'.. it is important to ensure that there are sufficient amounts of ALA, which is
necessary for the production of EPA and DHA. Most healthy vegetarians
would be well advised to double their intake of ALA, providing  1% of
energy from n-3 fatty acids or 1.1 g/1000 cal. For those with increased needs
or decreased capacity to convert, an intake of 2% of energy or 2.2 g/1000 cal
may be necessary. The primary sources of ALA are selected seeds, nuts, and
legumes (flaxseed, hempseed, canola, walnuts, and soy) and the green leaves
of plants, including phytoplankton and algae.
..
Practical guidelines for achieving optimal EFA intake in vegetarians are as
follows. 1) Make a wide variety of whole plant foods the foundation of the
diet. 2) Get most fat from whole foods- nuts, seeds, olives, avocados, and
soy foods. 3) If using concentrated fats and oils, select those rich in
monounsaturated fats, such as olive, canola, or nut oils. n-3-Rich oils can
also be used but should not be heated. Moderate use of n-6-rich oils is
recommended. 4) Limit intake of processed foods and deep-fried foods
rich in trans and n-6 fatty acids. 5) Reduce intake of foods rich in saturated
fat and cholesterol. 6) Include foods rich in n-3 fatty acids in the daily diet.
Aim for 2-4 g ALA/d.  7) Consider using a direct source of DHA. Aim for
100-300 mg/d. '
...
 For those with increased needs for EPA and DHA (eg, pregnant and
lactating women) or at greater risk for poor conversion (persons with
diabetes, those with neurological disorders, premature infants, the elderly),
it may be prudent to ensure that there is a direct source of EPA and DHA.'

While they are the original sources of EPA and DHA (fish do not produce
long-chain n-3 fatty acids), most are not concentrated sources because of
their extremely low total fat content. An important exception is a DHA-rich
microalgae that provides 10-40% DHA by dry weight and is currently
available in supplement form. When supplementing with a direct DHA
source, 100-300 mg/d is recommended. Blue-green algae (spirulina and
Aphanizomenon flos-aquae) are low in long-chain n-3 fatty acids. Spirulina
is rich in -linolenic acid (GLA, n-6), while A. flos-aquae is more
concentrated in ALA. Though blue-green algae is not a significant source
of EPA or DHA, some research indicates that it has a very high conversion
rate in comparison to other plants (R Kushak et al, unpublished observations,
1999). Macroalgae, otherwise known as seaweed, is even lower in fat than
most vegetables (< 1-14% of calories from fat), although it does contain
small amounts of long-chain fatty acids. A 100-g serving provides, on
average, 100 mg EPA but little DHA. Seaweeds do not contribute
significantly to EPA intakes in the Western world but are important sources
where people use large quantities of seaweed on a daily basis (eg, Japan
and other parts of Asia). Thus, while vegetarians can rely on eggs and/or
microalgae supplements for DHA, most consume little if any EPA.
However, < 10-11% of DHA is retroconverted to EPA; thus, if sufficient
ALA and DHA are consumed, total EPA production would be expected
to be adequate (61).
...'
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