for anyone to analyze or it truly has no
nutritional benefit. Though it has zero nutrients in a
standard
nutrition table, that hasn’t kept various websites from
touting
its “amazing benefits.” Lychee and longan
are related
to rambutan. Lychee contains epicatechin (a polyphenol tannin
like in tea), rutin (a flavonoid) and some copper.
Back to rambutan: It’s hard to find accurate
information
about its nutritional content. The pulp contains fruit sugar
and
the hairy skin contains some polyphenolic anti-oxidants, vitamin C and
fiber, but is too hard for most people to eat.
Scientists
probably haven’t fully analyzed rambutan’s
phytochemical
content, leaving an information void and no justification for claims of
wondrous health properties.
Curiosity drove my choice to eat one, and with it I might or might not
have consumed an as yet undiscovered healthy nutrient.
Variety is
important in nutrition, Eating apples and citrus fruits is
healthy, but wouldn’t it be boring if those were the only
fruits
we ate?